Effect of RBI-81 on CBR and Swell Behaviour of Expansive Soil

Abstract

Many ground improvement techniques have been evolved in the past decade in order to reduce the potential of severity of the expansive soils. Out of those techniques, soil stabilization is the most effective technique. This paper presents results of the investigation carried out to stabilize an expansive soil using RBI grade 81 stabilizer. Free swell index, CBR and SEM analysis were carried out on both untreated and treated soils. There was a considerable reduction in swell potential and an increase in the strength of the soil with the addition of stabilizer. Stabilization of soil involves the enhancement of soil properties by addition of stabilizer which may be organic or inorganic in nature. Among various ground improvement techniques, soil stabilization is an effective method that enables to re-use the in-situ soil upon application of stabilizer having the potentiality of modifying the existing property of a soil. Generally soils have varying engineering properties that may or may not be suitable for construction. As far as road construction is concerned, cohesive clayey soil is a tough challenge for highway engineers due to its swelling and shrinkage characteristics which are the sole reasons for pavement failures. Stabilization of such Kaolinite and Montmorrillonite soils by means of mechanical or chemical methods helps to re-use the soil instead of road cutting for replacing the in-situ soil with suitable carted earth as subgrade. Conventionally, lime stabilization, bitumen stabilization and cement stabilization were practiced as ground improvement techniques. There are other cementious stabilizers used for soil stabilization in case of soils having very low CBR. Reddy and Moorthy (2004) have shown that pond ash along with small amount of lime when added to poor clayey sub-grade, improves CBR and thereby increases the pavement life and reduces the thickness. In this study RBI grade 81 (Road building international) soil stabilizer is used for improving the soil properties of an A-7-6 (HRB classification) soil. RBI grade 81 is ecofriendly natural inorganic cementious soil stabilizer. Objective of the study deals with the comparison of the strength and microstructural changes of virgin soil sample and RBI grade 81 stabilized soil at various curing days mixed with various dosages i.e., 2%, 4% and 6%. II. Literature Review