Preparation and performance evaluation of different bitumens modified by antioxidant/PABA-LDHs composites

The para-aminobenzoic acid intercalated layered double hydroxides (PABA-LDHs) were prepared through intercalating ultraviolet absorbent para-aminobenzoic acid (PABA) into the layers of layered double hydroxides (LDHs) through anion exchange. Then the PABA-LDHs were compounded with antioxidants (Irganox 1076 and Irganox 1010, which are abbreviated as 1076 and 1010, respectively) to modify-two base bitumens with penetration grades of 70 and 90, respectively, and the physical properties, rheological properties, molecular weight distribution and four generic fractions of the modified bitumen before and after thermal- and photo-oxidative aging were analyzed to investigate the effects of antioxidant/PABA-LDHs on the aging resistance of bitumen. The results showed that PABA was successfully inserted into the interlayer of LDHs to form organic LDHs, and PABA-LDHs can effectively improve the aging resistance of both 70 and 90-base bitumens due to their excellent reflectance and absorption of ultraviolet (UV) rays and the blocking effect on oxygen. The composite modification of PABA-LDHs with 1076 and 1010 could further enhance the thermal- and photo-oxidative aging resistance of bitumen, exhibiting a complementary effect. In addition, 1076/PABA-LDHs modified bitumen presented superior anti-aging property in comparison with 1010/PABA-LDHs modified bitumen.