Evaluation of micro-metakaolin and ferric chloride solution in stabilising expansive soils

Abstract

Expansive soils are generally characterised by their volume change when subjected to variation in water content. This may result in significant damage to supported and nearby structures. In this study, the swelling properties of bentonite material as an expansive soil are first determined. The expansive soil is then improved using two different approaches, namely, micro-metakaolin (Mm) and ferric chloride (FeCl3) solution. The optimum percentages for both additives are determined using laboratory experiments, which are 25 and 1% for the Mm and the ferric chloride solution, respectively. The free swell index of the bentonite after being treated with Mm and ferric chloride solution at the optimum percentages is found to decrease by about 54 and 62%, respectively. Meanwhile, the swelling pressure for the expansive soil decreased by 33 and 43% when mixed with the same optimum values of Mm and ferric chloride solution, respectively. On the basis of the results obtained in this study, the addition of ferric chloride solution achieved better results compared with Mm. This improvement technique may be used to enhance the properties of expansive soils that support different construction engineering projects.