Synthesis of antioxidant-intercalated layered double hydroxides with different particle sizes and their effects on the anti-aging performance of asphalt

Asphalt tends to age when exposed to ultraviolet light, heat, oxygen and other environments. Antioxidants intercalated layered double hydroxides (OLDHs) is an effective anti-aging agent for asphalt. The particle size of OLDHs not only influence its ultraviolet reflection and free radical scavenging abilities but also the compatibility with asphalt. However, the effects of particle size of OLDHs on the basic properties and anti-aging performance of asphalt remains unclear. To resolve this problem, the antioxidant (3,5-di-tert-butyl-4-hydroxyphenylpropionic acid) was inserted into LDHs to prepare various OLDHs by adjusting the Mg/Al molar ratio, crystallization temperature and time. The morphology, crystal structure, ultraviolet reflection and free radical scavenging ability of OLDHs were characterized. The basic properties, storage stability, rheological properties and functional groups of OLDHs-modified asphalt before and after thermal oxidative aging and ultraviolet aging were studied. Finally, the entropy weight-technique for order preference by similarity to ideal solution method was used to comprehensively evaluate the optimal particle size and corresponding synthesis parameters of OLDHs. The research results show that crystallization temperature exerts a more pronounced influence on the particle size of OLDHs compared to Mg/Al molar ratio and crystallization time. The free radical scavenging efficiency of OLDHs at 165.45 nm exhibited a maximum value of 84.2 %, conferring superior thermal oxidative aging resistance to the corresponding asphalt. OLDHs with a particle size of 290.34 nm exhibit maximum UV reflectance, significantly enhancing resistance to UV aging of asphalt in UVB range (280–315 nm). After comprehensive evaluation, OLDHs of 265.45 nm synthetized with a Mg/Al molar ratio of 2, crystallized at 120 °C for 24 h exhibits optimal synergistic resistance to thermal-oxidative and UV aging in asphalt.