Effects of polypropylene based graft copolymer carrying methyl metacrylate units on the properties of bitumen and bituminous mixtures

In this study, it was aimed to synthesize a unique graft copolymer suitable for the physical and chemical structure of bitumen from thermoplastic wastes and to investigate the effect of this polymer on bitumen and bituminous hot mixtures. For this purpose, methyl methacrylate (MMA) monomer was obtained by thermal depolymerization of polymethylmethacrylate (PMMA) from thermoplastic wastes, which became waste first and are widely available commercially. After the monomer was characterized by FT-IR spectroscopy, a unique polypropylene-graft-(methylmethacrylate-co-maleicanhydride) additive was produced by passing it through a chemical process with different weight ratios of waste polypropylene (PP) and maleicanhydride (MAH). The produced graft copolymer additive was characterized and modified bitumens were prepared by adding in the range of 3%-6% by weight to pure bitumen with B 100/150 penetration. Physical and rheological properties of pure and modified bitumens were investigated by conventional and Superpave tests, and chemical properties by SEM, XRD and FT-IR spectroscopy analyzes. In addition, bituminous hot mix samples were prepared according to Marshall Mix Design Method using modified bitumens. These samples were subjected to Marshall stability and flow, Retained Marshall Stability (RMS), Indirect Tensile Stiffness Modulus (ITSM), Indirect Tensile Strength (ITS) and Static Creep tests. According to the test results, it has been observed that the copolymer reacts with bitumen, increases the hardness of the bitumen and decreases the temperature sensitivity, and has a positive effect on the high and low temperature performance of the bitumen. In addition, it has been found that the copolymer has an improving effect on the stability, moisture damage and permanent deformation resistance of bituminous hot mixes.