Study on the feasibility of desulfurized-high-calcium-fly-ash (DHCFA) used in asphalt mixture as mineral powder

Harmless treatment and resource utilization of wastes like fly ash have always been a social difficulty and a research hot spot in the field of pavement. In this paper, samples of fly ash generated from a coal-fired power plant in Yan’an City, Shaanxi Province were collected; and a desulfurized-high-calcium-fly-ash (DHCFA) was selected as the representative to be used for the alternative of traditional limestone fine powder (LFP) in asphalt mixture. Specifically, the chemical and physical characteristics of DHCFA and LFP were studied and compared firstly. Then the performance of asphalt mortar and asphalt mixture containing different amounts of DHCFA were further investigated. XRF and XRD results show that DHCFA and LFP both have significant alkalinity, and DHCFA has relatively richer chemical composition and phase distribution. TG-DSC results show DHCFA and LFP both satisfy the construction requirements on thermal stability. Asphalt mortar results showed DHCFA had the similar effect as LFP (control sample) on the whole. Asphalt mixture results revealed that the characteristics of DHCFA such as density, composition and compaction influence the performance of asphalt mixture. DHCFA could improve the low temperature performance and water stability of asphalt mixture, while reducing the high temperature performance and strength. Above results indicates that DHCFA could be used for mineral powder in asphalt mixture, however, its dosage should be carefully verified since it has adverse impact on the high temperature performance and strength of asphalt mixture.