Abstract
By means of limiting oxygen index (LOI), cone calorimeter, and TG-DSC tests, this paper investigated the effect of unmodified montmorillonite (MMT), organically modified montmorillonite (OMMT), and aluminium trihydrate (ATH) additions on the flame retardancy for asphalt combustion. Experimental results showed that adding a small amount of montmorillonite did not significantly increase the oxygen index of the asphalt but reduced the heat release rate during asphalt combustion. TGA tests had indicated that the montmorillonite (MMT and OMMT) could suppress the release of flammable volatiles and form more asphaltenes, which hence postponed the burnout time of asphalt. Furthermore, the combination of montmorillonite (MMT and OMMT) and ATH had yielded a synergistic effect, which had further reduced the heat release rate and also increased the oxygen index of asphalt. In particular, after further addition of OMMT, the barrier layer showed less crack, leading to a significant decrease in the heat release rate as compared to the adding of ATH alone.
Highlights
Asphalt is a viscoelastic liquid or semisolid with remark rheology properties and impermeability
The usage of metal hydroxides will reduce the ductility of asphalt, which leads to the requirement of excessive metal hydroxides addition in order to pass the flame retardancy tests [7] and renders the asphalt fragile and brittle [8]
Bonati et al [15] proved that when aluminium trihydrate (ATH) was coupled with organically modified montmorillonite (OMMT), a dramatic decrease of heat and smoke releases as generated by asphalt mixture combustion could be achieved, which was proposed due to the enhanced protective char layer that acts as an insulator and mass Journal of Chemistry transport barrier
Summary
Asphalt is a viscoelastic liquid or semisolid with remark rheology properties and impermeability. Bonati et al [15] proved that when ATH was coupled with organically modified montmorillonite (OMMT), a dramatic decrease of heat and smoke releases as generated by asphalt mixture combustion could be achieved, which was proposed due to the enhanced protective char layer that acts as an insulator and mass. Wu et al [16] reported that a 5 wt% OMMT could improve the LOI of asphalt from 19.8% to 23.6% and reduce the heat release rate of the asphalt combustion. Bourbigot et al [17] reported an inconsistent result that a 5 wt% OMMT did not enhance the fire behavior of asphalt, but the peak heat release rate was even increased by 18%. We expect that the work conducted could provide a scientific basis and reference for the selection of high performance and cost effective flame retardant for asphalt combustion
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