The study involved investigating the performance of ordinary Portland cement (OPC) stabilized soil blocks amended with sugarcane bagasse ash (SBA). Locally available soil was tested for its properties and characterized as clay of medium plasticity. This soil was stabilized using 4% and 10% OPC for manufacture of blocks of size 19 cm × 9 cm × 9 cm. The blocks were admixed with 4%, 6%, and 8% SBA by weight of dry soil during casting, with plain OPC stabilized blocks acting as control. All blocks were cast to one target density and water content followed by moist curing for a period of 28 days. They were then subjected to compressive strength, water absorption, and efflorescence tests in accordance with Bureau of Indian standards (BIS) specifications. The results of the tests indicated that OPC stabilization resulted in blocks that met the specifications of BIS. Addition of SBA increased the compressive strength of the blocks and slightly increased the water absorption but still met the standard requirement of BIS code. It is concluded that addition of SBA to OPC in stabilized block manufacture was capable of producing stabilized blocks at reduced OPC content that met the minimum required standards.
Soil has been one of the primary components of construction since ancient times, finding applications in a variety of forms like mud plaster, adobe blocks, and rammed earth to name a few. With the development of technology, fired brick came into existence which improved the performance of soil and made them more water resistant and durable. Other forms of soil utilization slowly faded into oblivion due to their inability to resist damage due to water ingress in moist environments. Thus, fired bricks have been the primary building material for construction for a long time. However, in the recent years there has been a shift away from the utilization of fired bricks towards eco-friendly building materials. Utilization of waste based construction materials like flyash bricks has become one of the popular choices. However, in developing countries like India, where there is a need for low cost building materials for housing, earth construction is one of the best alternatives. Housing is one of the basic needs of all human beings, particularly for the economically weaker section and low income groups who cannot easily afford the cost of construction. With the housing requirements in developing countries touching unmanageable proportions, various governments are taking conscious efforts to bridge the gap, especially undertaking housing schemes to ensure housing for the poor. The current housing shortage in India is 6 crore units, which will jump to 11 crore units in 2022 requiring an investment of US$250–260 billion [
The materials adopted in the manufacture of the compressed stabilized earth blocks include the locally available soil, cement, and SBA. The soil adopted in the study was collected from a lake shore in Kolathur village, Kanchipuram district, Tamil Nadu, India. The geotechnical properties of the soil were tested in the laboratory in accordance with the Bureau of Indian Standards (BIS) codes and are tabulated in Table
Properties of soil.
Property | Value |
---|---|
Liquid limit [ |
41.8% |
Plastic limit [ |
14.5% |
Plasticity index | 27.3% |
Shrinkage limit [ |
10.1% |
Maximum dry density [ |
18.5 kN/m3 |
Optimum moisture content [ |
11.9% |
Unconfined compressive strength [ |
523.4 kPa |
BIS classification [ |
CI |
The cement adopted in the stabilization of the soil for the manufacture of compressed stabilized block is OPC. The typical composition of OPC is given in Table
Chemical composition of OPC [
(%) of |
SiO2 | Al2O3 | CaO | Fe2O3 | K2O | MgO | Na2O | P2O5 | TiO2 | SO3 |
---|---|---|---|---|---|---|---|---|---|---|
OPC | 21.45 | 4.45 | 63.81 | 3.07 | 0.83 | 2.42 | 0.20 | 0.11 | 0.22 | 2.46 |
SBA | 35.17 | 0.281 | 2.07 | 5.22 | 3.75 | 0.91 | 0.01 | 1.03 | 0.02 | 0.03 |
India is one of the largest growers of sugarcane. The major solid wastes generated from the sugar manufacturing process include sugarcane trash, bagasse, press mud, bagasse flyash, and spent wash [
The series of steps involved in going into the investigation involved preparation and characterization of materials, selection of block size and mould fabrication, selection of stabilizer and additive content, casting and curing of blocks, and experimental investigation.
The preparation of soil was carried out in accordance with BIS code [
BIS code [
Steel moulds adopted for moulding of stabilized blocks.
There are three types of cement stabilized materials, namely, soil cement, cement bound material, and lean concrete. Soil cement contains less than 5% cement; cement bound material is stronger soil cement but with granular aggregate while lean concrete contains higher cement content than cement bound material [
The methodology adopted in casting of soil blocks was similar to that of preparing unconfined compression cylinders for testing soil specimens, the difference being that the sample was cast in the mould prepared for blocks. The soil blocks were cast to a fixed density of 18.5 kN/m3 and a moisture content of 12%. The mould was prepared by thoroughly tightening all the bolts and the interior was lubricated with oil for easy removal of the pressed block. The weights of soil, cement, and SBA were carefully measured and mixed in dry conditions thoroughly. The required content of water was measured, added to the mixture, and thoroughly mixed to get an even wet mix. The wet mix was then placed in the mould, and followed by the top plate and a compression test ram was used to press the top plate. The mould was so designed that the top plate cannot be lowered below the fixed dimensions of the block. Completely pressing the entire mix in the mould resulted in achieving more or less uniform density of blocks for testing. After the formation of the block, the mould was opened and the block was removed and was moisture-cured for a period of 28 days by sprinkling of water and covering with plastic gunny bags to prevent loss of moisture. Figure
Graphical description of casting and curing of stabilized earth blocks.
BIS code [
The cement contents of 4% (soil cement) and 10% (lean concrete) were adopted for stabilization of soil blocks. Three SBA contents were randomly adopted as 4%, 6%, and 8%. In an earlier study, Lima et al. [
The compression test on the stabilized soil blocks was done in accordance with BIS code specifications. Figure
Compressive strength of 4% cement stabilized soil blocks admixed with SBA.
It can be seen that addition of SBA results in increase in strength of the stabilized soil block with the exception of 4% addition of SBA wherein there is a marginal decrease. In contrast, Khobklang et al. [
Figure
Compressive strength of 10% cement stabilized soil blocks admixed with SBA.
Figure
Percentage of compressive strength gain with %SBA.
Earlier research adopting combinations of cement and SBA has been reported in the literature. However, two investigations in particular, done by Lima et al. [
Comparison of compressive strength of present study with earlier works [
The water absorption test in the present study was also done in accordance with BIS specification as in the case of compressive strength test. Figure
Water absorption levels of 4% cement stabilized blocks admixed with SBA.
Figure
Water absorption levels of 10% cement stabilized blocks admixed with SBA.
The efflorescence test on stabilized soil blocks was conducted in accordance with BIS specification [
Efflorescence of stabilized blocks.
Cement content (%) | SBA content (%) | Efflorescence |
---|---|---|
4 | 0 | Nil |
4 | 4 | Nil |
4 | 6 | Nil |
4 | 8 | Nil |
10 | 0 | Nil |
10 | 4 | Nil |
10 | 6 | Nil |
10 | 8 | Nil |
The study involved the utilization of combination of cement and SBA in the manufacture of stabilized soil blocks and gauges its performance with plain cement stabilized blocks as well as the minimum requirements stipulated by BIS code. Based on the results of the experimental investigation carried out, the following points can be concluded. Cement stabilization of locally available soil can be used in the manufacture of stabilized soil blocks to meet the compressive strength and water absorption norms of BIS specifications. Cement stabilization of soil at 4% cement content meets the specifications of class 20 blocks whereas cement stabilization of soil at 10% cement content meets the specifications of class 30 blocks. Addition of SBA to cement in stabilization results in an increased compressive strength of the blocks. However, SBA addition is more effective at lower cement content of 4% producing higher strength gains when compared to higher cement content of 10%. Addition of SBA to cement in stabilization results in an increase in the water absorption of the blocks but is still comfortably within the norms stipulated by BIS. However, the addition of SBA produces more water absorption at higher cement content of 10% than lower cement content of 4% for similar SBA contents, again reinforcing the inference that SBA addition is more effective at lower cement content. Addition of 8% SBA to 4% cement content increases its compressive strength to meet the strength requirements of class 30 blocks from the original category of class 20 blocks. Thus it can be seen that addition of 8% SBA can result in utilization of just 4% cement for achieving class 30 block specifications. This leads to saving of 6% cement in comparison with the other combination adopted in this study. The compressive strength of 4% cement with 8% SBA is just enough to meet the class 30 block specifications. Hence, in order to achieve a higher safety margin, slightly higher contents of SBA and cement combinations can be investigated to arrive at optimum combinations from the point of view of cost and performance. The durability aspect of the cement stabilized blocks has not been investigated in this study. Hence, it is recommended that the durability aspect of cement stabilized blocks admixed with SBA should be taken up in future investigations.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors are grateful to the management of Tagore Engineering College and Bharath University, Chennai, India, for providing the laboratory facilities for carrying out this investigation. They would also like to acknowledge the XRF facility provided by SAIF, IIT Bombay, Mumbai, India. The authors also extend their thanks to Mr. M. Sasi Kuamr, Laboratory Instructor, Soil Engineering Laboratory, Tagore Engineering College, for his help during the investigation.