Preparation and Performance of Hydrotalcite and Montmorillonite Composite as Flame Retardant in Asphalt Pavement

The increasing use of tunnel bitumen pavements has led to a corresponding rise in fire hazards. To improve the fire safety of these pavements, a novel flame retardant material has been developed, which incorporates carbonate intercalated magnesium aluminum hydrotalcite (MALC) and calcium-based montmorillonite (MMT) to form intercalation composites. The resulting MALC/MMT composite, along with 4,4'-methylenebis(isocyanate) (4,4'-MDI), was added in specific proportions to the bitumen, producing a flame retardant modified bitumen. The flame retardant performance was assessed through aging and combustion tests. The results indicate that the most effective flame retardant performance was achieved with a MALC:MMT ratio of 2:1 and a composite dosage of 5%. This study presents a straightforward and effective method for developing a novel inorganic flame retardant.