Experimental study of fracture damage in concrete subjected to freeze-thaw cycles

To study fracture performance and characteristics of concrete experiencing freeze-thaw cycles, applying the GBJ82-85 test method for frost resistance of concrete, freeze-thaw experiments were done with 72 concrete blocks which were classified into 24 groups. Four-point bending tests were used to examine the effects of water-cement ratio and air-entraining agents on fracture toughness, fracture energy and the dynamic elastic modulus of concrete subjected to 300 rapid freeze-thaw cycles. The microstructures of the concrete were also analyzed. The results showed that with increases in the number of freeze-thaw cycles, the fracture toughness of concrete, the loss of fracture energy, as well as the relative loss of dynamic elastic modulus showed a downward trend. The greater the water-cement ratio, the more severe the damage to the concrete as the number of freeze-thaw cycles increased. Air-entraining agents can significantly reduce the damage to concrete structures due to freeze-thaw cycles. The loss of fracture energy and the relative loss of dynamic elastic modulus keep a good linear relationship.