Freeze-thaw damage evaluation and model creation for concrete exposed to freeze–thaw cycles at early-age.

• Frost resistance of concrete exposed to E-FTCs worsen with the decrease in pre-curing time. • Subsequent curing conditions after E-FTCs significantly affects the later-age frost resistance of the damaged concrete. • There are good correlations between the parameters of the damage model and the pre-curing strengths of damaged concrete. • Prediction models of freeze–thaw damage suitable for damaged concrete exposed to E-FTCs are created. • For concrete expected to experience E-FTCs, adequate pre-curing strength and re-curing conditions are essential. Concrete subjected to freeze–thaw cycles action at early-age will suffer serious physical damage, resulting in degradation of the concrete's performance. The subsequent curing conditions after early-age freeze–thaw cycles (E-FTCs) are critical to the development of the properties of frost-damaged concrete. Four test environments were set up for this study, based on different numbers of E-FTCs and subsequent curing conditions. The later-age resistance to freeze–thaw of concrete exposed to E-FTCs was evaluated by analysing the influence of pre-curing times and curing conditions. Results show that the earlier the FTCs occur, the worse the later-age freeze–thaw resistance is. In particular, for the frost-damaged concrete with a pre-curing time of 18 h, its freeze–thaw resistance is significantly worse than that of other concretes that have a longer pre-curing time. The increase in the number of E-FTCs exacerbates the damage to early-age concrete, which causes the reduced later-age freeze–thaw resistance. Subsequent water curing can significantly improve the freeze–thaw resistance of damaged concrete, while air curing is the least effective. Based on previous freeze–thaw damage models, prediction models for concrete exposed to E-FTCs were created by using the test data obtained in this study. The critical pre-curing strengths which can ensure that the damaged concrete has satisfactory frost resistance at later-age were thus obtained. For concrete structures expected to experience E-FTCs, adequate pre-curing strength and good re-curing conditions are essential. [ABSTRACT FROM AUTHOR]