An examination of natural rubber modified asphalt: Effects of rubber latex contents based on macro- and micro-observation analyses

Abstract

Abstract At present, relatively no reliable conclusion regarding an optimum natural rubber content based on the theoretical and fundamental approach to understanding up to the micro-scale of chemical and mechanical interactions in the natural rubber-asphalt cement matrix as the natural rubber modified asphalt (NRMA) exists. This study aimed to examine the effects of natural rubber latex (NRL) contents in natural rubber modified asphalt (NRMA) binder. A series of micro-observation techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR), were performed. For the general performance tests, macro observations through a series of penetration tests, softening point, viscosity, ductility, and dynamic shear modulus (G*) for evaluating the asphalt binder properties were also conducted. Study results showed that the performance of NRMAs (3%–12% NRL contents) depended on their NRL contents due to varying internal interactions between NRL and the asphalt binder. The NRMA with an optimal content of 7% NRL revealed crosslinking and bridging interactions between NRL and an original asphalt cement was observed, and the chemical bonds were also identified.