Combination Effects of Internal Curing and Permanent Formwork on Shrinkage of High Strength Concrete

Abstract

In this paper, the influences of internal curing using pre-soaked lightweight aggregate (PSLWA) and pre-fabricated fiber reinforced engineered cementitious composite (ECC) board as permanent formwork on shrinkage and internal relative humidity of high strength concrete were investigated. Three mixture proportions with induced curing water-to-cement ratios (W_IC/C) of 0, 0.08 and 0.12 were utilized in the experiments. The test results show that the progress of the internal relative humidity of high strength concrete since casting exhibits first a vapor saturated stage (RH=100%, stage I), followed by a gradually reducing stage (RH<100%, stage II). As PSLWA is added, the reduction rate of internal relative humidity in stage II is greatly decreased. As ECC cover is used, the reduction on internal humidity of high strength concrete is further reduced. Shrinkage of high strength concrete decreases with increase of induced internal curing water. However, internal curing cannot completely eliminate the shrinkage of high strength concrete developed in the stage I. The combined effects of internal curing and ECC cover can reduce the shrinkage not only developed in the stage II, but also the shrinkage developed in stage I.