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

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