Investigation into the properties of asphalt mixtures containing magnesium hydroxide flame retardant

Abstract

In this study, horizontal burning, limiting oxygen index (LOI) and direct burning tests were conducted to evaluate the effects of magnesium hydroxide (MH) on flame retardancy for asphalt. The influence of MH on the mechanical properties of the asphalt mixtures was also evaluated using a Marshall stability test and an indirect tensile strength test. The results indicate that MH improves the thermal stability of asphalt. The presence of MH reduces the horizontal burning classification of asphalt from FH-3 to FH-1, and the LOI is also increased. Reductions in the average burning time and mass loss were observed. The volume of flammable volatiles released from asphalt was reduced. By replacing some of the mineral filler in asphalt with equal quantities of MH, the Marshall stability was increased, its loss decreased. Similarly, the indirect tensile strength (ITS) was increased, but the ITS loss increased slightly. It is concluded that MH can be used as flame retardant for asphalt mixtures without significantly reducing the original pavement performance. This may provide a novel and safer road material, especially for use in tunnel roadways.