Study On Anti-sulfate-chloride Composite Erosion Performance Of Steam Cured Concrete

The corrosion resistance and mechanism of steam cured concrete to sulfate-chloride compound corrosion have not been studied yet,in this paper,the parameters of steam curing process with good resistance to sulfate attack were optimized,and the diffusion law of related ions and the basic mechanical properties of concrete of steamed concrete with different admixtures in the case of sulfate-chlorine mixed solution erosion were studied.Investigate the evolution law of erosion damage of steamed concrete,and obtain the optimal blending ratio.Finally,a set of concrete preparation technical schemes is developed to select materials for concrete in areas with high requirements for sulfate and chloride corrosion resistance.The design provides technical parameters and basis.The main conclusions are as follows:By changing the steam curing parameters of mortar: static stop time(1h~6h),constant temperature time(1h~6h)and constant temperature(50 ~90 C),the changes of compressive and corrosion resistance coefficients of mortar at different ages were tested.The pore structure was analyzed by mercury intrusion test,and the steam curing parameters based on the improvement of sulfate corrosion resistance were obtained.On this basis,different kinds and dosages of admixtures(15%~35% fly ash,5%~15% silica fume,5%~15% metakaolin,5%~15% LDH)were added to the mortar to optimize the autoclave curing process.The changes of compressive and corrosion resistance coefficients of the mortar at different ages were tested and compared by mercury intrusion test and XRD test.The effects of different kinds and dosages of admixtures on the sulfate corrosion resistance of cementitious system were studied.The kinds and proportion of admixtures based on the improvement of sulfate corrosion resistance were obtained.On the basis of the types,proportions and steam curing parameters of the admixtures,the concrete was treated with compound admixtures and cured by steam.The dry-wet cycling test of concrete is carried out,and the compressive strength,quality and dynamic elastic modulus of concrete are tested when the concrete reaches its age.The mechanism of performance change is elaborated and analyzed by means of XRD,SEM,mercury injection,industrial CT and ion titration.The law of durability change of steam cured concrete under the erosion of composite solution is explored.Finally,the effect of sulfate-chloride compound corrosion resistance is obtained.Good admixture ratio and concrete production evaluation index which can be applied to areas with high sulfate-chloride corrosion resistance requirements are put forward.Finally,assuming that the damage process of concrete is a decay process,thedamage process of concrete is calculated and analyzed on the basis of Newton's cooling law.Based on the test results,two influencing factors(fly ash and silica fume content and wet-dry cycle)are established,which are three indexes(compressive corrosion resistance coefficient,relative dynamic elastic modulus and mass change rate).Damage model,that is,life prediction equation of concrete.