THE EFFECT OF EGG ALBUMEN ON THE PHYSICAL AND MECHANICAL PROPERTIES OF LIME MORTAR

1Tiong Ling Ling, 2Md Azree Othuman Mydin 1,2School of Housing, Building and Planning, Universiti Sains Malaysia 11800, Penang, Malaysia

1tionglingling_93@hotmail.com, 2azree@usm.my

ABSTRACTMost historic and traditional mortars were made with lime. Due to their nature and function, lime mortars erode and need to be replaced. However, lime mortars cannot be replace by the cement-based mortars due to incompatible with the construction materials of the original masonries, cement-based mortar doesn’t respect the features of the originally applied materials and traditional technology then will causing structural and aesthetic damage. The best solution is still conserving those heritage buildings by using the lime as it was proved that lime is mechanically compatible [1][2][3] with the old bricks and stones which are relatively weak and porous. There is scare of literary evidence to study the effect of organic materials on mechanical properties of lime mortar. This paper aims to investigate the effect of egg albumen on the mechanical and physical properties of lime mortar. A total of 5 mortar mixtures and 1 control mixture were designed having a constant lime/sand/water ration of 1: 2: 0.035. The control mixture include only lime putty as the binder while the remaining mixtures were mixed with different percentage of egg albumen range from 2% to 10%. An experimental work was carried out to investigate the axial compressive and flexural strength of lime mortar with different percentages of egg albumen and examine the water absorption. The results indicate that the strength of lime mortar increases directly proportional to the percentage of egg albumen added into the lime mortar until it reached 6% of the egg albumen. It dropped when the 8% and 10% of the egg albumen added into the lime mortar.

Keywords: Lime mortar; Lime putty; Egg Albumen; Workability; Compression test; Flexural Test; Water Absorption

1. INTRODUCTION

Currently, lime has become one of the principal materials used in the conservation and restoration of historic buildings. It is one of the most suitable and long lasting building materials used in mortars, plasters, and paints for centuries. This is because lime has many attributes that make it suited for use in masonry restoration. These mortars have a high mechanical resistance, increased waterproof protection, and antifungal properties. Unlike today’s framed structures with masonry veneers, traditional masonry structures were just that solid masonry [1]. The thickness of the walls kept moisture out of the living space and provided strength. Inevitably, the thickness of the walls also guaranteed they would constantly contain. This all worked very well with lime mortars, plasters, and paints (lime wash) because lime is able to absorb large amounts of water, and due to its porosity, very easily release the moisture back into the atmosphere. Substitution of modern materials for historic lime based materials can lock moisture into walls causing a myriad of problems including failure of masonry units, interior water damage and structural failure of interior wythes of the wall [2]. Traditional materials like lime mortar, natural cement, Roman mortar, etc are highly recommended because modern research and history have confirmed that some of them exhibit good compatibility, appropriate strength with ancient buildings, and are more effective than modern materials. The major advantage of lime is that when used in mortars, it has higher bond strength than unmodified non-lime mortars. Lime has a much smaller particle size than other common mortar binders (e.g. 1/500th the particle size of Portland cement) consequently lime more effectively fills and bonds the pours of your brick or stone. Additionally, because lime creates creamier mortars, there is no need to introduce air entraining agents to the mix. Air entrainment creates bubbles and lessens the surface area contact between the mortar and the brick and stone. The use of traditional lime materials exist some challenges. Lime cures differently and by different mechanisms than modern materials. The curing process can also be more affected by adverse weather conditions. In fact, masons and craftspeople well versed in modern materials often have problems installing lime materials. Figure 1 show the simplified lime cycle and hydraulic set [3].

This simple lime cycle is based on pure limestones producing ‘air limes’ (also termed ‘non-hydraulic’ limes). Lime production from limestones containing reactive materials (siliceous or argillaceous limestones), proceeds via a more complex cycle to produce ‘natural hydraulic limes’ (NHLs). Hydraulic limes set not only by carbonation, but via hydration reactions occurring between the silicate and aluminate components with water and calcium hydroxide. This ‘chemical’ setting mechanism enables the use of hydraulic limes in wet conditions, where air limes would fail to set. Natural hydraulic limes are typically stronger and less vapour and moisture permeable than air limes. The production of lime from limestone via this cycle is a well-established and ancient technology, probably brought to Britain by the Romans. Although the lime production process has remained largely unchanged for thousands of years, on site additions and modifications to the raw material have evolved over time. Builders have experimented with different materials for different applications, often making the lime more workable, quicker setting or achieve water resistant properties. Traditional additives used to achieve these qualities included animal fats and blood, milk and volcanic ash

Figure 1: Simplified lime cycle and hydraulic set

In conservation repair work, it is imperative that an understanding of the building or structure is gained before specifying and undertaking any works. This is particularly important for lime-based works. An original mortar might have inherent defects. Buildings and their surrounding environment may change over time: for example, a residential building may now be a roofless ruin. Repair mortars can, and sometimes should, be designed to perform in a different way from original mortars to meet new performance requirements. Lime mortar was not commonly used until it was utilized by the Greeks and this knowledge of mixing mortar was then took by the Romans around the 1st millennium BC. Another most important reference of lime mortar comes from Vitryvius, a Roman architect, the writer of Opus Incertum, which provide a guide for building works and for mixing lime mortar around 25 BC. Even though the Romans did not fully understand the properties and technology of how hydraulic lime works, they did notice the need of such mortar to include pozzolan such as crushed ceramic, volcanic ash and crushed brick within mortar mix to solve the problems. Romans were great innovators, they constantly looking to improve and experimented by modifying lime mortar mixes with controlled additions of naturally occurring deposits. There is only little known about the use of lime mortar during the fall of the Roman Empire and the medieval period, the traditions continued to have been implemented but on a smaller scale than before. In addition, the use of stone structures and lime as a binder rise rapidly in the construction of numerous castles and churches that built by William the Conqueror within England in 1066. The most significant evolution in the use of pozzolans in lime mortars can be traced back into 18th century. It was found out that burning limestone that containing clay would produce hydraulic product. John Smeaton was the first person who developed hydraulic lime product in 1756 and an Italian pozzolanic earth from Civita Vecchia also added in order to improve the strength. This mixture was used to construct Eddystone Lighthouse. In 1796, Roman cement or natural cement was invented by James Parker. Natural cement mortar was used in construction where masonry was subjected to moisture and high levels of strength were needed due to it had higher clay contents than hydraulic lime products that allow for better strength development. This mixture was widely used until the late of 1800’s. In 1824, Portland cement that consisted of a blend of limestone, clay and other minerals in carefully controlled proportions which were calcined and ground into fine particles was invented by Joseph Aspdin. Portland cement replaced natural cements in mortars due to its consistency and

higher strength. Mix design of different amounts of lime and Portland cement were developed because the addition of Portland cement to lime mortars will help to improve the speed of the construction process for masonry building due to its faster strength development. Due to the newly invented Portland cement, lime mortar was slowly phasing out from construction industry and replaced by Portland cement. In the late 19th century, the importance of preserving the heritage building and historic environment was realized. It requires full understanding of both structural and architectural qualities and the construction materials and methods used in order to successful repair of ancient buildings. However, the knowledge of lime and its inherent qualities, the mainly materials that mostly used in old buildings was lost. As a result, Portland cement based materials was largely applied to the existing lime mortar masonry for the repair and restoration work that carried out in the 20th century. In 1977, Building Research Establishment found that all the masonry buildings that repaired or restored by using the Portland cement tend to deteriorate faster than those without undergone any major repairing and renovation works. The old masonry buildings that repaired with Portland cement or plaster showed the sign of destructive failure in less than ten years. This is because hard cement mortar is physically and mechanically incompatible with old masonry buildings that built by lime products which are relatively weak and porous. It is important to identify the precise nature and means of production of historic mortars and lime based materials. In this study, the organic material which is egg albumen will be added into the lime mortar in order to modify the properties of lime mortar. No sound scientific explanation for the use of egg albumen in lime mortar is available. Nevertheless, egg albumen, due to its protein concentration, is a powerful binding agent since proteins are slightly elastic in nature, as well as tending to bind together. According to S. Chandra and J. Aavik (1987), egg albumen or also can be protein work as air entraining agents in cement mortar. Such additive was used to improve the properties of a mortar before or after set such as workability and durability. Being organic, this type of admixture would be expected to disappear from the mortar relatively rapidly, leaving no detectable traces.

2. LITERATURE REVIEW

2.1 The reason of using lime in mortar/building

Lime was used as universal binding material in mortars and plastering works for most of the historical masonry building. Lime has many advantages and one of the reasons is lime allows buildings to breathe [4]. They are vapour permeable thus reduces the risk of trapped moisture and consequent damage to the building fabric. In addition, lime provides a comfortable environment due to its porous and open textured materials such as lime plaster, it can help to stabilize the internal humidity of a building by absorbing and releasing moisture. Therefore reduces the surface condensation and mould growth. The use of lime has ecological benefits such as less embodied energy than cement; free lime absorbs carbon dioxide in the setting process of carbonation; it is possible to produce lime on a small scale; the gentle binding properties of lime enable full re-use of other materials and small quantities of lime can protect otherwise vulnerable, very low energy materials such as earth construction and straw bales. moreover, lime able to bind gently with the early adhesion because the fine particle size of lime, far smaller than cement, is linked to the root meaning of the word lime, which is “sticky material”. Due to the fine particle size, lime mixes penetrate minute voids in the background more deeply than other materials. They bind gently and the stickiness gives good adhesion to other surfaces. Besides, the characteristics of lime mortars with high free lime content are porous and permeable that allows lime mortars to protect adjacent materials by handling moisture movements through the building fabric and protecting them from harmful salts. The most important characteristic of the lime as to be used in building is self healing. The nature of ground conditions and the elements are such that all buildings are subject to varying degrees of movement over time. When buildings made with lime are subject to small movements they are more likely to develop many fine cracks than the individual large cracks which occur in stiffer cement-bound buildings. Water penetration can dissolve the “free” lime and transport it. As the water evaporates this lime is deposited and begins to heal the cracks. This process is called autogenous or self-healing [5].

2.2 Properties of fresh mortar

According to Mortar Industry Association, it stated that the role of fresh mortar during construction were a very important and complex one, where the mortar must spread easily and remain workable longs enough to enable the accurate laying to line and level of the masonry units. In addition, it also must retain water so that it does not dry out and stiffen too fast, especially when using the absorbent masonry units. As a result, it must then harden in a reasonable time to prevent it deforming or squeezing out.

2.3 Workability of fresh lime mortar

Workability may be defined as the behavior of a mortar in respect of all the properties required during application, subsequent working and finishing. Workability majority depends on water content and retention and internal friction, and this will highly affect compressive and flexural strengths, which in turn will determine the overall quality and durability of a mortar. Water content is the main factor of workability and it can directly determine the initial flow of a mortar. A mortar with higher water content will have larger flow value than the same mortar with less water. Mortar with good workability has characteristic like smooth, plastic quality, it is easily spread with trowel, readily sticks to vertical surfaces, easily extrudes from joints without dropping or swearing and permit easy positioning of masonry units. Moreover, in Masonry design and detailing book, Workability of a mortar was recognized as a complex rheological property including cohesion, adhesion, plasticity, density, viscosity and flowability, and hence there are no standardized tests to measure it. Workability often judged by the mason.

2.4 Permeability of lime mortar

Lime mortar has high porosity and high permeability that allows it to protect the other materials in a building by handling moisture movements through the building and thus protecting masonry materials from harmful salts. Breathability of lime mortar highly help to comfort the people that who using the buildings because it assists the drying out of buildings and able to avoid the problems of condensation. It depends on the high porosity and permeability characteristics of lime mortars [6].

2.5 Egg Albumen

Egg albumen also known as egg white. Depending on the size of the egg, egg albumen represents approximately 58-60% of the weight of the egg and consists of 88% water and 12% dry matter, primarily protein. The white of a large egg contains about 17 calories and no cholesterol. There are 3 parts in the egg albumen which are an inner and an outer liquid layer and in between those a liquid layer thicker consistency. It’s function to prevent external bacteria from penetrating the yolk. Egg albumen is an alkaline solution that contains approximately 40 different proteins. Table 1 below show the list of the proteins found in Egg albumen: [7]

Table 1: List of proteins found in Egg Albumen

Due to high concentration of protein of egg albumen, it could be a powerful binding agent in food. Proteins are slightly elastic in nature, as well as tending to bind together. Egg contains high percentage of protein that composed of amino acids which may influence the cement properties. There are some experimental studies showed that the higher the alkali content in the cement, the lower the ultimate strength of the corresponding tests specimens. According to the study with 199 commercial Portland cement, it was found that the higher the cement alkali content statistically resulted in a higher dynamic modulus of elasticity measured on 20 corresponding concrete specimens after 14 days. It was figure out that the higher alkali content in cement will increases the strength development in the short term but decreases the ultimate strength. [8]. Figure 2 shows the structure of egg.

54% Ovalbumin12% Ovotransferrin11% Ovomucoid4% Ovoglobulin G24% Ovoglobulin G33.5% Ovomucin3.4% Lysozyme1.5% Ovoinhibitor1% Ovoglycoprotein0.8% Flavoprotein0.5% Ovomacroglobulin0.05% Ayidin0.05% Cystatin

Figure 2: Structure of egg [8]

3. EXPERIMENTAL PROGRAM

3.1 Materials used

Materials used in the experiment including: Lime putty, manufactured from Great Lime Factory Co. Ltd; Egg Albumen and normal fine sand. Figure 3 shows that the egg albumen were removed and Figure 4 shows the egg albumen was beaten until it is foamy and stored in an airtight container.

Figure 3: The egg yolks were removed

Figure 4: Egg albumen was beaten until it is foamy and stored in an airtight container

3.2 Instruments used

The instruments that were used to prepare, measure and assess the characteristics of fresh and harden lime mortar including: electronic balance, mortar mixer (Figure 5), wood moulds (prism), vibrating table (Figure 6), flow table (Figure 7), oven, Autotest 3000 BS/ELE Compression Testing (Digital) Machine.

Figure 5: Mortar mixer which is equipped with 10 liter stainless steel mixing bowl and a blade

Figure 6: Compacting the mortars on the vibrating table

Figure 7: The diameter of the lime mortar was measured to determine the workability

3.3 Mix proportioning

The mix proportioning adopted was Lime Putty: Egg Albumen: Fine Sand: Water.

Table 2: Density of each material

Lime Egg albumen Sand Water1400kg/m³ 1040kg/m³ 2650kg/m³ 1000kg/m³

Table 3: Mortar designation ratio for each mix design

Mortar Group Lime Putty Egg Albumen solution Fine Sand Water

0% (Control group) 1 0 2 0.0352% 1 0.02 2 0.0354% 1 0.04 2 0.0356% 1 0.06 2 0.0358% 1 0.08 2 0.03510% 1 0.10 2 0.035

Table 4: Weight of each material needed for each mix design

Mortar Group Lime putty (kg) Egg Albumen (kg) Fine Sand (kg) Water (kg)0% (Control

group)2.2606 0 4.5213 0.0791

2% 2.2321 0.0446 4.4642 0.07814% 2.2043 0.0882 4.4085 0.07716% 2.1771 0.1306 4.3542 0.07628% 2.1506 0.1721 4.3013 0.075310% 2.1248 0.2125 4.2496 0.0744

3.4 Specimen preparation and curing

All the specimens were prepared according to the prescribed in ASTM C109/C109M-07[9]. All the mortars were mechanically mixed in laboratory by using mortar mixer. After that, the mortars were mechanically compacted in prism moulds by using vibration table. These specimens compacted in three layers as prescribed in ASTM standard. All the specimens allowed to cure in the moulds at least 24 hours prior to de-molding and allowed it in air-dried condition until reached the testing ages that is suitable to carry out the test. Figure 8 shows the prism wood mould with specimens

Figure 8: The prism wood mould with specimens

3.5 Experimental work

Egg albumen was added into lime mortar as an additive. The different proportion of admixture (egg albumen) will be 0%, 2%, 4%, 6%, 8% and 10%. Total 6 mix design groups. The prisms of 40x40x160mm were tested. The lime mortar specimens will be tested for following tests:

i. Workability of the fresh lime mortar with different percentages of egg albumen that according to BS EN 1015-3[10] and ASTM C109.

ii. Flexural strength after 7 days, 14 days, 21 days and 28 days curing using standard prism specimen according to ASTM C348-97[11]

iii. Compressive strength after 7 days, 14 days, 21 days and 28 days curing by using broken prism according to the ASTM C349-97[12]

iv. Water absorption test for 7 days, 14 days, 14 days and 28 days after the specimens had been stored in the oven for 3 days.

4. ANALYSIS OF RESULT AND DISCUSSION

The results obtained from the experimental programs of testing the flexural strength and compressive strength of lime mortar containing egg albumen in different percentages. Before flexural and compression test, the testing of workability of fresh mortar were carried out in order to study how does different percentage of egg albumen solution will affect the workability of the fresh mortar and the results were recorded. After that, the water absorptions of lime mortar containing egg albumen in different percentages were examined.

4.1 Workability of fresh lime mortar

The workability of the control group lime mortar that without any addition of egg albumen is 16.00cm. Based on the Figure 9, it is clearly showed that lime mortar that with 10% of egg albumen has the lowest workability, which is only 15.9cm. When 2%, 4% and 6% of egg albumen added into the lime mortar, mortar consistency increased to 16.3cm, 16.6cm and 16.8cm respectively. However, when 8% and 10% of egg albumen were added into lime mortar, the consistency of lime mortar started to decrease, which less than 16.8cm.

0% 2% 4% 6% 8% 10%15.60

15.80

16.00

16.20

16.40

16.60

16.80

17.00

Workability of fresh lime mortar

Percentage of Egg Albumen

Wor

kabi

lity

(cm

)

Figure 9: Workability of fresh lime mortar with different percentages of egg albumen

The reason that can explain this phenomenon probably is because as the concentration of egg albumen increased, the adhesive strength of egg albumen solution also increased. For egg albumen solution which have concentration until 6%, the lime and sand particles easier to slide with each other due to the egg albumen function as lubricant, thus made the mortar easier to spread. However, when the concentration reached 8%, the workability result dropped due to the high adhesive strength of it. High adhesive strength making the lime and sand particles easily to stick together and then prevent it slides with each other. In this condition, the microstructure of lime mortar will be less compacted and hence lead to lower compressive strength.

4.2 Compressive Strength

As shown in the Table 5 and Figure 10, the lime mortar at the addition of 2%, 4% and 6% of egg albumen on both day 7, day 14, day 21 and day 28 show an increase in the compressive strength as compared to the control mix of lime mortar which without any addition of egg albumen. In my opinion, this phenomenon is probably due to the effect of the proteins in the egg albumen on the mortar. This is because the potential of the proteins that able for bonding interactions with other proteins and surfaces. This can be proved by an experiment that if the egg albumen was spilled on two eggs and until it is dried, it is hard to pull two eggs without breaking at least one of them. The compressive strength of lime mortar increases until the percentage of egg albumen reached 6%, it started to fall when 8% and 10% of egg albumen were added into the lime mortar. It can proved that addition of more amount of egg albumen, the alkali content of mortar will increase since the egg albumen is an alkaline solution which may have harmful effect on the mechanical properties of aggregates which are not susceptible to alkali-silica reaction. [8]

Table 5: Compressive Strength of lime mortar with different percentages of egg albumen

Test Day COMPRESSIVE STRENGTH (N/mm2)0% 2% 4% 6% 8% 10%

7th day 1.4 1.6 1.7 1.9 1.7 1.314th day 2.3 2.8 2.8 3.3 2.8 2.121st day 3.2 3.4 3.7 3.9 3.5 2.828th day 3.3 3.5 3.7 4.1 3.4 3.1

0% 2% 4% 6% 8% 10%0.00.51.01.52.02.53.03.54.04.5 7-day

14-day21-day28-day

Percentage of Egg Albumen (%)

Com

pres

sive

Stre

ngth

(N

/mm

²)

Figure 10: Compressive Strength of lime mortar with different percentages of egg albumen

4.3 Flexural Strength

As seen in the Table 6 and Figure 11, the flexural strength of lime mortar showed increasing when 2% of egg albumen added into lime mortar until 6% of egg albumen was added on all the testing ages, which is day 7, day 14, day 21 and day 28. The lime mortar that contained 6% of egg albumen showed the highest flexural strength compared to other mix design. However, the flexural strength of lime mortar started to drop after 8% and 10% of egg albumen were added into the lime mortar. Flexural strength can be influenced by many factors. The decrease strength of lime mortars can be caused by formation of micro cracks due to drops in humidity in the room where the specimens were stored [13]. According to the recorded results, it can be seen that the lime mortar with 6% of egg albumen has the highest flexural strength while lime mortar with 10% of egg albumen is the weakest mix design groups.

Table 6: Flexural Strength of lime mortar with different percentages of egg albumen

Test Day FLEXURAL STRENGTH (N/mm2)0% 2% 4% 6% 8% 10%

7-day 0.32 0.39 0.41 0.48 0.44 0.3414th day 0.57 0.72 0.74 0.84 0.71 0.5421st day 0.79 0.87 0.93 0.99 0.89 0.71

28th day 0.85 0.89 0.95 1.05 0.86 0.82

0% 2% 4% 6% 8% 10%0.00

0.20

0.40

0.60

0.80

1.00

1.20 7-day14-day21-day28-day

Percentage of Egg Albumen

Flex

ural

Str

engt

h (N

/mm

²)

Figure 11: Flexural Strength of lime mortar with different percentages of egg albumen

4.4 Water Absorption

Table 7 and Figure 12 showing the result of water absorption test of lime mortar with different percentages. Based on the date collected, it shows that after 30 minutes of immersion in water, the water absorption of lime mortar showed decreasing when 2%, 4% and 6% of egg albumen were added into lime mortar on day 7 , day 14, day 21 and also day 28. However, it started to increase again during the addition of 8% and 10% of egg albumen. The lime mortar with 10% of egg albumen has the highest water absorption compare with other mix design due to it is less compacted and many pores, which are easily accessible to water if compare with other egg albumen lime mortars. While the mix design group that absorbed the lowest percentage of water is lime mortar that with 6% of egg albumen. It can be stated that the addition of egg albumen can decreasing the capillarity by various mechanisms. It makes a thin film spread evenly in mortar’s structure, covering the grains of binder, which results in the decreased connectivity between pores and this limited water transport. Furthermore, the addition of egg albumen is also changing the pore size distribution in a way which decreases the capillary transport.

Table 7: Water Absorption of lime mortar with different percentages of egg albumen

Test Day WATER ABSORPTION (%)0% 2% 4% 6% 8% 10%

7th day 17.8% 17.1% 16.2% 15.2% 16.6% 17.9%14th day 17.6% 16.9% 15.9% 14.9% 16.3% 17.7%21st day 17.3% 16.6% 15.3% 14.3% 16.0% 17.5%28th day 17.1% 16.6% 15.1% 14.1% 15.8% 17.3%

0% 2% 4% 6% 8% 10%12.0013.0014.0015.0016.0017.0018.0019.00

7-day14-day21-day28-day

Percentage of Egg Albumen

Wat

er A

bsor

ption

(%)

Figure 12: Water Absorption of lime mortar with different percentages of egg albumen

5. CONCLUSION Based on all the data obtained from laboratory investigation done on lime mortar mixes with various percentages of egg albumen, the following conclusion can be derived: The workability of fresh lime mortar increases when 2%, 4% and 6% of egg albumen added into lime

mortar. Lime mortar that with 10% of egg albumen has the lowest workability. Compressive and flexural strength of lime mortar increases with the increasing percentage of egg albumen

that added into lime mortar until it reached 6% of egg albumen. The addition of 8% and 10% of egg albumen made the compressive and flexural strength started to decrease. Lime mortar that containing 6% of egg albumen has the highest compressive and flexural strength compare

to other mix design groups. It is believed that the characteristic of egg albumen act as a lubricant in lime mortar made the mortar easier

to compact and it also filled the smaller void inside the mortar, thus it is stronger than plain lime mortar. 6% egg albumen lime mortar has the lowest percentage of water absorption. The addition of egg albumen changing the pore size distribution in a way which decreases the capillary

transport. The high surface water absorption decreased the compressive strength of lime mortar.

References

[1] Groot, C. (2012), RILEM TC 203-RHM: Repair mortars for historic masonry. Performance requirements for and plasters. Materials and Structures, 45, pp. 1277 – 1285.

[2] Hughes J.J. (2012), RILEM TC 203-RHM: Repair mortars for historic masonry. The role of mortar in masonry: an introduction to requirements for the design of repair mortars. Materials and Structures, 45, pp. 1287-1294.

[3] Maurenbrecher P. (2012) RILEM TC 201-RHM: Repair mortars for historic masonry. Requirements for repointing mortars for historic masonry. Materials and Structures, 45. Pp. 1303-1309.

[4] Jessica Snow and Clare Torney, (2014),”Short Guide: Lime Mortars in Traditional Buildings”, National Conservation Centre, Published by Historic Scotland, February 2014

[5] B. Lubelli, T.G. Nijland, R.P.J. van Hees, “Self-healing of lime based mortars: microscopy observations on case studies”, Faculty of Architecture, Delft University of Technology, the Netherlands, TNO Built Environment and Geosciences, Delft, the Netherlands.

[6] Andrew J. Edwards BSc (Hons), (2005), “Properties of hydraulic and non-hydraulic limes for use in construction”, Napier University, School of the Built Environment

[7] http://en.wikipedia.org/wiki/Anatomy of an egg[8] N. smaui, M.a, Berube, B. Fournier, Et. Al, “Effect of alkali addition on the mechanical properties and

durability of concrete”, 1740 Boulevard Lionel – Boulet, Canada, 2004[9] ASTM Standard C109/ C109M-07, (2007), “Standard Test Method for Compressive Strength of

Hydraulic Cement Mortars (Using 2-in. or [50mm] Cube Specimens)”, ASTM International, West Conshohocken, PA, 2007, DOI: 10.1520/C0109_C0109M-07, www.astm.org.

[10] British Standards Institution (1999) BS EN 1015-3:1999, “Methods of test for mortar for masonry. Determination of consistence of fresh mortar (by flow table)”, London: BSI, http://shop.bsigroup.com/

[11] ASTM Standard C348-97, (1997), “Standard Test Method For Flexural Strength of Hydraulic-Cement Mortars, ASTM International, West Conshohocken, PA, 1997, www.astm.org

[12] ASTM Standard C349-97, (1997), “Standard Test Method for Compressive Strength of Hydraulic-Cement Mortars (Using Portions of Prisms Broken in Flexure), ASTM International, West Conshohocken, PA, 1997, www.astm.org

[13] Hayri UN, Bulent Baradan, (2011), “The effect of curing temperature and relative humidity on the strength development of Portland cement mortar”, Department of Civil Engineering, Pamukkale University, Denizli, Turkey, Department of Civil Engineering, Dokuz Eylul University, Izmir, Turkey.