ABSTRACT
JCI Committee has been suggested by LAFARGE and SINTEF that autogenous shrinkage should be taken from the time of casting. Plastic shrinkage, of course, may be one of the key parameter influencing cracking in plastic phase. We think that deformations before setting are very important for prevention of cracking. It is necessary that the segregation and subsidence are considered in definition of deformations before setting. In our opinion, it is not easy to express the early shrinkage before setting briefly in one or two sentences. And crack formation before setting can be prevented by considering the curing method or the execution method such as water supply on the top surface and hand trowelling, as is not the case of autogenous shrinkage after setting. Autogenous shrinkage is generally used for prediction of stress related cracking in hardened concrete, the strain generated in a period when cementitious material is fresh is excluded. Therefore, the time of initial setting of cement is specified as the start point of autogenous shrinkage measurement.
