Effects of Climatic Factors on Mechanical Properties of Cement and Fiber Reinforced Clays

An experimental program was undertaken to investigate the effects of two climatic factors; i.e., freeze-thaw cycles and temperature, on the mechanical properties of clay, cement-reinforced clay and cement-fiber-reinforced clay. The stress-strain behavior, unconfined compressive strength, elastic modulus, cohesion, friction angle and residual strength were studied for all soil mixtures. All soil mixtures were subjected to 1, 3, 6 and 12 freeze-thaw cycles and were also tested at -20, -10, -5 and +20 degrees C. In addition, the brittleness index and freeze-thaw reduction index were introduced to investigate the effects of freeze-thaw cycles and temperature on brittleness and unconfined compressive strength of unreinforced and reinforced clay soils. The results showed that the addition of cement to the clay leads to a significant increase in brittleness, while the use of fiber contributed to the improvement of the ductile behavior of cement-reinforced clay. An increase in the freeze-thaw cycles and a decrease in temperature caused an increase in the brittle behavior of the clay and reinforced clays. The F-T reduction indexes of unreinforced and reinforced clays decreased by 30 and 55 %, respectively, after the soils were subjected to 12 freeze-thaw cycles. The cohesion of fiber-cement reinforced clay was reduced to half the original value after 12 freeze-thaw cycles, while the friction angle of the fiber-cement reinforced clay remained nearly unchanged. The test results indicated that the addition of cement and fiber to the clay increased the compression strength and elastic modulus of unfrozen and frozen clay soils.