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Design purchase of test equipment used in the ultra-low temperature environment, temperature and tensile strength of concrete cooling of ultra-low temperature environment through the test, the compressive strength of the proposed formula, mainly including the following aspects: 1. Before the test The system is ready, the test process cooling equipment and test instruments, including ultra-low temperature freezer, ultra-low temperature load box, cryogenic temperature measurement equipment and load measuring equipment, etc., and the instrument purchase, trial and test. 2 by the specimen of the produced three sizes of 10, placed in the specified position of the specimen temperature sensor, and at -20 ° C, -50 ° C, -80 ° C and the the -160 ℃ four temperature point temperature test, research change with time of the temperature of the center of the different specifications of the concrete specimens, and concrete test pieces formed at low temperatures, the temperature field variation with time. Cube specimens produced in three sizes 38 groups of 114, 20 ° C, 0 ° C, -20 ° C, -40 ° C, -60 ° C (-70 ° C), -80 ° C, -120 ° C and measuring the strength of the test block of the to -160 ℃ nine temperature points of temperature effects of compressive strength and tensile strength of the proposed cube compressive strength at different temperatures, prism compressive strength and splitting tensile strength formula On this basis, summarizes the low temperatures prism compressive strength, splitting tensile strength and cube compressive strength of the relationship and the effect of the size of the cube compressive strength at low temperatures. Following basic conclusions can be obtained through the test and analysis: 1. Laboratory equipment: temperature proved, ultra-low temperature refrigerator and ultra-low-temperature load box to control the temperature of the test block to any temperature between room temperature to -180 ℃ to meet the follow-up test temperature requirements. The temperature range used by the low-temperature measurement and loading device 50 ℃ ~ -290 ℃, able to meet the test of the control and intensity of the sample block temperature measurement. 2 on the temperature of the concrete: the temperature in the refrigerator is set to a certain point, the cooling rate of the concrete is reduced with the increase of the test block, the slow cooling rate in the temperature difference is smaller. When the test block is not removed by the beginning of the cooling stage, the six surface heat transfer the internal temperature of the concrete block is basically the same, can be seen as the entire isothermal sided non-steady-state heat transfer. (3) With regard to the strength of concrete: the compressive strength of the concrete as the temperature decreases significantly improve the tensile strength of the concrete is also improved as the temperature decreases, but the increased proportion is not the same as with the compressive strength. The compressive strength size effect of concrete block and prism specimens block compressive strength and cube test block conversion relationship varies with temperature changes in a range of basic linear relationship. This article provides concrete specifications for the construction of concrete building structures at low temperatures and low temperature perfect reference.
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