Rheological and Morphological Characterization of Modified Bitumen with Cup Lump Rubber

Natural rubber (NR) in the form of “cup lump” is used to significantly enhance the thermal stability and elasticity of bitumen. Despite these benefits, the paving industry has raised concerns about its increased energy use and carbon emissions when applied in hot mix asphalt (HMA). Warm mix asphalt (WMA) was invented to reduce this negative effect. In WMA, an additive is first added to the bitumen, which acts as a surfactant and allows the production and compaction of asphalt mixture at temperatures up to 50 °C less. As a result, the amount of energy consumed and carbon dioxide emissions during asphalt production are considerably reduced. In this study, CLR-modified bitumen (CMB) was blended with five percentages of Evotherm warm mix additive (0.3, 0.4, 0.5, 0.6, and 0.75%), and the properties were examined. According to the findings, the Evotherm modification lowered the viscosity of the binder by 26% and the contact angle by 6°, while the binder’s crack resistance at low temperatures marginally improves. Quantitative analysis from Fourier transform infrared spectra revealed a reduction in C=C stretch, C−O stretch, and C−H absorbance in response to the addition of Evotherm. Also, atomic force microscopy (AFM) scan shows an increase in the number of catana phases with a separation of peri- and para-phases. Only CMB with 0.75% Evotherm possesses 100% aggregate coating with sufficient air void; hence, it was selected as the optimum to be used in producing the warm mix asphalt mixture. Overall, the mixing temperature of the CMB can be lowered by 40 °C.