Modelling the severity of plastic shrinkage cracking in concrete

Plastic shrinkage cracking (PShC) is one of the earliest forms of cracking in concrete as it occurs within the first few hours after the concrete has been cast. Concrete elements with large exposed surfaces are especially vulnerable to PShC. Many researchers have proposed models to simulate plastic shrinkage, bleeding and to predict the occurrence of PShC. In this paper a model to predict the degree of PShC is proposed. This model, the so called PShC Severity Model, is based on the volume of water that evaporates from the concrete between the placing and the initial setting time of the concrete. This model was verified using a large number of PShC test results. A further study was also done on the effect of the addition of low volumes of synthetic micro fibres on the degree of PShC. It was found that the addition of the fibres effectively reduces the PShC Severity value.