Study on fire resistance and mechanical properties of modified recycled waste oyster powder in asphalt binder

In this study, an eco-friendly approach is presented for the innovative use of waste oyster shell (OS) powder modified with zinc stannate, aliphatic alcohols, and silane coupling agents blended with styrene-butadiene-styrene (SBS) modified asphalt to make a flame-retardant binder (modified oyster shell [MOS]/styrene-butadiene-styrene [SBS]/MA), which is rendered flame retardant and smoke suppressive. Compared with the original SBS/MA, MOS/SBS/MA with a 2% addition rate showed a 35.44% increase in ultimate oxygen index, a 30.62% reduction in peak exotherm, a 10.87% reduction in smoke density, and a 75% reduction in volatile organic compound (VOC) emissions. It also has excellent mechanical properties, with increases in composite modulus, elastic modulus, and storage modulus of 68.58%, 97.29%, and 59.59%, respectively, at 46°C. The thermal stability of MOS/SBS/MA is also improved, with a decomposition temperature 26°C higher than that of SBS/MA. Pavement performance tests show that the water-soaked Marshall's split strength has increased by 3.87% and the coefficient of rutting by 3.51%. Increased by 3.51%, this method effectively utilizes the waste OS, improves the fire-retardant properties of asphalt while retaining the mechanical properties of the modified asphalt binder, and provides a model for developing sustainable fire-retardant asphalt in coastal areas.