A novel application of industrial waste bischofite for the anti-aging property of asphalt: Synthesis of organic layered double hydroxide and performance evaluation

Asphalt aging causes significant distress to pavements, which risks driving safety and poses unsustainable repair and reconstruction works. Layered double hydroxide (LDH) is a promising anti-aging modifier for asphalt. A unique benefit of LDH is its potential raw material - bischofite, a fruitful by-product of salt lake industries and is often casually discarded. In this work, LDH with laminated structure and high crystallinity was synthesized from industrial waste bischofite, and the silane coupling agent A151 was grafted onto the LDH surface, which remarkably inhibits the adhesion and hydrophilicity of LDH and makes it more compatible with asphalt. Asphalt becomes hard and brittle after aging, and the rheological properties deteriorate considerably. At the micro-level, asphalt aging is manifested by the oxidation of light components to heavy ones, the increase of molecular weight, the accumulation of macromolecules, and the gelation of the colloidal structure. Comparative studies indicate that the LDH synthesized from waste bischofite is able to relieve performance deterioration, component oxidation, molecular polymerization, and structure gelation of asphalt during aging. Furthermore, the A151 surface organic modification can further improve the effect of LDH in bolstering the anti-aging property of asphalt. These favorable results provide a sustainable approach to building durable pavements.