Comparison of high temperature performance and microstructure for foamed WMA and HMA with RAP binder

- RAP binders improve the high temperature performance and temperature sensitivity.
- RAP binders compromise the low temperature performance and fatigue resistance.
- The optimum RAP binder content of foamed WMA is more than that of HMA.

The foamed warm-mix recycled asphalts and hot mix recycled asphalt with different reclaimed asphalt pavement (RAP) binder contents (0wt%, 20wt%, 40wt%, 60wt%, and 80wt%) were prepared in laboratory. The influence on the viscosity-temperature performance, rheological properties, temperature sensitivity, fatigue resistance, and microstructure were investigated by conventional tests, Brookfield viscosity tests, Dynamic Shear Rheometer (DSR) tests, and Fourier Transform Infrared Spectroscopy (FTIR) tests. The results show that the RAP binder content has great effect on the performance of foamed warm mix recycled asphalt and hot mix recycled asphalt, and there is different change between foamed warm mix recycled asphalt and hot mix recycled asphalt. Compared to foamed warm-mix asphalt, foamed warm-mix recycled asphalt provides better high temperature performance and temperature sensitivity. Adding the RAP binder compromise the fatigue resistance of asphalt and with the increase of RAP binder content, the fatigue resistance of asphalt becomes worse. And the high temperature performance and temperature sensitivity of hot mix recycled asphalt is better than that of foamed warm mix recycled asphalt, while the fatigue resistance is on the contrary. By the microstructure analysis, the foaming process could slow down the aging degree of asphalt, and the aging degree of hot mix recycled asphalt is deeper than that of foamed warm mix recycled asphalt. The optimum RAP binder content of foamed warm mix recycle asphalt is more than that of hot mix recycled asphalt.