Efficiently fire-safe asphalt achieved via synergistic effect of ferrocene and halloysite nanotube

Aiming to improve the flame retardancy efficiency and rheological properties of hydroxides commonly used in asphalt, a combined flame retardant was fabricated using aluminium hydroxide (ATH), halloysite nanotube (HNT) and ferrocene. The optimal loading of flame retardant and process parameters for asphalt preparation were determined through an orthogonal experimental design. Through microscopic observation, the combined flame retardant was evenly dispersed within the asphalt matrix, with minimal agglomeration and segregation. Asphalt containing the combined flame retardant achieved an improved limiting oxygen index (LOI) value of 28.1 %, accompanied by a 30.9 % and 41.2 % reduction in peak of heat release rate (PHRR) and peak of smoke production rate (PSPR) compared to conventional Styrene-Butadiene-Styrene (SBS) modified asphalt used in asphalt pavement. In-depth mechanism analysis revealed that the formation of high-quality charring layers was facilitated by the catalytic reaction of ferrocene and catalytic oxidation of gases produced during asphalt combustion. Moreover, the improved network crosslinking function in asphalt significantly enhanced the rheological properties observed in the dynamic shear rheometer (DSR) and multiple stress creep recovery (MSCR) tests. Prospectively, this study provides an effective approach for simultaneously achieving prominent fire safety and enhanced rheological properties of asphalt through a simple preparation method.