Analysis of physico-chemical properties for crumb rubber in process of asphalt modification

This study aimed to investigate the physical and chemical properties of crumb rubber in of asphalt modification. Dibutylphthalate (DBP) was chosen to simulate the light component in asphalt in the rubber soak test. After separatedfrom crumb rubber, the leaching solution sample was tested using gas chromatography-mass spectrometer (GC-MS) to analyze the interaction between crumb rubber and light component. Crumb rubber modified asphalt (CRMA) samples were respectively prepared under different conditions. Rubber particles were separated from asphalt by elution method and the morphology was studied with optical microscope. Volume expansion rate (Vr) was proposed to characterize rubber swelling in asphalt. In addition, infrared spectra (IR) and differential scanning calorimetry (DSC) tests were conducted on the asphalt samples removed from crumb rubber. The results and analysis indicated that physical change and chemical reaction exist in the interaction of crumb rubber with DBP. After swelling, the molecular chains of rubber were disentangled and released some smaller molecule materials and then dissolved into asphalt, which playing a role of asphalt modification, and the absorption peaks of typical functional groups increase significantly. But too high temperature or too much time may lead to excessive degradation or aggregation of crumb rubber as well as asphalt aging, which will cause the performances of CRMA deteriorate. The viscosity change is a macroscopic reflection of physical and chemical characterization of rubber in asphalt modification. From the perspective of swelling and degradation behavior, the optimalconditions are recommended that the dosage of crumb rubber is 20% approximately, preparation temperature is not higher than 195 °C and the processing time is less than 1.5 h.