Abstract
Layered Double Hydroxides (LDHs) have poor dispersibility in bitumen and limited effectiveness in enhancing its thermal oxidative aging resistance. To address these issues, this study aims to purify lignin to improve its radical scavenging efficiency and use the purified lignin to coat LDHs (Φ@LDHs), thereby increasing their lipophilicity and radical scavenging efficiency for use in bitumen. sodium lignosulfonate (SL) was fractionated into five parts using a stepwise water/ethanol fractionation method, and these fractions were then applied to coat the LDHs to produce Φ@LDHs. The morphology, antioxidant activity, and chemical structure of Φ@LDHs were analyzed. Subsequently, the effect of Φ@LDHs on the aging properties of bitumen was evaluated. The test results indicated that SL and its fractions effectively coated the surfaces of LDHs, thereby enhancing their interlayer spacing and hydrophobicity. Among all fractions, lower molecular weight fractions, F4 and F5, retained most of the phenolic hydroxyl groups in SL, demonstrating significant antioxidant activities. The incorporation of F4@LDHs and F5@LDHs effectively mitigated changes in rheological properties of bitumen and oxidation product formation during thermal oxidation and UV aging, with F5@LDHs showing the best performance. Furthermore, a synergistic anti-aging mechanism was elucidated for the F4@LDHs and F5@LDHs composites. The purified F4 and F5 fractions not only improved the compatibility of LDHs with bitumen but also delayed the oxidative reactions initiated by free radicals to achieve a synergistic anti-aging effect.
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