Thermal Crack Width Prediction Method for Mass Concrete Focusing on Thermal Stress of Surface and Drying Shrinkage Strain

It is important to predict thermal crack width in mass concrete accurately in order to satisfy the performance requirements of the structure in a reliable and reasonable manner. However, the authors found that the prediction accuracy of the currently used prediction expression is not sufficient for structures with large member thickness. Therefore, the purpose of this study is to propose a new crack width prediction expression in order to predict the thermal crack width accurately for various structures. First, the relationship between the relative humidity and the drying shrinkage strain was derived from the specimen experiment, and then it was input to the detailed analytical model of the actual structure with discrete crack, which shows that the crack width analysis can accurately predict the actual measurement. Second, a parametric study was conducted on the predicted crack width obtained by the detailed model and the thermal cracking index of the surface layer derived from the ordinary model, and it was shown that it is reasonable to focus on the stress to strength ratio (reciprocal of the thermal cracking index) of the surface layer when making a simple crack width prediction expression. Based on the knowledge a simple crack width prediction expression is proposed with organizing the measured crack width, the stress to strength ratio of the surface layer and the reinforcement ratio.