Characteristics study of Stabilized and Compressed Laterite Soil Bricks

    Stabilized and Compressed Laterite Soil Bricks

    There is a need for development of alternative materials for the building industry with low carbon footprint and at the same time to save energy. Clay has been used as a building material from the beginning of humankind. The Compressed Earth Blocks often referred to simply as CEB, is a type of manufactured construction material formed by the compression of the soil in a mould with the help of a manual or motorized press to form a regular block of appropriate shape and size. In this experimental investigation, a series of test bricks were fabricated using various percentage of laterite soil 91%, 90%, 89%, and 88% stabilized with 4%, 5%, 6%, and 7% of cement stabilizer with 5% of sand, compacted with a hydraulic press paver block and brick making machine. Results of dry compressive strength, wet compressive strength and water absorption were tabulated. Results show that 75 to 80% of compressive strength can be achieved at the age of 7 days as compared to 28 days maturity age and full strength can be attainable at the curing period of 28 days.

    Shanmuka K. N., Asst. Professor, Department of Civil Engineering, Smt. Kamala and Sri Venkappa M. Agadi College of Engineering and Technology, Laxmeshwar, Gadag Dist; Karnataka, India
    Manjunath K., Professor, Department of Civil Engineering, Malnad College of Engineering, Hassan, Karnataka, India
    Prahallada M.C., Professor, Department of Civil Engineering, Christ University Faculty of Engineering, Bangalore-560074, Karnataka, India

    Introduction

    Lateritic soils are formed in the tropics through weathering processes that favour the formation of iron, aluminum, manganese and titanium oxides [6]. These processes break down silicate minerals into clay minerals such as kaolinite and illite. Iron and aluminum oxides are prominent in lateritic soils, and with the seasonal fluctuation of the water table, these oxides result in the reddish-brown colour that is seen in lateritic soils [4]. These soils have served for a long time as major and sub-base materials for the construction of most highways and walls of residential houses in tropical and sub-tropical countries of the world [2]. Civil engineering applications of these lateritic soils are continually being developed with the use of different types of stabilizers. The stabilized soil-based products are as such viewed as environment-friendly and low-cost energy materials for sustainable building applications [5].

    High cost of building materials has been the bane of construction industry in the developing countries as a result of import of most of the building materials. As prices increase sharply, there is a growing awareness to relate research to local materials as alternatives for the construction of functional but low-cost dwellings both in the urban and rural areas [1]. One of such local materials that is being researched is lateritic soil. Lateritic soil has been one of the major building materials for a long time. The main reason lies on the fact that it is readily available and the cost of procuring it is relatively low [1].

    Lateritic soil possesses other advantages which makes it potentially a very good and appropriate material for construction, especially for the construction of rural structures in the developing countries. These merits include little or no specialized skilled labour required for laterized compressed blocks/bricks production and for its use in other construction works [6].

    The use of stabilized mud blocks is an alternative to burnt bricks, where soil is being stabilized with the stabilizers like cement, lime, molasses etc. and pressing them under high compaction, hence, avoid burning. In avoidance of process of burning, saves a lot of energy and hence, it becomes economical [3]. The question of economy and conservation energy arises, when burnt bricks are invariably used. The alternative, effective remedy is the use of STABILIZED BLOCKS. Soil stabilization techniques have been used for improving the properties of soil viz., compressive strength, erosion resistance, absorption etc [3]. The process of compaction can further improve the properties of stabilized soil. The process of compaction leads to higher densities, thereby, higher compressive strength, better erosion resistance, lesser water absorption and permeability. The stabilized mud blocks can be used for wall construction, as an alternative to conventional walls [3].

    The above approach not only offers significant saving in fuel, energy consumption, and conversion of materials, but also involves lower capital investment per ton of cement and provides solution to ecological problems created by disposal of waste.

    Experimental work

    The main aim of this experimental investigation was to stabilize the laterite soil by using various percentages of cement stabilizers with sand and to check suitability of the same for construction purpose.

    Materials used:

    Surface texture of laterite blocks before dressing and after dressing

    Laterite soil: The disturbed laterite soil was collected from the laterite quarries of Hosanagar, Chandragutti, Thyagarti and Anandapura of Shimoga district, in Karnataka. The residue (disturbed) laterite soil available after dressing of natural laterite building blocks was used, reddish brown in nature classified as A-2-7(0) using AASHTO soil classification system and GP by the United Soil Classification system. The physical and chemical properties of tested laterite soil are given in Table No.1 and Table No.2

    Table 1: Physical properties of laterite soil   Table 2:  Chemical properties of laterite soil
    Properties Results Properties Percentage
    Specific gravity 2.42 -2.48 Silica (SiO2) 20 - 50
    Optimum moisture content 15 – 17 %. Alumina (Al2O3) 30 - 50
    Maximum dry density 22.50 - 24.00 kN/m3 Ferric Oxide (Fe2O3) 20 - 40
    Soil classification   Titanium & Manganese 01 - 05
    Gravel 4.80%  
    Sand 57.60%
    Silt 22.20%
    Clay 15.40% Table 3: Physical properties of ordinary Portland cement-43 grade
    Liquid limit 28.00% Properties Results Permissible limit as per IS: 8112-1989
    Plastic limit 12.80% Normal consistency 34% ---
    Plasticity index 17.60 Setting time --- ---
    Soil group A-2-7(0) a. Initial 170 Min Should not be less than 30 Min
    Free swell index --- b. Final 280 Min Should not be less than 600 Min
    • Cement: Cement used in this investigation was Ordinary Portland Cement (OPC-43 grade).Which satisfies the requirements of IS: 8112-1989 specifications. The physical properties of tested cement are given in Table No.3
    • Sand: Sand collected from the river bed of Tungabhadra near Airani of Ranebennur taluk was used, having fineness modulus of 2.96 and confirmed to grading zone-III as per IS: 383-1970 specification.
    • Water: Ordinary potable water free from organic content, turbidity and salts was used for mixing and for curing throughout the investigation.
    Experimental procedure:

    Production of laterite stablized soil bricks
    Production of laterite stablized soil bricks, curing and testing
    For the production of pressure moulded laterite brick, the 4 kg of laterite soil was taken for each brick, based on the size of mould, soil was spread on clean and flat hard surface, to this known percentage of stabilizer (cement) and sand was added on weight basis followed by thorough hand mixing to get uniform mix, finally potable water (calculated as per optimum moisture content) was added to the dry mix by sprinkling, soil was mixed with water gently but quickly, care was taken to avoid formation of lumps in it during mixing. Entire mixing was carried out in an enclosed area and nearer to the compressing device, to avoid the evaporations of moisture content in the mix and to maintain the workability of wet mix. As soon as the wet mixture was prepared, the homogeneous mix was transported to compacting machine for pressing. The wet mix was placed in known standard size of the moulds and compacted through hydraulic pressure. After compaction, the mould was taken out from the machine by ejection process. Further, brick was lifted carefully from the mould base plate and placed in an open dry place. Since the bricks are not burnt and less initial handling strength, extra care was taken while lifting, placing and stacking of the bricks.

    The Hydraulic press paver block and brick making machine was used for the production of bricks. The bricks produced having uniform dimension of 230mm x 100 mm x 75mm. A net load of 10 tonne was applied over cross sectional area of 23000 mm2 of the brick. Since there was a constant compaction effort on all the bricks, there was less variation in strength characters of bricks that are produced and expected advantage of this research work. Because of heavy compaction, the difficulty of brick ejection from the mould may occur due to generation of suction pressure at the corners of mould.

    The curing method used in this investigation was “Hay curing”. The paddy straw was spread over bricks, such that it completely covers them. The bricks were cured by sprinkling water gently on straws, thrice a day. The curing was continued for 7, 14, 21, and 28 days based on testing cycle.

    The following tests were conducted on stabilized and compacted laterite soil bricks:

    Dry compression test and Wet compression test: The bricks were dried in sunshine for 2 to 3 days, to remove moisture content inside the bricks completely for dry compression test. To conduct wet compression test, completely dried bricks were immersed in water for duration of 24 hours, the bricks were removed from water and the wetted surface was wiped out cleanly for test. For each average result,five bricks per set were taken and the bricks were tested for compression as per IS: 3495-Part (1)-1992 specification on each specimen. The test results were tabulated in Table No.4 to Table No.10

    Absorption test: The dry weight (Wdry) of the bricks was taken and then it was immersed completely in clean potable water for 24 hours. After 24 hours, the bricks were removed from water and the wet surface was wiped out with a clean cotton cloth and the weight was taken (Wwet) as per IS: 3495- Part (2) -1992 specification. The absorption was given by the relation,

    Five bricks per set were taken and the average of five results was considered as ‘Water absorption’ of the bricks. The results were tabulated in Table No.4 to Table No.10

    Table 4: Test results of stabilized and compressed laterite soil bricks (B4) produced from combination of 91% laterite soil + 5% sand + 4% OPC
    Dry compressive strength (N/mm2) for various curing period in days Wet compressive strength ( N/mm2) for various curing period in days Absorption ( % ) for various curing period in days
    7 14 21 28 7 14 21 28 7 14 21 28
    6.304 6.957 8.043 8.696 3.478 2.913 4.348 4.130 7.452 6.232 6.427 4.902
    8.261 7.174 6.957 7.174 3.696 4.348 3.391 4.783 7.892 5.813 5.919 3.159
    6.739 8.261 7.391 6.522 3.261 3.695 4.130 3.913 8.148 7.016 7.147 4.973
    8.261 6.957 8.043 8.696 3.478 4.348 4.348 4.130 7.672 6.497 6.537 5.168
    6.739 7.174 7.391 7.174 3.696 3.695 4.130 4.783 8.258 7.240 6.279 4.984
    Table 5: Test results of stabilized and compressed laterite soil bricks (B5) produced from combination of 90% laterite soil + 5% sand + 5% OPC
    Dry compressive strength (N/mm2) for various curing period in days Wet compressive strength (N/mm2) for various curing period in days Absorption ( % ) for various curing period in days
    7 14 21 28 7 14 21 28 7 14 21 28
    7.609 7.609 8.478 9.000 4.739 4.130 3.695 5.652 7.272 6.682 6.087 4.388
    7.391 8.696 8.043 9.783 3.696 4.348 4.565 5.652 8.709 6.629 5.357 5.539
    6.304 7.826 8.261 8.478 4.130 4.565 5.217 5.869 7.609 6.886 5.673 4.444
    7.609 8.696 8.478 9.000 4.739 4.348 4.565 5.652 8.919 6.102 6.437 4.558
    7.391 7.826 8.043 9.783 4.130 4.565 5.217 5.869 8.139 6.910 5.567 5.869
    Table 6: Test results of stabilized and compressed laterite soil bricks (B6) produced from combination of 89% laterite soil + 5% sand + 6% OPC
    Dry compressive strength (N/mm2) for various curing period in days Wet compressive strength ( N/mm2) for various curing period in days Absorption ( % ) for various curing period in days
    7 14 21 28 7 14 21 28 7 14 21 28
    9.217 9.565 9.565 10.217 5.217 5.000 5.652 6.522 7.571 6.751 5.100 4.158
    7.826 8.826 10.435 10.000 5.652 6.304 5.957 6.739 6.489 5.827 5.001 4.641
    7.391 8.913 10.217 11.304 4.130 5.869 6.087 6.087 7.018 6.751 5.726 4.083
    9.217 9.565 10.435 10.000 5.217 6.304 5.957 6.522 7.489 5.961 6.001 4.268
    7.826 8.826 10.217 11.304 5.652 5.869 6.087 6.739 6.428 5.840 5.896 4.734
    Table 7: Test results of stabilized and compressed laterite soil bricks (B7) produced from combination of 88% laterite soil + 5% sand + 7% OPC
    Dry compressive strength (N/mm2) for various curing period in days Wet compressive strength (N/mm2) for various curing period in days Absorption ( % ) for various curing period in days
    7 14 21 28 7 14 21 28 7 14 21 28
    7.609 10.087 11.522 10.652 4.130 6.739 7.134 7.174 7.013 6.638 5.277 3.928
    8.478 10.000 10.304 11.522 4.130 6.087 5.869 6.522 6.587 6.483 4.931 3.255
    8.913 9.652 9.348 10.217 5.087 6.087 6.304 7.391 6.442 6.679 4.751 3.619
    8.478 10.087 11.522 10.652 4.130 6.739 7.134 7.174 7.246 6.497 7.615 3.915
    8.913 10.000 10.304 11.522 5.087 6.087 6.304 7.391 6.778 6.660 6.870 3.460
    Table 8: Average dry compressive strength and strength ratios test results of stabilized and compressed laterite soil bricks
    Bricks Average dry compressive strength (σacs, N/mm2) for various curing period in days Strength ratios
    7 14 21 28 σacs,14/ σacs,7 σacs,21/ σacs,7 σacs,28/ σacs,7
    B4 7.261 7.305 7.565 7.652 1.006 1.042 1.054
    B5 7.261 8.131 8.261 9.209 1.120 1.138 1.268
    B6 8.295 9.139 10.174 10.565 1.102 1.227 1.274
    B7 8.478 9.965 10.600 10.913 1.175 1.250 1.287
    Table 9: Average wet compressive strength and strength ratios test results of stabilized and compressed laterite soil bricks.
    Bricks Average wet compressive strength (σacs, N/mm2) for various curing period in days Strength ratios
    7 14 21 28 σacs,14/ σacs,7 σacs,21/ σacs,7 σacs,28/ σacs,7
    B4 3.522 3.800 4.069 4.348 1.079 1.155 1.235
    B5 4.287 4.391 4.652 5.739 1.024 1.085 1.339
    B6 5.174 5.869 5.948 6.522 1.134 1.150 1.261
    B7 4.513 6.348 6.549 7.130 1.407 1.451 1.580
    Table 10: Comparitive test results of burnt bricks and stabilized and compressed laterite soil bricks
    Bricks Times the more dry compressive strength Times the more wet compressive strength Times the less absorption
    B4 1.549 2.470 3.813
    B5 1.864 3.261 3.565
    B6 2.139 3.706 4.039
    B7 2.209 4.051 4.864
    Experimental results

    The following Table No.4 to Table No.10 gives the test results of stabilized and compressed laterite soil bricks produced from various combinations of laterite soil + sand + OPC.

    Observations, discussion and conclusions

    Based on the experimental results and observations, the following discussions and conclusions were made in comparison with traditional (red clay) burnt bricks.

    Observations
    1. It has been observed that increasing in OPC content with 5% sand and use of hydraulic press paver block and brick making machine for brick making process, density of stabilized and compressed laterite soil bricks increases, inturn it increases the compressive strength and reduces water absorption. Maximum dry (77.68%) and wet compressive strength (63.3%) can be obtained at the age of 7 days of curing period; further, strength can be achieved at the age of 28 days of curing period.
    2. It has been observed that from the test results of stabilized and compressed laterite soil bricks of the minimum of 4 percent and maximum of 7 percent OPC content is sufficient in order to obtain required dry (7.65N/mm2 to 10.91N/mm2) and wet compressive strength (4.34 N/mm2 to 7.13 N/mm2) and resistance to water absorption values (4.63 percent to 3.63 percent).
    Discussion

    Stabilized and compressed laterite soil bricks prepared in this experimental investigation are more stable than the traditional burnt red clay bricks to resist higher compressive loads and absorb very less water. Thus, higher the compressive strength of the brick, higher will be the serviceability of the wall, thus increasing serviceability/durability of the structure in case of load bearing walls too. Further, laterite soil, being more acidic in nature, not suitable for the process of traditional brick making, stabilisation of such a soil with stabilizers like cement, lime, pozzolana will enable in preparing stabilized and compressed laterite soil bricks. Production of stabilized and compressed laterite soil bricks, which do not require any heat treatment process to gain required compressive strength. Finally, stabilized and compressed laterite soil bricks are more economical and environmental friendly construction building material compared to conventional red clay bricks and it decreases threat to the environment by deforestation and by Global warming.

    Conclusions
    1. It can be concluded that the compressive strength shown by stabilized and compressed laterite soil bricks are nearly twice and in some cases more than twice the strength of red clay bricks, which satisfies requirements of IS: 3495-Part (1) - 1992 specifications.
    2. It can be concluded that the percentage of water absorption shown by stabilized and compressed laterite soil bricks are less than 20%, which satisfies requirements of IS: 3495-Part (2) - 1992 specification.
    3. It can be concluded that stabilized and compressed laterite soil bricks are fall under class 7.50 to class 12.50 of bricks category according to IS:1077 - 1992 specifications.
    4. It can be concluded that the stabilized and compressed soil laterite bricks can be used as a substitute to tradational burnt red clay bricks for construction purpose.
    References
    1. Amin Esmaeil Ramaji [2012]. “A Review on the Soil Stabilization Using Low-Cost Methods”, Journal of Applied Sciences Research, Vol.8, No.4, pp2193-2196, 2012
    2. IS: 1077-1992: Common Burnt Clay Building Bricks -Specification, Bureau of Indian Standards, India.
    3. IS: 8112-1989: 43 grade ordinary Portland cement, Bureau of Indian Standards, India
    4. IS: 3495 – 1992, Methods of tests of burnt building bricks – Part 1: Determination of compressive strength, Bureau of Indian Standards, India.
    5. IS: 3495 – 1992, Methods of tests of burnt building bricks – Part 2: Determination of water absorption, Bureau of Indian Standards, India.
    6. Fetra Venny Riza, Ahmad Mujahid Ahmad Zaidi, Ismail Abdul Rahman [2010]. “A Brief Review of Compressed Stabilized Earth Brick (CSEB)”, International Conference on Science and Social Research, Kuala Lumpur, Malaysia.
    7. Jagadish K. S [2008]. “Alternative Building Materials Technology”, New Age International Publishers, 2008.
    8. Kabiraj.K, Mandal.U.K [2012]. “Experimental investigation and feasibility study on stabilized compacted earth block using local resources”, International Journal of Civil and Structural Engineering, Vol 2, No 3.
    9. Maher O. Amin [2013]. “Effect of Gypsum Stabilization on Mechanical Properties of Compressed Earth Blocks”, Tikrit, Journal of Engineering Sciences, Vol.20, No.3, pp87-93.
    10. Nagaraj H.B., Sravan M.V., Arun T.G., Jagadish K.S [2014]. “Role of lime with cement in long-term strength of Compressed Stabilized Earth Blocks”. International Journal of Sustainable Built Environment.
    11. Pankaj R. Modak, Prakash B. Nangare, Sanjay D. Nagrale, Ravindra D. Nalawade, Vivek S. Chavhan [2012]. “Stabilisation of Black Cotton Soil Using Admixtures”, International Journal of Engineering and Innovative Technology, Vol 1, Issue 5.
    12. Veena A R, Siva Kumar P and Eapen Sakaria [2014]. “Experimental Investigation on Cement Stabilized Soil Blocks”, International Journal of Structural and Civil Engg. Vol. 3, No. 1.

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