Recycling of Flue Gas Desulfurization residues in gneiss based hot mix asphalt: Materials characterization and performances evaluation

On the one hand, huge amount of Flue Gas Desulfurization (FGD) residues, produced during scrubbing flue gas, is discarded as solid waste. Such solid waste would cause serious environmental problems. One the other hand, high quality aggregates, such as limestone and basalt, are running out due to the rapid development of highway construction. Ungraded aggregates such as gneiss are therefore considered in China to replace the high quality aggregates. The application of FGD residues as a filler in gneiss based asphalt mixture has benefits both in environmental and economic sides. The main objective of this research was to visualize the raw materials characterization and evaluate the effect of FGD residues on the performance of gneiss based asphalt mixture. X-ray diffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscope (SEM), Differential Scanning Calorimetric & Thermal gravimetric (DSC-TG) were used to investigate the features of raw materials. The performance of gneiss based asphalt mixture including high-temperature deformation resistance, low-temperature crack resistance and moisture-induced damage resistance were evaluated. Dynamic creep test, three-point bending test, Retained Marshall Stability (RMS), Tensile Strength Ratio (TSR), Indirect Tensile (IDT) strength and Resilient Modulus (MR) test were conducted and analyzed. Dissipated Creep Strain Energy to fracture (DCSEf) ratio, fracture energy and model analysis were also used to evaluate moisture resistance, crack resistance and deformation resistance of asphalt mixture respectively. Research results indicate that FGD residues can partly improve the moisture resistance and crack resistance of gneiss asphalt mixture, while it might worse the high-temperature deformation resistance.