# Effect of Aging and Moisture Damage on Fatigue Cracking Properties in Asphalt Mixtures
## 4 Test Results
### Fatigue Cracking Resistance Test Results of Asphalt Mixtures

Table 5: \(Cont.\)cracking resistance of each mixture according to moisture damage on HMA and WMA specimens collected in the field and reported that the HMA specimen showed fatigue cracking resistance of approximately 50% on an average and that of WMA specimen was approximately 20% or less [25]. In this study, both the mixtures showed similar behavioral characteristics with aging and after moisture damage. In particular, the WMA mixture showed similar behavior after moisture damage, with its fatigue cracking resistance slightly increasing as aging progressed. However, WMA generally showed lower fatigue cracking resistance than HMA. Table 8 shows the coefficient values of the fatigue cracking resistance test according to the moisture damage of each mixture for the bottom-up cracking prediction equation mentioned above. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Mix ID**} & \multirow{2}{*}{**No.**} & \multicolumn{2}{c}{**Tension Stress Amplitude**} & \multicolumn{1}{c}{**Peak-to-Peak Strain**} \\  & & **(kPa)** & **(Microstrain)** & **Cycle at Failure** \\ \hline  & 1 & 1141 & 151 & 6597 \\ HMA STA\_FT & 2 & 1384 & 372 & 1312 \\  & 3 & - & - & - \\  & 1 & 924 & 81 & 14,284 \\ HMA LTA\_1\_FT & 2 & 1090 & 135 & 6448 \\  & 3 & 1168 & 307 & 1323 \\  & 1 & 945 & 83 & 11,437 \\ HMA LTA\_2\_FT & 2 & 1145 & 160 & 3483 \\  & 3 & 1309 & 308 & 1016 \\  & 1 & - & - & - \\ HMA LTA\_3\_FT & 2 & 1076 & 77 & 10,530 \\  & 3 & 1289 & 265 & 1016 \\  & 1 & 788 & 101 & 3942 \\ WMA STA\_FT & 2 & 913 & 145 & 1844 \\  & 3 & 971 & 258 & 573 \\  & 1 & 722 & 89 & 6193 \\ WMA LTA\_1\_FT & 2 & 879 & 118 & 3914 \\  & 3 & 983 & 254 & 788 \\  & 1 & 742 & 82 & 8724 \\ WMA LTA\_2\_FT & 2 & 874 & 121 & 4354 \\  & 3 & 999 & 185 & 1837 \\  & 1 & 879 & 78 & 12,914 \\ WMA LTA\_3\_FT & 2 & 1041 & 104 & 5952 \\  & 3 & 1118 & 218 & 1688 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Fatigue cracking performance results of HMA and WMA due to moisture damage for each stage of aging. Figure 15: Allowable fatigue cracking cycles after moisture damage for each stage of aging: (**a**) HMA and (**b**) WMA. In the WMA mixture, the allowable loads for fatigue cracking increase with aging, unlike in the HMA mixture, which depends on the WMA additive used as well as the initial STA temperature and time. [PERSON] et al. (2020) statistically evaluated fatigue crack resistance according to LTA and STA for HMA and WMA mixtures and reported that the fatigue crack resistance of the WMA mixture was higher than that of HMA after LTA with the cumulative fatigue cracking cycles increasing with aging [26]. In addition, the WMA additive used in this study is a type of wax that does not react chemically owing to heat aging with no change in its physical properties following aging. In other words, waxes are oxidized because of aging caused by chemical reactions, such as those induced by UV rays rather than heat. In this study, the heat requirement for the aging condition of the additive was not met without causing the aging of the additive. Therefore, the WMA additive mixed in the asphalt binder impacted fatigue cracking resistance by maintaining the original state without aging. In the future, it is important to clearly analyze the effects of various WMA additives.