Effects of Wax-Impregnated Nanozeolites on Bitumen's Thermomechanical Properties

This study presents a new carrier for wax-based additives used in bitumen; the new carrier alleviates wax crystallization while improving bitumen's cohesion, adhesion, and elastic properties. The abovementioned wax carrier is a newly developed nanozeolite, which is impregnated with paraffin wax to form a hybrid additive referred to as Winz. Bitumen containing Winz showed an improved resistance to low-temperature cracking, which can be attributed to reduced wax crystallization when wax dispersed via nanozeolite. In addition, nanozeolite was found to adsorb acidic compounds of bitumen upon its release of wax. Our molecular modeling showed that while wax interacts with nanozeolite in the absence of acid, upon introduction of acid, wax molecules are replaced by acid molecules on the nanozeolite surface. Adsorption of acids to the nanozeolite surface was also evidenced in the significant change of shear-thinning behavior of bitumen doped with Winz when bitumen was exposed to water. Hydrolysis of acidic compounds at the surface of nanozeolite caused a 42% reduction in the shear-thinning rate (going from 3.25 to 1.89) after water conditioning. This in turn shows that bitumen acids were adsorbed to Winz and detracted from the interface of bitumen with stones. Therefore, Winz can be a promising candidate to promote sustainability by enhancing the durability of bituminous composites via reducing bitumen's wax crystallization and bitumen's acid accumulation at the stone interface. The study outcomes provide insights to synthesize multifunctional carriers for bitumen's wax-based additives to enhance their dispersion and effectiveness.