Investigation on long-term aging in nano-modified WMA using mechanical and thermodynamic-based approaches

WMA due to its softer structure and high content of oils is more exposed to aging. Herein, the behavior of WMA in two states of control (unaged) and long-term aging in different compositions was examined and compared. The effect of factors contributing to WMA moisture sensitivity was minimized by utilizing suitable additives. Thermodynamic and mechanical approaches were adopted for this purpose. Two types of aggregates (granite and limestone) and bitumens (PG 58-22 and PG 64-16) were modified with nano-hydrated lime (NHL) and nanocalcium carbonate (NCC). The application of long-term aging increased the cohesion strength of both types of bitumen. Bitumen modification with the additives reduced the bitumen-aggregate debonding energy in the presence of water in control and long-term-aged specimens, which indicated the improved moisture damage resistance of the asphalt mixes By fitting the long-term aging results, the correlation coefficients between the indirect tensile strength ratio and free debonding energy increased from 0.6 to 0.7 in the first, and 0.8 to 0.9 in the third and fifth cycles. Thus, increasing the freeze-thaw cycles led to a stiffer bitumen with greater contribution to bearing the applied load, thereby promoting the validity and precision of mechanical and thermodynamic test results.