Behavior of Collapsible Soils Improved by Fly Ash and Cement Kiln Dust

Abstract

Collapsible soils are metastable soils characterized by voids inside their building, at grain sizes ranging from silt to fine sand. On wetting, they collapse producing distortions that might cause failure of structures. In this study, addition to the natural collapsible soil, an artificial collapsible soil was prepared with the exact properties of the natural one taken from the deposit to avoid the remodel during transfer. Then, both the natural and artificial soil samples were stabilized with fly ash and cement kiln dust with several percentages. Kaolin particles were used to prepare the artificial samples with low density to represent the metastable soil structure. The fly ash and cement kiln dust were used in several percentages 5%, 10% and 15% to demonstrate the effect of using these stabilizing agents on Odometer test. The addition of fly ash (up to 15%) to the natural or artificial soil resulted in a decrease in the collapse potential (CP) from 15.4% to 4.4 % and from 13.8% to 2.6%, respectively. The obtained results showed that treatment of collapsing soils (natural and artificial) with CKD resulted in a reduction of collapse potential from 15.4% to 0.72% and from 13.8% to 0.95%, respectively. The results showed a significant improvement of the stabilized collapsible soil over the non-stabilized one whether treated by using fly ash or CKD. Additionally, CKD showed more effectiveness than fly ash in all the undergone tests.