J. Build. Mater. Struct. (2020) 7: 42-50 Original Article DOI : 10.34118/jbms.v7i1.137 ISSN 2353-0057, EISSN : 2600-6936 Stabilization of compressed earth block clayey materials from Adrar (Algeria) by lime and crushed sand Abbou M 1,2,*, Semcha A 1,2, Kazi-Aoual F 2 1 Université Ahmed Draia,Adrar, Algeria. 2 Laboratoire des Matériaux LABMAT, L’Ecole Nationale Polytechnique d’Oran – Maurice Audin, Algeria. * Corresponding Author: moh.abbou@univ-adrar.dz Received: 01-02-2020 Accepted: 25-03-2020 Abstract: The objective of this article is to determine the physical and mechanical properties of stabilized compressed earth bricks (SCEB), made from a mixture of clay with crushed sand, and stabilized by lime. In this study, we first examine the identifying properties of raw materials. Then an experimental study was conducted with cylindrical test pieces of a mixture of clay and crushed sand prepared by the addition of lime and statically compaction, to study the physical and mechanical characteristics of the mixture. The experimental study shows that for use as a building material, the clay mixture with 30% crushed sand and stabilized with 4% and 6% lime is the optimum mixture for as a stabilized compressed earth bricks. Key words: Clay, crushed sand, Lime, SCEB, physico-mechanical properties. 1. Introduction For almost 10,000 years, the earth has been one of the main building materials used on our planet. More than a third of the world's inhabitants today live in earthen habitats. There are very many earth construction methods which reflect the identity of the place; like adobe frames, compressed blocks, rammed earth … (Houben and Guillaud, 2006). In addition, several studies are devoted to the CEB technique and the various modes of stabilization (Rigassi, 1995), for the improvement of mechanical resistance as well as durability (porosity, resistance to erosion etc): (Winterkorn, 1975; United Nations, 1992; Symons et al., 1999; González-López et al., 2018). In these studies, it emerges that chemical lime treatment is one of the solutions adopted. The effect of adding lime causes physico-mechanical changes on treated soils (Le Roux and Rivière, 1969; Bell, 1996; Cabane, 2004; Malkanthi et al., 2020). These changes are very slow at room temperature. It takes several months or even years before its effects can be appreciated (Arabi and Wild, 1989; Rao and Shivananda, 2005; Lasladj, 2009; Cabane, 2004). In contrast, the granular composition of the earth is influenced on the mechanical properties and durability of SCEB (Mkaouar et al., 2019; Muhwezi and Achanit, 2019). Like other localities in the Adrar region (southern Algeria), earthen constructions made from local materials have proven their existence for millennia. In this context, experimental work is carried out in particular in the design of a stabilized compressed earth block (SCEB). The latter expresses the modern evolution of the block of molded earth (the Adobe), with the aim of inscribing a new technique of raw clay construction in the Adrar region which is known by the Adobe technique. This technique of compressed and stabilized earth brick, based on clay offers a new opportunity to the Saharan environment and meets the criteria of sustainability. Abbou et al., J. Build. Mater. Struct. (2020) 7: 42-50 43 2. Materials and technical methods 2.1. Identification of the materials used The study targeted two materials that are found in abundance in the Adrar region: the first is clay soil and the second is crushed sand from local quarries. 2.1.1. The clay The studied clay is localized in the lower cretaceous commonly called intercalary continental. In the first part of the Lower Cretaceous sediment area are covered by a thick layer of sand deposits, silt, sandstone debris, quartz pebble and locally anhydrite). The clay deposit of the Adrar region (Sbâa) in Algeria is located at few kilometers north of the town of Adrar (East of the national road N ° 06). The material has a red color. However, two complementary methods, wet sieving and sedimentation analysis, respectively according, to XP P94-041(1995) and NF P94-057(1992), determined the particle size distribution. The plastic properties of the fine fraction, particles smaller than 400 μm, were measured as defined in NF P94-051(1993). The density of the solid particles (Gs) was measured using a pycnometer NF P 94-054(1992). Moreover, analyzes of the chemical compositions are carried out at the Center for Studies and Technological Services in the Building Materials Industry laboratory in Boumerdès (Algeria). The reference used for the choice of earth proposed for the manufacture of SCEB is based on the recommendations of CRATerre (International Center for Earth Construction), Houben and Guillaud (1995), and the standard XP P 13-901. Table 1. Geotechnicals properties of the clay used. Proprieties Values Sand ( > 0,02mm) 9% Silt (0,02-0,002mm) 54% Clay ( <0,002mm) 37% Liquid limit WL 81% Plastic limit WP 34% plastic index IP 47 VB 8 Specific density γs 2.6 g/cm3 Table 2. Chemical Composition of the clay of the Adrar. Compounds Values (%) SO4 2- 0.41 CaCO3 3.6 Cl - 0.14 Insoluble (SiO2- Al2O3 - Fe2O3- CaO- MgO) 95.92 2.1.2. Crushed Sand The quarry is located on the southern part of the center of the city of Adrar. The trails leading to the deposit are easy to access. 44 Abbou et al., J. Build. Mater. Struct. (2020) 7: 42-50 Table 3. Physicals properties of the crushed sand. Proprieties Values Equivalent de sable 36.49 % Specific density 2.5 g/cm 3 Apparent density 1.46 g/cm 3 Finesse Model 2.79 100 10 1 0,1 0,01 1E-3 1E-4 0 20 40 60 80 100 % P e rc e n t fi n e r b y w e ig h t (% ) Grain size (mm) Recommendation range NF PX P13-901 % Crushed sand % Clay of Adrar(Sbaa) Fig. 1. Particle size distribution of clay and crushed sand. 2.1.3. Lime The lime used in this study is the slaked lime Ca (OH)2 ,obtained after the hydration of quicklime (CaO) produced in the wilaya of Ghardaia. 2.2. Technical methods 2.2.1. Formulation Houben and Guillaud (1989) highlight some feedback on the formulation of soil-based products and more specifically compressed earth bricks. Reference particle size zones are used to determine the ability of a soil to be compressed or not. According to the standard XP13-901, (2001) and the recommendation of the CRATerre, the approach is to bring on the same granulometric diagram the curves of sandy and clay soils as well as the outline of the desired optimal curve. This method gives the proportion of the finest earth to be mixed with the coarsest earth to obtain a texture that approaches the optimal curve, which can be the midline of the spindle. For the preparation of the mixture (clay and crushed sand), a study on different mixtures is carried out. As a result, the mixture is composed of 30% clay and 70% crushed sand, has shown a composition that approaches it to the middle line of the recommended spindle. The initial amount of lime required to stabilize the blends is 4% by dry weight of the mixture, was determined according to the method developed by Eades and Grim (1966), ASTM D 6276- 99a (1996). The PH measurement test assesses the lime content needed to produce a saturated solution of lime in a soil suspension in water and to fully satisfy the ion exchange. The pH threshold is set at 12.4. The amount of lime to obtain this pH is known as the point of attachment of lime. From this pH value, the additional lime is supposed to be available for the development of pozzolanic reactions. So lime dosages of 2%; 4%; 6% are chosen for the mixtures. Abbou et al., J. Build. Mater. Struct. (2020) 7: 42-50 45 100 10 1 0,1 0,01 1E-3 1E-4 0 20 40 60 80 100 % P e rc e n t fi n e r b y w e ig h t (% ) Grain size (mm) Recommendation range of NF PX P13-901 Mixture 30% clay+ 70% curshed sand Crushed sand Clay Fig. 2. Particle-size distribution of the clay and crushed sand mixtures. 2.2.2. Optimization, design and manufacture of test specimens According to studies by Mesbah et al. (1999) and P'Kla (2002), static compaction is better suited to clay soils, and the determination of optimal water content for CEB from the Proctor test is inappropriate because compaction is not the same as that of a static compaction used for the manufacture of the CEB. However, this theme is one of the objectives of this study. To optimize the water content of the mixtures, we have also based on the study conducted by Olivier and Mesbah (1986), which showed that regardless of the materials, the stabilization mode or the compression forces implemented, the optimum water content of manufacturing Wocs (OCS: Optimum static compaction), correspond to both the maximum dry density and the maximum compressive strength. The raw earth mixtures were compacted under a pressure of 3MPa, using a press with a constant speed is equal to 1.27mm / min. Before compacting, the raw material is mixed with a predetermined amount of water in a kneader for 15 minutes. This time is sufficient to ensure a good homogeneity of the mixture (Kouakou and Morel, 2009). The wet sample is then placed in a sealed environment to prevent loss of water for 24 hours. This step allows the homogeneous redistribution of the water content. Finally, the wet material is introduced into a hollow cylindrical mold (Fig. 3), in order to obtain cylindrical test pieces (10 × 5) cm of slenderness equal to 2, for each mixture. However, these specimens do not have the same dimensions as those used for concrete since our maximum particle size is less than 5mm (P’Kla, 2002) and compacted by applying the pressure level fixed by a press. The material is compacted vertically at the top and at the bottom by means of two cylindrical pistons (Fig.3). Five test pieces were made for each mixture. Fig. 3. Optimization of the water content of the crushed sand clay mixture. 46 Abbou et al., J. Build. Mater. Struct. (2020) 7: 42-50 2.2.3. Condition of cure All test specimens made from the crushed clay-sand mixture are stored in the laboratory at a temperature, T = 20 ° C to a constant mass (Fig.4.A). In addition, the covered cylindrical test pieces are stored in an oven at a temperature T = 65 ° C. for different durations of 7 days, 14 days, 28 days and 90 days (Fig.4.B). The test specimens concerned by this mode are the sand-cracked clay mixtures plus the different percentages of the slaked lime. To study of the effect of cure time on the mechanical properties of mixtures. Fig. 4. The method of conservation of the test pieces. 3. Results end discussions 3.1. Optimum water content and maximum density Fig. 5 shows the optimization obtained for the static Compression mixture of the order of 3 MPa. The optimization method is similar to the method used by Olivier and Mesbah (1986) when static compaction is used, the same method was used to optimize the clay-sand mixture with lime. In this work, the optimal water content and the maximum density of the mixture constituted by local materials are optimized. Fig.6 shows that increasing the proportion of lime on the mixture caused an offset of the optimal water content of compaction to higher water contents and a decrease in dry densities. This modification of the optimum is similar with the study conducted by Le Roux and Rivière (1969) on the introduction of lime into a soil of a different clay nature. 4 6 8 10 12 1,68 1,70 1,72 1,74 1,76 1,78 1,80 D ra y d e n s it y Water (%) Mixture clay +Crushed sand Fig. 5. Optimization of the water content of the crushed sand clay mixture. A B Abbou et al., J. Build. Mater. Struct. (2020) 7: 42-50 47 11 12 13 14 15 16 17 18 19 20 21 22 23 1,56 1,57 1,58 1,59 1,60 1,61 1,62 1,63 1,64 1,65 1,66 1,67 1,68 1,69 1,70 1,71 D ry d e n s it y Water (%) Mixture with 2%Lime Mixture with 4%Lime Mixture with 6%Lime Fig. 6. Optimization of the water content of the mixture with slaked lime. 3.2. Mechanical properties 3.2.1. Dry compressive strength Fig.7 shows the effect of lime through the results of variation in dry compressive strength as a function of lime dosage at the age of 7, 14, and 28 days of cure. Through the figure below we note that for a stabilization of 2%, 4% and 6% we have resistances to the dry compression at 28 days respectively of 3.2, 4.59 and 5.6 MPa. According to these results, it is noted that there is an increase in the dry compressive strength as a function of the lime content for the crushed clay-sands mixture. Indeed, at the age of 28 days, there is formation of portlandite and formation in very small quantities, hydrated calcium silicate and aluminates phases that ensure the bonds between the particles and enhance the mechanical performance of the mixture. These findings were observed by the authors Bell (1996), Maubec (2010). 0 2 4 6 0 1 2 3 4 5 6 D ry c o m p re s s iv e s tr e n g th ( M P a ) Lime (%) 0% Lime 7 Days 14 Days 28 Days Fig. 7. Dry compressive strength of lime-based test specimens based on lime-slurry dosage, and age of preservation. 3.2.2. Dry tensile strength The results of the tensile splitting test are presented in Fig. 7, which shows an increase in the tensile strength of the test pieces as a function of the increase in the dosage of slaked lime at the age of 90 days cure. 48 Abbou et al., J. Build. Mater. Struct. (2020) 7: 42-50 However, for stabilization with slaked lime, the tensile strength of the cylinders (mixtures) gradually increases. The maximum average resistance is reached with a content of 6% of lime that is 1.4 MPa. 0 2 4 6 8 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 D ry t e n s il e s tr e n g th ( M P a ) Lime (%) Dry tensile strength the 90 Days Fig. 8. Tensile strength of specimens as a function of 90-day slaked lime dosage. 3.3. Capillary absorption The results show that there is a difference between specimens at the age of 28 and 90 days of cure, different assays in lime and non-stabilized specimens. For a stabilization at 2, 4 and 6% of slaked lime, the percentage of capillary absorption decreases respectively 18.53, 17.56 and 16.92% at 28 days, at 15.95, 15.3 and 14.8 at 90 days. The difference in these values is approximately 2.3% Moreover; the value of the absorption of the mixture without the addition of lime is of the order of 20.14%. So, the slaked lime stabilization resulted in a more compact and less porous mix. 0 2 4 6 13,5 14,0 14,5 15,0 15,5 16,0 16,5 17,0 17,5 18,0 18,5 19,0 19,5 20,0 20,5 A b ( % ) Lime (%) 28 Days 90 Days 0% Lime Fig. 9. Capillary absorption as a function of lime dosage at 28 and 90 days of cure. 4. Conclusions The aim of this work was to study the effect of the content of slaked lime on the mechanical properties and the capillary absorption of test pieces made from local materials (Clay + Crushed Sand) statically compacted at 3MPa. Based on the results of this experimental study, the following conclusions are drawn: • Optimum moisture content increases with increasing rate of slaked lime. • Dry density decreases with increasing lime rate. Abbou et al., J. Build. Mater. Struct. (2020) 7: 42-50 49 • The dry compressive strength is improved by the addition of lime that depending on the age of preservation, so the maximum value of the dry compressive strength obtained at 28 days of cure with 6% lime off is equal to 5.6MPa. • Increasing and improving the splitting tensile strength as the percentage of slaked lime increases. 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