Investigation of high volume of CFBC ash on performance of basic magnesium sulfate cement

Basic magnesium sulfate cement has the advantages of fast setting, high strength, high toughness, water resistance, corrosion resistance, etc. But the cost has become a reason for limiting its widespread application. With the widespread application of circulating fluidized bed combustion (CFBC) technology in China, the accumulation of CFBC ash is increasing. Reasonable use of CFBC ash can not only reduce cost of basic magnesium sulfate cement but also protect environment. In this paper, the effect of a high volume of CFBC ash on fluidity, flexural strength and compressive strength of basic magnesium sulfate cement is studied. Hydration products and micromorphology analyses are measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results reveal that the strength of basic magnesium sulfate cement with 20% CFBC ash is the highest, and its microstructure is the model that CFBC ash and MgO fill a three-dimensional network structure established by needle-shaped 5·1·7 phase. When the amount of CFBC ash is more than 40%, the formation of 5·1·7 phase is affected severely, which greatly reduces the strength.