Abstract
This study presents the effect of high plasticity on swell potential, swelling pressure and micro-structural characteristics of kaolinite-bentonite mixed clays. Five different mix ratios of kaolinite bentonite mixture of 100:0, 90:10, 75:25, 50:50 and 25:75 in % by weight of dry kaolinite were used. All five synthesised soils were then mixed with 0%, 5% and 8% of cement by weight of dry soil, cured for 28 days and subjected to the Atterberg limit, one-dimensional oedometer and scanning electron microscope test. The inclusion of 5% and 8% cement reduces the plasticity index of the treated soils as the percentage of bentonite increases. The effects on plasticity of treatment with 5% and 8% cement after a 28-day curing period was evaluated, and the results show that reduction in plasticity index resulted in decreased swell potential and swelling pressure of the kaolinite-bentonite mixed clays. The results of microstructural analysis of 5% cement-treated soils show formation of flocculated fabric and cementation of soil particles, and filling with cementitious compounds of the voids of flocculated fabric in the soil. The reduction in swell can be attributed to the resulting compacted and dense mass of treated soils due to cementation of soil particles and cation exchange. The complex swell behaviour of high-plasticity kaolinite-bentonite mix is explained using the one-dimensional oedometer test, by further experimental study and examination of the microstructure of treated soils.
Highlights
The extensive geological spread of swelling clays around the globe presents a key challenge to engineers, especially in areas where construction and land development activities are intended
The increase in the liquid limit can be attributed to more water needed to make the cement-modified kaolin more fluid, whereas the increase in plastic limit suggests that the cement-kaolin mixture requires more water to change from its plastic state to a more semisolid state
The extent of the reduction in plasticity index with the addition of cement to the kaolin-bentonite mixture is highly dependent on the percentage of bentonite and cement content present in the kaolin-bentonite mixed soils
Summary
The extensive geological spread of swelling clays around the globe presents a key challenge to engineers, especially in areas where construction and land development activities are intended. Engineering structures intended for clay-rich soils of high plasticity would be at serious risk of failure if little or no solution is sought to salvage the foundation soil. What has become even more challenging nowadays is the continuous rise in world population and housing needs, making land development and construction activities on areas of weak or problematic soils unavoidable. Civil Engineering Cluster, Department of Geography and Environmental Management, Faculty of Engineering and Technology, University of the West of England, Bristol, UK The application of cement in treatment of weak and problematic soils have resulted in improved performance such as reduction in plasticity and swell potential, substantial strength gain, increase in elastic modulus and resistance against the influence of moisture
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