Abstract
Construction on locally available clayey soil is often problematic due to its swelling and shrinkage nature. Pavements are most affected as the upthrust due to regional swelling of clayey soil during monsoon season and shrinking during dry season causes unwanted cracks in the pavement. As a consequence, the pavement gets damaged. In places having extensive deposit of clayey soil, soil replacement becomes time-consuming and uneconomical. Hence the clayey soil to be considered as subgrade needs to be pre-treated. Fly ash, an industrial waste can be used for such treatment. To improve the engineering properties of on-site available clayey soil and sandy soil with lime and fly ash was studied. Based on the results obtained from experiments the suitability of fly ash and lime to be considered as additives to improve local clayey and sandy soil properties has been analyzed. It was observed that the on the addition of fly ash within 40-60% range can be satisfactorily used to replace the local clayey soil and fly ash percentage within 20-40% can be used to replace the local sand. Lime content in the range of 4-8% can be satisfactorily used in both in situ available soil and local sand with fly ash mixtures for the improvement of strength in terms of shear strength as well as CBR value.
Highlights
Properties of soil subgrade always take a paramount role in the behaviour of the pavement
Laboratory experiments was conducted to determine shear strength parameters, compaction characteristics, hydraulic conductivity and California bearing ratio (CBR) value of locally available soil, sand mixes with different proportions of fly ash with or without chemical stabilizer lime in a view to get a rough estimate of optimum proportioning required so that the mix has sufficient strength to be used as a subgrade or sub-base. 17 nos. of specimens with varying proportions of sand, clay, fly ash and 6 specimens of sand, clay, fly ash with addition of lime content varying between 4 to 12% and one specimen having 70% sand and 30% fly ash and one specimen having 50% clay and 50% fly ash were tested
From the experimental results it has been observed that the sudden increment of maximum dry density value was caused due to better packing of sand and fly ash up to 20-40% as the fly ash fills most of the voids present
Summary
Properties of soil subgrade always take a paramount role in the behaviour of the pavement. Ratio (CBR) values of subgrade materials determine its mechanical properties [1]. Fly ash produced in thermal power plant is disposed as a waste by-product can be used as a suitable soil stabilizing material. Enhanced engineering characteristics of soil by mixing fly ash can be used to construct roads and safely reuse the waste material. Experiments on specimens with varied proportions of sand, lime, fly ash and locally available clay has been conducted and correlations between the engineering properties i.e. cohesion, angle of friction, CBR and hydraulic conductivity has been established in this present study. The study has performed detailed laboratory analysis on the consequences of application of varying percentage of stabilizer and waste material on locally available soil and sand in order to observe the variation in shear strength; maximum dry density; hydraulic conductivity, and CBR values
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