Research Popularization And Application Of Key Technology For Cement Concrete Frost-resisting

In addition to the load,concrete structures in the engineering are also affected by the environment and climate conditions.Under the conditions of not very harsh environment,good quality concrete has enough strength and dense degree,so it is durable.However,for the erosion of concrete by the temperature and humidity,the change of water level and chemical medium,especially highway,bridge and water conservancy and other use of the environment,theproblem of the concrete durability is very prominent,serious damage,life is reduced,due to lack of durability of concrete,which is the reason of huge economic losses.Based on the demonstration engineering of Heda highway,this artical studies the freeze-thaw resistance environment,frost resistance grade,frost resistance technical index and improvement measures for cement concrete under various salt environment conditions.The main research work is as follows:(1)The relationship of concrete freeze-thaw cycle and the surface temperature are studied.The freeze-thaw damage of concrete surface is closely related to the lowest temperature,concrete subjected to freeze-thaw cycles per year with the lowest surface temperature is less than or equal to-3?,and annual average number of days the highest surface temperature of >0 ? to determine;annual average harmful freeze-thaw cycles according to the surface temperature of <=-5?(the surface temperature of <=-6?)annual average number of days the highest surface temperature of >0? to determine.The number of annual freeze-thaw determined by the surface temperature is more accurate than the result of the current temperature calculation.(2)The influencing factors of frost resistance of concrete are studied.A method for determining frost resistance grade of cement concrete based on the number of harmful freeze-thaw cycles at different structural locations is put forward.The frost resistance grade of concrete can be determined according to the annual average number of harmful freezing and thawing,combined with climate,environmental conditions and structure design life.(3)The framework to determine the optimal accumulation rate of sand coarse aggregategradation and the maximum density method,in order to determine the mixture ratio,concrete has high dense degree and ideal antifreeze effect,and put forward the mix optimization design method and antifreezing cement raw material of concrete,water cement ratio admixture and so on recommendations.(4)Through the influence of cement concrete mixed with different air entraining agents on the frost resistance of cement concrete,it is found that the influence rule of additive and admixture on freezing resistance is obvious.The main parameters of air entraining cement concrete are air volume,spacing coefficient and size of bubbles.The selection principle of antifreeze cement concrete admixture with water reducing and air entraining compound is put forward.