Experimental Study On The Influence Of Extreme Dry Curing Environment On Concrete Performance

Due to the influence of the environment in the dry regions of western China,the internal moisture loss of concrete is intensified,and the concrete is often not fully cured.During the curing period,microcracks and micropores are prone to form initial defects.These initial defects affect the macroscopic properties of concrete.Have a certain impact.Most of the existing researches focus on fully cured concrete.In order to explore the effect of these initial defects on the performance of ordinary and high-strength concrete,this article puts the ordinary and high-strength concrete specimens in a dry environment after standard curing for 3 and 7 days,respectively,to produce different degrees of initial defects..The macroscopic properties of concrete with initial defects were studied and quantitatively characterized.The main conclusions are as follows:(1)Through basic mechanical tests,the compressive strength and split tensile strength of concrete of different strength grades(C20,C60)are studied.The results show that compared to the standard curing environment,the compressive strength of concrete in a dry environment has been reduced to a certain extent.The compressive damage coefficients of normal and high-strength concrete for 3 days of standard curing are both greater than 0.5,and the compressive damage coefficient of standard curing for 7 days is obvious.Decrease,the compressive damage coefficient of ordinary concrete is always greater than that of high-strength concrete;in a dry environment,the split tensile strength of concrete shows a downward trend.(2)Through the chloride ion diffusion coefficient test and the rapid freeze-thaw test,the transmission performance and frost resistance of different strength grades of concrete are studied.The results show that whether ordinary concrete or high-strength concrete,the extreme dry environment will affect its chloride ion diffusion depth and frost resistance,and the shorter the standard curing time,the greater the chloride ion diffusion depth of the concrete,and the more obvious the decline in frost resistance.(3)The quantitative analysis system of elastic wave velocity,concrete slice water absorption and panoramic micro-crack is used to quantitatively characterize the initial defects of concrete.The results show that the damage degree of the concrete after standard curing for 3 days is greater than that of the concrete after standard curing for 7 days,and the damage degree of ordinary concrete is greater than that of high-strength concrete;the water absorption rate of 2cm-thick slices on the surface of ordinary and high-strength concrete is greater than that of internal slices;high-strength concrete has microcracks due to auto-shrinkage The density is higher,and the density of micro-cracks caused by the drying shrinkage of ordinary concrete is higher.