EFFECT OF FREEZING AND THAWING ON FRACTURE PERFORMANCE OF CONCRETE AT POLAR LOW TEMPERATURE

In order to study the durability performance changes of concrete after freeze-thaw cycles in polar and cold regions, freeze-thaw cycles and loading tests of 84 three-point bending beams were carried out by the slow-freezing method. The test was conducted with the lower limit temperature (down to −80 ℃), the number of freeze-thaw cycles, the concrete strength, and the concrete type as the study parameters, and the changes in the basic mechanical properties of concrete and key fracture parameters were compared and analyzed before and after the freeze-thaw cycles. The study results show that: with the decrease of the lower limit temperature of freeze-thaw cycles and the increase of the number of freeze-thaw cycles, the basic mechanical properties as well as the cracking toughness and fracture energy of concrete show a decreasing trend, but the instability toughness and characteristic length show a opposite trend, indicating that the ability of concrete to resist cracking decreases after experiencing freeze-thaw cycles, but the deformation properties of concrete improve significantly; with the increase of concrete strength, the freeze-resistance durability has been improved to a certain extent; the fracture performance of seawater sea-sand concrete after freeze-thaw cycles is not lower than that of ordinary concrete. The concept of freeze-thaw damage accumulation is proposed, which can be used to reflect the variation of fracture parameters and the quantitative comparison of different freeze-thaw conditions.