Prediction of Restrained Shrinkage Cracking of Shotcrete Rings Using Fracture Mechanics–Based Approach

Abstract

A fracture mechanics–based approach is developed to predict the shrinkage cracking age of shotcrete ring specimens under various curing regimes. Prolonged water curing and curing compound are considered to mitigate early-age shrinkage cracking. The maximum allowable tensile strain is determined based on a fracture criterion using R- and G-curves. The actual tensile strain of rings calculated from the measured free shrinkage and estimated creep is then used to predict the shrinkage cracking age by comparing the maximum allowable tensile strain. The determined maximum allowable tensile strain slightly increases as the age of a beam increases. Prolonged water curing has significant benefits on the mitigation of shrinkage cracking of shotcrete, and a lower increasing rate of actual tensile strain is observed. Specimens with curing compound show excellent shrinkage cracking mitigation, and cracks are never triggered owing to low shrinkage and creep. The theoretical predicted cracking ages exhibit a good correlation with measured ones. This proposed model is found to be capable of effectively and accurately predicting cracking tendency of ring specimens exposed to drying environments.