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Full text of "An investigation on the effect of brick dust on lime-based mortars"

UNivERsmy 

PENNSYIVANIA. 
UBRARIES 




f AN INVESTIGATION ON THE 
EFFECT OF BRICK DUST 
ON LIME-BASED MORTARS 



T 



John Glengary Carr 



A THESIS 



Historic Preservation 



Presented to the Faculties of the University of Pennsylvania in Partial 
Fulfillment of the Requirements for the 



Degree of Master of Science 



1995 



i^kAtSTv^ 




(\.^ 




ader 
'efanne Marie Teutonico 



Di^^./f^^ I'i^-^ 



UNIVERSITY 

OF 

PENNSYLVANIA 

LIBRARieS 



Acknowledgements 

The author would like to thank all those who have helped in fulfilling 
the demands of this thesis. A special thanks goes to my supervisor Frank G. 
Matero for his guidance throughout this research project. I am particularly 
grateful to Jeanne Marie Teutonico for inspiring and supporting this research 
project. Without her encouragement and expert criticism this research 
project would never have been realized. I would like to thank Dr. Alex 
Radine and Dr. Shu Chin Wang, of the Laboratory for Research of the 
Structure of Matter for guidance during the evaluation and Bill Weldon of 
Colonial Williamsburg for his cooperation. To all these my sincere thanks. 



Table of Contents 

Page 

Acknowledgements ii 

List of Tables v 

List of Photographs v i 

Introduction vii 
Chapter 1 Brick Dust as an Artificial Pozzolana - History, 
Characterization and Research 

1.1 Pozzolanas 1 

1.2 Chronology of Use of Natural and Artificial 12 
Pozzolanas with Lime Mortar 

1.3 Review and Discussion of Selected Research on 25 
the Addition of Artificial Pozzolanas to Lime- 
Based Mortars 

1.4 Characterisitics of Mortars for the Conservation of 31 
Historic Masonry Structures 

Chapter 2 Experimental Program 

2.1 Research Significance 33 

2.2 Research Objective 36 

2.3 Materials Used in Experimental Program 38 

2.4 Formulation of Facsimiles 44 

2.4.1 Mixing 45 

2.4.2 Molding 46 

2.4.3 Curing 51 

2.5 Experimental Program Standards 52 

2.6 Experimental Program 54 

2.6.1 Color 57 

2.6.2 Initial Water Content 59 

2.6.3 Workability as measured by a Flow Table 62 

2.6.4 Setting Rate 65 

2.6.5 Set Under Water 69 

2.6.6 Shrinkage 72 

2.6.7 Bulk Specific Gravity 76 

2.6.8 Compressive Strength 79 

2.6.9 Water Vapor Transmission 84 

2.6.10 Water Absorption Capacity 90 

2.6.11 Depth of Carbonation 94 

2.6.12 Resistance to Salt Attack 96 

2.6.13 Microcracking of the Mortar Mixes 102 

2.6.14 Microstructure of Mortar Mixes 110 



2.6.15 Porosity as Measured by Pore Size 123 
Distribution 

2.7 Conclusions 126 

2.8 Recommendations for Future Research 129 

Bibliography 131 

Appendix 1 - Results of Compressive Strength Testing 142 






List of Photographs 

Photo 1 - Tamping with a non-absorptive, non-brittle tamper into the 50 mm 

ot 2 in Wooden Cube mold. 

Photo 2 - Three part wooden cube mold, disassembled and assembled with 50 

mm or 2 in sample cubes. 

Photo 3 - Sample being demolded from PVC ring mold. 

Photo 4 - Vicat penetrometer measuring setting rate of mortar mix. 

Photo 5 - Length Comparator measuring shrinkage of the prism mold. 

Photo 6 - Samples after 12 cycles of 10% solution sodium sulphate 

crystalization test. 

Photo 7 - Samples after 10 cycles of 14% solution sodium sulphate 

crystalization test, note the cracking of the cubes and salts on the surface of the 

cubes. 

Photo 8 - Microphotograph, 10 X Mix 1. 

Photo 9 - Microphotograph, 10 X Mix 2. 

Photo 10 - Microphotograph, 10 X Mix 3. 

Photo 11 - Microphotograph, 10 X Mix 4. 

Photo 12 - Microphotograph, 10 X Mix 5. 

Photo 13 - SEM microphotograph, Mag. X 110, Brick Dust, (BDl) 

Photo 14 - SEM microphotograph, Mag. X 100, Brick Dust, (BD2) 

Photo 15 - SEM microphotograph, Mag. X 100, Mix 1 (1 part lime to 3 parts 

sand) 

Photo 16 - SEM microphotograph, Mag. X 1200, Mix 2 (1 part lime, 3 parts sand 

and 1 part brick dust) 

Photo 17 - SEM microphotograph, Mag. X 1200, Mix 4 (1 part lime 2.5 parts 

sand and 1 part limestone dust) 

Photo 18 - SEM microphotograph, Mag. X 1200, Mix 5 (1 part lime to 2.5 parts 

sand, and 1 brick dust) 






List of Tables 

Table 1 - Particle Size Distribution of Yellow Bar Sand 

Table 2 - Mortar Facsimile Compositions 

Table 3 - Schedule of Molds and Number of Samples 

Table 4 - Standards Consulted for Experimental Program with corresponding 

European Standards 

Table 5 - Color of Materials and Mortar Mixes 

Table 6 - Mean Water Content of Mixes 

Table 7 - Mean Percent Change as Expressed by Flow Table 

Table 8 - Mean Setting Rate of Mortar Mixes 

Table 9 - Observations of the Mortar Mixes Setting under Water 

Table 10 - Mean Percent Change of Length of Mixes 

Table 11 - Specific Gravity of Mortar Mixes 

Table 12 - Mean Compressive Strength, (Mean Mpa based on 4 cubes tested) 

Table 13 - Mean weight change of assemblies - (g) 

Table 14 - Mean Water Absorption Capacity of Mixes (g) 

Table 15 - Mean Water Capacity of Mixes - (g) 

Table 16 - Mean Measurement of Depth of Carbonation of Mixes 

Table 17 - Mean % Weight Change of Mixes (g) - Experiment 1 

Table 18 - Mean % Weight Change of Mixes (g)- Experiment 2 

Table 19 - Mean Pore Size Distribution of Mortar Mixes - Expressed as a % 

Table 20 - Mean % Porosity as measured by Pore Sizes of Mortar Mixes 



"Mortar a hundred years old is still in its infancy." 

Louis J. Vicat in A Practical and Scientific Treatise on Calcareous Mortars and 
Cements, Artificial and Natural, (Translated by Captain J. T Smith) 1837. 






J 



Introduction 

Mortar, an essential material to creating continuous masonry system, 
has been used in one form or another by many different civilizations, at 
different times. In antiquity, lime and sand were key ingredients in mortar. 
However, it seems to have been known by many early builders, masons and 
architects in the western world that with the addition of a certain quantity of 
burnt clay, a vast improvement would be obtained in the hardening and 
hydraulic qualities of the mortar. Hydraulic mortars possess the ability to 
harden in the presence of water. 

There is evidence that burnt clay in the form of crushed potsherds was 
added to lime mortar to impart it hydraulic qualities in the Minoan 
civilization of Crete. Similarly, the Romans may have used crushed tile 
additions to their building mortars before they discovered the material that 
changed the course of building technology even to the present day. How or 
exactly when Roman builders discovered a volcanic sand near Naples that 
when added to lime accelerated setting time and rendered the mortar 
hydraulic is not exactly known. However, this technology was known to 
those building at that time and accounts in part for the longevity of their 
buildings. Vitruvius, the first century architect, builder and writer says of it, 

"There is a species of sand which, naturally, possesses extraordinary 
qualities. It is found under Baiae and the territory in the 
neighbourhood of Mount Vesuvius; if mixed with lime and rubble, it 
hardens as well under water as in ordinary buildings"^ 






^ Vitruvius, The Ten Books of Architecture, M. H. Morgan trans., (New York: Dover 
Publications, 1960) 19. 



This extraordinary material referred to by Vitruvius is known as 
pozzoiana, found close to the town of Pozzouli, near Naples, thus the 
derivation of the name. However, when pozzoiana or volcanic earth was not 
available, Roman builders made use of powdered tiles or pottery or pounded 
bricks, known as artificial pozzolanas.^ This material is also referred to as a 
pozzoiana because the resulting mortar has similar properties to that made 
with natural pozzoiana. Such a substitution resulted in hydraulic and rapid 
setting mortars. Of this Vitruvius said. 



"if to river or sea sand, potsherds ground and passed through a sieve, 
in the proportion of one-third part, be added, the mortar will be the 
better for use."'^ 



In Roman masonry structures constructed throughout Europe, dust from 
either bricks or fired clay pots have been found in the lime mortar. 

Although at first pozzoiana referred only to the material found near 
Pozzuoli, in time the term came to be applied to other deposits of volcanic 
ash in Italy, Greece, France and Spain. Still later, pozzoiana was used to 
designate any natural or artificial material possessing properties similar to 
those of the ash from Pozzouli regardless of its origin. 

For the past three hundred years, research has been conducted on the 
materials responsible for the longevity of Roman buildings. On the subject of 
pozzoiana, the research has determined that whether in the natural or 
artificial form, when reduced to a powder, and mixed with lime and sand, it 



2 F. M. Lea, Investigations on Pozzolans, (Garsten: Building Research Technical Paper 27), 1940, 

4. 

^ Vitruvius, The Ten Books of Architecture, M. H. Morgan tmas.,, 9. 



displays the property of not only attaining much greater resistance to 
atmospheric influences, but also the quality of hardening underwater. As 
well it will impart to the material an increased degree of resistance to various 
agencies which are normally liable to cause disintegration. 

This rediscovery in eigthteenth century Europe permitted the building 
of maritime structures such as the Eddystone Lighthouse and contributed to 
the discovery of Portland Cement. Pozzolanas have impacted and continue 
to impact the way in which building and the repair of buildings is conducted. 

Not all brick dust possesses pozzolanic properties. It is not possible to 
determine the pozzolanicity of a material without testing it in combination of 
another material such as lime or cement. Microscopic, chemical or 
mechanical tests can not be performed to evaluate the pozzolanicity of a 
particular brick dust. The fundamental property of a pozzolana is its ability to 
chemically combine with lime. Thus a potential pozzolana must be tested in 
combination with lime to identify and understand its properties. 

Although it requires many to years to properly observe the properties 
imparted on lime mortar with the addition of a pozzolana, this research 
attempts to evaluate aspects of this phenomenon over a short period of time. 
In this time period, many factors of the phenomenon can be observed and 
discussed. Almost a half century ago the following statement was made. 

"The chemistry of pozzolanas is still not solved... and only when the 
chemical action is completely understood will it be possible to design a 
pozzolana of ideal composition for any particular purpose."^ 



/ 1 



^ R.H. Brogue, The Chemistry of Portland Cement, (New York: Rheinhold Publishing Corp. 
1947). 



Renewed interest in the phenomenon of the pozzolanic reaction is 
exempUfied by the Smeaton Project, a joint venture between English 
Heritage, ICCROM and Bournemouth University. The investigations of the 
first phase of the Smeaton Project have examined the use of brick dust as a 
pozzolaruc additive to lime based mortars used in the repair and 
conservation of historic structures. The first phase of the investigation set 
out to discover trends in the behaviour of modified Ume based mortars and 
concluded that the addition of brick dust did significantly alter the properties 
of lime mortars in regards to strength and durability .5 

This research program intends to apply a methodology similar to that 
used for the Smeaton Project to investigate the effect of brick dust on the 
properties of lime based mortars. Like the Smeaton Project, this investigation 
does not attempt to resolve the mystery of the chemical action of pozzolanas. 
However, it does attempt to examine and evaluate two potential pozzolanic 
materials and standardized tests methods. Before the experimental program 
commenced, a review of the published literature regarding the use of 
pozzolana was conducted. 

The selection of a methodology for evaluating artificial pozzolanas 
with lime mortar is made difficult by the absence of any generally accepted 
tests or standards. The difficulty is compounded because pozzolanas 
themselves have no cementitious properties and thus they must be tested in 
combination with other materials Thus, pitfalls involved in attempting to 



5 Jeanne Marie Teutonico, Iain McCraig, Colin Bums and John Ashurst, "The Smeaton Project: 
Factors Affecting the Properties of Lime-Based Mortars," APT Bulletin, Volim\e XXV, No. 3-4, 
32-49. 



characterize a pozzolanic material are great as many variables car\ exist. A 
standardized methodology was established in an attempt to eliminate many 
of the variables. 



1.1 Fozzolanas and Pozzolanic Reaction 

Pozzolanas are currently defined as natural or artificial materials which 
contain silica and /or alumina that are not cementitious themselves, but 
when finely ground and mixed with lime, in the presence of water, the 
mixture will set and harden at ordinary temperatures. ^ There are basically 
two categories of pozzolanas, namely natural and artificial. Natural 
pozzolanas are primarily of volcanic origin from geologically recent volcanic 
activity whereby the material has undergone considerable alteration after 
deposition. 2 Artificial pozzolanas are either calcined clays or byproducts of 
various industrial and agricultural processes whereby calcination has 
occurred. 

The fundamental property of a pozzolana is its ability to combine with 
alkaline lime or cement to yield a material with improved performance. As 
well, the addition of a pozzolana results in a fundamentally different setting 
process. Lime mortars modified with either artificial or natural pozzolanas 
produce a relatively insoluble and durable material that differ from lime 
mortars. Generally, lime-based mortars require long periods of time to set up 
or harden and are less resistant to destructive agents including water, 
freeze/thaw cycles and salts in solution than those modified with pozzolanas. 



^ ASTM C 593 -89 Standard Specifications for Fly Ash and Other Pozzolans for Use with Lime, 
289. Pozzolana, the term used in this research, is also referred to by other sources as pozzolan 
and pouzzolan. There is no difference, other than spelling, for these terms. 
2 F. M. Lea, Building Research Technical Paper No. 27 Investigations on Pozzolans, Pozzolnanas 
and Lime-Pozzolana Mixes, 1. 



Natural Pozzolanas 

Both the Greeks and the Romans had discovered that the addition of 
certain finely ground volcanic deposits mixed with lime and sand would 
result in a hydraulic mortar with superior strength and endurance. The 
Greeks still use volcanic tuff called Santorin Earth as a pozzolanic additive to 
lime mortar. The Romans used and understood that volcanic ash especially 
from Mount Vesuvius, found close by the town of Pozzouli, would affect the 
properties of lime based mortars. This region has been worked for centuries 
with small open pits whereby the material is screened and then ground. 3 

Naturally occurring pozzolanas include some types of volcanic ashes 
and certain properly calcined opalines, cherts and shales. Another source of 
natural pozzolana is certain types of diatomaceous earth^ The occurrence of 
known suitable natural pozzolanas is limited to only a few regions of the 
world. The natural pozzolanas known and employed in Europe are the 
Italian Pozzolanas, German Trass from the Rhine district and Bavaria, 
Santorin Earth from the Greek island Santorin; Tosca from Teneriffe, one of 
the Canary Islands, and Tetin from Portugal's Azores. In other parts of the 
world, natural pozzolanas have been discovered and utilized, such as 
volcanic ash in Japan. Natural occurring sources of pozzolanas have been 
sought and located after in North America for use in the concrete industry. 



3 Alfred Denys Cowper, Lime and Lime Mortar, (London, His Majesties Stationary Office, 
1927), 47. 

^ Diatomeaous earth has been classified as both a natural pozzolana and an artificial 
pozzolana. Popovics in Concrete Materials lists diatomaceous earth as a natural pozzolana. 
Wheras, Lea in The Chemistry of Cement and Concrete ,16, states that diatomaceous silica is 
both a natural and an artificial. Some types of diatomaceous earth have no pozzolanic 
properties at all. 



Although many potential sources were located, few if any seem to be utilized 
for use with lime-based materials. 

Naturally occurring pozzolanas are crystalline minerals in particulate 
form bound firmly together by mutual attraction. The reactivity of clays is 
related to the type of mineral and the proportions of clay in the material, 
called the clay fraction.^ Performance of the clay is improved by heating, thus 
disrupting the well ordered crystal structure. Temperature and duration of 
heating is critical as prolonged exposure to too high a temperature can result 
in re-crystallization and a decrease in reactivity. 

Artificial Pozzolanas 

Artificial pozzolanas had been known to the Romans, who substituted 
clays burnt in the form of powdered tiles or pottery for natural pozzolanas. 
Vitruvius said of this practice 

" if to river or sea sand, potsherds ground and passed through a 
sieve, in the proportion of one-third part, be added, the mortar 
will be the better for use." ^ 

In the sixteenth century, Biringuccio, made references to the term opus 
signinum, with potsherds, as in the recipe for cisterns.^ A similar technology, 
called Surkhi had been known and was used in India. In Egypt, this 
technology was known as Homra. It has not been established whether the 



^W. Mice and J. Allen. Locating Reactive Natural Pozzolanas , (Ellis and Moore Consulting 

Engineers), 3. 

^Lea, Investigations on Pozzolans, Pozzolnanas and Lime-Pozzolana Mixes , 7. 

'' Joan Mishara, "Early Hydraulic Cements," Early Pyrotechnology , The Evolution of the First 

Fire-Using Industries, eds. Theodore and Stephen Wertime, (Washington, Smithsonian 

Institute Press), 128. 



eastern or the western civilization first employed this technology. Surkhi, 
used for centuries in India, consists of finely ground bricks that replaces the 
whole or the part of the sand when hydraulic properties are desired. The 
lime and the brick are mixed wet until a sticky mass is formed, and this is 
added to the aggregate. The whole mixture is mixed thoroughly and tamped 
just before usage for masonry construction. 

The Romans took their knowledge with them in their Empire, and 
when no local naturally occurring pozzolanas could be found, they added 
artificial material in the form of potsherds and pounded bricks. In Roman 
brick work found in England, artificial pozzolanas thought to be brick dust 
have been identified in the mortar at Corfe Castle^. At the Roman elevated 
aqueduct in Caesarea, Israel, finely crushed red bricks, tiles or pot sherds were 
discovered in the multi-layered plaster lining^ . Ground tiles and potsherds 
were most commonly used; however, some evidence exists that pozzolanas 
from Naples were exported for the structures of the Roman Empire. 

Analysis of Roman mortars in Germany reveals the increased 
proportion of fines in the mortar. 1° This increase in fines has been attributed 
to the addition of brick dust. Brick chippings were used in the mortar as 
aggregates of varying sizes. The mortar was used for external rendering on 
the Badenweiler bath ruins; a location where hydraulic mortar and plaster 
would have been required for its hydraulic properties. The fact that the 



8 The Builder , June 18, 1892, 471. 

' Roman Malinowski, "Roman, Concretes and Mortars in Ancient Aquaducts," Concrete 

International, January, 1979, 

^^ Thorborg Perander and Tuula Raman, Ancient and Modem Mortars in the Restoration of 

Historic Buildings, (Technical Research Centre of Finland, Research Notes, 450 ), 67. 



mortar exists to the present day attests that this method was well under the 
control of the craftsmen and gave consistent and predictable results. 

In 1843 L. J. Vicat experimented with many materials and discovered 
that properly calcined psammites and schists, smithy slag, and the refuse of 
the combustion of turf and coal, would yield a hydraulic or pozzolanic set to 
lime based mortars. ^^ At this time Vicat stated that tile dust, "which has been 
used in buildings for time immemorial, is the most ancient of the artificial 
pozzolanas known" ^^ However, the main artificial pozzolanas are burnt clays 
and shales, pulverized fly ash, rice husk ash^^^ spent oil shales, burnt gaize, 
burnt moler, and ground granulated blast furnace slag. 

Presently the most utilized artificial pozzolanas are burnt clay in the 
form of brick or tile dust and pulverized fly ash. Pulverized fly ash (PFA), 
finely ground burnt coal from the furnaces of electricity generating stations 
which solidifies into spherical particles, is commercially available in Europe 
and North America for use by the concrete industry. In some cases 35-50 % of 
ordinary Portland Cement can be replaced by PFA with satisfying results. 
However, the addition of PFA significantly alters the color, and thus makes 
its use problematic for conservation. 



1^ L. J. Vicat, A Practical and Scientific Treatise on Calcareous Mortars and Cements, Artificial 

and Natural, translated by Captain J. T. Smith, (London, John Weale 1837), 50. Psammites are 

geological forms of sandstones. Schists are crystalline metamorphic rocks. Smithy slag are the 

vitrified byproducts from metal production in the blacksmithing shop. 

12lbid., 143. 

^ •^Calcined rice husks can be classified a pozzolana because a very high of the very high 

amorphous silica content. 



Pozzolanic Reaction 

In spite of the considerable research on this subject, the phenomenon 
of pozzolanic activity is not completely known. As previously mentioned, 
pozzolanas possess no cementing action without mixing with lime. The 
addition of this material increases the complexity of this phenomenon. As 
well, the composition of known pozzolanas and limes can vary widely 
making it difficult to identify what exactly renders a material pozzolanic. It 
has been determined that the material must contain silica and alumina 
which activate the reaction with calcium from the lime in an alkaline or high 
pH environment. i"* Agreement exists that pozzolanic activity can be 
described by the following simplified reaction known as C-S-H. Using cement 
technology notation the main components are C (=CaO), S (=Si02), and H 
(H2O). 

A test developed in 1847 by Vicat can be used as a satisfactory index to 
pozzolanic reaction. This test, presently adopted as an industry standard 
worldwide, quantifies the setting time or rate of pozzolanic reactivity to lime 
mortar. The test produces comparative data to evaluate potential pozzolanas 
and establish setting rates. 

Pozzolanic reactions are not always constant. They are dependent on a 
myriad of variables including the type of pozzolana, the type of lime, 
preparation and curing conditions. In the eighteenth century, Vicat 
established that different types of limes reacted in a clearly different way with 
pozzolanas to yield different results. Vicat observed that combinations of 



^'^Lea, Investigations on Pozzolans, Pozzolanas and Lime-Pozzolana Mixes, 7. 

6 



materials could be used to obtain mortars capable of acquiring a great 
hardness in water, or underground or in situations that are constantly 
dampi5 They include: 



with rich limes 


with slightly 


with the hydraulic 


with the eminently 




hydraulic limes 


limes 


hydraulic limes 


-very energetic 


-simply energetic poz. 


-feebly energetic 


- inert materials such 


pozzolanas, natural 


natural or artificial. 


pozz., nat or art. 


as the quartzose and 


or artificial 


-the very energetic 


-energetic pozz., nat 


calcareous sands.* 




pozz. nat. or art. 


or art, tempered by a 


-slag, dross, etc. 




tempered by the 


mixture of about one 






mixture of half of 


half sand. 






sand or other inert 


-energetic arenes 




' 


substance. 


psammites 






-energetic arenes, 








psammites 







* with the eminently hydraulic cements, it was found that the mixture of a highly energetic 
artificial pozzolana produced a much inferior cement to alike mixture of the same pozzolana 
with rich slaked lime. 



Vicat's observations indicate that many materials, when properly 
combined, result in what he considered to be a superior hydraulic mortar. An 
exact explanation does not accompany these observations, and perhaps no 
acceptable explanation will exist. Presently, many theories for pozzolanic 
reactions exist^^, although no agreement seems to have been established. 

Firing Temperature of Artificial Pozzolana 

Although various theories concerning pozzolanic reaction still exist, 
most academics have agreed that firing temperature has a direct and 
fundamental effect on rendering the material pozzolanic. It has been 



.^^Vicat, A Practical and Scientific Treatise on Calcareous Mortars and Cements, Artificial and 
Natural, 190. 

^^ F. M. Lea, The Chemistry of Cement and Concrete, (New York, Chemical Publishing 
Company, Third Edition, 1971). 



established that temperatures ranging from 500° to 950° F will transform 
certain types of clay into pozzolana. On this subject Lea stated: 

"optimum burning temperature for producing burnt clay 
pozzolanas can be fixed since the temperature of burning in the 
rotary kiln of satisfactory materials varied from 775-910 °C. 
From general experience with both lime and cement mixes it 
appears that the best pozzolanas are obtained from clays which 
can be burnt in the upper part of this range. "^'' 

Other research has produced similar conclusions. In the mid- 
nineteenth century, Totten published that the best results in terms of 
resistance came from mortars made with pulverized bricks and tiles which 
had been lightly calcined rather than those made of more highly burned 
bricks or tiles. ^^ Recently, it has been declared that the best pozzolana is 
yielded from clay burnt at temperatures between 500 and 900° C.^^ In this 
temperature range, calcined clays possess pozzolanic reactivity as the crystal 
lattice of the silicates is destroyed and causes the extreme disorder of the 
structure. In this state, the amorphous silica becomes more reactive with the 
calcium hydroxide from the slaked lime, resulting in the formation of an 
insoluble product which slowly hardens. ^o Thus, heating to high 
temperatures will destroy the pozzolanic reactivity of some effective 
materials. Modem brick firing kilns average temperatures considerably 
higher, roughly 1500°C which renders the material unsuitable as an effective 
pozzolana. In general, the pozzolanic activity of burnt clay is optimum at 



i^ibid., 418. 

^^J. G. Totten, Essays on Hydraulic and Common Mortars and on Limebuming, Translation of 

General Treussart, M. Petot and M. Courtois, (Philadelphia, Franklin Institute, 1838), 149. 

l^Guilia Baronio and Luigia Binda, "Characterization of Mortars and Plasters from Ancient 

Monuments of Milan (Italy)," The Masonry Society Journal, (January - June, 1988, Vol. 7, No. 1), 

T28. 

20lbid. 

8 



temperatures whereby the material would be considered underfired by 
present day standards. 

Although firing temperature has been established as a key factor in 
pozzolanic activity, it can also be influenced by particle size of the clay, 
mineralogical composition of the clay and the length of calcination time. 

Particle Size 

Even though there is an understanding that the pozzolanic activity 
increases with the fineness of the pozzolana, there still exists some question 
regarding the effect of range in particle size. Fine grinding of the pozzolana 
whether artificial or natural has been recommended starting with the 
writings of Vitruvius. In mortars which have endured for centuries, a range 
of particle sizes has been discovered. It has been established that a range in 
particle size has ameliorating affects which render lime mortars hydraulic. 
Research has established that fine grinding of a calcined clay stimulates the 
pozzolanic reaction and thus the early carbonation of lime mortars. 21 
However, the role of larger particle sizes has yet to be fully researched. One 
theory is that brick dust groimd to larger sizes may have a beneficial effect on 
lime mortars as a porous particulate.22 A porous particulate is a solid particle 
with a large internal porosity and suitable pore sizes to act in a fashion similar 
to that of an air void. Thus, there is the uncertainty as to whether the larger 
size particles of brick dust behave as an artificial pozzolana or a porous 
particulate. In lime mortars, these larger size porous members may 



21 Lea, The Chemistty of Cement and Concrete, 372. 

22 Ibid., 435. 



i 



accelerate the initial carbonation by the release of CO2 to the subsurface. After 
initial carbonation, the brick dust may act to increase the degree of 
permeability as well as porosity of the mortar. Resistance to frost and salt 
damage improves with higher levels of porosity. As lime mortars experience 
carbonation and the pozzolanic reaction continues for a long period of time, 
the larger size particles act to absorb and slowly release CO2 and H2O to 
facilitate the reaction. Thus, it could be stated that a range of particle size 
imparts different but favourable factors for lime mortars. 

Mineralogical Composition of the Clay 

As previously stated the composition of known artificial and natural 
pozzolanas can vary widely, making it difficult to identify what exactly 
renders a material pozzolanic. It has been determined that the material must 
contain silica and alumina, the principal components of most clays. 
Generally, most clays are made up of hydrated alumina silicates with about 
10-15% water content.^^ Upon firing, the water content is lost and the 
calcined clay is rendered pozzolanic. 

Length of Calcination 

Depending on the mineralogical composition and the ultimate firing 
temperature, the length of calcination can effect the pozzolanic properties of 
the material. Some materials, such as kaolinite type clays require longer 



23 Ibid., 420. 

10 



periods of calcination.24 However, prolonged periods of calcination can 
actually decrease or eliminate the pozzolanic activity of a material. 



'f . . 

* V ^'* Ibid., 421. 

11 



\ 



1.2 Chronology 

The following chronology does not pretend to be exhaustive. Instead, 
it attempts to pull together information from the published research on the 
lime, cement, concrete and grouting industries. This chronology includes the 
dates of publications, patents and treatises as well as pertinent projects where 
the hydraulic properties of mortar or cement were desired. This chronology 
demonstrates the discovery and rediscovery of pozzolanic materials, the 
renaissance of pozzolanas and hydraulic lime, followed by their replacement 
by other patented hydraulic materials such as Portland Cement. Interestingly 
it was the need to understand and maximize the hydraulic qualities of 
limestone that led to the invention of Portland Cement. Although the use of 
brick dust or calcined clay as pozzolanic materials was the impetus for the 
literature search, other directly related developments are included in the 
chronology. 

Roman Period 

The first written material regarding the technology of lime-based 
mortars with hydraulic additives dates from the Roman period. Mortars 
were used in combination with hydraulic admixtures such as brick dust, 
pozzolanic earth and trass in other cultures such as the Greek, Egyptian, and 
Indian. However, it is from the Romans that hydraulic mortars have been 
inherited, both through written and physical evidence. 



12 



25 B.C. The Ten Books on Architecture by Vitruvius is published, containing 

a section on the use of pozzolanas as a building material.^s 

79 A.D. Mount Vesuvius erupts covering Pompeii and the environ w^ith 

another layer of volcanic sediment. 

138 AD - Hadrian's Wall, constructed with lime and calcined clay particles is 

completed by the Romans.26 

532 - Construction of the Hagia Sophia is begun. Analysis of the mortar has 

concluded that brick dust and chimks of brick were added to the lime based 

mortar.27 - 

Middle Ages 

In the Middle Ages following the decline of Rome's power, the art of 
making hydraulic mortars seemed to be lost as physical or written evidence of 
the use of this technology has not survived. Some structures may have been 
constructed using this technology, but it is generally believed that it was not 
common building practise in Europe. 

1000 A.D. - Corfe Castle was constructed. Analysis of mortar revealed that 
brick dust was included as a hydraulic additive.^s 



" Vitruvius, The Ten Books on Architecture, M.H. Morgan trans., (NY:Dover Publications, 

1960). 

2^ D. L. Rayment and K. Pettifer, "Examination of Durable Mortar from Hadrian's Wall," 

Materials Science and Technology, 1987, 293. 

2'' R. A Livingston, R. Marks and M. Erdik, "Analysis of the Masonry of the Hagia Sophia 

Basilica in Istanbul," Materials Research Society, Spring Meeting, San Francisco, CA, May, 

1992, and R. A. Livingston and P. E. Stutzman, "Materials Science of the Masonry of the Hagia 

Sophia Basilica, Istanbul," Proceedings of the Sixth North American Masonry Conference, 

PhUadelphia PA, Vol. 1, 1993, 49. 

28 The Builder, June 18, 1892, 471. 

13 



1290 - one of the earliest found uses of the word mortar - Oxford English 
Dictionary.29 

13th C. - In the thirteenth century in England, lime plaster was used on the 
interior and exterior of buildings after an edict by King John. It has been 
noted that pounded tiles were added as an aggregate, thus unwittingly 
imparting a pozzolanic effect.^o 

Rediscovery in the Western World 

The use of hydraulic additives to mortar was rediscovered in England 
and France in the sixteenth and seventeenth centuries and became 
progressively widespread across Europe. Research on the Roman techniques 
of lime and concrete construction led to the understanding of hydraulic lime 
and the eventual discovery of Portland Cement. Until the development of 
natural cements, the only hydraulic cements were those composed of 
hydraulic lime or a mixture of pozzolana and lime. However, traditional 
Indian building methods demonstrate an appreciation for pozzolanic 
additives in the form of surki or burnt clay to lime mortars, which had been 
used locally for centuries. 

16th C. Vanoccio Biringuccio, an Italian, wrote Pirotechnica.. The text 
discussed the addition of pozzolanic sands to lime mortar to achieve a 
hydraulic material. 31 



2^F. M. Lea, The Chemistiy of Cement and Concrete, (New York, Chemical Publishing 

Company, Third Edition), 5. 

^"Alfred Denys Cowper, Lime and Lime Mortars (London, His Majesties Stationary Office 

1927), 5. 

■'■^ Joan Mishara, "Early Hydraulic Cements," Early Pyrotechnology, The Evolution of the First 

Fire-Using Industries, eds. Theodore A. Wertime and Stephen F. Wertime, (Washington, 

Smithsonian Institute Press, 1982), 128. 

14 



1600 - A recipe for fine lime plaster during the period of the famous 
Nonesuch Royal Palace near Sutton, was 

"take three parts of pounded Parian marble, add one part of lime which 
is to be perfectly slaked by letting it lie in a heap covered with 
pozzolana and exposed to the sun and rain for at least a year. Mix a day 
before with sufficient water on a tile floor. "32 

mid 18th C. - Bagge of Gothenburg, Sweden experimented with burnt clay 

pozzolanas for hydraulic projects. He heated schist, powdered it, mixed it 

with lime and determined that the mortar had the same properties as mortar 

made with pozzolana.33 

1756 - John Smeaton (1724 - 1792) was called upon to build a new lighthouse 

on Eddystone Rock. He made inquiries as to the best materials and 

discovered that the mortar made from limestone containing a considerable 

proportion of clay gave the best results. This led him to discover the 

properties of hydraulic lime. Smeaton experimented with artificial and 

natural pozzolanas. He used brick dust, powdered forge scales and slag.34 

The lighthouse was built with blue Lias hydraulic lime from Aberthaw mixed 

with pozzolana from Civita Vecchia in equal quantities. ^5 

1774 - Practical Essay on a Cement and Artificial Stone, by M. Loriot. Included 

a hydraulic mortar recipe consisting of one part brickdust finely sifted, two 

parts of fine river sand and one part old slaked lime.36 

1776 - Treastise on Building in Water, by G. Semple is published in Dublin. 



^2 Cowper, Lime and Lime Mortars, 5. 

^^ J. G. Totten, Essays on Hydraulic and Common Mortars and on Limebuming, translated from 

the French text by General Treussart, M. Petot and M. Courtois, (Philadelphia, Franklin 

Institute), 62. 

^^ L. J. Vicat, A Practical and Scientific Treatise on Calcareous Mortars and Cements, Artificial 

and Natural, translated by Captain J.T. Smith (London, John Weale, 1837), 50. 

■^^Lea, The Chemistry of Cement and Concrete, 5. 

^° Totten, Essays on Hydraulic and Common Mortars and on Limebuming, 32 

15 



1777 - de la Faye published Recherches sur la preparation sur la theorie de la 
chaux dont Us se servient pour leurs constructions, et sur la composition et 
I'emploi de leurs mortiers in Paris. In this memoir the author stated that the 
secret to the durability of Roman mortar laid in the mode of slaking the 
lime. 37 

1778 - Faujas de Saint-Fond (1741- 1819) published Recherches sur la 
pouzzolane, sur la theorie de la chaux, et sur la cause de la durete du mortier 
in Grenoble and Paris. He discovered a naturally occurring pozzolana near 
the extinct volcanoes of Vivarais, France, and claimed that they equalled 
those from Naples. ^^ 

1780 - Bryan Higgins published Experiments and Observations made with 
view of improving the art of composing and applying calcareous cements and 
of preparing quick-lime: theory of these arts; and specifications af the 
Author's cheap and durable cement for Building, incrustation or Stuccoing, 
and Artificial Stone in London. Higgins' research into the particle size of 
volcanic terra for use with lime indicated that finer particles had more effect 
at rendering the mortar hydraulic than coarser particles. ^^ 
1780 - T. Bergman (1735-1784) a Swedish Chemist, after analyzing a limestone 
yielding hydraulic properties, found that it contained maganese and 
concluded that this element imparted hydraulic properties to lime.^o 



37rbid., 96. 

•^°Vicat, A Practical and Scientific Treatise on Calcareous Mortars and Cements, Artificial and 

Natural, 48. 

^" Bryan Higgins, Experiments an dObservations made with the view of improving the art of 

composing and applying calcareous cements and of preparing quicklime: Theory of these arts, 

and specifications of the author' scheap and durable cement for building incrusaion or stuccoing 

and artificial stone, (London, T. Cadell, 1780), 124. 

^^ Jasper A Draffin, "A Brief History of Lime, Cement, Concrete and Reinforces Concrete," 

Journal of the Western Society of Engineers (Chicago, Volume 48, No. 1, March 1943), 6. 

16 



1786- Mr Chaptal repeated the experiments of Faujas de Saint -Fond, on the 
pozzolanas of Vivarais, and claimed that they were inferior to those of Italy .^i 
1788 - Belidor, published Architecture Hydraulique in Paris. He 
recommended the use of pozzolana or trass whenever available for water 
resistant mortars or plasters. He also recommended the mixture of tiles, 
stone chips and scales from the a blacksmiths forge, carefully grovmd and 
washed of coal, seived and added to freshly slaked lime as a substitute for 
pozzolana or trass.^^ Belidor gave the name of beton to lime which had the 
quality of hardening in water.'*^ 

1791 - Narrative of the Building of the Eddystone Lighthouse by John 
Smeaton is published. This work included the results of the experiments for 
the selection of materials for the construction of the lighthouse. This work is 
cited as the first research addressing the elements which increased the 
strength of lime mortar and permitted it to harden under water.^"* 
1791 -Count Chaptal (1756-1852) of France and Switzerland published results 
of experiments with burnt clay from Languedoc, France. He likened their 
behaviour and performance to Italian pozzolanas.^^ 
1796 - Parker patented a hydraulic cement made by calcining nodules of 
argilliceous limestone. The patent, number 2170, was taken out in London."*^ 
1796 - Lesage, Fench Military Engineer, produced a hydraulic cement from 
pebbles found at the beach at Boulogne-sur-Mer.'*'' 



^1 Totten, Essays on Hydraulic and Common Mortars and on Limebuming, 62. 

'*2 Lea, The Chemistry of Cement and Concrete, 5. 

'^•'Totten, Essays on Hydraulic and Common Mortars and on Limebuming, 3. 

^'* Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 6. 

^^ Vicat, A Practical and Scientific Treatise on Calcareous Mortars and Cements, Artificial and 

Natural, 182. 

4^ Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 7. 

47 Ibid., 6. 

17 



1800 - Parker's patented product was given the name Roman Cement.48 
1802 - Charles Berigny successfully grouted a sluice at Dieppe, France with a 
mixture of Italian pozzolanas and lime.'*^ 

1805 - Rondelet published L'Art de Batir in Paris. Rondelet carefully 
examined Roman mortars for content and theorized on the method of their 
preparation. He attributed their durability to their long slaking time. 

1810 - Dutch Society of Science discussed why lime made from limestone was 
better than that made from shells and launched the experimention into 
methods to improve shell lime to produce a better quality lime mortar.^o 

1811 - James Frost first patented a cement product and established works at 
Swanscombe, England. ^i 

1813 - CoUet-Descotels (1773-1815) Professor of Chemistry at the School of 
Mines in France, stated that it is essential for limestone to contain a high 
quantity of fine grained siliceous material to yield good hydraulic lime 
mortar.52 

1818 - J. Louis Vicat (1786- 1861) a French Engineer, published Reserches 
Experimentales in Paris. Vicat investigated the suitablity of of the various 
French limestones for the production of lime, and stated that lime or cement 
with hydraluic properties must contain lime, silica or alumina. At this time 
Vicat invented the method of testing the hydraulic properties of a mortar by 
time required to set, called the Vicat needle.^^ 



48lbid., 7. 

49 History of Grouting, 271. 

^"Oraffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 7. 

^^ Lea, The Chemistry of Cement and Concrete, 6. 

^■^ Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 6. 

53lbid., 7. 



18 



1818 - The first natural cement was made in America near Chittenango, 
Madison County, New York, by Canvass White, an Engineer working on the 
construction of the Erie Canal. 54 

1818 - The navy dry docks at Rochefort, France were successfully grouted 
using a pozzolana and lime mortar grout.55 

1819 - J.F. John (1782- 1847) Professor of Chemistry, published a disseration 
titled Lime and Mortar in Berlin. He concluded that the presence of clay, 
silica and iron oxide improved the quality of lime for mortars. He 
independently came to the same conclusion as Vicat.^^ 

1822 - James Frost patented "Britsh Cement," an artificial cement whereby the 
raw material was calcined until all the carbonic acid was expelled, and the 
material was finely ground. ^^ 

1824- James Aspdin (1779-1855) took out the first patent for a new and 
improved natural cement called Portland Cement. It was so named, because, 
when hardened, it resembled the limestone of the Isle of Portland. Aspin 
acheived this material by burning argillaceous limestone nodules found in 
London clay and in the shale beds of the Lias formation^^ 
1825 - 1836 - Col. J. G. Totten, Colonel in the United States Army, 
experimented with lime based, natural cement and patented cement mortars 
at Fort Adams, Newport Harbour, Rhode Island. He observed that brick dust 
or the dust of burnt clay, improved the quality of mortars both as to durability 
and hardness. Hydraulic cement, burnt clay, or brick dust was added to every 
kind of mortar made at Fort Adams in proportions varying with the purpose 



54lbid., 8. 

55 History of Grouting, 271 

5° Lea, The Chemistry of Cement and Concrete, 6. 

5' Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 

5° Lea, The Chemistry of Cement and Concrete, 6. 

19 . 



to which the mortar was to be applied. Totten experimented with concrete 

mix consisting of lime, sand and brick fragments and granite fragments. He 

did not publish the results of these experiments until 1838.^9 

1826 - Sir Charles Pasley (1780-1861) started to research the effect of firing 

temperature and vitrification of the calcined clay added to produce hydraulic 

mortar and cement. ^^ 

1828 - Portland Cement is experimented with for the construction of the 

Thames River Tunnel in London, but is only used in a limited capacity.^i 

1828 - Vicat published a treatise on his experiments. 

1828 - Cement works were established at Rosendale, Ulster County, N.Y. 

Rosendale Cement was quarried from magnesium limestone deposits, and 

was one of the most widely used and long lived commercial natural cements 

in North America.^2 Experimentation and development of natural cement 

at Rosendale was directly related to the construction of the Erie Canal. 

1829- Limestone deposits producing good quaUty natural cement were 

discovered and utilized near Louisville, Kentucky ^3 

1837- Vicat's A Praticial and Scientific Treatise on Clacareous Mortars and 

Cements, Artificial and Natural was translated into English by Captain J. T. 

Smith.64 



^^ Totten, Essays on Hydraulic and Common Mortars and on Limebuming. 238 and 231. 

^•^Sir Charles Pasley, Observations on limes, calcareous cements, mortars, stuccos and concrete; 

and on pozzolanad natural and artificial, (London, J. Weale, 1838), 187. 

61 Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 11. 

62 Ibid., 8. 

63 Ibid. 

64 Vicat, A Practical and Scientific Treatise on Calcareous Mortars and Cements, Artificial 
and Natural. 

20 



1837 - Raynal wrote a paper on the use of grouting for repairing masonry. He 
recommended the use of hydrauhc Ume, whereby 2 parts Hme were mixed 
with 3 parts pozzolana and sufficient water to make it semiUquid.^^ 

1838 - C.W. Pasley published Observations on Limes, Calcareous Cements, 
Mortars, Stuccos and Concrete. 

1840 - First commercial Portland Cement plant in France was established at 
Boulogne Sur Mer.66 

1850 - Natural cement works were established at Seigfried Pennsylvania, 
establishing the Lehigh Valley district as an important cement producing 
center in North America.^'' 

1851 - Isaac Charles Johnson set up cement works at Rochester.^^ 

1855 - First commercial portland cement plant is established in Germany at 

Ziillchow near Stettin.^^ 

1859-1867 - First extensive use of Portland Cement in a construction project 

during the construction of the sewage system of London70 

1868 - The Practical Manufacture of Portland Cement, by A Lipowitz was 

published, spreading this technology to Germany. 

1870 - General Scott took out a patent for selenitic lime and a company was 

formed to carry on its manufacture''^. 

1870 - General Quincy Adams Gilmore (1825-1888) published Practical Treatise 

on Limes Hydraulic Cements and Mortars in the United States. 



^^ History of Grouting, 271. 

6^ Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete ,11. 
^' Uriah Cuininings, American Cements, (Boston, Rogers and Manson, 1898), 19. 
^^Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 11. 

69 Ibid. 

70 Ibid. 

' ^Selenitic Lime is a lime, usually hydraulic, to which a small proportion of calcined gypsum 
has been added. This was considered to resuh in increased strength. From Cowper, Lime and 
Lime Mortars, 78. 

21 



1871 - Practical Treastise on Coignet Beton and Other Artificial Stones by 

General Q. A. Gillmore was published. 

1871 - Portland Cement became commercially available in the United States 

from a plant at Coplay, Pennsylvania, operated by David A. Saylor, Adam 

Woolever, and Esias Rehrig72 

1871- Thomas Millen (1832-1907) began to manufacture Portland Cement in 

South Bend, Indiana73 

1874 - Robert W. Lesley (1853-1935) organized a cement selling business in 
Philadelphia and sold 10, 000 barrels of Portland Cement on his second day of 
cement sales 7^ 

1875 - John K. Shinn, began to manufacture Portland Cement in Wampum 
Pennsylvania/^ 

1883 - J. N. Fuchs identified that quartz and other forms of crystalline silica are 
inactive while the amorphous and hydrated silica behave as pozzolanas. 

1886 - Jose F de Navarro (1823- 1909) revolutionized the cement industry by 
introducing an inclined rotary kiln capable of producing 160 - 300 barels a 
day76 

1887 - Experimental Researches on the Constitution of Hydraulic Mortars, by 
H. LeChatelier, was published, but by this time, the use of Portland Cement 
has begtm to dominate construction practices 

1888 - Notes on the Compressive Resistance of Freestone, Brick Piers, 
Hydraulic Cements, Mortars and Concretes by General Q. A. Gillmore was 
published in New York. 



^^Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 11. 

73 Ibid. 

74ibid. 

75lbid. 

76lbid., 12. 



22 



1893 - Manual on Lime and Cement by A.H. Heath is published in New York. 

1898 - American Cements, by Uriah Cummings was pubHshed in Boston. 

1902 - Burnt clay was effectively used as a pozzolana in the construction of the 

Asyut Nile Barrage^^ 

1909 - Mr. White published in the Journal of English Industrial Chemistry, 

that a micro-chemical test based on phenol as a reagent could effectivly detect 

quicklime in the presence of slaked lime.^^ 

1909 - Thomas A. Edison, produced a rotary kiln capable of producing 1000 

barrels a day.''^ 

1909 - C.J. Potter described the process of mixing ground burnt clay with 

Portland Cement yielding Potter's Red Cement, for use in freshwater and 

seawater construction. 8° 

1914 - Documented report of fly ash being used as a pozzolanic material in 

concrete.si 

1919-1925 - Construction of the Sennar Dam on the Blue Nile, used cement 

composed of 70% Portland and 30% burnt clay produced on site. 

1937 - R. E. Davis et al. U.S. studied the use of Pulverised fly ash for use in 

concrete. 

1939-1945 - Revived use of burnt clay to Portland Cement during World War 

II as an economic measure.^^ 



'''Cowper, Lime and Lime Mortars, 48. 

78T/je Builder, (April 23, 1922), 663. 

"^^ Draffin, A Brief History of Lime, Cement, Concrete and Reinforced Concrete, 12 

^0 Lea, The Chemistry of Cement and Concrete, 420. 

^iRichard Helmut, Fly Ash in Cement and Concrete, (Skokie Illinois: Portland Cement 

Association, 1987), 2. 

^^Symposium on the Use of Pozzolanic Materials in Mortars and Concrete, San Francisco, 1949. 

(ASTM, Philadelphia, 1950) 

23 



f 



1940 - F. M. Lea, working in the United Kingdom, commences research on the 

production, properties and the ulitilisation of pozzolanas manufactured by 

the burning of suitable clays and shales. 

1940's - Established that the addition of Pozzolana to concrete will eliminate 

or greatly reduce the effects of alkali-aggregate reaction.^^ 

1949 - ASTM Symposium on Pozzolanic Materials held in San Francisco. 

1981 - ICCROM International Symposium on Mortars, Cements and Grouts 

used in the Conservation of Historic Buildings is held in Rome. First large 

scale attempt at the organization of a scientific approach to the problem of 

mortars for repair. 

1987 - Smeaton Project in England establishes a testing program to contribute 

to the understanding of the characteristics and behaviour of lime based 

mortars for the repair and conservation of historic buildings. 



83 R. Mielenz, L. Witte, and O. Glantz, STP 99, (ASTM, Philadelphia) 45. 

24 



1.3 Review and Assessment of Published Literature on Lime-Pozzolana 
Mortars for the Repair of Historic Structures 

Interest in mortars from the point of view of repair and conservation 
of historic structures is relatively recent. The first attempts to characterize 
and standardize repair mortars dates to 1981, on the occasion of the 
International Symposium on Mortars, Cement and Grouts used in the 
Conservation of Historic Buildings held at Rome. 

At this time three fundamental parameters were identified. They 
include^^: 

1) Research should be carried out in parallel on both new and ancient 
mortars. Restoration mortars must be prepared taking into account the 
characteristics of the materials to which they are applied or which they 
substitute. 

2) New mortars for restoration should be characterized clearly, by 
identifying certain fundamental parameters. 

3) Methods for measuring these parameters should be standardized. 

Since that seminal symposium, the formulation of repair mortars by 
those in the field of architectural conservation usually involves identification 
of the properties and constituent parts of the original mortars coupled with 



^^P. Rota Rossi-Doria, "Mortars for Restoration: basic requirements and quality control," 

Materiaux et Constructions, Vol.19, No. 114, 1986, 445. 

25 



the examination of the physical and mechanical properties of the repair 
mortar. This first step of examination of the constituent parts of the original 
mortar has resulted in the identification of natural and artificial pozzolanas. 
For the formulation of a repair mortar, researchers have investigated the 
properties of lime based mortars modified with both natural and artificial 
pozzolanas. The following review and assessment of selected published 
research will identify the objectives, the materials, the examination methods, 
and the results of each investigation. 

The Smeaton Project 

The Smeaton Project,^^ a joint research program of ICCROM, English 
Heritage and Bournemouth University, grew out of experimental work to 
identify suitable mortars for use in the conservation of Hadrian's Wall. 
Samples of jointing and core mortar samples were found to contain lime, 
crushed tile, crushed sandstone, sand and kiln debris, as well as some animal 
fat, probably tallow.^^ j^ thg fij-gt phase of this research project, the broad 
objectives were to "contribute to the understanding of the characteristics and 
behaviour of lime-based mortar by attempting to identify - and where possible 
quantify - the material and practice parameters that affect mortar 
properties."^'' In doing so the experimental program focused on the effects of 
set additives, specifically brick dust and cements on the performance of lime 
and sand mortars. 



^^Jeartne Marie Teutonico, Iain McCraig, Colin Bums and John Ashurst, "The Smeaton Project: 
Factors Affecting the Properties of Lime-Based Mortars," APT Bulletin, Volume XXV, No. 3-4, 
32-49. 
S^Ibid., 34. 
87rbid., 33. 

26 



d 



Brick dust was investigated in order to understand the effects of such 
factors as optimum particle size, firing temperature, and proportion of brick 
dust in the mix. The experimental program included moisture content, 
stiffening or setting rate, compressive strength, depth of carbonation, sodium 
sulphate crystallization test, as well as monitoring exposed samples at regular 
intervals. 

The results of the first phase of the project concluded 1) that the 
addition of brick dust does significantly alter the properties that were tested, of 
lime mortars, 2) low-fired brick dusts seem to have the most positive effect on 
the strength and durability of the mixtures, 3) the addition of small amounts 
of cement to the mixtures has a negative effect on the strength and durability 
of the mortars. Similarly, it was found that a particle size ranging from <75 
microns results in the brick dust acting as a pozzolana and that a firing 
temperature below 950°C produces the best quality brick dust for the addition 
to lime mortar.s^ 



88lbid., 42. 

27 



Research at Aristotle University of Thessaloniki, Greece 

In three pubUshed works from the Aristotle University of 
Thessaloniki^^, ^°, researchers have examined the role of both artificial and 
natural pozzolanas in mortars and grouts for the repair of historic masonry 
structures. The aim of these research projects was to determine the 
composition and proportions of repair mortar and grout which will 
compatible to the materials used in the historic structures in Thessaloniki 
from the 4th to the 15th century A. D. 

In a paper entitled "Pozzolanic Mortars for Repair of Masonry 
Structures," mortars from historic structures were examined and determined 
to contain sand, lime and in some, fragments of powdered brick. Those that 
contained hydraulic components such as pozzolana or brick dust, determined 
by X-ray analysis, were stated to have a higher compressive strength than 
those without hydraulic components. To demonstrate the contribution of 
pozzolanic additives to strength development of the mortars, physical tests 
were conducted. These tests included compressive strength, tensile strength 
and modulus of elasticity. Although this research focuses on the mechanical 
properties of the lime based mortars, others properties of lime based mortars 
have been included in this methodology. The results of the research indicate 



^^ Penelis, G., Papayianni, J, and M. Karaveziroglou. "Pozzolanic Mortars for Repair of 

Masonry Structures," Structural Repair and Maintenance of Historic Buildings, (Boston: 

Computational Mechanics Publications, 1989), 161-169. 

^9 Penelis, G., Karaveziroglou, M. and Papayianni, J. "Grouts for Repairing and Strengthening 

Old masonry Structures" Structural Repair and Maintenance of Historical Buildings, (Boston: 

Computational Mecharucs Publications, 1989), 179-188. 

'^^ Karaveziroglou-Weber, Maria and Papayianni, loarma. "Long-term Strength of Mortars and 

Grouts Used in Interventions" Structural Preservation of the Architectural Heritage, Report of 

the lABSE Symposium, (Rome, 1993), 527-532. 

28 



that appropriate gradation and a particle size maximum of 2 mm for the 
pozzolanic additives increases the mechanical strength of the mortars. 

The fundamental problem associated with this research is the 
predisposition to include cement as an additive to the lime based mortars in 
order to achieve increased mechanical strength. The results of this research 
indicate that the compressive strength of lime-sand-pozzolana mortars was 
equal to some of the mortars with lime- sand-cement in small proportions. 
This research seems to overlook the problems associated with the addition of 
cement, even in small proportions to lime-based mortars. 

In a paper titled "Long-term Strength Development of Mortars and 
Grouts used in Interventions," the same principal researchers have set up a 
testing program for "traditional materials" including lime, natural pozzolana, 
brick powder and crushed bricks. In this paper, the researchers have stated 
that pozzolanic reaction follows a slow, time-dependent process. In addition 
to these traditional materials, high proportions of cement has been added to 
the mortars and grouts being evaluated. Not surprisingly, those mortars 
modified with cement mortar exhibit higher values of compressive strength, 
tensile strength and modulus of elasticity over a period of four years. Again, 
the evaluation of strength should not be the only criteria for which to judge a 
lime-based mortars. 



29 



V 



Research at University of Seigen, Germany 

In a short paper delivered at the 1988 International Stone Conference^!, 
researchers discussed the use of microscopical methods to understand the 
interactions of mortar components. In this research, historic lime-based 
mortars known to contain brick dust and pozzolana were compared to lime 
-based mortars made with commercially available hydraulic products such as 
diatomaceous earth, condensed silica fume, fly ash and blast furnace slag. 
Using microscopical methods, lime mortars modified with various 
admixtures were examined with the electron microscope to compare the 
reactions. The researchers identified and determined that C-S-H fiber did 
exist in historic and replicated mortars. However, in the historic mortars, 
redepositions of calcium carbonate were visible in some of the microcracks, 
effectively waterproofing the surface. It was noticed that some artificial 
pozzolanas from industrial processes had the tendency to effloresce. 



91 wisser, S.; K. Kraus, and D. Knofel. "Composition and Properties of Historic Lime Mortars,' 
Proceedings of the VI^" International Congress on Deterioration and Conservation of Stone, 
(Torun, Poland, 1988), 484-491 



30 



1.4 Desirable Properties of a Mortar for the Repair and Conservation of 
Historic Structures 

Generally, mortar is the most frequently repaired component element 
of a masonry system. In most cases, the repair of deteriorated mortar involves 
replacement. The approaches to mortar replacement include: 1) replacement 
in kind; 2) replacement with modem materials that are similar to the 
properties of the original mortar; and 3) replacement with modern materials 
that are deemed "better" than the originals. For replacement in kind or with 
similar modem materials, mortar characterization must be conducted. Even 
if characterization of the original mortar has been conducted, few preliminary 
tests are conducted to evaluate the properties of the repair material.^^ 

For the selection of a repair mortar, the parameters and behavior of the 
new mortar must first be understood. First, the purpose or role of the mortar 
must be defined, as differences in properties and constituencies can exist 
between bedding and pointing mortars. Similarly, the desired properties of a 
repair mortar must be understood. Generally the following are desired 
properties of a mortar for the repair and conservation of historic structures. 

1) Good workability, as defined by both the mortars' ability to be 
manipulated by masonry tools and its cohesiveness and adhesion to 
the masonry unit to form a well packed continuous mass. 



'^P. Rota Rossi-Doria, "Mortars for Restoration: basic requirements and quality control,' 

Material et Constructions, Vol. 19, No. 114, 446. 

31 



2) A consistent and reliable setting rate whereby the initial set of the 
mortar will not cause delays to the repair or conservation work. 

3) Low or no shrinkage of the mortar to reduce microcracking or 
cracking at the interface of the masonry unit. 

4) Elasticity. As masonry systems are often subject to movement, the 
mortar should act to cushion the masonry unit without cracking or 
causing cracking to the masonry unit. 

5) Relative strength as related to the strength of the masonry unit and 
the masonry system. 

6) Water and water vapor permeability to reduce water or water vapor 
from being trapped and freezing in the masonry system. 

7) Resistance and durability to the increase of liquid water. This 
property is related to the open and closed pore sizes of the outer zone of 
the mortar. 

8) Resistance to salt attack or other deleterious solutions. This property 
is related to the pore sizes and distribution in the masonry system. 

9) Retreatability in that the mortar as a repair material should be a 
sacrificial component of the masonry system which can be easily 
removed without causing damage to the masonry unit. 



32 



2.1 Research Significance 

A review of the Uterature dealing with the addition of artificial 
pozzolanas to lime-based mortars reveals a rich source of information on 
usage yet few explanations on performance. Included in the technological 
literature are the historical developments, ingredients and uses of these 
mortars. In recent conservation literature reviewing historic mortars, careful 
consideration is given to the ingredients, uses and appropriateness for a 
repair material. However, what is generally lacking is a quantitative 
description of the composition of mortar and the affect that composition has 
on overall physical, mechanical and chemical characteristics. The Smeaton 
Project has been set up in to contribute to the understanding of the 
characterisitcs and behavior of lime-based mortars by attempting to identify 
and where possible quantify the materials and practice parameters that affect 
their properties.^^ 

This experimental program attempts to act as a compendium to the 
Smeaton Project by examining the characteristics and behaviour of the 
components of traditional mortars made with North American materials. By 
examining the mortar characteristics that concerned the Smeaton Project, it is 
intended that the research presented in this experimental program will 
produce some comparable data on the materials and practice parameters of 
lime-based mortars modified with brick dust. 



f 



^^ Teutonico, "The Smeaton Project: Factors Affecting the Properties of Lime-Based Mortars, 
33. 

33 



In addition to shedding light on lime mortars modified with brick dust 
in the North American context, the methodology presented in this study has 
the potential for further implications and applications. These include: 

1) Application of the experimental testing program to other potential 
artificial pozzolanas for use with lime or cement. These include bricks 
salvaged from construction sites, pulverized fly ash, calcined clay, rice 
husk ash and ground granulated blast furnace slag. 

2) Reconsideration of the standards available for the evaluation of 
mortars used in the repair of historic masonry structures so that 
mortars replicating traditional ones will not fail to meet these 
standards. 

3) Application of the testing program on lime and pozzolana traditions 
as an appropriate technology for developing nations whereby lime 
with hydraulic additives could be an affordable and renewable 
material. This would reduce the need for Portland Cement, which is 
more expensive and often depends on importation. In countries 
where Portland Cement is expensive or in short supply, pozzolanas, 
such as brick dust have been and could be substituted to up to 40% of 
the total mixture without significantly reducing the quality of the final 
product.9^ 

4) To help reduce environmental pollution. Portland Cement 
production requires a lot of pollution producing energy, so reducing its 



^^Appropriate Building Technology, 65. 

34 



use when appropriate would be environmentally sound. As well, 
many potential pozzolanic materials are by products of the 
manufacturing, agricultural or construction industries. By using these 
byproducts, such as fly ash, salvage historic bricks, or com husks, land 
fill space can be reduced. 



35 



2.2 Research Objective 

In broad terms, the goals of this study are to contribute to an 
understanding of lime-based mortars for the repair of historic structures in 
North America. In more specific terms this examination will attempt to 
address research questions ranging from evaluating the materials to testing 
standards and methods. The objectives of this experimental program include: 

1) To observe, evaluate and when possible, quantify the affect of the 
addition of two types of brick dust to the properties of lime-based 
mortar through an experimental program of physical and mechanical 
testing. 

2) To understand and appreciate the phenomenon of pozzolanic 
reaction as evidenced by the addition of two types of brick dust to lime- 
based mortar. 

3) To evaluate and compare the phenomenon of pozzolanic reaction to 
that brought about by a porous particulate as evidenced by the addition 
of brick dust and limestone dust to lime-based mortar through an 
experimental program of physical and mechanical testing. 

4) To observe, evaluate and quantify the behaviour of materials 
presently being used in North American repair practices. 

5) To establish a testing program for the evaluation of prospective 
materials for use in the repair of historic structures. 



36 



6) To review, evaluate and comment on the appropriateness of North 
American testing standards for lime-based materials. 

7) To identify research priorities and possibilities regarding the effect of 
the addition of brick dust to lime-based mortars. 



37 



2.3 Materials 

The selection of materials used in this study was based on two main 
criteria. The firs, was that the materials be commercially available in North 
America. The second was the availabiUty of informaHon regarding the 
chemical and physical properties of the material. Although one of the two 
brick dusts examined is not commercially available, it was selected because 
mformation regarding some of the physical and mechanical properties was 
available. The materials used reflect standard contemporary conservation 
practice." The lime putty and sand were constant throughout the study. To 
these materials were added two different types of brick dust. For one aspect of 
the study, limestone dust was added to the lime and sand mixture as an inert 
porous particulate. 

Sand 

A sharp well-graded comniercial n^asorrry sand. Yellow Bar Sand, 
supplied by Dunrite Sand and Gravel, P.O. Box 681, Vineland, New Jersey 
08360, was selected for its compliance to ASTM C778-89 Standard Specification 
for Standard Sandand because its chemical composition was known.96 
Analysis reveals 99.5% silica dioxide with trace amounts of various other 
minerals. 



9^;;;;::;:7;:^~;^^ BmUin, Conser.aUon, Volume 3, Mortars Plasters and 

Renders, (New York , Halstead Press), 66. ,.h in 1990 bv Testwell Craig, Testing 

96 Chemical Analysis for the YeUow Bar Sand was conducted in 1990 by Testwell g. 
Laboratories, Mays Landing , New Jersey. 

38 



Table 1 - Particle Size Distribution of Yellow Bar Sand 



Sieve # 


% Retained 


% Passing 


4 





100 


8 


0.2 


99.5 


16 


4 


95.5 


30 


21.5 


74 


50 


34.7 


39.3 


100 


27.7 


11.6 


200 


9.4 


2.2 



Lime 



Lime used in this study was supplied by Beachvilime Limited, (P.O Box 
190, Ingersoll, Ontario, N5C 3K3, Canada) and produced at the Beachville East 
Plant, Beachville, Ontario. It is obtained by the calcination of high calcium 
limestone to produce calcium oxide (CaO), commercially available as masons 
quicklime. Masons quicklime is a calcined limestone capable of slaking with 
water, and suitable for use for masonry projects. It is considered a High 
Calcium Lime indicating less than 5% magnesium carbonate was found in 
the mixture. Generally, commercial hydrated lime available in North 
America is magnesian lime, with 5 to 35% magsesium carbonate present in 
the limestone used. 

Composition and Physical Properties of Beachvilime:^'^ 



Chemical - 

Calcium Oxide (CaO) 
Magnesium Oxide (MgO) 
Silica (Si02) and Insolubles 
Ferric Oxide (Fe203) 
Alumina (Al 2O3) 



95.5% 
1.0% 
0.75% 
0.15% 
0.15% 



^'Physical properties supplied by product manufacturer, Beachvilime Limited. Based on 
ASTM C-110-87 Standard Test Method for Physical Testing of Quicklime, Hydrated Lime and 
Limestone. 



39 



Total Sulphur (S) 0.03% 

Loss on Ignition ^-^ '° 

Available Lime as calcium Oxide (CaO) 92% 

Carbon Dioxide 2°/° 

Physical - 

Bulk Density 

Angle of Repose 45 degrees 

Specific Gravity 3.4 (relative density) 

Solubility in Water L3 g/ litre @ 20° C 

Basicity Factor 0-93 
Slaking Raters 

(1) Temp. Rise 30 sec 25 degrees 

(2) Total Temp. Rise 48 degrees 

(3) Total Active Slaking Time 6 minutes 



The slaking of the lime was conducted on May 15, 1993. Slaking of the 
lime was achieved in a large metal mortar tray (Im x Im). Water was added 
to the tray followed by the quicklime. The mixture was slowly stirred with a 
hoe until the reaction of the lime with the water ceased. A thick white 
substance called lime putty was the result of this initial slaking process. The 
putty was pressed through a 2.5 mm or 1 in sieve to remove any lumps of 
unreacted quicklime and was stored in plastic pails and sealed with lids to 
prevent carbonation. Approximately 3 cm of water laid on top of the lime 
putty. The putty was then stored roughly 5 months until the commencement 
of the experimental program. 

Brick Dust 

Two types of brick dust were selected and tested for the experimental 
program. The first type (Brick Dust 1) was supplied by Martin Clay Products, 



98Based on ASTM C 110-87 Slaniard Test Method for Physical Testing of Quicklime, Hydraled 
Lime and Limestone, (modified 1:4 liine:water) 



40 



Parkhill, Ontario. This material is produced for the construction of clay 
terinis courts. Underfired bricks considered seconds by brick manufacturers 
are collected by Martin Clay Products and ground into a powder. Although 
not manufactured for masonry purposes, this material has been used in 
Canada for repair mortars where hydraulic properties are desired. This 
material was selected for the experimental program due to its apparent 
success as a pozzolana and its commercial availability in North America. The 
exact firing temperature of these bricks is not known. The exact mineral 
composition of the brick dust is unknown, although they do contain silica 
and alumina. Particle size was determined. 

The second brick dust (Brick Dust 2) used in the experimental program 
was supplied by Colonial Williamsburg. This material was selected after 
numerous inquiries to brick manufacturers to locate a low fired brick. 
Colonial Williamsburg has a brick yard with a kiln used for brick production 
for repair work done on site. Although this material is not commercially 
available as an additive, it was selected because of the ideal firing temperature 
of the clay of 1650° F. or 898.8° C.99 Research has estabhshed that an optimum 
burning temperature for producing burnt clay pozzolanas varies from 775-910 

0^.100 101 



^^ Records of Brick Kiln, 1992, Supplied by Colonial Williamsburg. The firing temperature was 

monitored by eighteen gauges at different locations in the kiln. The four day firing period 

achieved the maximum temperature in some locations of 1650° F or 898.8° C 

l^Ojeanne Marie Teutonico et al., "The Smeaton Project: Factors Affecting the Properties of 

Lime-Based Mortars", APT Bulletin, Vol. XXV, No. 3-4, 41. 

^^^ Luigia Binda and Guilia Baronia state in "Characterization of Mortars and Plasters from 

Ancient Monuments of Milan (Italy)," The Masonry Scoiety Journal, (January-June 1988), T23, 

that the best pozzolanic activity is yielded from clay burnt at temperatures between 500 and 

900°C. 

41 



Both BD 1 and BD 2 were ground in a metal grinder and sieved with 
standard sieves yielding a well-graded product type ranging from 75 to 300 
[im. The same amount, measured by volume was taken off each sieve 
(ASTM #50 to #200) to form the additive. Thus an even distribution based on 
particle size was established for both types of brick dust. 



42 



Stone Dust 

Stone dust, derived from crushing and grinding limestone was used in 

the experimental program. The limestone was supplied from 

Northumberland County, Pennsylvania, and commonly known as 

Helderberg Limestone. It is a high-calcium limestone with trace amounts of 

magnesium, silica and alumina. The composition of this stone was reported 

as:i02 

96 % Ca CO 
1.5 % Mg CO3 
1% Al2 03+Fe2 02 
1% Si O2 

The ground limestone was sieved and an even amount measured by 
volume was taken from each sieve to yield a particle size equal to that of the 
brick dust. A simple porosity test determined the limestone to have a 
porosity of about 20%. 

This limestone dust was selected as an inert porous particulate, as it has 
20 % porosity while not reacting chemically with the lime-based mortar. 



^^2 Benjamin Miller, Limestones of Pennsylvania, (Pennsylvania Geological Survey, Fourth 
Series, 1934), 551. 

43 



2. 4 Formulations of Facsimiles 

Consistency of the preparation of the facsimile samples for the 
experimental program was guided by testing standards and a single 
operator/ mixer. This resulted in a high degree of uniformity during the 
preparation of the samples. 

Proportions of the mixes were determined after a review of the 
historical literature^ ^^^ contemporary conservation practice and contemporary 
experimental work presently being conducted in Europe^o^ a comparison of 
these practices reveals no significant change in proportion over a two 
hundred year period^^^ 106 

Proportioning of the mixes was completed by volume. The sand and 
brick dust were measured dry. 

Table 2 - Mortar Facsimile Compositions 



Mix 


Lime 


Sand 


Brick Dust 1 
(Williamsburg) 


Brick Dust 2 
(Martin Clay) 


Limestone Dust 


1 


1 part 


3 parts 








2 


1 part 


3 parts 


1 part 







l^'^In 1756 during the construction of the Eddystone Lighthouse, Smeaton specified "two bushels 
of lime powder, one bushel of pozzolana, and one bushel of common sand." resulting in what is 1: 
1: 2 mix. Sir Charles William Pasley, Observations on limes, calcareous cements, mortars, 
stuccos and concrete; and on pozzolanas, natural and artificial, (London, J. Weale 1838), 182. 
1"^ In the Smeaton Project, the ratio of sand:lime: brick dust ranged from 2 1/2:1:1 to 5:1:1. 
Jeanne Marie Teutonico,et al., "The Smeaton Project: Factors Affecting the Properties of Lime- 
Based Mortars," APT Bulletin, Vol. XXV, No. 3-4, 36. 

^''^Monsieur Loriot 1774, Paris, 32 Called for: Take one part of brickdust finely sifted, 
two parts of fine river sand screened, and as much old slaked lime as may be sufficient 
to form mortar. 

106pgnelis, Papayianni and Karaveziroglou, "Pozzolanic Mortars for the Repair of Masonry 
Structures," Structural Repair and Maintenance of Historic Buildings, 165. Twentieth century 
specification for repair mortar consisting of 1 part lime, 4 parts sand and 2 parts of brick dust 



44 



3 


1 part 


2.5 parts 


1 part 






4 


1 part 


2.5 parts 






1 part 


5 


1 part 


2.5 parts 




1 part 





2.4.1 Mixing 

Test Standard Consulted - ASTM C 305 Test Method for Mechanical Mixing of 
Hydraulic Cement Pastes and Mortars of Plastic Consistency. 

Initial mixing of the roughage, lime putty and sand, was conducted in a 
laboratory but in a manner similar to masonry practice. In addition to the 
mechanical mixing, the roughage was tamped before storage in 4 litre plastic- 
lidded pails. Immediately following mechanical mixing, the material was 
tamped or rammed with a wooden tamper or paddle. All the roughage was 
tamped in a large plastic mortar tray for 15 minutes. The roughage was 
tamped for 5 minutes for every 6 cm of material added into the pail. The 
value of this impact is to increase the overall lime-sand contact. Traditional 
techniques reveal that mortars were beaten thoroughly during mixing. The 
thorough mixing of the mortars affected their good adhesion properties and 
long-term durabihty. In modem free-fall mixers, the mortar is unlikely to 
undergo sufficient homogenization. The short mixing times may cause 
insufficient mixing of the lime and the sand. Tamping or beating the mixture 
with a wooden tamper after mechanical mixing will insure that the lime and 
the sand are well blended. 

Two mixes of roughage were made and separately stored based on 
proportion of lime to sand. One type of roughage made of 1 part lime to 3 



45 



J 



parts sand was used for Mix 1 and 2. The other type of roughage consisted of 1 
part lime to 2 1/2 parts sand which was used for Mix 3, Mix 4 and Mix 5. 

The roughage was stored in lidded pails with a damp piece of burlap to 
minimize drying. The pails were sealed and stored for one month in a 
shaded cool location until the addition of the brick dust or limestone dust. 

Addition of Brick Dust and Limestone Dust 

The correct proportions of brick dust (BD) and limestone dust (LD) 
were added by volume to the roughage and mixed mechanically for 15 
minutes. The mortar mixtures were then tamped for 15 minutes with a 
wooden tamper in a plastic mortar tray. The mixtures were then added to the 
appropriate molds for the experimental program. 

2.4.2 Molding 

Molding of the samples was determined by the standard consulted for 
each test of the experimental program. When no standard existed, the sample 
size and shape was selected by the author and the supervisors of this research. 
The material was added to the mold in levels and tamped with a wooden 
paddle. Excess mortar was struck off with a trowel, and the surface was left 
unworked by the trowel. 

Demolding of the samples occurred after 24 hours and the samples 
were stored on wire mesh racks in the laboratory for further curing. The 



46 



humidity and temperature in the laboratory were recorded. (See Curing 
Conditions, Section 2.4.3) 




Photo 1 - Tamping with a non-absorptive, non-brittle tamper into the 50mm or 
2 in Wooden Cube mold. 



50 mm or 2 in Wooden Cube Molds 

For the tests requiring 50 mm or 2 in cube samples, wooden three gang 
molds were designed and constructed following the ASTM Standard C 109 - 
90. Hardwood maple molds were used as they permit water absorption 



47 



without warping on all sides of the sample, thus simulating the absorption of 
excess water in masonry construction. 

The maple molds are held together with stainless steel hardware. They 
are tight fitting yet come apart to facilitate removal of the sample. Before the 
addition of the mortar, the wooden molds were soaked in water and toweled 
off to remove surface water. Soaking was done to control the rate of 
absorption from the setting mortar sample to the wooden mold. This in 
certain respects mimics the masonry practice of soaking the bricks before 
building with lime-based mortars. Wooden molds, rather than standard steel 
molds used for cement mortars, were selected for the lime-based samples in 
order to absorb water during the critical early period of setting. 




Photo 2 - Three part wooden cube mold, disassembled and assembled with 
t 50 mm or 2 in sample cubes. 



Plastic 2 3/4 in diameter by 3/4 in high Ring Molds 
^ 48 



The molds used are rings made of rigid PVC with an interior diameter 
of 2 3/4 in and a height of 3/4 in high. The molds were rigid enough to 
prevent deformation, yet permitted removal of the mortar before full cure. 
The interior of the rings were sprayed with WD 40, a releasing agent. The 
rings were placed on porous brick in order to absorb water during the setting 
of the lime based material. The mortar was tamped into the mold with a 
wooden tamper. The brick was first soaked in water to reduce immediate 
absorption of water from the mortar. Prior to placing the sample on the brick, 
excess water was removed with a towel. 




Photo 3 - Sample being demolded from PVC ring mold. 



49 






25 cm or 10 in Prism Molds 

For measuring shrinkage, molds conforming to ASTM C 490 were 
used. These molds have two compartments containing 1 in by 1 in by 11 1/4 
in prisms having a 10 in. gage length. The parts of the mold are tight-fitting 
and firmly held together when assembled, and their surfaces are smooth and 
free of pits. The molds are constructed of steel, and the sides are sufficiently 
rigid to prevent spreading or warping. A releasing agent was applied to the 
steel surfaces of the mold. 

Conical Ring 

To quantify setting time, a conical ring conforming to ASTM C191-82 
was used. The mortar was tamped into a conical ring, resting on a glass plate 
about 100 mm square. The ring is made of plastic, nonabsorbent material, 
with an inside diameter of 70 mm at the base and 60 mm at the top and a 
height of 40 mm. 



50 



Table 3 - Schedule of Molds and Number of Samples 



Test 


Mold shape and size 


# of samples 


setting rate 


conical ring, 70 mm/60 mm by 40 mm 


1 


water content 


50 mm or 2 in cube 


3 


set under water 


50 mm or 2 in cube 


2 


workability 


conical ring, 70mm/60mm by 40 mm 


2 


shrinkage 


1 in by 1 in by 11 1/4 in prisms 


2 


bulk specific grav. 


50 mm or 2 in cube 


2 


comp. strength 


50 mm or 2 in cube 


4 


H2O vapor trans. 


2 3/4 in diameter and 3/4 in high ring 


4 


depth of carbon.. 


50 mm or 2 in cube 


3 


salt resistance 1 


2 3/4 in diameter and 3/4 in high ring 


4 


salt resistance 2 


50 mm or 2 in cube 


1 


water absorption 


50 mm or 2 in cube 


2 



2.4.3 Curing Conditions 

As curing conditions have a significant impact on the properties of 
lime-based mortars, an attempt was made to achieve appropriate and overall 
consistent conditions for the batches. All samples were demolded after 24 
hours. The demolded samples were cured on wire mesh racks in the 
Architectural Conservation Laboratory. The laboratory is not a climatically 
controlled environment and temperature and humidity fluctuated according 
to exterior conditions. The range of atmospheric conditions was recorded 
from 12.5°C to 24°C or 40°F to 75°F and 45% RH to 78% RH. This method of 
curing was selected as it roughly replicates exterior curing conditions, like a 
sheltered masonry construction. Other experimental programs have selected 
curing methods involving controlling temperature and relative humity.^^'^ 



l^^Teutonico, "The Smeaton Project: Factors Affecting the Properties of Lime-Based Mortars," 
37. 



51 



A 






An environmentally controlled space was not available for this experimental 
program. However, all the samples were subjected to the same 
environmental conditions, thus, a level of consistency amongst the samples 
was achieved. 

2.5 Experimental Program Standards 

When possible, testing standards were used to provide a methodology 
for the experimental program. North American standards were consulted for 
the experimental program as the materials being evaluated were North 
American and one of the objectives of this research was to assess the 
appropriateness of the standards. Some British (BRI) and Italian (NORMAL) 
Standards were consulted when ASTM standards did not exist. Generally, 
ASTM standards are geared to evaluating cement-based mortars and grouts 
that behave differently in terms of setting, strength development, and 
shrinkage. 

For certain tests in the experimental program, no standards exist and 
thus test methods were created and closely followed. The following table 
includes North American Standards consulted for the experimental program. 
Corresponding European standards are included when known. 



52 



Table 4 - Standards Consulted for Experimental Program with 
corresponding European Standards 





Standard Used 


Related Standard 


terminology/definitions 


ASTMC 51-90 




preparation of samples 


ASTM C 305-82 
(Reapproved 1987) 


DIN 1053 


color 


ASTM E284 




water content 


no standard 




flow 


ASTMC 110 


DIN 18555 


setting rate 


ASTM C807 




set under water 


no standard 




shrinkage 


ASTM C 490-89 




bulk specific gravity 


ASTM C 97 




compressive strength 


ASTM CI 09 


Uni7102 (03.06 1968) 


water vapor transmission 


ASTM E96 


Normal, 7/81 


durability as defined 
resistance to salt attack 


BRE, Salt Crystallization 
Test, 1992 




water absorption 
coefficent 


Normal 7/81 


Rilem 25-Pem 


microstructure 


no standard 




surface morphology 


ASTM 856 




pore size distribution 


no standard 


Normal 4/80 



53 



2.6 Experimental Program 

The characterization of mortar performance requires a variety of tests 
to determine physical, mechanical and chemical properties. Therefore many 
different tests had to be reviewed and selected before the experimental 
program commenced. After several consultations with experts in the field of 
materials analysis and architectural conservation, a set a tests that would yield 
information on the properties of lime-based mortars modified with brick dust 
was selected. 10^ The overall criteria shaping the experimental program was 
that the tests had to be reproducible in another laboratory. 

Many of the selected standardized tests were borrowed from the cement 
industry, as few tests or testing programs have been developed specifically for 
lime and brick dust mortars. The testing of brick dust as a pozzolan is 
complex since it has no cementing properties itself and only develops in the 
presence of another material. Thus, it is the combination of lime and brick 
dust which was quantified and characterized. As a result the experimental 
program produced both comparative values and subjective interpretations 
about the materials, the mortar mixes and the test methods. 



lOSgeveral meetings in Fall, 1992 and Spring 1993 were held with Professors Jean Marie 
Teutonico and Frank G. Matero to select tests for the evaluation of the samples. Most of the 
tests are the same as those conducted in Phase 1 of the Smeaton Project, however the test 
standards differ slightly. The test Set under Water was derived from the experiments of Vicat. 
Examinations such as as pore size distribution, microstructure and surface morphology were not 
included in Phase 1 of the Smeaton project but were included in the research conducted by G. 
Baronio and L. Binda, "Survey of the Brick Binder Adhesion in Powdered Brick Mortars and 
Plasters," Masonry International, Vol 2, No. 3, 1988, and research conducted by the cement 
industry on pozzolaruc additives such as A. Al-Manaseer, M. Haug and L. Wong, 
"Microstructure of Cement-Based Grouts Containing Fly Ash and Brine," Proceedings of the 
Cor\ference on Cement, 1992, Istanbul, 635-654.. 

54 



The mortar mixes were tested on their own without masonry unit 
such as brick or stone. Tests such as adhesion and unit strength were not 
conducted, but would yield valuable information if they were performed. 

The experimental program was influenced by time constraints; 
therefore the curing time of the samples was relatively short considering the 
nature of this material. It would have been preferable to evaluate the mortar 
mixes repeatedly over a longer curing period. In this research program, some 
conclusions about the hardened material were made after three months 
curing which, given the nature of lime-based mortars, could be premature. In 
related research programs, the curing time was considerably longer. 
Researchers, investigating the mechanical properties of mortar and grout 
modified with natural pozzolana, brick powder and crushed bricks, 
performed tests after a four year curing period.i09 Historically, Vicat made 
observations on mortar after many years of curing. However, many mix 
samples will be maintained for further investigations. If a longer testing 
period had been followed, perhaps the results would be considerably different. 



1^ Maria Karaveziroglou-Weber and loanna Papyianni, "Long-Term Strength of Mortars and 
Grouts Used in Interventions," Structural Preservation of the Architectural Heritage, lABSE 
Symposium, Rome, 1993, 527. This research was aimed at evaluating the long-term strength 
development of lime-pozzolana mortars as pozzolaruc reaction follows a slow and time 
dependent process. 

55 



The following is a schedule of the tests selected to evaluate the 
properties and characteristics of the mortar mixes. 



Fresh Mortar 


Setting Time 




Water Content 




Workability 




Set under Water 


Hardened Mortar 


Color/Appearance 




Bulk Specific Gravity 




Water Absorption Coefficent 




Shrinkage 




Compressive Strength 




Water Vapor Transmission 




Depth of Carbonation 




Durability - resistance to 
damage by salt 




Microcracking 




Microstructure 




Pore Size Distribution 



i f 



56 



2.6.1 Color 

Natural pozzolanas can be found in a great variety of colors, white, 
black, yellow, gray, brown, red and violet. Those from Naples are 
predominately red, much resembling brick or tile dust.^^o Tetin from the 
Azores is reddish in color due to the high presence of ferric oxide. m Trass 
from Audernach Germany, (used by Smeaton at Eddystone) is yellowish gray 
in color.^^2 

The addition of brick dust to lime-based mortar will impart color to the 
mixture, which should be considered before use in a masonry program. The 
amount, particle size, and water content are factors which will effect coloring 
of the mortar. Historically, it was noted that the use of coarsely poimded 
fragments of bricks found in the lime matrix of the Roman hydraulic works 
resembled a breccia. ^^^ of the use of brick dust as a pozzolanic additive in the 
18th century, Vicat said that the brick could not be broken up without leaving 
a small quantity of rather fine powder that when mixed with lime tinged 
slightly red or yellow, according to the color of the brick used.^^'* 

Although the color of the materials and mixes was not pertinent to this 
experimental program, it is important to note that the addition of brick dust 



^^^ J. G. Totten, Essays on Hydraulic and common mortars.and on limebuming ^ translated from 
General Treussart, M. Petot, and M. Courtois, (Philadlephia, Franklin Institute, 1842), 53. 
^^^ Alfred Denys Cowper, Lime and Lime Mortars, (London, His Majesties Stationary Office, 
1927), 47. 
112ibid., 48. 

^^^ L. J. Vicat, A Practical Treastise on Calcareous Mortars and Cements, Artificial and 
Natural, (Translated by Captain J. Smith, London, J. Weale, 1837), 119. 
114 Ibid. 

57 



changes the color of the mixture. Munsell Soil Color Charts were consulted 
to determine the colors of the materials and the mortar. 

Results 



Table 5 - Color of Materials and Mortar Mixes 
Brick Dust 



Brick Dust 1 (Martin Clay Products) 


Brick Dust 2 (Colonial Williannsburg) 


2.5 YR 5/8 


5 YR 6/8 



Sand 



Yellow Bar Sand from Dunrite Aggregates Co. 
wet- 10 YR 6/6 dry - 2.5 Y 7/6 



Mortar Mixes 



Mix1 


Mix 2 


Mix 3 


Mix 4"5 


5 


2.5 Y 8/4 


5 YR 7/3 


5 YR 7/3 


7.5 YR 7/0 


7.5 YR 7/6 



115 ivlix 4, Limestone Dust, Sand and Lime was included in this analysis, although neither the 
additive nor the mortar is considered pozzolanic and thus resultant colour is not a consideration 
for use. 



58 



/ f 



2.6.2 Initial Water Content 

For the preparation of lime-based mortars made from lime putty, the 
standard practice is not to add water during the mixing process but to ram or 
beat the mortar until a plastic consistency is achieved^^^. Lime putty, if 
prepared properly, has a consistency somewhat like yogurt. It possesses 
enough water to be mixed with sand and other additives to yield what would 
be considered in the field a workable mortar. The two types of brick dust and 
the limestone dust were added to the mix in a dry state and no water was 
added to the mix. All mixes were mechanically mixed for the same period of 
time and then stored in lidded containers. All the mixes were handled in the 
same manner in an attempt to a achieve a certain level of consistency. 

The amount of water in the mixture is an important factor as it may 
affect how the mixes will perform on tests like flow and shrinkage. As well, 
water is the other critical component which influences the chemical reaction 
of lime and pozzolana. This test serves to provide basic information on the 
mixes but in itself is not comparative as different mixes require different 
amounts of water for their optimum performance. 

Standard Test Consulted - No test standard addresses this examination. 

Scope of Test - The water content is determined weighing the freshly mixed 
sample. After drying the mortar at 80 °C for 24 hours, the sample is weighed 



^'°John and Nicloa Ashurst, Practical Building Conservation, Vol. 3, Mortars Plasters and 



f Renders, (New York, Halstead Press), 4. 

t 59 



again. The water content of the mortar is calculated, in % by weight, from the 
difference in weight of the wet and dried mortar mass. 

Apparatus - 1) Oven, 2) scale. 

Method - A representative amount of the wet mortar mixture was weighed 
and placed in the oven at @ 80°C and dried for 24 hours. At the end of the 
drying period the weight was measured and the percent water content 
calculated. 



Results 

Table 6 : Mean Water Content of Mixes 



Mix 


Wet Weight (g) 


Dry Weight (g) 


Water Content (%) 


1 


169.0 


138.4 


18% 


2 


197.3 


173.6 


13% 


3 


420.1 


370.2 


12% 


4 


285.3 


241.6 


15% 


5 


354.6 


312.1 


12% 



Graph 1- Mean Water Content of Mixes 

WATER COhfTENT 

100%T-,- 



50%-|- 
0% 



Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 



Water n Solid 



60 



Discussion of Results 

The mean water content was calculated for each mix three times. All 
the mixes fell within a 3% difference in water content. The water content of 
Mix 1, lime and sand, was determined to be 18% of the total weight. As brick 
dust and limestone dust were added, the water content of the mixture was 
reduced. This is due to the fact that the brick dust and limestone dust were 
added in a dry state. Mixes 2, 3, and 5 contained brick dust and had similar 
water content percentages. 

In future investigations, the brick dust and limestone dust, or other 
porous particulates, should be added in a slurry form. This would reduce the 
amount of water or moisture absorbed from the lime putty and result in a 
more consistent rate of water content and better distribution in mixing 
amongst the mixes being examined. 



61 



2.6.3 Workability as measured by a Flow Table 

The term workability refers to the ease of spreading on an absorbent 
surface or the suitabiUty for handling on a mason's tools. Workability is 
linked to the term plasticity, which is properly applied to clay.i^^ 

The workability of mortar is an important characteristic to define, as it 
directly affects performance and durability of the material in the field. A good 
lime-based mortar is evaluated on three characteristics: 1) that it adheres to 
the trowel or slicker without slumping; 2) that it spreads easily and; 3) that it 
retains water against the suction of the masonry units sufficiently to allow it 
time to be spread and worked it into place. Historically, attempts have been 
made to quantify workability of mortar. These include the Carson Blotter 
Test and the Emley Plasticimeter.^i^ Workability of a mortar relates to 
consistency, thus for this experimental program it is quantified by using a 
flow table. This experiment does not test the properties of the mortar mixes 
but serves to characterize and compare them. 

Standard Test Consulted- ASTM C 110 Standard Test for Flow Table. 



^^^ Norman V.Knibbs and B.J. Gee, Lime and Limestone: The Origin, Occurance, Properties, 
Chemistry, Analysis and Testing of Limestone, Dolomite and Their Products, and the Theory of 
Lime Burning and Hydration, (Toronto, H. L. Hall, 1951), 96. 

^^° Both tests were created to evaluate the workability or plasticity of lime putty. The Carson 
Blotter Test involves the placing lime putty on a piece of blotter paper, filter pad, and spread 
with strokes of a spatula over the surface. The number of strokes before the putty left the 
surface and rooled up imder the spatula is the measure of workability. The Emley 
plasticimeter involves an absorbent surface and a moving trowel. A porous porcelain base on 
turntable is rotated with the putty being spread with simulated trowel. The torque required to 
rotate the turntable is indicated on a scale on the Plasticimater. from Knibbs and Gee, Lime and 
Limestone: The Origin, Occurance, Properties, Chemistry, Analysis and Testing of Limestone, 
Dolomite and Their Products, and the Theory of Lime Burning and Hydration, 96. 

62 



Scope of Test - To test the consistency and workability of mortars as expressed 
by a flow table being dropped 1/2 in, 25 times in 15 seconds. The percentage 
change in diameter at the base, or slump, of the mortar sample is measured to 
determine the consistency and thus workability of the mixture. Calculations 
are based on two samples of each mix being evaluated. The results are 
expressed as a percentage change in the diameter of the base of the sample. 

Apparatus - 1) Flow table conforming to ASTM C 230-90. 



Results 

Table 7 - Mean Percent Change as Expressed by Flow T able 





% Change 


Mix 1 (lime and sand) 


6.2 % 


Mix 2 (lime,sand, BD1) 


5.5 % 


Mix 3 (lime,sand, BD1) 


5.3 % 


Mix 4 (lime,sand, LSD) 


9.3 % 


Mix 5 (lime, sand, BD2) 


5.1 % 



Discussion of Results 

From this test, it was observed that the addition of brick dust to the 
lime-based mortar reduced the slump relative to unmodified lime mortar. 
Mixes 2, 3 and 5, (all with brick dust) did not slump as much as Mix 1, (lime 
alone) on the flow table. These calculations were based on the evaluation of 
two samples for each mixture, whereby a maximum spread of 3% existed 
between the samples. Mix 4 (mixed with limestone dust) had a higher 
percentage of slumping relative to the other samples. Mix 4 experienced 
cracking and loss of cohesion during the flow table test. 



63 



1 



In terms of workability, a lower percentage of slumping indicates that 
the mortar is not susceptible to crumbling and falling off the trowel or slicker 
during application. As well, these values influence the performance of the 
mortar in terms of consistency and cohesion. This relates to how the mortar 
will set up and whether cracking either in the mortar or at the interface of the 
mortar and the masonry unit could exist. A lower percentage of slumping 
relates to the level of consistency and cohesion of the mix, and ultimately, its 
performance in the masonry system. 

It should be noted that these percentages have probably been affected by 
the water content of the mixes. As observed in 2.6.2, the initial water content 
of the mixes was not consistent. They ranged from 12-18%. Thus, the 
performance of Mix 4, (lime, sand and limestone dust) may have been 
adversely affected because it was the "driest" mix. 

Another test, purely subjective in nature was performed concurrent to 
this standard test. It included working and spreading the mixes in a mortar 
tray with a steel masonry trowel. A certain amount of mortar adhered to the 
trowel and the trowel was held up from the mortar tray. The mortar was 
evaluated based on the length of time for the mortar to fall from the trowel. 
Although this test is not qualitative, it did conclude that the mixes modified 
with brick dust tended to stay on the trowel longer. The mix modified with 
limestone dust was rather crumbly and quickly fell from the trowel. Again, 
the water content of the mixes may have affected the results of this 
evaluation. 



64 



2.6.4 Setting Rate 

The rate of setting of mortar is a critical test to determine if the brick 
dust imparts an early or pozzolanic set to the lime-based mortar. If the brick 
dust is pozzolanic, the rate of setting should be shorter than for a pure lime 
and sand mortar. This technique was invented by Louis Vicat in 1837 for his 
experiments on natural and artificial hydraulic limes and additives. 
Presently, this test is an industry standard used to identify and determine the 
setting rate of cement and concrete. 

Standard Test Consulted .ASTM Designation C 191-82 - Standard Test Method 
for Time of Setting of Hydraulic Cement by Vicat Needle 

Scope of Test - This method covers determination of the setting time of 
hydraulic cement by means of the Vicat needle. 

Apparatus - 1) Vicat Apparatus consisting of steel needle 1 mm in diameter, 2) 
conical ring with a diameter of 70 mm at the base and 60 mm at the top and a 
height of 40 mm. 

Method - Immediately after mixing of the mortar, the standard test methods 
were followed. The mortar was added to the conical ring with the minimum 
amount of additional manipulation. The top of the ring was struck with a 
trowel to remove excess mortar. The Vicat needle was allowed to drop and 
penetrate the mortar. This operation was conducted immediately after 
mixing and was repeated every six hours with the depth of penetration being 
recorded. 



65 



The Vicat needle is used to determine when the initial and final set 
have occurred. Initial set is considered to have occurred when the needle 
stops under 35 mm from the surface of the paste. When the needle shows no 
appreciable indentation on the surface of the specimen, final set is considered 
to have occurred. The depth of penetration is measured in millimeters. 




Photo 4 - Vicat Penetrometer measuring setting rate of mortar mix. 



66 



Results 



Time 


Mix 1 


Mix 2 


Mix 3 


Mix 4 


Mix 5 


h 

















6 h 

















12 h 





27 


29 





35.7 


18 h 


24 


32 


31.7 


30.7 


45.3 


24 h 


37.7 


41.7 


45.7 


41.3 


48.3 


30 h 


41.7 


46.3 


48.7 


45.3 


50 


36 h 


45.3 


48.7 


50 


48 




48 h 


47.7 


50 




49 




60 h 


47.7 






50 




72 h 


49.7 











Graph 2 - Mean Setting Time of Mortar Mixes 



Setting time in hours 



80 
60 

hours 40 

20 





12 3 4 5 
mixes 



■ final set 
D initial set 



Discussion of Results 

Mix 1, (lime and sand) had the slowest final setting rate of all the mixes 
at 72 hours. An initial set occurred after 24 hours, again the slowest initial set 
of all the mixes. Mix 1 serves as a control from which the other samples can 
be evaluated in terms of the impact of the brick dust affecting setting rate. 



67 



Mix 5 (lime, sand, brick dust 2) had the most rapid setting time at 30 
hours. This mix also achieved the most rapid initial set after 12 hours. If 
setting time can be used to identify pozzolanicity of a brick dust, then this 
material could be considered the most pozzolanic of the brick dusts tested. 

Mixes 2 and 3 (Irme sand and brick dust 1) achieved final set 
respectively at 48 and 36 hours. They had initial setting times between 18 and 
24 hours. If compared to the setting rate of Mix 5, it would indicate that this 
material is slightly less pozzolanic. As well, this seems to indicate that a 
slight difference in proportioning of brick dust to lime appears not to effect 
the setting rate. 

Mix 4 (lime, sand and limestone dust) set up after 60 hours. The longer 
setting rate may have been influenced by the limestone dust absorbing water 
from the mixture and thus impeding the curing of the lime. However, this 
inert additive did reduce the setting time of the mixes when compared to Mix 
1. In terms of other properties, the early setting rates of the lime and brick 
dust mortars had little relationship to eventual durability or strength. 



68 



2.6.5 Set Under Water 

In an attempt to establish the degree of pozzolanicity or hydraulicity of 
the brick dust additives, the freshly mixed samples were placed under water 
and observed after demolding the 24 hour old samples. After a period of 24 
hours, initial set, as indicated in 2.6.4 had occurred. Although it was 
anticipated that the samples would not set under water, this experiment was 
included to make observations about its appropriateness as an evaluative tool 
and to observe the behavior of the mortar mixes. In historic masonry 
practice, lime mortars modified with brick dust were used in projects where 
they would get wet or submerged in water after application. In contemporary 
conservation practice, lime mortars modified with brick dust have been used 
in maritime environments. ^^^ Vicat described a mortar modified with brick 
dust or other pozzolanas with the capacity to set under water as an eminently 
hydraulic or pozzolanic mortar.^^o These mortars were composed of 
eminently rich lime and a very energetic pozzolana. 

Referenced Standard - No standard exist for this test, however a test described 
by Vicat served as a model for the test. 

Methodology - Mix 1, 2, and 5 were used in this test, as Mix 4 had no hydraulic 
component, and Mix 3 was made up of the same material as Mix 2. The 2 in 
or 50 mm cube samples were demoulded after 24 hours of setting. One day of 



^^^ For example, at Caeserea, Israel, architectural conservators have used lime and brick dust 
mortars for the conservation of archaeological ruins in a maritime environment. In a 
conversation with one conservator, the situation was described whereby the mortar was used at 
low tide, and then hours later was completely submerged in sea water. On inspection the low 
tide, the mortar was not damaged. 

120 Vicat, A Practical and Scientific Treastise on the Calcareous mortars and Cements, 
Artificial and Scientific, 243. 

69 



curing was necessary in order to demold and move the samples to the water 
filled beakers. The cubes were placed under water and observed. Photographs 
and descriptive notes were taken after 15 minutes, 30 minutes, 1 hour, 3 
hours, 6 hours, 12 hours and 24 hours. 



Results 
Table 9 



Observations of the Mortar Mixes Setting under Water 



time 


Mix 1 


Mix 2 


Mix 4 


15 min 


-bubbles, disaggregation 
of surface particles 


-bubbles, disaggregation 
of surface particles 


-bubbles, disaggregation 
of surface particles 


30 min 


-disaggregation of surface 
in flakes, quick rate 


disaggregation of surface 
in flakes, slow rate 


-disaggregation of surface 
in flakes, slow rate 


1 hr 


- disaggregation of 
subsurface particles 


disaggregation of surface 
in flakes, slow rate 


-disaggregation of surface 
in flakes, slow rate 


3 hrs 


- disaggregation of 
subsurface particles 


- disaggregation of 
subsurface particles 


- disaggregation of 
subsurface particles 


6 hrs 


- disaggregation of inner 
core of cube sample 


-disaggregation of 
subsurface particles 


-disaggregation of 
subsurface particles 


12 hrs 


-complete disaggregation 
of cube, slump in beaker 


-disaggregation of inner 
core of cube sample 


-disaggregation of inner 
core of cube sample 


24 hrs 


-complete disaggregation 
of cube, slump in beaker 


-disaggregation of all but 
inner core of cube 


-disaggregation of all but 
inner core of cube 



Discussion of Results 

By placing the curing samples into water, a great deal is learned about 
the mortar mixes and the validity of this test. After 30 minutes mix 1 was 
viewed as disaggregating at a quicker rate than mixes 2 and 4. After 6 hours, 
■^ the inner core of mix 1 had begun to disaggregate, while mixes 2 and 4 were 
disaggregating around the periphery of the still discernible cube. Although 



70 



f » 



the brick dust modified mortars were marginally more resistant to 
disaggregation than those without, no mix could be described as eminently 
hydraulic. 

Although this test yielded some information regarding the hydraulicity 
or pozzolanicity of the mixes with brick dust relative to the unmodified lime 
mortars, the short period of time, 24 hours in the molds, before submerging 
the samples was not long enough for the samples to achieve an initial set. 
This test may have provided further information on water resistance if the 
sample had been submerged after a longer curing period. 



71 



2.6.6 Shrinkage 

Shrinkage is a fundamental characteristic of mortar which affects 
performance and longevity of the masonry system. As a mortar sets, it will 
experience a certain amount of shrinkage, resulting in some internal 
microcracking or cracking at the interface of the mortar and the masonry unit. 
However, too much shrinkage is detrimental to the masonry system. The 
addition of pozzolana to lime based mortars has been documented as assisting 
in the control of shrinkage as a stronger matrix is established by the chemical 
bonding of the pozzolana and the lime.121 xhis test attempts to evaluate the 
role of brick dust in controlling shrinkage of lime mortars. 

Referenced Standard - ASTM C 490 -89 Standard Practice for the 
Determination of Length Change of Hardened Cement, Mortar and Concrete. 

Scope - This practice covers the requirements for the apparatus and 
equipment used to prepare specimens for the determination of length change 
In hardened mortar, the apparatus and equipment used for the determination 
of these changes and the procedures for use. Length change is defined as an 
increase or decrease in the linear dimension of a test specimen, measured 
along the longitudinal axis, due to causes other than applied load. 

Apparatus - 1) Two molds consisting of two compartments to form 1 in by 1 
in by 11 1/4 in prisms. 2) A length comparator for determining the length 
change of samples, with a dial micrometer graduated to read 0.0001 in units. 



121 J. G. Totten, Essays on Hydraulic and common mortars and on Umebuming, translated from 
General Treussart, M. Petot and M. Courtois, (Philadelphia, Franklin Institute, 1842), 140. 

72 



Calculations - The length change is calculated at any age as follows: 

L=[(Lx-LiKG]X100 

L=change in length at x age, % 

Lx= comparator reading of specimen at x age minus comparator 

reading of reference bar at x age; in inches 

Li= initial comparator reading of specimen minus comparator reading 

of reference bar at that same time, in inches 

G= nominal gage length, (10). 

The length change values for each specimen are calculated to the 

nearest 0.001"/) and report findings to the nearest 0.01% 




Photo 5 - Length Comparator measuring shrinkage of the prism mold. 



73 



Results 



Table 10 - 


Mean 


Percent Change 


of Length of Mixes 






Day/Hour 


1.1 


1.2 


2.1 


2.2 


3.1 


3.2 


4.1 


4.2 


5.1 


5.2 


Day 1 - 24 h 
































Day 2 - 36 h 


0.01 


0.000^ 


0.002 


0.002 


0.007 


0.001 


0.005 


0.005 


0.001 


0.003 


-48h 


0.013 


0.003 


0.005 


0.005 


0.009 


0.004 


0.015 


0.016 


0.005 


0.009 


Day 3 - 60 h 


0.013 


0.008 


0.007 


0.008 


0.01 


0.012 


0.025 


0.024 


0.011 


0.011 


-72h 


0.015 


0.012 


0.008 


0.011 


0.01 


0.015 


0.034 


0.034 


0.014 


0.014 


Day 4 - 84 h 


0.016 


0.013 


0.011 


0.012 


0.012 


0.017 


0.039 


0.038 


0.015 


0.015 


-96h 


0.016 


0.013 


0.014 


0.013 


0.014 


0.018 


0.042 


0.042 


0.016 


0.016 


Day 5-108h 


0.018 


0.014 


0.017 


0.014 


0.015 


0.02 


0.044 


0.045 


0.018 


0.017 


-120h 


0.02 


0.016 


0.023 


0.017 


0.017 


0.021 


0.046 


0.045 


0.019 


0.017 


Day 6-132h 


0.022 


0.016 


0.023 


0.018 


0.018 


0.021 


0.053 


0.049 


0.02 


0.018 


-144h 


0.022 


0.017 


0.024 


0.019 


0.019 


0.022 


0.053 


0.051 


0.02 


0.018 


Day 7-156h 


0.023 


0.017 


0.024 


0.02 


0.019 


0.022 


0.056 


0.055 


0.02 


0.019 


-168h 


0.024 


0.022 


0.025 


0.022 


0.019 


0.023 


0.059 


0.057 


0.022 


0.02 



Discussion of Results 

In terms of shrinkage, Mix 1, 2, 3 and 5 displayed marginal differences 
after a seven day period. The addition of brick dust to the lime-based mortar 
decreased shrinkage negligibly, by 0.001% or 0.0001 ins over 10 in bar. From 
these results it appears that the addition of brick dust does not appear to affect 
shrinkage within a seven day curing period. Perhaps the brick dust does play 
a role in shrinkage after a seven day period, but this experiment did not 
address this factor. 

In comparing Mix 1 to Mix 4, there does not appear to be any 
appreciable difference in shrinkage in the eary period of the experiment, 
however, by day seven, a slight difference 0.035% or 0.0035 ins over 10 in bar 



74 



did exist. The relative increase in shrinkage of Mix 4 compared to the other 
mixes could be a factor of its low initial water content or the addition of an 
inert particle that does not contribute to the formation of the crystalline 
matrix. Further investigations into the miccrostructure of the mixes can be 
found in 2.6.13. 

Although siginificant differences were not observed for shrinkage the 
behaviour of the mixes, this experiment serves to evaluate the 
appropriateness of this standard test for lime-based materials. Essentially, this 
standard test is intended for cement-based materials that tend to harden and 
develop strength at a faster rate than lime-based materials. This standard test 
is not appropriate to measure the rate of skrinkage of these samples because of 
the slower hardening and strength development rates of lime-based 
materials. The size of the sample being tested (1 by 1 by 11 1/4 in prisms) does 
not lend itself to lime-based materials, as they are susceptible to breaking 
during demolding and measuring. As lime-based materials tend to harden 
over a longer period of time than cement-based mortars, measuring the daily 
rate of skrinkage over a seven day period is not long enough to evaluate 
skrinkage rates of the mixes. 



75 



2.6.7 BULK SPECIFIC GRAVITY 

The bulk specific gravity of a material is a property that in itself is not 
fundamental, but influences other properties such as compressive strength, 
water absorption and durability. The bulk specific gravity of a material relates 
to its real density. Real density relates to the real, or impermeable volume of 
the sample. This value informs the porosity of each mix as it relates to the 
space of the 50 mm or 2 in cube that is permeable to water. 

Scope - These test methods cover the tests for determining the bulk specific 
gravity. Bulk Specific Gravity is defined as the mass of a given volume of a 
substance divided by the mass of the same volume of water. ^22 

Standard Consulted - Standard Chemistry Procedure 

Bulk Specific Gravity = A/(B-C) 

A=weight of the dried specimen 

B=weight of the soaked and surface dried in air 

C=weight of the soaked specimen in water 

Apparatus - 1) scale. 



^^ Shugar, Gershon J. and Ballinger, Jack P. Chemical Technician 's Ready Reference 
Handbook, Magraw-Hill, New York, 3rd, 1990, 396. 

76 . 



Results 

Table 11 - Specific Gravity of Mortar Mixes - kg/m^ 



Mix 


Specific Gravity 


1 (lime & sand) 


1.74 


2 (lime, sand & BD1) 


1.84 


3 (lime, sand & BD1) 


1.86 


4 (lime, sand & LSD) 


1.94 


5 (lime, sand & BD2) 


1.86 



Discussion of Results 

Not surprisingly, the addition of brick dust and limestone dust to a 2 in 
or 50 mm cube of lime and sand mortar does change the specific gravity of the 
mix. In the mixes modified with additives, more material occupies the same 
volume, thus increasing the bulk specific gravity. These results are not 
intended to be comparative, but contribute to the understanding of the 
behviour of these samples in other tests such as porosity, compressive 
strength, water vapor transmission, and resistance to salt attack. 

In comparing these results to published research conducted on 
pozzolanic lime-based mortars, the density of the samples prepared by 
Pennelis et al, (1 part lime, 1 part pozzolana (Santorin), to 6 part sand) was 
reported as 1.86 kg/m^ and (1 part lime, 1 part pozzolana (Santorin), to 3 parts 
sand and 3 parts crushed brick) to be 1.84 kg/m^.^^s As well, these results are 
comparable to research conducted on pozzolanic lime mortars in Tanzania 
which determined the density of mixtures with varying proportions of 



123 G. Penelis., J. Papayianni, M. Karaveziroglou, "Pozzolanic Mortars for Repair of Masoriry 
Structures," Structural Repair and Maintenance of Historic Buildings, 165. 



77 



I 



pozzolanas falling between 1.72 and 1.81 kg/m3.i24 xhe similar results 
indicate that the proportioning and mixing of the samples reflects some 
contemporary practice standards. 

In comparing the bulk specific gravity of lime and brick dust mortars to 
that of Portland Cement, calculated as 3.5 kg/m^, and hydraulic cement 
calculated at 3.15 kg/m^, the porosity of these materials can be roughly 
compared and they are significantly more dense. ^^s These differences in bulk 
specific gravity relate to the differences in other physical and mechanical 
properties between these materials. 



^24 p. Cappelen, Pozzolanas and Pozzolime, (Dar as Salaam, Building Research Unit, 1978), 22. 
125popovics,p. 183 

78 



2.6.8 Compressive Strength 

The compressive strength evaluation of a Ume-based mortar modified 
with brick dust proves problematic because a pozzolonic reaction follows a 
slow and time-dependent process. Unlike Portland Cement based mortars 
which achieve maximum strength in approximately 28 days, research 
indicates that a lime-brick dust mortar takes longer to develop strength 
potential. Research on the effect of particle size and on determining the 
reactivity of a pozzolana reports that the lime-pozzolana mortars gain 
strength more slowly, and reach a considerably lower ultimate strength than 
Portland Cement mortars.i26 For this experimental program, compressive 
strength evaluation was conducted at the end of the experimental program to 
permit the mortars a longer curing time. The mortar mixes were tested after 
approximately four months curing. 

Compressive strength testing was included in order to further 
compare the brick dusts being evaluated and not as an indicator of overall 
final performance or durability of the mortar. The mortar was evaluated as 
an isolated material and not in a masonry system as it would be expected to 
perform. 

Presently, the construction industry, including those involved in the 
repair of historic masonry structures, tend to think purely about compressive 
strength when selecting a repair mortar. As a result, mortar tends to be 



126 p. Cappelan, Pozzolanas and Pozzolime, (Dar as Salaam, Building Research Unit, 1978), 7. 
and ASTM STP 99, Symposium on the Use of Pozzolanic Material in Mortar and Concrete, 
(Philadelphia, 1949). It has been determined that a mixture of 60% Port Cement and 40% 
Pozzolana has a strength equal to 75% of pure Portland Cement after 6 months, 95% after one 
year and 102%) after 5 years. 

79 



evaluated and specified based on strength. But in many applications, high 
strength is not a desired property of a masonry mortar. Other characterisitics 
such as flexibility, adhesion and permeability are important factors for a 
mortar to perform its role of integrating the masonry units. Although 
strength of mortar can not be completely overlooked for reasons of safety, it is 
only one of many more important factors in good masonry. 

Standard Consulted - ASTM C109-90 Standard Test Method for Compressive 
Strength of Hydraulic Cement Mortars (Using 2-in. or 50-mm Cube 
Specimens) 

Scope - This test method covers determination of the compressive strength of 
hydraulic mortars, using 2 in. or 50-mm cube specimens. 

Apparatus - 1) Specimen molds for the 2 in or 50 mm cube specimens 
consisted of three cube compartments. 2) The molds used were constructed of 
maple hardwood milled to conform to the specifications. The parts were 
firmly held together with stainless steel hardware. 3) An electrically driven 
mechanical mixer of the type equipped with paddle and mixing bowl 
conforming to ASTM C 305 - Practice for Mechanical Mixing of Hydraulic 
Cement Pastes and Mortars of Plastic Consistency. 4) A tamper, non- 
absorptive, non-brittle with a convenient length of about 5 to 6 ins. (120 - 150 
mm). The tamping face shall be flat and at right angles to the length of the 
tamper. 5) Testing Machine: Instron Testing Machine Model 1331, stroke 
control (5% range) and Ramp Test Fr. 0.002 MZ. 



80 



Methodology - Three samples of each mix were selected for testing. Each 
sample was placed in the centre of the podium of the compression strength 
machine. The compressive strength machine was equipped with a sensor 
that detected exact moment of failure from the increased load. A computer 
printout for each sample was generated. 

Compressive Strength testing was completed on March 25, 1994 at the 
Laboratory for Research on the Structure of Matter, University of 
Pennsylvania. Testing was conducted under the direction of Dr. Alex Radine. 
Data from this experiment can be found in Appendix 1. 



Results - 

Table 12 - Mean Compressive Strength, (Mean Mpa based on 4 

cubes tested) 





Age/days 


Mean Mpa. 


Mix 1-Lime + Sand 


141 


1316.7 


Mix 2- L + S + BD1 


139 


1055 


Mix 3- L + S + BD1 


134 


1640 


Mix 4- L + S + LSD 


122 


1782.5 


Mix 5- L + S + BD2 


119 


1757.5 



Graph 3 - Mean Compressive Strength of Mixes 




81 



Discussion of Results 

The results of this experiment indicate that the addition of brick dust to 
the lime based mortars did not significantly increase the compressive strength 
of lime-based mortars after a four month cure. For two of the mixes 3 and 5, 
the compressive strength was increased marginally. However, factoring in 
the results of mix 2, with a lower compresive strength than lime-based mix, 
indicates that no overall improvement in compressive strength was 
achieved. 

The results of this test are rather inconclusive as they are below the 
results reported in related research. The research completed on the 
calcination of natural pozzolanas reported the compressive strength of 
calcined opaline shale/lime mixture at 1790 Mpa, and of calcined shale/lime 
mortar at 1746 Mpa after a 30 day curing period. ^27 In the Smeaton Project, 
the addition of brick dust to lime-based mortars appeared to increase the 
compressive strength when the particle size of the brick dust was small. 
Compressive strength of these mortars was reported at 2.18 N/mm^ to 2.43 
N/mm2 or Mpa after a 120 day curing period. ^^s 

Generally, the addition of brick dust increased the compressive 
strength of the mortar samples. An explanation for this could simply be that 
more material is packed into the volume. As witnessed by the bulk specific 



^27r.c. Mielenz, "Mineral Admixtures - History ar\d Background," Concrete International, 

1983. 

l^^Teutonico, "The Smeaton Project: Factors Affecting the Properties of Lime-Based Mortars, 

APT Bulletin, 41. 

82 



gravity values, the modified mixes are denser and thus could have higher 
rates of compressive strength. 

Factors affecting this experiment that may have caused the 
inconclusive results include: 1) the rough surface of the mortar cube causing 
the sample to crack during compression. The compresive strength testing 
machine is sensitive to cracking or any movement of the sample; 2) The 
samples were not always placed in the compressive strength testing machine 
in the same orientation. Because the top trowelled surface was sometimes 
rough, the samples were turned on their side. This difference in placemant 
may have impacted this test, as tamping during the molding may have 
created statifications in the cubes which were susceptible to premature 
cracking. 

For more conclusive results, this examination should be repeated. If 
this test was repeated, it should examine the different mortar mixes after a 
longer curing period and examine the development of strength at various 
stages of the curing of the mixes. A three point rupture test could shed light 
on the compressive strengths of lime-based mortars. 

This test was included in the experimental program in order to give 
quantifiable and comparable figures to the mixes being examined. Generally, 
the results of compressive strength testing should not strongly inform the 
selection of a repair mortar. Strength of the mortar is not an important 
property as it is relative to the masonry unit and the masonry system. As 
well, high compressive strength does not equate good performance or 
durability in a masonry system. 



83 



2.6.9 Water Vapor Transmission 

The purpose of this test is to obtain, by means of simple apparatus, 
reliable values of water vapor transfer through the mortar samples, expressed 
in suitable units. Water vapor transmission is an important quality of mortar 
in a masonry system as it relates to the permeability of the material to allow 
water vapor to exit the masonry system via the mortar joint. In some historic 
masonry systems, the mortar joint was generally designed to be the conduit 
for water and water vapor to escape. As well, water vapor transmission rates 
are important factors for determining compatibility of masonry systems. 
Therefore, depending on the nature of the masonry system, it is desirable to 
use a durable mortar that can transfer liquid water and water vapor. This 
ability to transfer liquid water and water vapor out of the masonry system 
reduces the susceptiblity to deterioration. Trapped liquid water or water 
vapor can freeze resulting in cracking of the mortar and /or masonry unit. As 
well, wet materials have a lower compressive strength and thus could fail 
under stress or load. 

Standard Consulted - ASTM E 96-90 - Standard Test Methods for Water Vapor 
Transmission of Materials 

Scope- To determine the water vapor transmission of the mortar. The 
methods are limited to samples not over 1/4 in. (32 mm.) in thickness. The 
water method was selected because it has been successfully used on mortars 
and paints. 



84 



In the water method, the test specimen is sealed to the open mouth of a 
dish containing distilled water, and the assembly placed in a controlled 
atmosphere with desiccant. Periodic weighing determine the rate of water 
vapor movement from the specimen into the desiccant. 

Terminology - Water vapor permeability is defined as the time rate of water 
vapor transmission through unit area of flat material of unit thickness 
induced by unit vapor pressure difference between two specific surfaces, 
under specified temperature and humidity conditions. 

Water vapor transmission rate is defined as the steady water vapor 
flow in unit time through unit area of a body, normal to specific parallel 
surfaces, under specific conditions of temperature and humidity at each 
surface. 

Apparatus - 1) Scales. The scale was checked daily with a known weight. 2) 
The molds used for this test were rings made of rigid PVC with an interior 
diameter of 2 3/4" and 3/4" high The molds were rigid enough to prevent 
deformation, yet permitted removal of the mortar. 3) The test dish used was 
a tri-comered polypropylene 250 ml. beaker. These beakers have an inner 
diameter of 2 3/4 ". 5) For a desiccating chamber, a glass fish tank with a glass 
lid fighted with a gasket was used. Three glass trays were filled with desiccant. 
The desiccant used was Drierite or Ca SO4 (anhydrous calcium sulphate) size 
8 mesh, manufactured in USA by W. A. Hammond Drierite Co. Xenia, Ohio. 
The desiccating chamber was covered with a sheet of glass. The top of the fish 
tank was sealed with rubber weather stripping to assist in maintaining a 
controlled atmosphere. 6) Two hygrometers were used, one to measure the 



85 



humidity in the tank, the other to measure the humidity of the laboratory. A 
second hygrometer was periodically used to verify the primary hygrometers. 
7) Two thermometers, one to measure the temperature in the tank and the 
other for outside the tank. 

Temperature and Humidity - The relative humidity in the desiccating 
chamber was maintained between 5 and 10 % RH and measured on a daily 
basis. The desiccant was changed as required as determined by changes in the 
relative humidity inside the tank and by the color change of the desiccant 
indicator. The temperature of the chamber fluctuated from 14 to 24°C. It was 
impossible to control the temperature of the chamber as the temperature 
outside of the chamber could not be controlled. 

Methodology - Sample rates were measured on an electronic scale that was 
calibrated after each weighing by adding or subtracting the differences in the 
weight of known weight. 

The daily rate of water loss due to water vapor transmission was 
calculated for each sample. The mean value for each mortar mix was 
calculated and graphed. Calculations were based on the mean of four samples 
for each mix. 



86 



Results 

Table 13 - Mean weight change of assemblies - (g) 





Mix 1 


Mix 2 


Mix 3 


Mix 4 


Mix 5 


Day 1 

















2 


0.61 


0.79 


0.69 


0.62 


0.74 


3 


1.04 


0.85 


0.71 


0.6 


0.8 


4 


1.07 


0.95 


0.66 


0.58 


0.9 


5 


1.06 


0.97 


0.76 


0.52 


0.84 


6 


0.99 


0.89 


0.72 


0.68 


0.89 


7 


0.91 


0.86 


0.84 


0.71 


0.94 


8 


0.88 


0.79 


0.9 


0.52 


0.93 


9 


0.86 


0.78 


0.92 


0.49 


0.85 


10 


0.84 


0.82 


0.88 


0.59 


0.95 


1 1 


0.83 


0.87 


0.91 


0.64 


0.93 


12 


0.8 


0.94 


0.84 


0.59 


0.98 


13 


0.87 


0.93 


0.83 


0.55 


1.01 


14 


0.8 


0.88 


0.84 


0.42 


0.98 


15 


0.79 


0.95 


0.81 


0.47 


0.94 


16 


0.84 


0.87 


0.79 


0.48 


0.99 


17 


0.81 


0.86 


0.75 


0.46 


0.97 


18 


0.91 


0.78 


0.76 


0.49 


0.93 


1 9 


0.86 


0.82 


0.69 


0.49 


0.85 


20 


0.94 


0.89 


0.82 


0.43 


0.89 


21 


0.94 


0.88 


0.81 


0.53 


0.87 


22 


0.91 


0.80 


0.78 


0.54 


0.94 


23 


0.85 


0.82 


0.77 


0.52 


0.95 


24 


0.79 


0.75 


0.75 


0.42 


0.9 


25 


0.77 


0.75 


0.73 


0.44 


0.91 


26 


0.81 


0.82 


0.71 


0.42 


0.96 


27 


0.89 


0.78 


0.71 


0.56 


0.93 


28 


0.78 


0.65 


0.62 


0.43 


0.85 


29 


0.76 


0.67 


0.61 


0.41 


0.87 


30 


0.73 


0.69 


0.68 


0.51 


0.85 



87 



Graph 4 - Mean Water Vapor Transmission 









Mix 1 




2n 


p 








1.5 - 


- 








grams 1 - 


- 








0.5- 


- 








f) - 












1 5 


9 


13 17 21 
days 


25 29 









Mix 2 


2-1 


r 






1.5- 


- 






grams 1 - 


■ 






0.5- 


■ 




1 II 


n . 






J Jij 




1 5 


9 


3 17 21 25 29 
days 





88 






Discussion of Results 

The results indicate that a slight difference in the water vapor 
transmission between the some of the mixes existed. In mix 1 (lime and 
sand) and mixes 2 and 3, (lime, sand and brick dust 1), there was no significant 
difference in the WVT. The addition of this type of brick dust, irrespective of 
proportion, has little or no affect on the WVT of the lime-based mortar. 
However, the addition of brick dust 2, as witnessed by mix 5, did marginally 
increase the WVT of the lime-based mortar. In comparing these results to the 
observations made in 2.6.13, Microcracking, mix 5 had the smallest and least 
number of microcracks. This suggests that the addition of this type of brick 
dust to the lime did create a strong, yet permeable matrix. 



89 






2.6.10 Water Absorption Capacity 

From this simple test, water absorption level and rate can be calculated. 
The rate of water absorption is measured to compare the behaviour of the 
lime mortar with the addition of brick dust or a porous particulate. W.A.C. 
results will influence other tests such as water vapor transmission and 
porosity. 

Standard Consulted - Normal 7/81, as reported by Jeanne Marie in A 
Laboratory Manual for Architectural Conservators, Teutonico, 1988. 

Methodology - Two 2 in cubes of five different mixes were washed with 
deionized water to remove powdered material from the surface.The samples 
were dried for 24 hours at 60°C. The samples were permitted to cool in a 
humidity controlled environment (see water vapor transmission) Intial 
weighing of the sample took place, recorded as Mq- The drying process was 
continued vmtil the mass of the sample was constant. This was acheived after 
3 cycles. The samples were placed in 500 ml glass beakers and deionized water 
was added until the samples were covered with 2 cm of water. The samples 
were weighed at regular increasing intervals; at each chosen time, the sample 
was taken out of the water, blotted with a paper towel, and then weighed. 

Calculations - At each interval, the quantity of water absorbed with respect to 
the mass of the dry sample was expressed using the following calculations: 

AM/Mo % = [Mn - Mq / Mq] x 100 



90 



where Mn = weight of the wet sample at time tn and Mq = weight of 

the dry sample. 

Mq = weight of the sample after drying. 



The Water Absorption Capacity was then calculated using the following 
calculations: 

WAC = [Mmax - Md / Md] x 100 

where Mmax = the mass of the sample at maximum water absorption 

Md = the mass of the sample after redrying at the termination of the 

test. 



Results 

Table 14 - Mean Water Absorption of Mixes - (g) 







lUlix 1 


Mix 2 


IVIix 3 


Mix 4 


Mix 5 


5 min 


WA 


9.6 


12.3 


10.2 


9.4 


11.29 


15 min 


WA 


10.7 


12.7 


11.2 


9.5 


11.85 


30 min 


WA 


10.8 


13.6 


11.8 


9.8 


12.1 


1 hour 


WA 


11.0 


13.7 


12.0 


10.1 


12.3 


2 hour 


WA 


11.0 


13.8 


12.2 


10.3 


12.4 


3 hour 


WA 


11.0 


13.8 


12.3 


10.3 


12.5 


6 hour 


WA 


11.1 


13.9 


12.3 


10.4 


12.5 



Table 15 - Mean Water 


Capacity of Mixes - 


(g) 






Mix 1 


Mix 2 


Mix 3 


Mix 4 


Mix 5 


WAC 


10.9 


13.7 


12.2 


10.1 


12.5 


acheived at 


1 hr 


1 hr 


2hr 


1 hr 


3hr 



91 



Graph 6 - Water Absorption Curve - Mean Value - (g) 



15 J 
12 -- 



Mix 1 



5 15 30 60 120 180 360 
T- min 



Mix 2 




5 15 30 60 120 180 360 
T- min 




92 






Discussion of the Results 

From this experiment it can be seen that the addition of both types of 
brick dust marginally increased the water absorption capacity of lime-based 
mortars. Although this experiment does not have any direct relationship to 
the performance of these mortars in a masonry system, it does shed light on 
the results of water vapor transmission rate and the liquid water 
permeability. In comparing the results of the two experiments, it can be said 
that the addition of brick dust slightly improves the ability of the samples to 
absorb and transfer water through the lime based mortar. However, no 
statements can be made regarding water effectively getting out of the masonry 
system. 



93 



J 



f 



2.6.11 Depth of Carbonation 

The measuring of the depth of carbonation evaluates the long term 
curing rate of the sample. It should be noted that this test is not a standard, 
but can be effectively used to establish trends in the curing of the mixes. As 
all the mixes were subjected to similar curing conditions, the test serves to 
indicate how the constituents of the mix affect curing of the sample. 

Standard Consulted - Exercise 26, "Investigation of the carbonation process in 
lime mortars by means of phenolphthalein," A Laboratory Manual for 
Architectural Conservators, Teutonico, 1988. 

Scope 

This test indicates the progress of carbonation or curing of a lime based 
sample through the use of phenolphthalein indicator. Phenolphthalein 
reacts to alkaline materials and is colorless in an acid or neutral 
environment. In a freshly cut or broken sample, the phenolphthalein will 
indicate the depth or progress of carbonation of the mortar sample by reacting 
to the alkalinity of the free or uncarbonated lime. This level was measured 
with a ruler calibrated in millimeters on three different samples (50 mm or 2 
in cube) at the 30, 60 and 90 day cure. Three samples of each mix were 
measured to yield the average measurement of depth of carbonation. 



94 



Results 
Table 16 


- Mean 


Depth of Carbonation of Mixes - i 


mm) 


Days 


Mix 


1 


Mix 2 


Mix 3 


Mix 4 


Mix 5 


30 


2 


2.5 


3 


1.8 


3.1 


60 


4.3 


5.2 


5.3 


4.2 


5.8 


90 


5.5 


6.2 


6.4 


5.4 


6.7 



Discusion of Test Results 

Though not a precise measurement, this test does indicate certain 
characteristics about the mixes and their constituent parts. The test indicates 
that the addition of brick dust does have an affect on the curing or 
carbonatization of Hme-based mortars as exhibited by those mixes with brick 
dust versus the unmodified mixes. In comparing the efficacy of the brick dust 
additives. Mix 5 exhibited deeper levels of curing at the 30, 60 and 90 day rate 
than Mix 2 and 3. 

It should be noted that it was difficult to achieve an accurate reading for 
Mix 4 as the limestone dust was affected by the phenolphthalein and marred 
the line or level of carbonatization. In future experimental programs the 
measurements should be continued for a longer curing period, as 90 days may 
not be long enough for lime-based materials. In comparing these results to 
those recorded in 2.6.4, Setting Rate, the same trends exist. 



95 



2.6.12 Resistance to Salt Attack 

Historically, it was found that the addition of pozzolanas improves the 
resistance of lime-based materials to salt attack. Vitruvius mentioned this 
phenomenon and investigations of Smeaton lead to the addition of 
pozzolana to his lime mixture at Eddystone. In this century, the cement 
industry has appreciated that the addition of pozzolanas improves resistance 
to sulphate waters. ^29 

A mortar resistant to salt attack has been a long sought after material in 
conservation which in part has led many to use cement-based mortars or to 
add cement to lime-based mortars, thus equating strength with durability. 
The addition of a pozzolanic material is thought to improve salt resistance 
because a strong yet porous and permeable matrix is established whereby salts 
in solution can pass through the mortar to the surface without deteriorating 
the material along the way. This experiment attempts to compare the 
durability of lime mortar to that of lime mortars modified with brick dust or 
porous particulate as measured by the Salt Crystallization Test. 

Standard Consulted - British Research Establishment Report, Crystallization 
Test, 1992 (modified by the author) 

The test standard was designed to be used for building stone. It was 
modified for this research in terms of concentration of the salt solution and a 
desiccator was not used.. The crystallization test involves 12 cycles of 
submerging the 2 in disc-shaped samples in a 10% solution of sodium 
sulphate by weight. The samples were dried in an oven at 100°C for 24 hours 



^^^ Symposium on the Use of Pozzolanic Materials in Moriar and Concrete., 12. 

96 



prior to submerging. The samples were weighed and then submerged in 
sodium sulphate solution for 2 hours. The samples were then placed in the 
oven for 24 hours at 100°C. The samples were weighed and photographed. 
The cycle was repeated 12 times. Disc samples were used for this experiment 
due to availability. 

During the wetting cycle, the porous and permeable samples are 
saturated with the salt solution. Upon drying in the oven, the liquid water is 
removed and soluble salts return to the solid or crystal state in the pores and 
on the surface of the samples. The force of this action often causes the host 
material to crack or diaggregate. Thus, this examination measures weight loss 
as a factor of resistance to salt attack. 

It should be noted that a small amount of material was sometimes lost 
in the handling of the samples. When an appreciable amount of material 
was lost, this was noted. 

Calculations 

Calculate the mean percentage weight loss for each set of samples 

% weight loss = 100 (Wf - Wi)/Wo 
Wf= weight of sample after cycle 
Wi= weight of sample after label 
Wo= weight of sample after oven drying 



(note: there was no change in weight after label was added 
permanent felt type marker was used to identify samples) 



as a 



97 



Results 
Table 17 



Mean % Weight Change of Mixes (g) - Experiment 1 



Mix 


1.3 


1.4 


2.3 


2.7 


3.3 


3.4 


4.1 


4.8 


5.3 


5.4 


weight g. 


129.9 


123.5 


110.5 


125.4 


122.7 


132.8 


140.3 


140.4 


135.5 


133.7 


Cycle 1 


+0.81 


+0.83 


+0.77 


+0.69 


+0.66 


+0.79 


+0.59 


+0.61 


+0.82 


+0.75 


Cycle 2 


+ 1.46 


+ 1.51 


+ 1.26 


+ 1.35 


+ 1.35 


+ 1.58 


+ 1.25 


+ 1.51 


+ 1.68 


+ 1.44 


Cycle 3 


+ 1.92 


+2.03 


+ 1.59 


+ 1.77 


+ 1.79 


+2.16 


+ 1.67 


+ 1.98 


+2.42 


+2.16 


Cycle 4 


+2.41 


+2.34 


+ 1.77 


+2.17 


+2.19 


+2.34 


+2.53 


+3.4 


+3.1 


+2.63 


Cycle 5 


+2.84 


+2.74 


+ 1.92 


+2.59 


+2.6 


+2.81 


+2.37 


+2.86 


+3.52 


+3.29 


Cycle 6 


+3.13 


+2.89 


+ 1.97 


+2.88 


+2.75 


+3.06 


+2.73 


+3.15 


+4.12 


+3.56 


Cycle 7 


+3.31 


+3.18 


+2.07 


+2.95 


+2.91 


+3.41 


+2.87 


+3.37 


+4.34 


+3.79 


Cycle 8 


+2.94 


+2.92 


+ 1.73 


+3.08 


+2.9 


+3.24 


+2.76 


+3.27 


+0.66 


+3.46 


Cycle 9 


+2.82 


+2.89 


+ 1.45 


+3.23 


+2.9 


+2.88 


+2.46 


+3.27 


+0.09 


+3.18 


Cycle 10 


+2.69 


+2.75 


+ 1.38 


+3.35 


+2.72 


+2.78 


+2.27 


+3.19 


+0.07 


+2.94 


Cycle 11 


+2.62 


+2.63 


+1.29 


+3.12 


+2.5 


+2.63 


+2 


+2.83 


-0.57 


+2.71 


Cycle 12 


+2.57 


+2.49 


+1.18 


+3.03 


+2.35 


+2.42 


+1.86 


+2.45 


-1.49 


+2.35 


% change 


+1.9 


+2.02 


+ 1.07 


+2.41 


+ 1.91 


+1.82 


+ 1.32 


+ 1.74 


-1.09 


+ 1.75 



Discussion of Results 

Interpretation of the results of the salt resistance test indicate several 
trends, but also yields some inconsistencies in the test program. The samples 
tended to gain as opposed to lose weight. Weight gain was probably caused by 
the salts forming in and on the surface of the samples, without causing the 
samples to lose material. As well, all the samples seemed to offer some 
resistance to sulphate action with the addition of the brick dust not clearly 
impacting the lime mortar. 



98 



Preparation of the samples may have had an impact on this test, as the 
trowelled surfaces of the disc tended to crack after the sixth cycle. The cracks 
widened and surface delamination was apparent. The perimeter of the disc 
was susceptible to disaggregation because this area of the disc was not 
finished. 




Photo 6 - Samples after 12 cycles of 10% solution sodium sulphate 
crystallization test 



Due to these rather strange results, it was decided to conduct this 
experiment a second time. The concentration of the sodium sulphate 
solution was increased to 14%. 2 in or 50 mm cubes were used rather than 
discs. Only one cube of each mix was available for the experiment. 



99 



Results 

Table 18 - % Weight Change of Mixes (g) - Experiment 2 



Day 


Mix 1 


Mix 2 


Mix 3 


Mix 4 


Mix 5 


1 


+1.58 


+ 1.57 


+1.56 


+ 1.48 


+ 1.43 


2 


+5.25 


+5.33 


+5.94 


+5.42 


+6.52 


3 


+8.84 


+6.18 


+9.02 


+8.09 


-6.76 


4 


+9.73 


+4.76 


+8.27 


+9.29 


-15.32 


5 


+9.86 


+ 1.67 


+10.88 


+ 10.00 


-31.51 


6 


+13.06 


+6.28 


+ 14.55 


+ 12.42 


-31.23 


7 


+6.58 


+2.91 


+14.62 


+12.53 


-46.28 


8 


+6.37 


+2.65 


+15.06 


+12.91 


-48.43 


9 


+2.85 


+2.66 


+17.18 


+ 15.42 


-56.11 


10 


-2.89 


+1.65 


+17.78 


+2.61 


-57.1 



Discussion of Results of Experiment 2 

In experiment 2, the increased concentration of the sodium sulphate 
did have dramatic effects on some of the mixes. As only one sample of each 
mix was used for the experiment, conclusions are tenuous. In this 
experiment it can not be stated that the addition of brick dust improved the 
resistance of the samples to salt attack. The mixes modified with brick dust 
behaved significantly different. Mix 2 exhibited a slight increase in weight. 
Mix 3 exhibited a sigruficant increase in weight. While mix 5 exhibited a very 
significant decrease in weight. Mixes 2 and 3 exhibited cracking at or near the 
tenth cycle, while mix 5 had lost one quarter of its original mass due to 
cracking. Perhaps an explanation for the dramatic weight loss of mix 5 is the 
clay type. Further study of this material is required as other experiments 
suggest it behaves as a pozzolana. 



100 



The weight gain for mixes 2, 3 and 4 is attributed to the sahs in solution 
entering the porous structure and crystallizing upon drying. Although the 
use of cubes rather than discs permits better observations for this experiment, 
this experiment makes comparison of highly porous materials difficult. In 
future related experimental programs other methods of durability testing 
should be considered. 




Photo 7 - Samples after 10 cycles of 14% solution sodium sulphate 
crystallization test, note the cracking of the cubes and salts on the surface of 
the cubes. 



101 



I 



2.6.13 Microcracking of Mortar Mixes 

Thin section microscopical examination of the mirostructure of mortar 
mixes can provide supplementary information that can not be obtained from 
standard physical and chemical tests. Microcracking of the mortar can be 
identified and quantified by using micrometry. The long term performance 
of the mortar is a function of microcracking as these small fissures can trap 
water and harmful salts. Microcracking indicates shrinkage and lack or loss of 
intergranular bond. Similarly, the role of the brick dust and the porous 
particulate can be evaluated by observing the character and location of the 
microcracks. 

Apparatus - 1) Nikon Optiphot Polarized Light Microscope, 2) Micrometer, 3) 
prepared thin section of mortar samples. 

Methodology - Using thin section microscopy, each mortar sample was 
examined in transmitted, plain and polarized light. Three representative 
areas were selected to make the observations and measure the size of the 
microcracking. The width of all the cracks in each selected area were 
measured and recorded. The measurements reported are the averages of the 
three representative areas. As the sand in the mix is 99.5% silica, (see Section 
2.3) it is clearly distinguishable in polarized light. The samples were viewed 
in the microscope at 10 x. A photomicrograph was taken of each 
representative area. 

Measurements - The micrometer at 10 x was calibrated at Ifim equal to 0.012 



102 



Observations 




Photo 8 - Microphotograph, 10 X Mix 1 



Mixl 



This mix, consisting of lime and sand, exhibits microcracking in the 
lime paste. No cracks were located at the interface of the paste and aggregate 
which suggests that the samples are well mixed and that aggregate-alkali 
reaction! 30 js not present. The cracks measure approximately 2-5 ^im or 0.024 
mm to 0.06 mm wide and the length varies considerably. Microcracking in 
the lime paste was anticipated based on other researchers obervations. 



!^ Alkali- aggregate reaction is a phenomenon associated with the use of a reactive form of 
silica from the aggregate reacting with certain alkaline constituents from the cement. 
Although most conunonly associated with cement and concrete, it has been noted in lime based 
materials when the reactive aggregate has been used. Lea, The Chemistry of Cement and 
Concrete, 569. 



103 




Photo 9 - Microphotograph, 10 X Mix 2 



Mix 2 



In this mix, brick dust and lime comprise the paste. Microcracks 
observed range from approximately 2 to 3 ^im or 0.024 to 0.036 mm wide, less 
than in the lime matrix. Like Mix 1, the length of the cracks varies 
considerably. These cracks generally occur in the paste matrix, but some 
microcracks exist at the interface of the lime and brick dust and at the 
interface of the lime and the sand. The smaller particles of brick dust appear 
to be well mixed into the lime. 



104 




Photo 10 - Microphotograph, 10 X Mix 3 



Mix 3 



Microcracks in this mixture have been measured at 2-3 |im or 0.024 to 
0.036 mm wide, and the length varies considerably. The microcracking 
generally occurs in the paste matrix between either particles of sand or brick 
dust. Some microcracking can be found at the interface of the lime and brick 
dust and the sand particles, as was foimd in mix 2. 



105 




2^Aȣ*i<^ 



Photo 11 - Microphotograph, 10 X Mix 4 



Mix 4 



In this mix, lime mortar modified with limestone dust, the 
microcracks range in measurement at approximately 4-6 fim or 0.048 to 0.072 
mm wide. These cracks are a little larger than those found in mix 1. 
However, these microcracks were the largest observed amongst the mixes. 
The cracks are both in the lime matrix and at the interface of the lime and 
limestone dust. The existence of microcracking around the porous particulate 
is expected, as no special reaction or chemical bonding appears to be formed 
between the lime and limestone dust. The microcracks are probably the result 
of the absorption of available water from the paste by the limestone dust. 



106 




icrocracking in the lime paste ' 







Photo 12 - Microphotograph, 10 X Mix 5 



Mix 5 



In this mix; lime sand and brick dust 2, microcracks measure from 1 to 
3 |im or 0.012 to 0.036 mm wide and appear to be fewer than in the other 
samples. These microcracks appear to be in the paste matrix, and around the 
sand. There does not appear to be microcracking around the brick dust 
particles. 



107 



Discussion of Observations 

The presence of microcracking in all the mixes indicates that the 
addition of a brick dust does not eliminate microcracks in lime-based mortars. 
However, the addition of brick dust does reduce the size and number of the 
microcracks. The addition of BD 2 to the lime-based mixes tends to reduce the 
size and number of microcracks more than does BD 1. The difference in 
proportions of BD 1 does not seem to have any effect on microcracking. 

The addition of the limestone dust seems to increase the size and 
number of microcracks in the lime-based mixture. However, these cracks 
could be caused by the limestone dust absorbing available water in the mix, 
and thus causing microcracking in the lime. This mix was particularly dry at 
the time of initial curing. The same phenomenon appeared to have occurred 
in the setting rate of the mixes. Section 2.6.4, whereby the setting was impeded 
by a reduced water content. 

The minimizing of microcracking in a mortar is sought after in the 
field, as microcracks significantly reduce durability. Microcracks permit water 
and deleterious solubles to enter and wick deeper in to the masonry system 
where they can become trapped. As well, microcracks create weaknesses in 
the mortar, and may result in larger cracks. The addition of brick dust to 
lime-based mortars does seem to reduce the size and amount of 
microcracking rendering a more durable cured matrix. 



108 



In relating these observations to 2.6.12, Resistance to Salt Attack, no 
correlations can be made. Samples with the least microcracks, mix 2, 3 and 5 
had no consistent resistance to salt attack. Similarly, mix 4, had the largest 
microcracks but yet performed comparatively well in the salt resistance 
testing. 






109 



2.6.14 Microstnicture of Mortar Mixes 

Additional study of the microstructure of the mortar mixes involved 
the utilization of scanning electron microscopy to permit observation of the 
samples under greater magnification coupled with X-ray analysis of the 
constituent elements. For the purposes of this examination, SEM was used in 
an attempt to view the relationship of the constituents and the interface of 
lime and brick dust. Mapping of the constituent elements of the mixes was 
also conducted. 

Apparatus - 1) Prepared samples of mortar mixes 2) JAOL 6400 Scanning 
Electron Microscope equipped with X-ray analyser. 

Methodology - After a six month curing period samples of Mix 1, Mix 2, Mix 
4, Mix 5 and BD 1 and BD2 were carbon-coated and observed using the SEM. 
Each sample was observed on the SEM and a photo taken of a representative 
area. Qualitative energy dispersive x-ray analysis was also conducted on each 
sample. 

The photographs and the elemental analysis generated from the SEM 
are included in this report. This experiment was conducted at the Laboratory 
for Research on the Structure of Matter at the University of Pennsylvania on 
July 19, 1994 under the direction of Dr. Xue Chin Wong. 



110 



Observations 



Brick Dust 1 













^^^^H^H^HQ^^B brick dust> 






• ?^-:'' T**..- i^ ^ "^ ■■ 


SB^pMrM .'1 '"f-^-''- ^v 1 


^KM 






i##^-::^ 


'-.rr^.; - ;: ^ 

1 00^-'m 
XI 10 15rn^tos. 













Photo 13 - SEM microphotograph, Mag. x 110, Brick Dust, (BD 1) 

The particles are generally subrounded and highly porous with rough 
surfaces ranging from 300 \im to 75 |im (based on sieve analysis). 



Ill 



X-RRV: - 10 keU Nindow : Be 

Live: 300s Preset: 300s Remaining: Os 

Real: 31 Hs H'/, Dead 




< -.1 5.023 keU 10.1 > 

FS= 4K ch 512= 97 cts 

MEM1:hrick dust Cmartin) 



Graph - Elemental Spectragram, Brick Dust, BD 1 

Elemental analysis of brick dust 1 indicates a high silicon content as 
would be expected. Other elements detected include aluminum, calcium, 
potassium, iron and trace amounts of titanium. The high silicon content of 
the brick dust suggests the presence of silica and the potential pozzolanic 
reactivity of the material. 



112 



Brick Dust 2 




Photo 14 - SEM microphotograph, Mag x100. Brick Dust 2, (BD 2) 

Particles are subangular to subrounded surface. They range in size 
from 300 ^im to 75 |im (based on sieve analysis). 



d 



113 



X-RRV: 0-10 keU Nindow : Be 
Live: 199s Preset: 300s Remai ni ng: 101s 
Real: 219s 9'/. Dead 



T 




F 



< -.1 5.023 keU 10.1 > 

FS= SK ch 512= 129 cts 

MEM1 :i)r i ck dust-wi 11 iamsburg 



Graph - Elemental Spectragram, Brick Dust 2, (BD 2) 

Elemerital analysis of brick dust 2 indicates silicon as the primary 
constituent. Other accessory elements detected include aluminum, calcium, 
iron, maganese and titanium. BD 2 is similar in general composition to BD 1. 



114 



Mixl 




Photo 15 - SEM microphotograph, Mag. x100, Mix 1 (1 part lime to 3 parts 
sand) 

Interface between sand particle and the lime paste matrix. 



115 



X-RnV: 

Live: 

Real: 



- 10 keU Window : Be 

S5s Preset: 300s Remaining: 215s 
94s 10?i Dead 




5.023 keU 

ch 512= 



MEMI: sample 1-1/s 



10.1 > 
54 cts 



Graph - Elemental Spectragram, Mix 1 



Elemental mapping of the lime and sand mix reveals a high content of 
calcium attributed to the lime paste binder. Trace quantities of magnesium, 
aluminium, silicon, potassium, titanium, and iron can be attributed to 
impurites in the lime and the sand. 



J 



116 



Mix 2 




Photo 16 - SEM microphotograph, Mag x1200, Mix 2 (1 part lime, 3 parts sand 
and 1 part brick dust) 



The addition of brick dust to the Ume mixture appears to result in a 
microstructure different than mix 1. The particles of brick dust appear to be 
covered with lime, which bridges the interstitial space between the sand 
particles. 



117 



X-RflV: - 10 keU Nindow : Be 

Live: 300s Preset: 300s Remaining: Os 

Real: 321s 77, Dead 





< -.1 5.023 keU ■? 10.1 > 

FS= SK -' ch 512= 109 cts 

MEMi: sample 2 l/s/bd1 



Graph - Elemental Spectragram, Mix 2 

The addition of brick dust to the lime and sand mix is demonstrated by 
the large silicon peak and an increase in the presence of aluminum. 



118 



Mix 4 




Photo 17 - SEM microphotograph, Mag x1200. Mix 4 (1 part lime. 2.5 parts 
sand and 1 part limestone dust) 



Here limestone particles are clearly discemable and do not appear to 
have good contact with the lime binder.. 



119 



X-RRV: - 10 keU Nindow : Be 

Live: 3005 Preset: 300s Remaining: Os 

Real: 315s 5'/. Dead 




< -.1 5.023 keU 10.1 > 
FS= 4K ch 512= 117 cts 
MEMis sample H-l/s/lsd 



Graph - Elemental Spectragram Mix 4 

Elements detected include silicon, calcium, aluminum and potassivun. 
The silicon is contributed from the sand in the mix. 



120 



Mix 5 




Photo 18 - SEM microphotograph, Mag. x1200, Mix 5 (1 part lime, 2.5 parts 
and 1 part brick dust 2) 



Brick dust particles can be clearly identified in the lime matrix. As 
demonstrated in mix 2, the brick dust particles are covered by the lime. The 
lime appears to be strongly attracted to the brick dust. 



121 



X-RRV: - 10 keU Window : Be 

Liv/e! 222s Preset: 300s Remai ni ng: 7Ss 
Real: 241s BX Dead 



flllllllllMnnnhiTnniim 



F F 



< -.1 5.023 keU 10.1 > 

FS= SK ch 512= 100 cts 

MEMI: sample 3-l/s/hd2 



Graph - Elemental Spectragram, Mix 5. 

The elements identified in this mix reflect those in Mix 2. Peaks 
representing calcium and silicon dominate, while aluminum is also detected. 



122 



2.6.15 Porosity as Measured by Pore Size Distrubution 

Studies have shown that the porosity of cured mortar is an important 
property as high porosity leads to poor strength and adhesion and low 
porosity leads to poor frost or salt resistance. The right level of porosity has 
been established at approximately 15% ± 3% in order to achieve high frost 
resistance, good workability and bond strength, ^^i 

The porosity of a mortar is a function of binder type, aggregate, mixing, 
water content and curing conditions. As an attempt was made to keep these 
factors consistent amongst the mixes, any differences in porosity should be a 
result of the addition of the brick and the limestone dusts. 

The porosity of a mortar can be determined by the use of a mercury 
porosimeter or can be measured optically using microscopy. For the purposes 
of this experiment, porosity was determined by measuring the pore size 
distribution of a given area of the mortar sample. 

Measuring the pore size of a sample differs from measuring 
microcracking, in that the cracks are long and narrow whereas voids are open 
space of any shape and size. The measurement is expressed as a percentage of 
a given area of the sample. A certain amount of operator error does exist, but 
more than one sample area was observed and the average measurements 
were calculated. 



^31 W. H. Harrison and G. K. Bowler, "Aspects of Mortar Ourability, " T ransactions and Toumal 
of the Institute of Ceramics. August 1989, 6. 

123 



Methodology - After a 120 day period of curing, thin sections of the samples 
were made. Thin sections were observed under plane polarized transmitted 
light and the pore sizes were measured using a grid micrometer. Pore size 
was measured using Martin's diameter defined as the dimension that 
divides a randomly oriented pore into two equal projected areas. Martin's 
diameter is the simplest means of measuring and expressing the diameters of 
irregular pores and is considered sufficiently accurate when averaged for a 
large number of pores. Using a calibrated grid micrometer, the pore size was 
measured. This procedure was repeated in three representative areas for each 
sample and averages were calculated and expressed as percentages of a range 
of pore sizes found in the total area studied. 

Apparatus - 1) prepared thin section, 2) polarized light microscope, 3) grid 
micrometer. 



Results 

Table 19 - Mean Pore Size Distribution of l\/lortar IVIixes 

as a % 



Expressed 



Mix 


1- 5 }xm 


6-9^m 


10 -14 ^im 


1 5 -20 |im 


Mix 1 (lime & sand) 


35% 


42% 


14% 


7% 


I\/Iix2 (lime, sand & BD1) 


46% 


30% 


23% 





Mix 3 (lime, sand & BD1) 


39% 


35% 


19% 


7% 


Mix 4 (lime, sand & LSD) 


21% 


22% 


27% 


30% 


Mix 5 (lime, snad & BD2) 


64% 


24% 


11% 






124 



Table 20 - Mean % Porosity as measured by Pore Sizes of IVIortar 
Mixes 



Mix 


% Porosity 


Mix 1 (lime & sand) 


17% 


Mix 2 (lime, sand & BD1) 


14% 


Mix 3 (lime, sand & BD1) 


16% 


Mix 4 (lime, sand & LSD) 


20% 


Mix 5 (lime, sand & BD2) 


14% 



Discussion of Results 

Although a certain margin of error exists by calculated the pore size 
and pore size distribution optically, error was slightly reduced by examining 
three different areas of the sample and expressing the results as an average. 
An examination of the results of pore size distribution. Table 19, reveals that 
the addition of brick dust to the mixes does reduce the size of the pores. As 
more fine particles are added to the mixture the spaces and sizes of the spaces 
are reduced. In the case of Mix 4, larger pore size were found even though the 
more fine particles were added to the mix. The pore sizes of Mix 4 are 
probably related to the high rate of microcracks exprerienced in this mixture. 

In calculating the percent porosity based on pore sizes, the mixes tend 
to fall within the acceptable level of 15% ± 3%. Mix 4 falls just outside of this 
level, however, it has been established that this mix was hampered from a 
low water content during initial mixing. 



A 



125 



J 



2.7 Conclusions 

In this experimental program certain trends in the behavior of brick 
dust added to lime-based mortars have been witnessed. Although the results 
do not indicate significant changes in behavior of the lime-based mortars, 
statements can be made about the role of brick dust as a pozzolanic additive. 
As pozzolanas must be tested in combination with other materials, many 
variables exist that hinder the formulation of tangible conclusions. 

A certain degree of uniformity was achieved in the mixing, curing, and 
standardized testing which reduced many of the variables in this research. 
However, a margin of error existed as many of the tests were subjective or 
involved using non precision equipment. To reduce this margin of error 
statistical analysis was conducted when possible. 

The results of the experimental program appear to be the first 
quantifiable data produced on the properties of these North American mortar 
materials. Future testing on these or related materials can use these results 
for comparative purposes. The results have potential implications for related 
research, for example future phases of the Smeaton Project. The materials, 
the selected standardized testing and the results could serve as a guide for 
future avenues of research. Similarly, the problems incurred in this 
experimental program could be avoided. 

In terms of the materials selected for the program, it can be stated that 
the lime putty and both types of brick dust demonstrate promise for use in the 
repair and conservation of historic structures. Although the focus of this 



126 



research was not to evaluate the Ume putty, Mix 1 did perform well in its 
resistance to salt attack. Both types of brick dust appear to impart pozzolanic 
properties as witnessed by experiments like setting rate and depth of 
carbonation and observations like microcracking and pore size distribution. 
BD 2 appeared to perform slightly better than B D 1, on many of the 
comparative tests such as setting rate, water vapor transmission, depth of 
carbonation. As well BD 2 appeared to exhibit less microcracking than did BD 
1. At this time, this difference can not be explained. 

The differences in proportioning between Mix 2 (1:3:1 - lime:sand:BD) 
and Mix 3 (1:2 1/2:1 - lime:sand:BD), did not appear to impact their behavior 
in the experimental program. At the onset of the research, it was thought 
that the tests and examinations would be discreet enough to observe 
behavioral differences in the mixes. The selected program did not detect any 
distinguishable trends due to the difference in proportioning as the difference 
was too small. 

Mix 4, modified with limestone dust rather brick dust, was included in 
the experimental program to evaluate whether the brick dusts were behaving 
as a pozzolana and /or a porous particulate. As porous particulate may have 
ameliorating affects on lime-based mortars, it is important to juxtapose the 
behavior both materials impart on lime mortars. Clearly a distinction could 
be made between the properties imparted by the two different materials. In 
terms of setting rate, depth of carbonation, and microcracking, the brick dusts 
distinguished themselves as imparting pozzolanic properties. However, it 
was discovered at the end of the testing program that the limestone dust may 
have been too small to behave as a porous particulate. In the case of this 



127 



experiment it did serve to distinguish the role of the addition of the brick dust 
to the hme based mortar as a control. 

This experimental program did serve to evaluate the available North 
American standardized tests for mortars. Many of these tests are intended to 
evaluate cement-based materials and not lime-based materials. It appears that 
these two materials can not be measured with the same scale, as lime-based 
and cement-based mortars do not have the same properties. Tests that clearly 
demonstrated this observation are those that measure shrinkage and flow. 
Both tests yielded values that could not be used to distinguish the properties 
of the materials. In future testing programs, these tests should be substituted 
by ones that can address the behavior of lime-based mortars. 

The results of the experimental program were significantly influenced 
by the period of time available for this research. Although some comparative 
tests were conducted on fresh mortar, performance and durability tests were 
conducted after a 120 day curing period. This period of time may not have 
been sufficient, as pozzolanic reaction in lime-based mortars is a time 
dependent process. Consequently the results derived after a 120 day period 
may be different than those observed after a longer period of time. 



128 



2.8 Recommendations for Further Research 

The completion of this experimental program has resulted in many 
recommendations that would improve future reseach on this subject. These 
recommendations include: 

1) Moist cabinets should be used for the initial curing (30 days) of 
lime/pozzolana mortars. This procedure provides essential moisture 
for the pozzolanic reaction to occur and some controls over variables 
for better compatibility of results. As well, the experimental results 
will be more comparable as this procedure is practised by researchers in 
the field. 

2) The use of the flow table as a test to indicate workability should not 
be used as a comparative test, but should be used to establish 
consistency amongst the mixes. The correct proportion of water added 
to the mix could be established by using the flow table, thus reducing 
the risk of comparing mixes that have differences in basic properties. 

3) In addition to firing temperature and particle size, the mineralogy of 
the brick dusts should be established. 

4) Some of the experiments on hardened mortar should be conducted 
after a longer curing period. One year of curing should result in more 
conclusive results. 



129 



5) Improvements need to be made to test skrinkage of lime-based 
materials. The present standards for cements and test methodology do 
not yield effective results. 

6) The rate of water absorption should be compared to the rate of water 
evaporation, as it is important to understand how water or moisture 
can escape the mortar. 



130 



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Baronio, Guilia, and Luigia Binda. "Study of the Interface between Binder 
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Blake, Marion Elizabeth. Ancient Roman Construction in Italy from the 
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Boynton, Robert S. Chemistry and Technology of Lime and Limestone. New 
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Bogue, R.H. The Chemistry of Portland Cement,. Rheinhold Publishing 
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Burnwell, George Rowdon. Rudimentary Treatise on Limes, Cements, 
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Campbell, Donald H. Microscopical Examination and Interpretation of 
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Cowper, Alfred Denys. Lime and Lime Mortars. London: His Majesties 
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131 



Cummings, Uriah. American Cements. Boston: Rogers and Manson, 1898. 

Dancaster, Ernest Augustus. Limes and Cements, their nature, manufacture 
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Dibdin, William Joseph. Lime, Mortar and Cement; Their characteristics and 
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Draffin, Jasper O. "A Brief History of Lime, Cement, Concrete and Reinforced 
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Eckel, Edwin C. Cements, Limes and Plasters. New York: J. Wiley and Sons, 
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Furlan, V. "Causes, Mechanisms and Measurement of Damage to Mortars, 
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Gilmore, Quincy Adams. Practical Treatise on Limes, Hydraulic Cements and 
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132 



Higgins, Bryan. Experiments and Observations made with the view of 
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Knibbs, Norman Victor and B. J. Gee. Limes and Limestone: The Origin, 
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Lazell, Ellis Warren. Hydrated lime; History, manufacture and uses in plaster, 
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Lea, F. M. The Chemistry of Cement and Concrete. New York: Chemical 
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Lesley, Robert W. The History of the Portland Cement Industry in the United 
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Malloy, D. J. Lime, Plaster and Plaster Products. Washington D. C: The Lime 
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140 



f » 



International Conferences 

Symposium on Use of Pozzolanic Materials in Mortars and Concrete. 
Presented at the First Pacific Area National Meeting, American Society for 
Testing Materials. San Francisco, October, 1949. Philadelphia: ASTM, Special 
Technical Publication No. 99, 1950 

Second International Conference on Fly Ash, Silica Fume, Slag and Natural 
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Third International Conference on Fly Ash, Silica Fume, Slag and Natural 
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Standards and Studies of Standards Applied to the Study of Lime and 
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American Concrete Institute, Standard Definitions of Terms Relating to 
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141 



Appendix 1 - Results of Compressive Strength Testing 



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