Effects of freeze-thaw cycles on fatigue performance of asphalt mixture and a fatigue-freeze-thaw damage evolution model

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To study the effect of freeze-thaw (FT) cycles on the fatigue performance of composite crumb rubber modified asphalt mixtures (CCRMA), a semicircular bending fatigue test based on the digital image correlation technique (DIC) was used to measure the fatigue life (Nf) of CCRMA and SBS modified asphalt mixtures (SBSMA) and the horizontal strain (Exx) of the DIC deformation field under repeated loading. The variation laws of Nf, Exx and the damage factor (D) defined based on Exx were analyzed under FT cycle conditions. In addition, considering the important influence of FT cycles on the Nf and damage evolution characteristics of asphalt mixtures, based on the classical Chaboche damage evolution model, the influence of FT cycle was considered, a fatigue-freeze-thaw damage evolution model that reflects the effects of FT cycling variables and stress levels on asphalt mixtures was constructed. The results indicate that the Exx peak of asphalt mixture shifts forward with increasing FT cycle number. After 20 FT cycles, the Nf of CCRMA decreased by 73.4 %, 62.1 %, and 75.1 %, while that of SBSMA decreased by 76.5 %, 58.6 %, and 74.6 % at stress ratios of 0.2, 0.3, and 0.4, respectively. The fatigue-freeze-thaw damage evolution model predictions were in agreement with experimental results, with the goodness of fit (R2) of all Nf prediction models being greater than 0.9. With the exception of a few outliers, the relative error between the measured and predicted Nf for the two asphalt mixtures was within 15 %. This indicates that the model can effectively predict the Nf and damage evolution laws of asphalt mixtures at different stress levels after an arbitrary number of FT cycles. The related research results provide a theoretical basis for predicting the Nf of new roads in cold regions under FT cycles.