Evaluation of the role of fibres and admixture(s) on sustainable crack reduction in expansive soil

Abstract

Many geotechnical infrastructure facilities such as canals, farm ponds, reservoirs, natural slopes and landfills are prone to cracking during wetting/drying cycles, mainly due to the presence of expansive soils. The formation of cracks may result in significant ingress/loss of water and leachate percolation from landfills causing contamination of land/ground water. Proper lining/stabilization of the above stated geotechnical facilities would minimize loss of water/migration of leachate. In this context, the present study evaluates the performance of expansive soil blended with fibres, and with/without admixtures, on its cracking behaviour. Desiccation drying tests have been performed on expansive soil blended with fibres, by varying the type of fibres (viz., natural coir and polypropylene fibres), proportion of fibres (0.5% to 2% of dry soil weight) and exposure temperature, viz., 27 °C (ambient temperature) and 45 °C (representing hot arid conditions). Crack and shrinkage intensity factor (CSIF) has been computed as ratio of area of crack and shrinkage to total area of specimen. It has been observed from the study that addition of fibres substantially reduces the CSIF values, with 1% polypropylene fibres yielding maximum reduction. Further, the expansive soil has been blended with optimum proportion of polypropylene fibres (1%) and admixture with proportion varying from 2.5% to 10%, wherein a maximum reduction in CSIF values upto 73% were achieved for soil with 1% polypropylene fibres and 10% ultrafine slag. Though, complete crack mitigation could not be achieved, attributed to high cracking potential of expansive soil due to differential stresses during drying, size and area of the cracks has been substantially reduced. The study results are quite encouraging in utilization of fibres with admixtures, for sustainable reduction of cracking in expansive soil, and optimizing the thickness of lining/usage of thinner water proofing membranes for canals, farm ponds and other similar construction on expansive soils.