Investigation of Aging Resistance of Organic Layered Double Hydroxide/Antioxidant Composite-Modified Asphalt

Two organic layered double hydroxides (OLDHs) intercalated by UV absorbents of para-aminobenzoic acid (PABA) and cinnamic acid (CA) were synthesized by the anion-exchange method, and their structures and properties were characterized. Then, the two OLDHs were applied to modify asphalt together with two different antioxidants, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate (1076) and pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)­propionate) (1010), aiming at synergistically enhancing the aging resistance of asphalt. The aging behaviors of modified asphalt were evaluated by the analyses of physical properties and chemical structures of modified asphalt after pressurized aging vessel (PAV) and ultraviolet (UV) aging tests. The results indicated that PABA and CA were successfully intercalated into the interlayers of LDHs and that the lipophilicity and UV absorbance of LDHs were significantly improved due to the organic intercalation. Hence, OLDH-modified asphalt presented enhanced anti-UV aging performance compared with LDH-modified asphalt. Meanwhile, the addition of organic LDH/antioxidant composites could further improve the antiaging performance of asphalt, including thermal-oxidation and photo-oxidation aging resistance, exhibiting a synergistic effect. Furthermore, different combinations of OLDHs and antioxidants had different improvement effects on the aging properties of asphalt; to be specific, the composites of 1076/PABA-LDHs and 1010/CA-LDHs were superior to those of 1010/PABA-LDHs and 1076/CA-LDHs, respectively, in promoting the aging resistance of asphalt.