Freezing Resistant Durability Of Pavement Concrete

It is one of the important problems to study of cement concrete durability. Freezing andthawing of concrete affects pavement life in much large degrees. There is evidently influencethat freezing and thawing cycling to concrete strength. Concrete strength decreases withfreezing and thawing cycling times. Flexural strength is a mostly sensitive parameter varyingrapidly and largely. Being not efficient only with relative dynamic elastic modulus and masschanging rate, a parameter was discussed in which to appraise the damage degrees of concreteas freezing and thawing. The losing rate of flexural strength parameter should be used inappraising concrete freezing and thawing property. For pavement concrete freezing andthawing test，the parameters of relative dynamic elastic modulus and mass changing rate aretoo loose, so it should be determined again based on concrete air volume. For freezingresistant concrete, the limit of relative dynamic elastic modulus should be80%and masschanging rate1%. For common concrete, the limit of relative dynamic elastic modulus shouldbe60%and mass changing rate5%. Based on site and laboratory condition, freezing andthawing cycling times of concrete in site was changed to equivalent cycling times inlaboratory environment which was named as equivalent freezing and thawing cycle times.Servicing life of concrete in freezing and thawing may be estimated based on the equivalentfreezing and thawing cycle times and laboratory test data. It was been set up that the freezingand thawing times when dynamic elastic modulus losing by40%. There is evident influencethat freezing temperature to concrete damage. There is an abruptly change for concretefreezing and thawing damage effect when freezing temperature falls from-5℃to-10℃.Freezing and thawing damage force would be much great when temperature falling to-10℃.For construction concrete would endure freezing temperature lower than-10℃, the highfreezing-resistant grade concrete should be used in design. There is an influence betweentemperature decreasing rates to concrete freezing damage. Concrete would be badly damagedwhen temperature decreasing rapidly. Based on concrete freezing and thawing damagingmodel, relation between resistance grade to freezing-thawing of pavement concrete andnatural freezing and thawing cycle times was calculated out which is about1:14. Based onlaboratory and site test result and a certain safety factor,1:14was chosen as the quantityrelation.