Effects Of Water Reducing Agent And Expansion Admixture On Early-age Shrinkage Of Concrete

This paper studied the early age shrinkage of the concrete added with water reducing agent and expansion admixture,studied the composite effect on early age shrinkage,also studied the influences of the initial curing age, the curing time and the curing methods on early age shrinkage of HEA concrete, this paper also studied the effect of different admix method of water reducing agent on the early age shrinkage of the concrete. The research results can be concluded as follows:The shrinkage-compensation of expansion admixture must be based on an appropriate curing system, otherwise, the shrinkage-compensation won't happen,and the expansion admixture will cause even more early age shrinkage.this paper analyzed it,and blieved that the lack of water in the concrete is the mainly reason.The shrinkage-compensation of expansion admixture effects mainly between 1～24 hours after the initial setting,so it is suggested that the curing should be started from the initial setting or even from the casting. If the initial curing age is appointed, the early age shrinkage of concrete will depend on the curing time.the research shows that the early age shrinkage could be controlled effectively if cured for 4 hours after the initial setting.Sealed curing+expansion admixture could inhibit the early age shrinkage very well. But sealed curing can't replace water curing.pervious membrane+sealed curing could keep the humidity level of concrete surface, and it is an ideal method of water curing.Early admixing of water reducing agent will cause more shrinkage than admixing in the same time.to explore the mechanism,we can explan it by adsorption theory of water reducing,and it also can explan how the water reducing changes the microstructure of gelled material to effect the early age shrinkage.