Effect of acid rain on chemical structure and rheological properties of bitumen at different depths

Abstract

The rapid development of economy has led to an increase of acid rain that can react with the bitumen physically and chemically, causing further damage to the bitumen properties. Therefore, the effects of acid rain on the chemical composition and rheological properties of bitumen at different depths were investigated in this study. Fourier transform infrared spectroscopy and dynamic shear rheometer tests were performed on the bitumen samples after immersion in acid rain. The results show that in the early stage of immersion, acid rain leads to carbonyl dissolution, reduction of complex modulus, increase of phase angle, and softening of bitumen, thus improving the fatigue cracking resistance. In the late stage of immersion, bitumen is gradually oxidized to form carbonyl group. The change degree of complex modulus and phase angle decreases, and the fatigue cracking resistance is weakened with time. The effect of acid rain on the fatigue cracking resistance fluctuates more for bitumen at 0~50 μm and is more stable for bitumen at 50~100 μm.