Durability of air-entrained shotcrete exposed to cyclic freezing and thawing effect

In this study, the long-term performance of air-entrained shotcrete under cyclic freezing and thawing (F-T) is investigated and predicted. The dynamic modulus of elasticity and cohesive fracture energy of shotcrete at different F-T cycles are determined following ASTM C215 and RILEM TC 50-FMC, respectively. Both the test methods are found to be capable of examining material deterioration as a result of accumulative F-T damage; however, the fracture energy property tends to be more sensitive and degrades faster than the dynamic modulus of elasticity under the same number of F-T cycles. Probabilistic damage analysis is conducted to establish the relationship between the life (i.e., the number of F-T cycles in this study) and the damage parameter using the three-parameter Weibull distribution model. An exponential trend between the degradation of dynamic modulus of elasticity and the number of F-T cycles is observed at any given damage level. The failure rate of shotcrete increases as the number of F-T cycles increases, indicating that shotcrete exhibits more potential risk of failure and becomes less reliable when undergoing more F-T actions. The predicted results based on the polynomial probability model at 50% reliability level are consistent with the experimental results. Overall, the proposed probabilistic damage model is competent in evaluating freeze-thaw durability and predicting life of shotcrete.