Experimental Research On The Concrete Properties At Cryogenic Temperatures

Test equipments used at cryogenic environment were designed and purchased. the temperature conditions, tensile strength and compressive strength were studied through experiments, and relevant calculation formulas were put forward. The main content are as follows:Firstly, the cooling equipments and test instruments used in the experiments were studied through systematic prepare,including ultra cold storage freezer, cryogenic loading boxes, ultralow temperature measuring equipment and load measuring equipment. And the purchase of equipment, trial-produce and testing was carried out. Secondly, through the production and experiments of three sizes of test blocks totally 10, the temperature in the center of different sizes concrete block and temperature gradient in the concrete with the time were studied.Thirdly, through the production and experiments of three kinds of specimens total 38 groups and 118 blocks, the effects of temperature on compressive strength and tensile strength are studied and corredponding formulas are put forward. On this basis,the relationship between them are bring forward.Following conclusions can be found through test and analysis:Number one, experimental equipment, the related test about the temperature proved that the temperature of test blocks can be controled at any temperature between room temperature and -180℃. and it can satisfy the requirement of temperature following tests.Low temperature measurement and loading equipment can be used at temperature range from 50℃to -290℃, which can satisfy the control to the temperature of the block and the measurement of strength in the experiments .Number two, temperature of concrete, when the temperature in the refrigerator is set to a certain point, the cooling rate of the concrete test block and decreases with the size of block becoming binger. If the temperature between invirement and block is smaller,cooling rate slows down. When the test block is not big, ignorance start cooling off period, the temperature in the internal of a concrete block is basically the same by six heat transfer. Therefore temperature in the block can be seen throughout the same, which is different from single non-steady state heat transfer.Number three, strength of concrete, the compressive strength of concrete increased with the decrease of temperature. Tensile strength of concrete also increased with the decrease of temperature, but it does not increase the same proportion with compressive strength. Size Effect of concrete block and the compressive strength conversion relationship between prism specimen and cube specimen varies with temperature, within the range found in a linear relationship.This text will provide reference for the construction of concrete structures at low temperature and the consummation of the concrete code at low temperature.