In this study, thermogravimetry (TG) experiments were employed to study the influence of magnesium hydroxide (MH) on the pyrolysis characteristics of an asphalt binder. Pyrolysis models of the asphalt binder were developed to reveal the flame-retarding mechanism of MH. The TG experimental results showed that the pyrolysis process of the asphalt binder in N-2 was a one-stage reaction. The asphalt binder containing MH had a higher residue yield ratio at a high temperature, and TG and differential TG curves showed a dramatic shift toward higher temperatures with an increase in the MH concentration; this indicated that MH inhibited the thermal decomposition of the asphalt binder. By optimal identification of the pyrolysis mechanism function, the pyrolysis reaction of the asphalt binder was found to follow the model of one-dimensional diffusion (parabolic law), whereas that of the flame-retarding asphalt binder followed the model of three-dimensional diffusion (the Ginstling-Brounshtein equation). On the basis of the models, the calculation results for the pseudo activation energy indicated that the thermal stability of the asphalt binder in the pyrolysis process was obviously improved by the addition of MH. We conclude that the flame retardancy of asphalt binders can be enhanced by the use of MH, and MH may be a potential flame retardant for asphalt binders used in tunnel asphalt pavement. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 2661-2665, 2011