Performance of vegetable oil activated waste crumb rubber/SBS composite modified asphalt

ObjectiveThe study investigates to solve the technical issues, e.g., high viscosity, low workability and poor storage stability, of waste crumb rubber/SBS composite modified asphalt (CR/SBSMA) and promote its application in practical road engineering. The vegetable oil activated waste crumb rubber (OCR) and SBS composite modified asphalt (OCR/SBSMA) was prepared.MethodFirst, the influences of different mixtures of OCR and SBS on OCR/SBSMA performance were analyzed through the penetration, softening point, 5 ℃ ductility and segregation tests, as well as Brinell viscosity and elastic recovery tests. Then the optimal blending ratio was determined. Second, the conventional properties, viscosity-temperature properties and rheological properties of OCR/SBSMA were studied. Finally, the modification mechanism of OCR/SBSMA was studied by means of fluorescence microscopy and Fourier transform infrared spectroscopy.ResultThe optimal mixture combinations of two OCR/SBSMA are 32% soybean oil activated waste crumb rubber (OCR-S) combined with 3% SBS; and 28% used edible oil activated waste crumb rubber (OCR-W) combined with 3% SBS. OCR obviously reduces the viscosity and segregation difference of CR/SBSMA, and greatly improves the construction workability and storage stability of CR/SBSMA. OCR significantly decreases the high temperature rutting resistance factor and low temperature stiffness modulus of CR/SBSMA, and increases the low temperature creep rate. It indicates that vegetable oil activated rubber powder decreases the high temperature rutting resistance of CR/SBSMA, but significantly improves the low temperature cracking resistance. After the activation treatment, the waste crumb rubber has higher degree of desulfurization and degradation in the modified asphalt, and the distribution uniformity is significantly improved. SBS particles and OCR particles interweave to form a dense elastic network structure. The modification mechanism of OCR/SBSMA is mainly physical mixing, accompanied by a few chemical reactions, e.g., condensation of phenol and formaldehyde, oxidative cracking of alkane, and combination of SBS and oil.ConclusionThe findings can provide a theoretical basis and technical guidance for the application and promotion of vegetable oil activated waste crumb rubber/SBS composite modified asphalt in road engineering.