Prediction of restrained plastic shrinkage cracking in plain cement concrete

Tests were conducted using specimens that were cast directly on a hardened substrate base as a bonded overlay to simulate restrained plastic shrinkage cracking of concrete. Three concrete mixtures with a fine aggregate/coarse aggregate ratio of unity were tested under four ambient conditions. The test parameters of the study were cement/ total aggregate ratio, water/cement ratio and environmental condition. Shrinkage cracking behaviour was studied over a period of 24 h from the time of casting. Partial correlation and multiple regression models based on statistical methodology were developed to predict total crack area induced as a result of plastic shrinkage in Portland cement concrete. The results available in the earlier literature were compared with the results obtained from the model developed. From the results of comparisons the confidence level of the predictive model was found to be more than 95%. This paper reports the test details, the test results, development of the model and the comparisons of test results with the results of the model.