Effect of Phosphogypsum Whiskers Replacing Limestone Mineral Powder on the Rheological Properties of Asphalt Mastic

Abstract

As a product after the secondary refining of phosphogypsum, the application of phosphogypsum whiskers (PSW) to asphalt pavement not only effectively alleviated the negative effect of phosphogypsum on the economy and the environment, but also promoted the resourceful utilization of solid wastes. For this, this study investigated the feasibility of PSW as a substitute filler for asphalt mastic. The PSW was selected as the solid waste substitute filler, limestone mineral powder (LMP) was selected as the traditional filler, and PC42.5 cement (PCC) was selected as the traditional substitute filler, then the PSW and PCC were used to replace the LMP inside the asphalt mastic at five substitution ratios, respectively. The rheological properties of several asphalt mastics were evaluated by conventional performance tests and rheological tests, and the interaction mechanism between PSW and asphalt was explored by Fourier transform infrared spectroscopy (FTIR) test and surface free energy (SFE) test. The results showed that the enhancement effect of PSW on the high and low temperature performance, rutting resistance, and rutting resistance of asphalt mastic was superior to LMP and PCC, but its enhancement effect was affected by the substitution ratio. Particularly, the replacement effect of PSW and PCC would exacerbate the elastic behavior of asphalt mastic to a certain degree. The interaction between several fillers and asphalt only involved physical reactions, the new characteristic peaks observed in the wavenumber range of 400–1,350 cm−1 in the asphalt mastic originate from the filler, and the differences in the intensity of characteristic peaks in this range are related to the physicochemical properties of the fillers. The hydrophobicity of several asphalt mastics exhibited different degrees of attenuation, but it remained the hydrophobic material. The enhancement in cracking resistance and adhesion properties of PSW to asphalt mastic was better than LMP and PCC, and the limestone could provide more reliable adhesion properties for several asphalt mastics. This study investigated the feasibility of using PSW as a substitute filler, which could promote the resourceful utilization of solid waste and the sustainable development of asphalt pavement to a certain degree.