Effect of Layered Double Hydroxide on Rheological and Flame-Retardant Properties of Styrene-Butadiene-Styrene–Modified Asphalt

Abstract

In this study, we evaluate the flame-retardant properties of styrene-butadiene-styrene (SBS)/layered double hydroxide (LDH-) –modified asphalt. We performed physical tests, dynamic shear rheological tests, and limit oxygen index measurements to evaluate basic physical properties as well as rheological and flame-retardant properties of SBS/LDH-modified asphalt samples. Fourier transform infrared spectrometry and fluorescence microscopy were performed to elucidate the mechanism reaction between LDH and SBS-modified asphalt. In addition, a novel flame-retardant analyzer was developed and used to analyze the changes in mass and temperature during asphalt combustion. Kinetics analysis and thermogravimetry measurements were performed to determine the most probable mechanism and activation energy. The microstructure of the combustion residue was analyzed using scanning electron microscopy. The results indicate that LDH increases the viscosity of SBS-modified asphalt and its resistance to deformation at high temperatures. However, when added in high concentrations, it has a negative effect on asphalt ductility. The |G*|, G′, and G″ values for the SBS-modified asphalt increase with the addition of LDH. However, the effect is not statistically significant over the entire investigated frequency range. Moreover, the addition of 5% LDH reduces the phase angle of SBS-modified asphalt for frequencies greater than 30 Hz. Also, its effect is not statistically significant over the entire investigated temperature range. LDH increases the nonflammable grade and activation energy of SBS-modified asphalt and results in the formation of denser char, which significantly improves its flame-retardant properties.