EXPERIMENTAL RESENRCH ON CRYOGENIC TEMPERATURE TENSILE STRENGTH OF CONCRETE UNDER COUPLING ACTION OF KEY INFLUENCING FACTORS

The effects of three key factors, including cryogenic temperature, concrete water content and strength grade, on concrete tensile strength were discussed through the splitting tensile experiment under cryogenic temperatures from -40 ℃ to -180 ℃ for the concrete with different water contents (2.0% to 5.5%) and strength grades (C30, C40 and C50), and the corresponding coupling action relationship was also fitted out. From the test results it was shown that the higher the strength grade and water content of concrete, and the lower the cryogenic temperature, the more flat the failure surface and the more obvious the splitting phenomenon of coarse aggregates located in the failure surface. The tensile strength of concrete increased with the increase of water content, and decreased with the decrease in cryogenic temperature at same other conditions, and then tended to be stable. However, the influence of concrete strength grade on its cryogenic temperature tensile strength was relatively small, and the higher the water content, the smaller the increase in splitting tensile strength for the concrete with higher strength grades. These test results and the expressions of concrete splitting tensile strength at cryogenic temperature, including three key factors of cryogenic temperature, water content and strength grade, could be used as references for the improvement of relevant theories and the design and safety evaluation of ultralow temperature concrete structures.