Investigation of the potential application of biodiesel by-product as asphalt modifier

The potential application of biodiesel by-product as an asphalt modifier was investigated in terms of chemical composition and performance grades tests. Modified asphalt binders were prepared by adding four contents of biodiesel by-product into control binder. First, Fourier transform infrared spectroscopy (FT-IR) test was conducted to investigate the chemical composition and modification mechanism of experimental materials. Then, rotational viscometer test for original asphalt, dynamic shear rheometer test for original, rolling thin film oven-aged and pressure ageing vessel (PAV)-aged asphalt, bending beam rheometer test for PAV-aged asphalt were carried out to investigate the effect of biodiesel by-product on performance grades of control asphalt binder. Finally, storage stability test was conducted to analyse the segregation tendency of by-product-modified asphalt binders. The FT-IR test results indicated that no chemical reaction occurred between control asphalt and biodiesel by-product. Meanwhile, the addition of biodiesel by-product reduced the rotational viscosity of the asphalt binder, hence lowered the optimum mixing and compaction temperatures of asphalt concrete. Moreover, the addition of biodiesel by-product decreased the high-temperature performance of asphalt binder, while improved the low-temperature performance and fatigue resistance performance. In addition, a good storage stability of by-product-modified asphalt binders was noticed. Finally, considering the performance variations of by-product-modified asphalt and environmental requirements, the content of by-product recommended to be used as PG64-16 asphalt binder's modifier in cold region was 4%.