Shenzhen Daxue xuebao. Ligong ban (Jan 2025)
Effect of hybrid accelerator on the property of CFBFA-based foamed concrete
Abstract
Circulating fluidized bed fly ash (CFBFA) is a major by-product of modern coal combustion technologies. Foamed concrete with a high CFBFA content can meet insulation requirements for building partition walls. However, a high CFBFA content slows the setting process of foamed concrete, reducing turnover efficiency in industrial production. A hybrid accelerator was developed using a mixture of aluminum sulfate and calcium hydroxide. With the mass fraction of aluminum sulfate fixed at 3%, the effects of varying mass ratio of calcium hydroxide to aluminum sulfate 0, 0.25, 0.50, 0.75 and 1.00, respectively, on the setting time, compressive strength, and thermal conductivity of CFBFA-based foamed concrete were investigated. The effects of hybrid accelerator on the early hydration of CFBFA-based foamed concrete were studied by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and isothermal conductivity calorimetry. The pore structure was analyzed using a 3D profiler combined with Image-Pro. The results showed that when the mass ratio of calcium hydroxide to aluminum sulfate in the hybrid accelerator was 0.25, the initial setting time of CFBFA-based foamed concrete was reduced by 220 min compared to the control group without calcium hydroxide. When the mass ratio of calcium hydroxide to aluminum sulfate in the hybrid accelerator was 0.75, the 3 d strength of CFBFA-based foamed concrete reached 10.39 MPa, with a thermal conductivity of 0.30 W·m-1·K-1. The hybrid accelerator promoted the generation of needle-like ettringite (AFt) during early hydration, making the CFBFA-based foamed concrete more compact and the pore size distribution more uniform. The hybrid accelerator enables efficient mass production of CFBFA-based foamed concrete and shows promising prospects for engineering applications.
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