Effect of Beginning Curing Time on Early Age Shrinkage of Concrete

The relationship between begenning curing time and early shrinkage of concrete was studied.The experiments results show that,for the concrete without superplasticizer,although the effect of beginning curing time on shrinkage is very great,the total shrinkage of concrete is low,so the beginning curing time has no special effect on early shrinkage.While the early shrinkage of concrete with superplastisizer increases sharply,and the shrinkage rate reaches maximal(500×10~(-6)) at first 8 h after initial setting of concrete,which is far more than the crack limit of concrete.There are few differences in early shrinkage between concretes whose curing begin from 8 h after initial setting and without any curing.Curing beginning at 8 h after initial setting,the purpose to avoid cracking will not be achieved.But early shrinkage can be reduced to a level less than the crack limit of concrete by successful timely curing.Therefore,for the concrete with superplasticizer,curing measures must be conduced before initial setting and the early shrinkage cracks of concrete can be controlled soundly.