Macro- and Microscale Properties of Stone Mastic Asphalt Mixtures Containing Calcium Sulfate Whisker

Abstract

In this paper, research was conducted to evaluate and analyze the macromechanical properties and micromechanism of stone mastic asphalt (SMA) containing an eco-friendly fibrous substance, calcium sulfate whisker (CSW). The investigation included the preparation of SMA specimens containing the lignin fiber (0.3% by wt. of mixture) and CSW (0%, 6%, 8%, and 10%, by wt. of asphalt binder). Then, wheel tracking, low-temperature flexural bending, Marshall immersion, freeze-thaw indirect tensile strength, and flexural bending fatigue tests were carried out to evaluate the pavement performance of these mixtures. Scanning electron microscopy (SEM) analysis were selected to observe the microstructure and micromorphology of the mixture. The results of laboratory tests revealed that the rutting resistance, moisture susceptibility, and fatigue performance of SMA were improved by the addition of CSW, while the crack resistance at low temperatures decreased slightly. The flexural bending tensile strain, tensile strength ratio, and fatigue life of the mixtures (under different stress levels) showed a trend of initial increase followed by a decrease with increasing CSW content, while optimal results were present at 8% CSW. SEM images revealed that CSW and lignin fiber were uniformly distributed and formed a three-dimensional network structure. Besides physical infiltration and adsorption effects, an anchoring force similar to the mechanical bonding force also existed between CSW and asphalt binder. The economic benefit analysis indicated that SMA with 8% CSW showed the most cost-effective performance. Consequently, about 8 percent should be the ideal CSW content. The outcomes provide critical insights into improving the performance of SMA pavement and serve as an important reference for the development of sustainable pavement.