Effects of freeze-thaw cycles on the mechanical properties of cement-fiber composite treated silty clay

A composite improvement method was proposed by adding cement and fiber into the silty clay in order to enhance the stability and durability of the subgrade structure in the seasonally frozen area. The frost resistance of the composite treated silty clay is studied. Results show that the resilient modulus and unconfined compressive strength of cement-fiber composite treated soil decreases with increase of initial moisture content and the freeze-thaw cycles; the mechanical properties change obviously under the first freeze-thaw process, and tends to be stable after six freeze-thaw cycles. For the composite treated soil with 6% cement content, the optimum dosage of basalt fiber and polypropylene fiber is 1.0% and 0.15%–0.25%, respectively. Under the same moisture content and freeze-thaw cycles, the unconfined compressive strength of 0.15% polypropylene fiber composite soil is higher than that of 1.0% basalt fiber. Besides, a good linear relationship was found between unconfined compressive strength and resilient modulus of composite treated soil.