Effects of solvent-free bentonite fluid on physical, rheological and aging properties of SBS modified bitumen

Abstract

Layered silicate materials were often used for bitumen modification, but their improvement effect on bitumen performance was limited due to their poor compatibility with bitumen. Introducing long-chain organic compounds on the surface of inorganic materials can make them exhibit solvent-free fluid characteristics, which can significantly enhance the compatibility between inorganic and organic materials. In this study, 3-(trimethoxysilyl propyl) dimethyl octadecyl ammonium chloride (DC5700) and nonylphenol polyoxyethylene ether sodium sulfate (NPES) were used to organically treat bentonite (Ben) to prepare solvent-free bentonite fluid (Ben-fluid) so as to effectively improve the overall performance of styrene-butadiene-styrene copolymer (SBS) modified bitumen (SMB). Ben and DC5700 organically treated bentonite (DC5700-Ben) were used as comparative samples. The microstructure, ultraviolet reflectance and lipophilicity of Ben, DC5700-Ben and Ben-fluid as well as fluidization characteristics of Ben-fluid were tested and characterized. The results of X-ray diffraction spectrometer and Fourier transform infrared spectrometer (FTIR) demonstrated that DC5700 intercalated into the layers of the Ben and chemically grafted on the Ben surface, and the NPES was anchored on DC5700 molecules through ionic bonds. Compared with Ben and DC5700-Ben, Ben-fluid had the highest ultraviolet reflectance and the best lipophilicity. As the temperature exceeded 82.3 ℃, the fluidization characteristics of Ben-fluid began to appear. Meanwhile, the effects of Ben-fluid on physical, rheological and aging properties of SMB were investigated. Ben-fluid was more conducive to enhance the high-temperature stability of SMB than Ben and DC5700-Ben, and has less adverse effects on the low-temperature physical and rheological properties. The aging results of different SMBs revealed that the change in physical properties of SMB containing Ben-fluid after thermal and ultraviolet aging was significantly lower than that of SMB containing Ben and DC5700-Ben. In addition, FTIR showed that compared with Ben and DC5700-Ben, the Ben-fluid could inhibit the increase of carbonyl index and the decrease of butadiene index of SMB after aging. Comprehensive analysis suggested that Ben-fluid was more conducive to improve the physical, rheological and anti-aging properties of SMB.