Effectiveness of Different Categories of Light Oils in Partially Reactive Crumb Rubber-Modified Asphalt

Rubber-modified asphalt (RMA) faces several challenges, including poor workability, difficult construction, and high energy consumption. The incorporation of renewable light oils offers a promising solution to address issues such as high viscosity and elevated carbon emissions in asphalt modified with a high dosage of rubber powder. The investigation of light oil and rubber powder composite-modified asphalt under low-temperature (160 °C) and short-term (30 min) shear processes is essential for understanding its rheological behavior and modification mechanism. This study explores composite-modified asphalt prepared with four types of light oils (fatty acids, aromatic oil, tall oil, and paraffin oil) at dosages of 10% and 15%, combined with 20% rubber powder. Conventional penetration and viscosity tests were carried out to assess the overall physical properties of the composite-modified asphalts, while rheological tests were conducted to examine their performance at high temperatures. Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) were employed to explore the interaction mechanisms that occurred between the light oils, rubber powder, and asphalt. The results suggest that the addition of various light oils leads to a reduction in the viscosity of rubber-modified asphalt, with the extent of reduction varying across different oils. Notably, 10% tall oil demonstrates the most significant reduction in viscosity while also facilitating the dissolution of rubber powder. The high-temperature PG-grade rubberized asphalt improved with the incorporation of light oils, with 5% tall oil yielding the highest PG grade of PG 82-34. FTIR analysis confirmed that light oils and rubber were physically blended in the asphalt, with the light components of the oils being absorbed by the asphalt. FM observations revealed that light oils promote the swelling of rubber particles, with the rubber particles fully swelling in tall oil. Considering the reduction in viscosity, the performance at both high and low temperatures, elasticity, and the extent of rubber particle swelling, tall oil is identified as the most effective material for preparing light oil-rubber composite-modified asphalt using the low-temperature, short-term shear process.