Gypsum-Induced Volume Change Behavior of Stabilized Expansive Soil With Fly Ash-Lime

An attempt was made to study the efficiency of fly ash and lime on the volume change behavior of soil to mask the effect of gypsum. Swell and compressibility of soil mixed with 10 % fly ash and treated with various lime contents (0 %-6 %) in the absence and presence of 1 % gypsum after curing for different periods of up to 28 days were studied. It was established that an increase in lime content improved swell and compressibility in the soilfly ash mix but that it led to rapid swelling and increased compressibility in the presence of gypsum, particularly when the specimens were not cured. Higher amounts of lime and a longer curing period were found to be essential to conquer the adverse effect of gypsum. The behavioral changes in the swell and compressibility of both specimens, with and without gypsum, were attributed to consequent alterations in the microstructure by the formation of cementitious products and the growth of ettringite crystal. It was observed that the formation of cementitious compounds with a curing period enables to the compound to overcome the adverse effect of ettringite, leading to control of undesirable volume change behavior