Composite modification mechanism of blended bio-asphalt combining styrene-butadiene-styrene with crumb rubber: A sustainable and environmental-friendly solution for wastes

Using bio-asphalt from bio-waste to replace petroleum-based asphalt could decrease the dependence on petroleum and shift toward more environmental-friendly and sustainable development of pavement. This study investigates the composite modification mechanism of blended bio-asphalt (BBA) combining styrene-butadiene-styrene (SBS) with crumb rubber (CR) through a comprehensive procedure. Chemical characteristics proposed by Fourier-transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) show that the blending and modification was a physical process. Morphological features conducted by atomic force microscopy (AFM) and fluorescence microscopy (FM) indicate that the bio-asphalt could promote the swelling and homogeneous distribution of the polymers, and thus strengthens the polymer's cross-linked network. Rheological properties implemented by multiple stress creep and recovery (MSCR), bending beam rheometer (BBR) and frequency sweep (FS) tests indicate that composite modification could enhance both the high and low-temperature performance of the BBA. Moreover, the Han curves illustrate that the compatibility between the asphalt and polymers was improved by the bio-asphalt addition. Furthermore, performances of modified asphalt processing on industry-scale are superior to that in the laboratory due to the high-effective equipment. In summary, the composite modification not only enhances the comprehensive performances of the BBA, but also makes it possible to reuse bio-waste and scrap tire.