Study On The Coupling Action Performance Of Concrete Structure Resistance Of Alkali-aggregate Reaction And Chloride Ion Diffusion

The reaction product of alkali-aggregate reaction (AAR) will produce theexpansion stress in the internal of concrete, lead to cracking of concrete. With thereaction proceeds slowly, the reaction products increased, result in serious damage ofconcrete. What’s more, the chloride ions erosion will make the steel rust which stayedin the internal of concrete and lead to failure finally, the continue rust will also bringthe expansion of volume. The concrete cover will loose and peel off due toextrusion. The two kinds of damage produced enormous security hidden danger of thebuilding, and they are also hot issues in today’s concrete durability research.In this paper, concrete specimens of6kinds of mixture ratio were madecombined with the underground engineering of the comprehensive renovation projectof xining railway station, and keep the alkali content1.2%of the amount of cement ashigh alkali condition. After standard curing of28d，put the concrete specimens in20℃and40℃brine environment soaked for28d,180d and360d，and then test andrecord the7performance indexes regularly: length change, mass loss, surface crack,compressive strength change, flexural strength change, free chloride and totalchloride content. The performance of the specimens are studied under the couplingaction between the resistance of concrete alkali-aggregate reaction (AAR) andchloride ion diffusion. Through the analysis of experiment and the data，andcombined with the engineering practice, the comprehensive performance of Ca40,Ca45, C50z, Ca50, Ca50z and Ca60z6were summarized, The conclusions are asfollows:(1) Under the condition of high equivalent alkali content of the internalconcrete, if the temperature of underground brine environment near the roomtemperature (20℃), among the6kinds of mixture ratio of concrete specimens thatsuffer from the the coupling action between the alkali-aggregate reaction (AAR)and chloride ion diffusion, the durability performance of Ca40, Ca50z and Ca60zconcrete is better and Ca40concrete is the best; while the durability performance ofCa45and C50z concrete is poor and Ca45concrete is the worst. (2) Under the condition of high equivalent alkali content of the internalconcrete, if the temperature of underground brine environment near the roomtemperature (20℃), among the6kinds of mixture ratio of concrete specimens thatsuffer from the the coupling action between the alkali-aggregate reaction (AAR)and chloride ion diffusion, the durability performance of Ca40and Ca60z concrete isbetter and Ca40concrete is the best; while the durability performance of Ca45、Ca50z、C50z�'�Ca50concrete is poor and Ca50concrete is the worst.(3) Research also shows that for the comprehensive renovation project of xiningrailway station that lies in the underground brine environment, if the internalequivalent alkali content of concrete beyond the requirements of the specification(equivalent alkali content higher than0.6%), and then the underground concretestructure project may damage caused by AAR.Therefore, the internal equivalent alkali content of concrete must be controledstrickly in the comprehensive renovation project of xining railway station, the activealkaline aggregate must be forbidden. This paper explores the durability of concretein a harsh environment relatively of Qinghai province preliminarily, has a certainguiding significance to the comprehensive renovation project for xining railwaystation and other concrete structure engineering that in such similar environmental.