Effect of metallurgical slag cementitious material on solidification characteristics of ultra-fine tailings backfill

The hydration properties of 3 typical backfill binders were experimentally investigated from macro and micro perspectives through X-ray diffraction, thermogravimetry, scanning electron microscope and strength tests. The effects of binder type, temperature, mixture composition and ultra-fine particle content on the tailings solidification characteristics were explored. The findings reveal that metallurgical slag-based binder (MSB) can completely consume self-generated calcium hydroxide to produce more gel-like products through alkali, sulfate and combined activation methods, which is favorable for binding ultra-fine tailings. The similar mechanical strength is obtained for MSB-CPB at halved cement to tailings ratio compared to ordinary Portland cement. Ultra-fine particles have a more significant impact on the backfill early strength. High-temperature of 40 ℃ curing accelerates the early MSB-CPB strength, which is proportional to the long-term strength at normal 20 ℃ curing. This correlation can be applied for the material quality fast check. The material cost and regional variance should be considered when employing the MSB in a practical case. Some related standards and grade level evaluation systems should be improved. Attention should be paid to the effects of heat stress and high ambient temperature on the MSB-CPB long-term stability. © 2022, China Science Publishing & Media Ltd. All right reserved.