additives influence on the earth characteristics used in ... · 2015, volume 12, issue 1 additives...

ECOTERRA - Journal of Environmental Research and Protection

www.ecoterra-online.ro 2015, Volume 12, Issue 1 7

Additives influence on the earth characteristics used in vernacular construction 1,2Gabriela Călătan, 1Andreea Hegyi, 1Carmen Dico, 2Calin Mircea

1 INCD URBAN-INCERC Cluj-Napoca Branch, Cluj-Napoca, Romania; 2 Technical University of Cluj-Napoca, Cluj-Napoca, Romania. Corresponding author: A. Hegyi, [email protected]

Abstract. Since the 90s there were numerous research studies attesting possibility of using sandy clay as a building material for making structures that meet the criteria of sustainability, reliability and thermal comfort, bringing economic benefits and especially environmental. This work shows the possibility of improvement of physical and mechanical characteristics of sandy clay (axial shrinkage, density, mechanical strength), by introducing the mixture of filler material (sand, lime paste, bone glue, NaCl, NaOH). The experimental results showed major benefits obtained by using sand (reducing axial contractions, increased bulk density (indicator Storage/disposal of heat). The mixture with 65% sandy clay, 35% sand and 33% water presented physico-mechanical indicaters that fits best within the limits reported in the literature. By inserting slurry lime or substituting mixing water with NaOH solutions and/or bone glue, it identified the opportunity for achievement mixtures that meet the provided criteria with the condition of concomitant use of the sand, too. Substituting of the mixed water with NaCl solution did not help to improve the parameters studied. To determine the optimal proportions and combining modalities of filler materials, further studies are needed in order to optimize the physical-mechanical parameters that were found wanting, but to be kept the identified benefits (workability, plasticity, small axial shrinkage, high mechanical resistance). The studied sandy clay is a suitable choice, but it is necessary to add other filler materials, the sand being essential. Key Words: sandy clay, fillers, strength, density, axial shrinkage.

Introduction. Since ancient times people have tried to create their comfortable living conditions using available materials at the time. Currently there are many technologies and building materials, industrial made, that cause pollution, loss of vegetation, erosion, flooding, changes in micro-climate and increasing of the climate instability phenomena (Pushplata & Kumar 2012; Kumar & Munoth 2011).

Vernacular materials, as their name implies, they were always at the hand users and further shows the advantages of operation, easy assembling and maintenance work, through environmentally friendly technologies, with low energy consumption and low cost.

They have a low pollution potential and after the end of the life structure can be easily reintegrated into nature. There are studies that attest to the durability of buildings made with local materials and indigenous techniques (Bui et al 2009a; Pushplata & Kumar 2014) in different geographical and climatic conditions. Although the interest in these materials increases from year to year, is still recorded an inertia of building materials users, who prefer classical construction materials, sintered ones (cement, concrete, steel, glass). This may be due to specific problems vernacular buildings: the necessity to realize thicker walls so to be achieved the stability and reliability, namely that the thermal insulation, need periodic maintenance, the need for skilled workers to work with such materials, sensitivity to water erosion if there is an inadequate treatment of external surfaces and, why not, a much longer construction period, being a technological process that is difficult to automate. One of the most commonly used vernacular materials is the clay soil. It is suited for masonry bodies of soil mixed with sand, lime, oils, natural resins, etc.. Rewarding good behavior and durability of constructions made of beaten soil and ground masonry buildings is documented since the nineteenth century (Arango-Gonzalez 1999).

Use of beaten ground walls and ground masonry bodies offers the possibility to create a pleasant construction, useful, healthy, without toxic emissions, which adapts to the needs of users; ensuring indoor air relative humidity adjusting at 50 ± 5% and a coefficient of water vapor permeability with values between 156 ng/m2sPa and 479 ng/m2sPa (depending on the material density throughout the year) (Hall 2008, 2009; Hall



2007); fire resistance; resistant to insects attack, rodents and mold attack (Rautela & Joshi 2008). Currently, in the world, numerous studies in this direction have been made (Bui et al 2009a, b; Burroughs 2008, 2010; Ciurileanu & Bucur Horvath 2012; Hall & Djerbib 2004; Jayasinghe & Kamaladasa 2007; Karim et al 2011; Kiroff & Roedel 2010; Minke 2005; Taylor & Luther 2004; Vural et al 2007). Many developed countries have proposed and implemented standards governing the home construction of the ground. New Zealand has a tradition in this area since still the nineteenth century.

From the analysis of bibliographic data was established that the ideal soil for intended use must contain at least 15 to 16% clay (Hall & Djerbib 2004; Jayasinghe & Kamaladasa 2007; Karim et al 2011; Kiroff & Roedel 2010; Minke 2005). Also, to achieve a good thermal insulation, namely a good thermal inertia that allows a good heat storage in the warm period and its release in the cold one, the density of the mixture have to be within 1800-2000 kg/m3 (Burroughs 2008; Hall & Djerbib 2004; Jayasinghe & Kamaladasa 2007; Minke 2005).

A good plasticity and workability are essential for getting the finished product - a good quality natural bric. In the preparation of the primary mixture, water is required to activate the bonding strength and to achieve the workability. However, too much water will damage the mixture because drying will cause cracks. It was concluded that a linear shrinkage between 3 and 12% for blocks of soft mixtures (mud bricks) or a linear shrinkage between 0.4 and 2% for more dry mixtures is satisfactory to obtain of finite elements without cracking (Bui et al 2009b; Burroughs 2008; Burroughs 2010; Taylor & Luther 2004).

In terms of strengths, New Mexico Code ASTM D1 633-00 indicates a compressive strength of the material, the minimum needed for the walls of earth, of 2.07 N/mm2. The beaten earth walls Code of Zimbabwe requires a minimum compressive strength for a 400 mm wall housing, with a single level, of 1.5 N/mm2 and in the case of two-level dwellings, of 2.0 N/mm2. Australian Standard indicates a compressive strength of at least 1.15 N/mm2 and ASTM International E2392/E2392M-10e1 (2010) indicates a value of 2.068 N/mm2. ACI Material, Journal Committee indicates compressive strength values depending on the composition of the earth, as follows: 2.76 to 6.89 N/mm2 for sandy soil and 1.72 to 4.14 N/mm2 for clayey soil.

In the present context, although it is obviously growing interest for such construction with walls of beaten ground and/or masonry ground bodies, there still are many unclear issues. One of these is the constant quality of raw material and finished product quality: the quality and the composition of the earth varies depending of extraction area and it requires a rigorous chemical analysis and particle size in order to evaluate the possibility of using the appropriate technology for the material.

So far, there is not a generally valid methodology regardind the use of the ground depending on specific features. The literature shows up till now a classification of grounds according to the chemical composition, to the clay content and to the grain size. Of these, the sandy clay soil type is recommended to be used in vernacular buildings type (Bui et al 2009a, b; Burroughs 2008, 2010; Ciurileanu & Bucur Horvath 2012; Hall & Djerbib 2004; Jayasinghe & Kamaladasa 2007; Karim et al 2011; Kiroff & Roedel 2010; Minke 2005; Taylor & Luther 2004; Vural et al 2007).

Also, the literature does not fully cover through specific research studies, the influence of inorganic and/or organic additions, traditionally used, on the physico-mechanical properties of elements made of earth (mechanical strength, thermal resistance, water and water vapor behaviour, etc.). For these reasons there are necessary studies and research concerning the characterization of raw materials, of ground mixtures with other additions and of the elements made of them, with the specification of the extraction area geographical location and the way the pot of earth, so that they can achieve a basis for developing further studies.

Based on the literature review it was considered necessary a study on establishing an optimal composition of the mixture made of a ground with determined characteristics and other additives (sand, inorganic and organic binder nature or not) continued with an



assessment of influence of these fillers on physical and mechanical characteristics of the finished product. In this paper we present a study on the characterization of ground extracted from Valea Draganului, Cluj, Romania. Subsequently, we present the results of studies concerning the influence of various additives (sand, lime paste, bone glue, NaCl, NaOH) on the physico-mechanical features (axial shrinkage, density, mechanical strength). These fillers were selected because according to the literature (Minke 2005) there are specified the following benefits they bring to the technology or product manufacturing put in work: - sand and lime help to reduce axial contractions and reduce the risk of cracks on drying. Additionally, the lime, an air binder material, contributes also to the improvement of strength developed on the long term, improves adherence and increases the resistance to water; - NaCl reduces the drying speed and regulates moisture balance, thus reducing the risk of cracking and drying shrinkage; - NaOH improves the plasticity and workability of the mix; - Bone Glue improves mechanical strength and contributes to the increasing of waterproofing meaning increasing water resistance.

Although these fillers are indicated in literature, there are not specified the recommended quantities to obtain benefits on the material, without be induced major negative side effects, too. Material and Method. To achieve experimental mixtures it used soil with a sandy clay type composition, extracted from Valea Draganului, Cluj, Romania (Figure 1). Grain characteristics, in conjunction with data from the literature (Bui et al 2009a, b; Burroughs 2008, 2010; Ciurileanu & Bucur Horvath 2012; Hall & Djerbib 2004; Jayasinghe & Kamaladasa 2007; Karim et al 2011; Kiroff & Roedel 2010; Minke 2005; Taylor & Luther 2004; Vural et al 2007) have indicated that this ground is appropriate to the chosen goal.

Figure 1. Characterization of the used sandy clay ground.

The used filler materials were sand, lime paste, bone glue, NaCl, NaOH. The sand (natural aggregates grade 0-4) was characterized by size analysis presented in Table 1.

The used paste lime was analyzed according to SR EN 459-2:2011 and it is characterized by the data presented in Table 2.

Table 1 Size analysis of the sand

Mesh size (mm) 0.063 0.125 0.25 0.5 1 2 4 8

Passes (%) 0.5 1.6 8.8 28.5 56.9 82.4 98.0 100.0

sand 7.34%medium sand 18.26%

fine sand 16.72%

powder 20.15%

clay 37.53% clay d<0.005

powder 0.005<d<0.05fine sand 0.05<d<0.25medium sand 0.25<d<0.5sand 0.5<d<2



The used NaCl and NaOH were high purity substances, used routinely in the laboratory. By dissolution in water of crystalline substances, it have been made for aqueous solutions of predetermined concentrations.

The used bone glue was commercially available in granular form and dissolved in water.

Table 2 Paste lime features

Fineness of grinding Setting time (hours) Free water Mechanical strength

residue on the 0.2 mm sieve

(%)

residue on the 90 m sieve

(%)

began setting

end setting

% Rf (N/mm2)

Rc (N/mm2)

0.84 0.40 120 168 52.9 0.5 1.6 Rf - flexural strength; Rc - compressive strength. In INCD URBAN-INCERC, Branch Cluj-Napoca laboratory were made mixed grounds with fillers, each encoded, as shown in Table 3. Of these mixtures were made prismatic specimens (40x40x160 mm) for a series of experimental studies. These were conducted in order to establish an optimum ground – filler proportion, in terms of physical and mechanical strenghts, density, axial contractions.

Table 3 The composition of the experimentally tested mixtures

Code

mixture Materials

Earth [% of total dried material]

Sand [% of total dried material]

Paste lime [% of total dried

material]

Mixture Liquid [33% - based on the total dried material]

1 100 0 - water 2 70 30 - water 3 67 33 - water 4 65 35 - water 5 60 40 - water 6 55 45 - water 7 50 50 - water 8 45 55 - water 9 35 65 - water 10 30 70 - water 11 25 75 - water 12 20 80 - water 15 100 - - 3% NaCl solution 16 100 - - 13% NaCl solution 17 100 - - 3% NaOH solution 19 100 - - 0.7% bone glue solution 33 100 - - 1.25% bone glue solution 20 100 - - 3% bone glue solution 21 100 - - 0.6% bone glue and 2.6% NaOH sol. 22 100 - - 1% bone glue and 1.5% NaOH solution 23 100 - - 1.5% bone glue and 2% NaOH solution 24 100 - - 3% bone glue and 1% NaOH solution 25 99 - 1 water 26 98 - 2 water 27 97 - 3 water 28 96 - 4 water 29 95 - 5 water 30 94 - 6 water 31 93 - 7 water



Apparent density of the prepared and cured mixtures was determined according to SR EN 1015-10, being the ratio between mass at balance moisture and the volume of the specimens.

Axial contraction of the prepared and cured mixtures, was determined according to STAS 2634 by using the Graff device, reporting specimen length variation (upon reaching equilibrium moisture) at the initial length. Results were expressed in mm/1000 mm.

Mechanical strengths of specimens made of different mixtures were determined according to SR EN 1015-11, using prismatic specimens with dimensions 40x40x160 mm. The material was prepared by mechanically mixing and placed in a metal mold in layers, each layer being beater to reduce the thickness by half. After demoulding the specimens were kept in laboratory conditions (23º C and 50% URA) to achieve moisture balance. Subsequently, the samples were subjected to bending and the two resulted pieces were achieved the compression tests. For flexural strength it has been used the concentrated load method in the midway.

We calculated the flexural strength and compressive strength according to equations (1) and (2).

23 /

5,1mmN

bxlxF

R ff (1) 2/

1600mmN

FR c

c (2)

where: Rf - flexural strength (N/mm2), b – side of prism square section (mm), Ff – the applied load at break in the middle of the prism (N), l - distance between supports (mm). Rc - compressive strength (N/mm2), Fc – max load at break (N), 1600 = 40x40 mm – platters area (mm2). There are examples in Figure 2 of specimens made of ground mixtures/additions, according to Table 3.

100% ground - 33% water

67% ground - 33% sand - 33% water

55% ground – 45% sand - 33% water

95% ground – 5% paste lime - 33% water

100% ground - 33%aqueous solution 3% bone clay

100% ground - 33%aqueous solution 3%

NaCl

Figure 2. Examples of specimens made from mixtures of ground - sand – water.

Figure 3 presents images from the determination of flexural tensile strength (a) and compressive strength (b) of the prismatic specimens made of the above-mentioned mixtures.



a). b). Figure 3. Determination of flexural (a) and compressive (b) strength of hardened samples.

Results and Discussion. The major objective of this study was to analyze the influence of fillers mentioned in the literature (sand, paste lime, bone glue, NaCl, NaOH) on the physico-mechanical characteristics (axial shrinkage, density, mechanical strength) of the sandy loam soil mixtures to achieve some masonry fixtures for vernacular structures.

Figures 4-7 present the experimental results obtained for the determination of axial contraction. Based on literature, it is marked the lower limit of recommended axial contractions (3 mm/m) and the upper limit of 12 mm/m it is not found on the figures because none of the obtained results does not equal or exceed this value.

Based on the experimental results obtained and shown in Figure 4, we can say that in this case, the addition of sand in controlled proportions improves the mixtures axial contraction in the most of the analyzed cases. We can see that compared with sandy loam soil type without the addition of sand (mixture no 1), adding sand in a proportion of 30-80% of the dry mixture (mixtures no 2-9) the axial contractions are significantly reduced (approximately 30% lower for the mixture no 4 with 35% sand, than mixture no 1, which is considered the control mixture). However, although the amount of sand more than 65% of the dry mixture (mixtures no 10-12) reduces the axial contractions below the recommended lower limit from literature, but adversely affects the cohesiveness of mixture, which needs some extra water.

As shown in Figure 5, the addition of paste lime also contributes to the reduction of axial contraction, but to a smaller extent than the sand. The addition of 1-2% paste lime (mixtures no 25 and 26) do not contribute significantly to the reduction of axial contraction of the mixture, these values being close to those of control samples (mixture no 1). Amounts of 3-9% added paste lime (mixtures no 27-31) in mixture help to reduce the axial contraction, the more so the amount of paste lime is higher.

Adding NaOH and bone glue was performed separately and simultaneously, too. Substituting the water with 3% NaOH solution (mixture no 17) it contributed significantly to the increase of workability and plasticity of obtained specimens material, with more smooth surfaces compared to the control mixture (mixture no 1), but it did not significantly affect the axial contractions recorded as can be seen in Figure 6.

Using a solution of bone glue dissolved in water, instead of mixing water, it contributed also to the increasing of workability and plasticity of the material. A concentration of about 1.25% bone glue in water (mixture no 33) determined the best axial shrinkage reduction, compared with the control sample (mixture no 1) and also compared with similar samples prepared with solutions with concentrations of 0.7% and 3% bone glue (mixture no 19 and no 20), as shown in Figure 6.

In this case, it can be said, that the best concentration of bone glue dissolved in the mixing water is about 1.25%, lower or higher concentrations causing an increasing trend of the axial contractions.

Because the dissolution of bone glue was difficult (in a long time and imposing water heating) it was investigated further to improve this by reducing the time required for complete dissolution and eliminate the need for heating the solvent (water). So, four mixtures were made (no 21-24 mixtures) in which, the mixing water was substituted with a solution of NaOH in which the bone glue was dissolved. This method was chosen because they have similar influences NaOH and bone glue on the workability and plasticity of the mixture. Based on the results shown in Figure 6 it could be said that a



balance between the ease of dissolution of bone glue and an axial shrinkage reduction was obtained for a mixture to which the water was substituted with a mixed solution of a small amount of NaOH and higher of bone glue, 1% NaOH and 3% of bone glue solution (mixture no 24). Comparative values of axial contractions were recorded for the mixture no 23, too; in this mixture, the mixing water was substituted with a solution of 2% NaOH and 1,5% bone glue.

In this context, it was considered that more extensive studies are needed to establish the final composition of NaOH and bone glue to substitute the mixing water so that the results will be optimal.

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shrin

kage

[mm

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ar sh

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ge

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m]

Figure 4. Axial Shrinkage of the soil mixtures, sandy loam type with sand.

Figure 5. Axial Shrinkage of the soil mixtures, sandy loam type with paste lime.

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8,608,809,009,209,409,609,80

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Figure 6. Axial Shrinkage of the soil mixtures, sandy loam type with bone glue and/or NaOH

Figure 7. Axial Shrinkage of the soil mixtures, sandy loam type with NaCl.

Using NaCl solutions instead of water (mixtures no 15 and 16) does not significantly affects the axial shrinkage of the mixtures compared with the control sample (mixture 1), as can be seen in Figure 7. Indeed, with the water substitution with NaCl solution it showed a reduction of the rate of specimens drying speed compared to the drying speed of the control sample, but without significant benefit regardind the axial shrinkage reducing. Since there were not any visual cracks at witness specimens (mixture no 1), we cannot confirm if using NaCl solutions it contributes positively to improving this aspect, but it can record the negative phenomenon of "blooming" (deposits of crystallized NaCl on the specimens surface) in the case of mixtures prepared with more concentrated NaCl solution (mixture no 16).

The apparent density to achieve a good thermal insulation, that an optimal thermal conductivities, according to the literature, must be within 1800-2000 kg/m3. The sandy type soil mixed with watter (mix 1) has a density below the minimum required, so, it was considered necessary to identify opportunities for improvement in this parameter. As can be seen in the graph in Figure 8, addition of sand increases the apparent density of the mixture.

On the chart in Figure 8, were marked the maximum and minimum apparent density value, and it can be said that, in this case, mixtures made with 30-55% sand fall between these limits. A quantity of sand greater than 55% in the blend result in exceeding the maximum upper limit of apparent density value, which led to the consideration of the maximum amount of sand that can be introduced is 55% of the total dry matter.



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m2 ]

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[Kg/

m3 ]

Rti Rc density

Figure 8. Apparent density and mechanical strength in the cured state of mixtures

of sandy clay type soil and sand.

From the point of view of strength recorded, as presented in the graphs in Figures 8-11, it can be said that, in general they are influenced by the materials from which are made the mixtures.

Introduction of sand (Figure 8) generally determined the reduction of strength of the specimens compared with the control mixture (mixture 1). With the increasing amount of sand in the mixture was found an evolution of Gaussian bell with maximum values represented by the corresponding mixture of 35% sand (mixture 4). Yet, mechanical resistances felt tip Gaussian mixture (Mix 4) are about 9-10% lower than those of specimens from the sandy clay type soil without the addition of sand (mixture 1). According to experimental results plotted in Figure 8, we can say that: - flexural strength of the mixture with 35% sand (mix 4) is about 1,5% higher than comparable values for mixtures with 30% and 33% sand (mix 2 and 3) and with values between 20% and 36% higher than the 40-80% sand mixtures (mixtures 5-12); - compressive strength of the mixture with 35% sand (mix 4) is with 12% and 8% higher than the mixtures with 30% respectively 33% sand (mix 2 and 3) and with values between 11% and 67% higher than the 40-80% sand mixtures (mixtures 5-12). Accumulating experimental results obtained on shrinkage, mechanical strength and apparent density, it can be said that, in this case, a mixture made from 65% sandy clay type soil, 35% sand and 33% water (Mix 4) is the best option.

Analyzing the experimental results for the best mixture, mix 4, it was found that: - axial contraction is 6.51 mm/m and is within the range 3-12 mm/m indicated in the literature; - apparebt density is 1890 kg/m3 in cured state and is within the range 1800-2000 kg/m3 indicated in the literature; - compressive strength is 3.77 N/mm2 value that satisfies the criteria imposed by the ASTM D1 633-00 from New Mexico, Code of the walls of beaten earth Zimbabwe, Australian standard, ASTM International E2392/E2392M-10e1 (2010) and are within the values reported by ACI Material, Journal Committee.

With the introduction of lime paste to sandy clay, keeping constant the amount of mixing water, asa as shown in Figure 9, there was a slight increase in density for the specimens made with 1% lime slurry (mixture 25). This was followed by a continuous downward trend of apparent density, with increasing amount of lime paste mixture (mixtures 26-31). None of the made mixtures did not enclosed the apparent density limit values recommended in the literature, values recorded were below minimum 1800 kg/m3.

Mechanical strength recorded for specimens with lime paste, Figure 9, falls into a similar downward trend corresponding to apparent density. We notice a slight increase in flexural tensile strength (2.6%) and a greater increase in compressive strength (20.5%)



corresponding to 1% lime slurry mixture, compared with those recorded for the mixture ground - water, considered a witness (mix 1). His increase of strength is followed by a reduction in their values between 17 and 68% for flexural strength and 18-76% for compressive strength, in mixtures made with the addition of 2-9% lime slurry (26-31 mixture).

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[N/m

m2 ]

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2200

[Kg/

m3 ]

Rti Rc density

Figure 9. Apparent density and mechanical strength of sandy loam type soil mixes with

lime paste. Accumulating experimental results obtained on axial contractions, mechanical strength and bulk density, it can be concluded, when using lime slurry as the sole filler material, the results are not satisfactory, because shrinkage are reduced only at addition of more than 2% lime slurry, but induces large reduction of strength. One possible explanation for the lower mechanical strength for mixtures with lime paste may be that the specimens were tested once they reached equilibrium moisture. Lime slurry as a binder air, is possible to develop higher mechanical strength after longer periods of time. Comparing the experimental results obtained for mixtures of soil with lime paste with permissible limit values indicated in literature it was found that the addition of up to 3% lime in mixed keep the compressive strength value in limits that satisfy conditions imposed by the ASTM D1 633-00 New Mexico, Code of the walls of beaten earth from Zimbabwe, Australian standard, ASTM International E2392/E2392M-10e1 (2010) and values indicated by ACI Material, Journal Committee.

Because in literatura exist information on the advantages of using this filler, it is considered that further studies are needed to be conducted on mixtures of sandy loam soil type - sand - lime slurry at a rate of 2-3%, thus combining the advantages of sand (reduction of shrinkage, increasing of apparent density and mechanical strength developed in short time at satisfying values) with the advantages of lime paste (improving adherence, development of mechanical strength after longer periods of time and improve the behavior of water).

From the graphs shown in Figures 10 to 11 it can be said that other fillers used in this study did not influence the apparent density of the hardened mixture so it is not influenced the value framing in limits specified in the literature.

There was an irregular variation of the apparent density of blends made by substituting water mixed with NaOH solution and/or bone glue, Figure 10, variation has been attributed to the influence they have on the workability of the material and, therefore the degree of compaction of specimens that reduce the amount of entrapped air.

In the case of substitution of the water with NaCl solution (specimens 15, 16), as shown in Figure 11, apparent density slightly increases with increasing concentration of NaCl solution. NaCl solution effect is not satisfactory on the one hand due to the emergence of the phenomenon of "blooming" reported at specimens with more concentrated solution of NaCl (specimens 16), and on the other hand due to the recorded bulk density values below the minimum recommended by literature.



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Rti Rc density

Figure 10. Apparent density and mechanical strength in the cured state of sandy loam

type soil mixes with bone glue and/or NaOH.

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Figure 11. Apparent density and mechanical strength in the cured state of sandy loam

type soil mixtures with NaCl. From the point of view of strength recorded when changing the mixing water with solutions of NaOH and/or bone glue, it can be said that, in general, it was found an improvement in their levels for mixtures made with 0.7% and 1.25% bone glue (specimens 19 and 33) and for mixture with 1.5% bone glue solution and 2% NaOH (mixture 23). Comparing the experimental results obtained with permissible limit values indicated in literature was found that all variants of the mixture analyzed in this case (Figure 10) are higher than the minimum value specified compressive strength in the literature, what they indicate is especially suitable for the purpose.

On the other hand, mixture with 1.25% bone glue (mix 33) has the apparent density nearest to the lower limit specified in the literature and has the lowest shrinkage (Figure 4). All this indicates the possibility of achieving a mixture, with sandy clay - solution 1.25% of bone glue and small admixture of sand, to fit in terms of mechanical strength and axial contraction, but to satisfy the requirements of thermal resistance so to have requested apparent density.

Given the difficulty of dissolution of bone glue in water, as was shown in this paper, made by substituting the water from mixture with solution of bone glue 1.5% and 2% NaOH (mixture 23) shows the advantage of mechanical strength compared to those recorded for 1.25% solution mixed with bone glue and made with lower effort. In this case axial contractions are higher than those reported for the mixture 33 (9.02 mm/mm



compared to 8.75 mm/m), but is within the limits indicated in the literature (3-12 mm/m), and apparent density is lower (1700 kg/m3 compared to 1745 kg/m3), but these can also be enhanced by using sand.

In this caande it was considered that to can be used these additions for the benefits they bring, will require a new study which aims to analyze mixtures made of sandy clay type soil – sand– solution of NaOH and/or bone glue wich substitued the watter.

The experimental results on the mechanical strength and apparent density, recorded for the mixing with NaCl solution, Figure 11, pooled with those of shrinkage, Figure 7, and with visual observations, indicated the possibility of using saline solution with a concentration of max. 3%, but for other purposes than the improvement of the parameters examined in this study and not as a unique addition. Experimental results obtained partly confirmed the hypotheses that were the basis for defining the scope of this study. Thus, it was shown that if the sandy clay type soil characterized by composition shown in Figure 1, addition of sand can help to reduce shrinkage, and from visual observations has revealed no cracks. Lime slurry introduced as an additive in the mixture of clay sand and water, can reduce the axial contractions, but not confirmed improvements in mechanical strength. This may be related to how test, and the samples were tested when reaching equilibrium moisture, without being tested a similar set of samples stored for a longer period of time. Based on observations recorded during the manufacturing of specimens, was found an improvement in workability of mixtures substituting water with NaOH solutions, bone glue or combinations thereof. Also, mechanical resistances recorded in these cases were improved compared with those of the control mixture of clay sand and water. The tests performed in this study revealed no improvement waterproof after using NaOH solutions, bone glue or combinations thereof. Substituting water with NaCl solution did not induce benefits on features that were the subject of this study (apparent density, shrinkage and strength).

From the point of view of strength experimentally recorded, most mixtures used have satisfied the conditions imposed by various codes and regulations and are within the range of values reported in the literature.

After analyzing the results it is estimated that in the case of sandy clay used is recommended that, to identify an optimal composition for achieving bodies masonry for vernacular structures, o take into account the addition of sand and lime paste, and the possibility of substituting water with a solution of NaOH and bone glue. This combination of several fillers creates the possibility of identifying a mixture that best meets the criteria of the thermal resistance true a satisfactory apparent density, and criteria for strength and durability (strength, shrinkage and water resistant) also satisfying the need for an easy commissioning work with minimum energy effort.

Conclusions. According to the literature, currently there is an increased interest in the study and use of vernacular materials. This is due to the economic benefits and environmental protection that they shows.

The purpose of this study was to analyze the potential that they have different materials used as filler (sand, lime paste, bone glue, NaCl, NaOH) to improve the physical and mechanical properties of sandy clay land type (axial shrinkage, density, mechanical strength).

Based on the experimental results, considering that not vary the amount of water, in mixtures soil - sand were noted:

- addition of sand has positive influences on shrinkage and thus reducing the risk of cracking. Most mixtures of soil - sand - water were within the limits recommended by the literature on axial contractions, visual analysis indicating no cracks;

- apparent density is positively influenced by the addition of sand under control. Specimens with 100% soil had a apparent density below the permissible value indicated in the literature. Apparent density increases with sand content of the mixture, surpassing the maximum allowable value indicated in literature for quantities greater than 65% sand. Apparent density obtained for mixtures analyzed are compared to the apparent density of ceramic filled bricks;



- compressive strength and flexural tensile tested on specimens at moisture equilibrium was influenced by the amount of sand mixed introduced. There was a trend of Gaussian values of strength with increasing amount of the introduced sand in mixture. The maximum was recorded when at mixture 65% soil - 35% sand, values that satisfy boundary conditions imposed by the different standards, as they were presented in the first part of the paper.

In case of mixtures with soil and lime slurry were found following: - the addition of lime slurry has positive influences on shrinkage and thus,

reducing the risk of cracking, with increasing the amount of lime slurry in mixture. All blends made showed shrinkage within the range of values recommended in the literature;

- apparent density is not influenced positively in this case. None of the tested mixtures has reached the minimum apparent density indicated in the literature.

- mechanical strength recorded a downward trend with the increasing the amount of lime slurry in the mixing. There was a slight increase in flexural tensile strength (2.6%) and a greater increase in compressive strength (20.5%) corresponding to 1% lime slurry mixture, compared with those recorded for the mixture ground - water, considered a witness. In the case of mixtures made with the addition of 2-9% lime slurry, this increase of strength is followed by a reduction in their values between 17 and 68% for flexural strength and 18-76% for compressive strength. This development of strength was attributed to the possibility that to develop higher mechanical strength after longer periods of time due to the lime;

- accumulating experimental results obtained, it can be said that, if using lime slurry as the sole filler material, results are not satisfactory because the shrinkage are reduced at addition over 2% of lime slurry, which induces large reduction of strength.

In case of mixtures with soil and solution of NaOH and/or bone glue were found the following: Substituting the water with solutions of NaOH and/or bone glue contribute effectively to improved workability and plasticity of the mixture

- a concentration of about 1.25% bone glue in water determined the best reduction of shrinkage. Comparative values of shrinkage were recorded for mixture with 2% NaOH and 1.5% bone glue solution;

- from the point of view of recorded strength, it can be said that in general, it has been found an improvement in their values, with high values for mixtures made with 0.7% and 1.25% bone glue and for the specimen made with solution of bone glue 1.5% and NaOH 2%;

- the speciments with 1.25% bone glue presented apparent density nearest to the lower limit specified in the literature and the lowest shrinkage, a density close to that registering for the mixture with bone glue solution 1.5% and 2% NaOH. The latter one presented the advantage of reducing the technological effort too;

- accumulating experimental results obtained, it can be said that there is the opportunity of a mixture of sandy clay - NaOH and bone glue solution and a small amount but enough of sand, for apparent density adjustment, so that it can meets all the criteria from this study;

- in the case of soil with NaCl solutions mixtures was found that the experimental results indicated the possibility of using saline solution with a concentration lower to 3%, but for other purposes, not to improvement the parameters examined in this study and not as a unique addition.

Based on the experimental results, it was deemed useful further study analyzing these possibilities:

- confirm or not the hypothesis that lime slurry develop higher mechanical strength after longer periods of time and brings other advantages if used at a rate of 2-3% in the mixture;

- achievement mixtures whose physical and mechanical characteristics are within the specification from literature, used concomitantly sandy clay, sand and lime paste, substituting or not the water with solution of bone glue and NaOH. Thus, it will achieve the mixture of materials that combine the most effective way the thermal resistance criteria wich is satisfied by the optimum value of apparent density, and the criteria for



strength and durability (strength, shrinkage and resistance to water), also satisfying the need for an easy commissioning work with minimum energy effort.

In general, studying the literature and experimental results obtained, it can be appreciated that the sandy loam soil type extracted from Valea Draganulu, Cluj, Romania, can be used to achieve the brick masonry for building houses, provided to mix with sand and other materials added in controlled proportions.

References Arango- Gonzalez J. R., 1999 Uniaxial deformation-stree behaviour of the rammed earth

of the Alcazaba Cadima. Materials and Stuctures 32:70-74. Bui Q. B., Morel J. C., Venkatarama Reddy B. V., Ghayad W., 2009a Durability of rammed

earth walls exposed for 20 years to natural weathering. Building and Enviroment 44:912-919.

Bui Q. B., Morel J. C., Hans S., Meunier S., 2009b Compression behaviour of non-industrial materials in civil engineering by three scale experiments: the case of rammed earth. Materials and Structures 42(8):1101-1116.

Burroughs S., 2008 Soil property criteria for rammed earth stabilization. Journal of Materials in Civil Engineering 20(3):264-273.

Burroughs S., 2010 Recommendations for the selection, stabilization, and compaction of soil for rammed earth wall construction. Journal of Green Building 5(1):101-114.

Ciurileanu G. T., Bucur Horvath I., 2012 Modular building using rammed earth. Acta Technica Napocensis: Civil Engineering & Architecture 55(2):173-181.

Hall M. A., 2008 Assessing the efect of soil grading on the moisture-content-dependet parameters of stabilised earth materials usig the cyclic-response admittance method. Energy and Building 40:2044-2051.

Hall M. A., 2009 Analysis of the hygrothermal funcation properties of stabilised rammed earth materials. Building and Enviroment 44:1935-1942.

Hall M. R., 2007 The enviromental performance of stabilised earth walls using a climatic simulation chamber. Building and Enviroment 42:139-145.

Hall M., Djerbib Y., 2004 Rammed earth sample production: context, recommendations and consistency. Construction and Building Materials 18(4):281–286.

Jayasinghe C., Kamaladasa N., 2007 Compressive strength characteristics of cement stabilized rammed earth walls. Construction and Building Materials 21(11):1971-1976.

Karim M. R., Zain M. F. M., Jamil M., Lai F. C., Islam M. N., 2011 Use of wastes in construction industries as an energy saving approach. Energy Procedia 12:915-919.

Kiroff L., Roedel H., 2010 Sustainable construction technologies: earth buildings in New Zealand. Second Internatiol Conference of Sustenable Constructions Materials and Technologies, 28-30 June, Ancona, Italy.

Kumar A., Munoth N., 2011 Vernacular architecture – a prerequisite for sustainable development. Arch Time Space People 11(7):16–22.

Minke G., 2005 Building with earth. Design and Technology of a Sustainable Architecture, Birkhause Publisher for Architecture, Basel, Berlin, Boston.

Pushplata, Kumar A., 2012 Building regulations: as a means of ensuring sustainable development in hill towns. Journal of Environmental Research and Development 7A(1A):553–560.

Pushplata, Kumar A., 2014 Vernacular practices: as a basis for formulating building regulations for hilly areas. International Journal of Sustainable Built Environment 2(2):183-192.

Rautela P., Joshi G. C., 2008 Earthquake-safe Koti Banal architecture of Uttarakhand, India. Current Science 95(4):475–481.

Taylor P., Luther M. B., 2004 Evaluating rammed earth walls: a case study. Solar Energy 76(1–3):79–84.

Vural N., Vural S., Engin N., Sumerkan M. R., 2007 Eastern Black Sea region. A sample of modular design in the vernacular architecture. Building and Environment 42:2746–2761.



*** SR EN 459-2:2011, Building lime - Part 2: Test methods. *** SR EN 1015-10:2002, Methods of test for mortar for masonry - Part 10:

Determination of dry bulk density of hardened mortar. *** SR EN 1015-11:2002, Methods of test for mortar for masonry - Part 11:

Determination of flexural and compressive strength of hardened mortar. *** STAS 2634-80, Regular mortar for masonry and plaster. Test methods. *** New Mexico Code ASTM D1 633-00. *** ASTM International E2392/E2392M-10e1 (2010).

Received: 20 January 2015. Accepted: 21 February 2015. Published online: 31 March 2015. Authors: Gabriela Călătan, INCD URBAN-INCERC Cluj-Napoca Branch Calea Floresti, no. 117, Cluj-Napoca, Romania Andreea Hegyi, INCD URBAN-INCERC Cluj-Napoca Branch Calea Floresti, no. 117, Cluj-Napoca, Romania, e-mail:[email protected] Carmen Dico, INCD URBAN-INCERC Cluj-Napoca Branch Calea Floresti, no. 117, Cluj-Napoca, Romania Calin Mircea, Technical University of Cluj-Napoca, Cluj-Napoca, Romania This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited. How to cite this article: Călătan G., Hegyi A., Dico C., Mircea C., 2015 Additives influence on the earth characteristics used in vernacular construction. Ecoterra 12(1):7-20.

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