Effects of Curing Conditions on Unconfined Compressive Strength of Cement- and Cement-Fiber-Improved Soft Soils

Abstract

Cement-soil mixing is an effective ground improvement technique. The introduction of cement to soils can effectively increase their shear strength, but at the same time the mixture becomes brittle. To increase the ductility of the mixture, fiber can be added to the mixture. The current design criterion only requires the measurement of unconfined compressive strength without considering the effects of curing time and curing stress and the simplified design criterion does not reflect the field behavior of cement soil mixtures. A series of unconfined compression tests on cement- and cement-fiber-improved soft soils were conducted with special attention being paid to the combined effects of curing time and curing stress. It is found that the introduction of cement to soft soils can increase the unconfined compressive strength, which also increases with curing time and curing stress. The existence of fiber in the cement-soil mixture can significantly improve its ductility without changing the unconfined compressive strength too much. The stiffness of the mixture can be significantly increased when the mixture is cured under curing stress when compared with the mixture without curing stress.