Improvement of swelling-collapsible behaviors of silty clay by calcium carbide residue

Abstract

The natural soil in northeast Thailand is silty clay, which is deposited from clay stone. The soil in the dry state exhibits excellent engineering characteristics with high bearing capacity. However, the soil bearing capacity decreases when the water content increases. The change in water affects the swell and collapse of the soil mass significantly. This research presents the experimental study on the swelling and collapsible behaviors under the one-dimensional swelling and collapse tests of the silty clay stabilized by the Calcium Carbide Residue (CCR), which is adopted from the waste products in acetylene gas factories. Based on the test results, it is seen that the silty clay shows the swelling and high collapsion index, which are problematic for the silty clay. The swelling and collapsible properties were reduced by increasing the CCR. The results of swelling and collapse can be classified into two zones. Firstly, the swelling and collapsible strains decrease with an increase in the CCR content. Secondly, they increase with an increase in the CCR content. The increase is because of the excess CCR that remains in the soil. The excess CCR or the free lime has unsoundness properties, therefore, the high free lime (CCR content > CCR fixation point) causes the CCR stabilized clay to swell. The CCR fixation point is noteworthy; since, it helps determine the right amount of the CCR content that should be added into the silty clay. The CCR fixation point can simply be obtained from the laboratory consistency index tests.