Frost resistance and life prediction of equal strength concrete under negative temperature curing

The compressive strength of concrete cured at −3 °C increases with age and can reach an equal strength to that of concrete cured at 28d of standard curing. However, the frost resistance of concrete with equal strength remains unclear. The mass loss, relative dynamic elastic modulus, peak stress, and peak strain of concrete are selected for evaluating the frost resistance of equal strength concrete. The results show that the negative temperature curing reduces the frost resistance of equal strength concrete, and the frost resistance of concrete decreases with the water-binder ratio. The optimal initial air content of equal strength concrete for frost resistance is between 4% and 5%. The calculation models of the relative peak stress and relative peak strain of equal strength concrete are established considering the initial air content and freeze–thaw cycle times. Based on the rapid coefficient method, the relationship between laboratory accelerated testing and the on-site service life of concrete is established, taking the relative dynamic elastic modulus reduced to 60% as the criterion of freeze–thaw failure, the life prediction of equal strength concrete is carried out. The equal strength concrete cured at −3 °C cannot achieve equal frost resistance and service life.