Experimental Study on Flyash-Stabilized Expansive Soil

Abstract

About 51.8 million hectares of India are covered with expansive black cotton soils. The expanding road network has compelled engineers to build roads over these weak soils. Constructing pavements on expansive subgrades involves a threefold problem of a poor supporting strata, heavy vehicular loading and lastly, scarcity of good-quality aggregate. Roads constructed on expansive soils incur large capital costs and maintenance costs. Flyash produced in several thermal power plants is largely unutilized. It can be used as a stabilizing material in the road pavements, as an alternative to replacement of locally available (substandard) materials, thereby reducing the problems associated with disposal of flyash, and also leading to economical constructions. Laboratory investigations were undertaken to study the stabilizing effect of locally available Class F-type flyashes, when used in combination with lime. Index tests to determine free swell index, linear shrinkage and pH along with detailed tests to determine UCS, CBR and heave were performed. The free swell and linear shrinkage were significantly reduced. UCS improved consistently with time. The soaked CBR test of LFA-treated samples indicate excellent improvement in strength and reduction in volume-change behaviour. The performance of the LFA treatment was largely affected by the type of flyash.