Improvement of CBR of gypsum subgrade soil by cement kiln dust and granulated blast-furnace slag

Abstract

Abstract Most construction projects face the problem of a high percentage of gypsum in the soil. To get rid of the unwanted effects of gypsum, which lead to the dissolution of gypsum in the presence of water and the settlement of the foundations of buildings and subsoil of roads, the researchers used several materials that can be added to the soil to improve its properties in resisting loads. This research presents a study of the effect of adding cement kiln dust (CKD) and ground-granulated blast-furnace slag (GGBS) on the California Bearing ratio (CBR) of gypsum sandy soil. The percentages of 2.5, 5, 7.5, and 10% of additives by the weight of the soil sample were collected, and CBR tests were performed on dry and soaked samples. The main results showed that the ideal CKD ratio, which improves the CBR soil in a dry state, is 5% and in a soaked condition is 7.5%. Also, CBR in dry and soaked states increases slightly when the GGBS percentage increases reaching 10%. The use of GGBS gives an increment in CBR, which is around 1.6 times in a dry condition and 4 times in a soaked state.