EXPERIMENTAL RESEARCH ON CRYOGENIC TEMPERATURE COMPRESSIVE STRENGTH OF CONCRETE UNDER COUPLING ACTION OF KEY INFLUENCING FACTORS

The water content of concrete specimen was pre-treated by soaking and baking without changing the internal pore structure and distribution, then through the axial compressive test at different cryogenic temperatures, the influencing regularities of three factors including cryogenic temperature action (-40 ℃ to -180 ℃), concrete water content (1.5% to 5.5%) and strength grade (C30, C40 and C50) on cryogenic temperature compressive strength of concrete were systematically discussed, and corresponding coupling function was fitted out. The test results showed that the higher the concrete water content and strength grade, and the lower the cryogenic temperature, the greater the damage-induced sound and crispness extent, meanwhile the more obvious the brittleness failure and eccentricity feature; the broken residual blocks of the upper and lower cones became more different and the fragments became finer, and the phenomenon of aggregate splitting was more apparent. The compressive strength of concrete increased greatly at cryogenic temperature, the higher the concrete water content, and the lower the concrete strength grade and the cryogenic temperature, the more obvious this changing trend, and it was closer to the linear relationship with increase in concrete water content. Among the three key factors, the effects of concrete water content and cryogenic temperature on concrete compressive strength were obvious, but the influence of concrete strength grade was weaker.