Upcycling industrial waste bischofite to anti-aging agents for asphalt: Macro-properties, micro-characteristics, and statistics-based mechanistic analysis

Asphalt aging causes severe pavement failures, while follow-up maintenance and reconstruction activities pose a series of ecological, health, and economic concerns. Simultaneously, the substantial by-product bischofite output from salt-lake industries triggers environmental pollution and resource wastage. To address both challenges concurrently, waste bischofite was utilized to develop anti-aging agents for paving asphalt. Crystal structure and chemical composition confirmed that layered double hydroxide (LDH) and SCA surface organic modified LDH (SOM-LDH) anti-aging agents were successfully synthesized from waste bischofite. The SCA surface organic modification reduced adhesion and agglomeration among LDH particles, thereby enhancing their compatibility with asphalt. Both LDH and SOM-LDH retarded the macro-property degradation of asphalt during aging, improving its anti-aging capability. Four-component coupling correlation analysis revealed the transformation pathway of aromatics-resins-asphaltenes in asphalt during aging. Statistical analysis of the relationships between asphalt micro- and macro-aging indices suggested that the gelation of the colloidal structure dominated macro-property deterioration, while molecular weight growth contributed secondarily. LDH and SOM-LDH shared identical operating patterns, as they hindered component transformation, colloidal structure gelation, and molecular weight growth during aging through their UV- and oxygen-barrier functions. Compared with LDH, SOM-LDH demonstrated higher efficiency in strengthening the anti-aging capability of asphalt.