Influence of mix and environment on plastic shrinkage cracking

The influence of mix constituents (including corresponding concrete grade), retarding and air entraining admixtures and PFA additives, and the effect of environmental factors on plastic shrinkage cracking of mortar specimens is reported, supplemented by concurrent evaporation and bleeding tests. The dominant effect of environmental factors on evaporation, and that of corresponding concrete grade on plastic shrinkage cracking, were clearly established. Both retarding and air entraining admixtures were found to increase such cracking, as did the inclusion of increasing amounts of PFA in the mix. The test results are discussed in the light of the literature and supported by field observations. The opposing effects on plastic shrinkage cracking caused by various factors are used to explain some inconsistencies among the results of various investigators.