Recycling flue gas desulfurization ash in enhancing the comprehensive moisture susceptibility of asphalt mixtures

Abstract

Moisture susceptibility of asphalt mixtures is a major concern in areas with heavy rainfall or humid climates, as it can lead to premature pavement failures. As a typical industrial by-product during the flue gas desulfurization process of coal-fired, flue gas desulfurization ash (FGDA) with alkali mineral can facilitate the water damage resistance of asphalt mixtures. However, low density and high hydrophilic coefficient of FGDA limit its improvement effect. Hence, the comprehensive moisture susceptibility of asphalt mixtures with FGDA deserves systematic investigation. In this study, the properties indexes of FGDA and FGDA-limestone filler (LF) composite fillers were characterized. And the moisture susceptibility of asphalt mixtures containing six dosages of FGDA-LF fillers under hydrostatic damage and moisture induced sensitivity tester (MIST) hydrodynamic damage conditions were determined. The comprehensive assessment index of FLAM was explored based on radar chart assessment mean. The results indicate that FGDA with high alkali minerals and flocculent sphere morphology promotes the improvement of dispersivity and compatibility and the generation of homogeneous integral structure. Incorporating FGDA in FGDA-LF composite filler degrades its apparent density and elevates fineness and hydrophilic coefficient. Under MIST hydrodynamic damage, FLAM demonstrates the larger RMS and TSR than asphalt mixture with LF, accompanied by smaller attenuation compared to hydrostatic treatment. FLAM with F3 reveals the lowest rutting depth of 8.65 mm and creep slope of 1.92 × 10−4 and the largest comprehensive assessment index of 0.9998, indicating its optimal comprehensive moisture susceptibility. It is suggested that 30% FGDA might be an appropriate substitution amount for LF in FLAM.