Research on the performance of concrete materials under the condition of freeze-thaw cycles

Durability of concrete has been a social concern due to the poor performance of concrete caused by various environmental conditions. This paper aims to study the effects of damage caused by freeze-thaw cycles which often appeared in cold areas on the performance of concrete with polypropylene fibres, such as strength, carbonation depth and chloride ion diffusion. Concrete samples with different degrees of damage were produced by different freeze-thaw cycles. The concrete sample shows great water absorption after freeze-thaw cycles. Due to damage by freeze-thaw cycles, the total pore volume, porosity and average pore diameter of concrete samples damaged by freeze-thaw cycles were generally larger than that of normal concrete samples. Compressive strength and splitting strength of concrete exposed to freeze-thaw cycles decreased with the number of freeze-thaw cycles and greater damage caused higher loss of strength, especially for the splitting tensile strength. The carbonation depth of the concrete after freeze-thaw cycles was also greater than that of the concrete before freeze-thaw cycles. Chloride ion diffusion rates were evaluated using the free chloride ion concentration titration method and the steady state migration testing method. Results indicated that freeze-thaw cycles could accelerate chloride ion diffusion rates. More severe concrete damage results in greater chloride diffusion.