Plasticity and Swelling Characteristics of Geopolymer Treated Expansive Soil

Abstract

Expansive soil causes extensive damage to geotechnical structures owing to its high volume instability. Cement and lime are most commonly used to improve these soils both in terms of reduction in plasticity, swelling characteristics and for the improvement of strength. However, the production process of these traditional stabilizers is energy intensive and it also serves as a major source of green-house gas emission leading to serious problems like global warming. Geopolymer is a new generation alternative binding material for conventional cement. This is primarily produced from industrial wastes like slag or flyash which are rich in alumino-silicates. When activated with alkalis, these products form geopolymers, which provides high strength to soil and have low cost, low energy consumption and is eco-friendly. This study explores the efficiencies of ground granulated blast furnace slag (GGBS) based geopolymer binder in improving the properties of expansive soil in comparison to cement and lime. In this study the expansive soil is mixed with 0, 5, 10,15 and 20% of GGBS and activated with sodium hydroxide solutions of 0.5, 1, 2 and 4M concentrations. However, cement and lime are mixed with the soil in the proportions of 1, 2, 4, 8, 12 and 15% by weight of the soil. The consistency limits and swelling characteristics of geopolymer, lime and cement treated soils are evaluated at 0, 3, 7 and 30 days of curing. It is found that the plasticity characteristics are improved and swelling and shrinkage of the expansive soil is greatly reduced with increasing concentration of these admixtures. Curing period also influences these properties. It is also observed that the performance of geopolymer is comparable to that of cement and lime. So, geopolymer can be effectively used as an alternative stabilizing agent to modify the plasticity and swelling properties of expansive soil.