Preliminary Fatigue Analysis of a Common TxDOT Hot Mix Asphalt Concrete Mixture

Over the past decade, the Texas Department of Transportation (TxDOT) focused research efforts on improving mixture design to preclude rutting in the early life of the pavement, which also offered increased resistance to moisture damage, but fatigue cracking may surface in the long term particularly if the binder stiffens excessively due to aging. The primary goal of this project is to evaluate and recommend a fatigue analysis system for TxDOT environmental and loading conditions. A secondary goal of comparing fatigue resistance of commonly used TxDOT mixtures including investigating the effects of aging will also be realized. Two fatigue analysis approaches, the mechanistic empirical (ME) and the calibrated mechanistic (CMSE) with surface energy measurements, based on one common TxDOT mixture including the effects of aging are presented in this interim report. Results showed that both the ME and CMSE approaches were comparable in terms of predicting mixture fatigue resistance. The results also showed that aging reduces the mixture's resistance to fracture damage and its ability to heal. A preliminary comparison of the ME and CMSE approaches showed that although the ME analysis procedure is simple and straightforward, there is a relatively high variability in both the mixture air voids (AV) and the final fatigue results. The input data for the HMAC mixture properties that affect fatigue performance. However, research is still ongoing to further: (1) investigate the effects of binder aging on the HMAC mixture fatigue properties, (2) review other fatigue analysis approaches including the proposed NCHRP 1-37A Pavement Design Guide, and (3) investigate the applicability and validity of the CMSE fatigue analysis approach, and finally recommend an appropriate fatigue analysis system to TxDOT.