Preparation and performance evaluation of microcapsules for asphalt fume reduction and deodorant stability enhancement

Abstract

Although conventional organic deodorants can inhibit the emissions of volatile organic compounds (VOCs) in asphalt, their practical application is limited by high volatility, poor storage stability and difficulty in transporting them over long distances. To address these issues, the deodorant was encapsulated in urea-formaldehyde resin through in-situ polymerization, forming microcapsules that can maintain the stability of the deodorant and release them at the mixing temperature of asphalt. The deodorant-microcapsules were first characterized in terms of their microscopic morphology, particle size, rupture temperature and deodorant-loading capacity. The deodorant-microcapsules were then incorporated into the 70# base asphalt to study their impact on the fundamental properties, storage stability, high, medium and low-temperature rheological behaviors of the modified asphalt. Furthermore, the inhibitory effects of the deodorant-microcapsules on VOCs and H₂S emissions from asphalt were explored. Results demonstrated that the microcapsules produced in this study were structurally intact, with uniform size distribution and up to 73.8% deodorant-loading capacity. Deodorant-microcapsules strengthened the intermediate/low-temperature properties of asphalt while slightly weakening its high-temperature properties. Furthermore, the microcapsules effectively reduced both concentration and variety of VOCs released from asphalt, with enhanced inhibitory effects as dosage increased. The optimal dosage of microcapsules was 0.13%. Compared to base asphalt, the deodorized asphalt containing 0.13% microcapsules showed 82.86% and 90.00% reductions in number of chain hydrocarbons and aromatic hydrocarbons, respectively, with total VOCs concentration and average H₂S concentrations decreasing by 61.84% and 70.06%. This research can provide a novel approach for producing deodorant-asphalt.