Rheological and Morphological Characterization of Modified Bitumen with Cup Lump Rubber

Abstract

Pure bitumen is not suitable for heavy traffic loads; hence modifiers are used to improve the bitumen performance. Recently, cup lump rubber (CLR) has become a preferred modifier due to its outstanding performance and less cost. However, little is known about the interactions between CLR and bitumen. Thus, this study investigates the behavior of bitumen with CLR. Four percentages of CLR (2.5%, 5.0%, 7.5%, and 10.0% by weight of bitumen) were used to modify conventional 60/70 penetration grade bitumen. The modified bitumen was evaluated through different laboratory testing such as dynamic shear rheometer, rotational viscosity, softening point, bending beam rheometer, ductility, and elastic recovery. The testing results show that the addition of CLR increased the bitumen’s rutting resistance by 3 PG grades at high temperatures. At low pavement temperatures, the cup lump rubber modified bitumen (CMB) can withstand up to −34°C. Fourier Transform Infrared (FTIR) analysis shows that the Aromaticity index at 1600 cm-1 rose as the CLR percentage increased, indicating the formation of a binder with a compact structure. This is expected to improve the elasticity of bitumen through π – π interactions. Atomic Force Microscopy (AFM) results showed the Catana phase increased in size and quantity at 5.0% and 7.5% CLR content. While contact angle measurement revealed that the binders are hydrophobic and tend to repel the dropped water on the bitumen surface.