Utilization of magnesium slag to prepare CO2 solidified fiber cement board

Magnesium slag is a solid waste produced during industrial magnesium refining. The large amount of magnesium slag produced each year not only causes environmental pollution, but also poses a risk to human health. This paper proposes the use of magnesium slag as a carbonation binder, to produce a new type of CO2 solidified fiber cement board (CSFCB) by accelerated carbonation curing. The mechanical properties, microstructure, durability, and volumetric stability of CSFCB were investigated, and its environmental benefits were evaluated. The results indicate that, under optimal process conditions, CSFCB can attain a water-saturated flexural strength of more than 14 MPa, a carbonation degree higher than 40%, and a water absorption rate as low as 14.9% after 24 h carbonation curing. Phase assemblage and microstructure analysis attribute the high performance mainly due to the voluminous precipitation of calcium carbonate, and the strong bonding of reinforcing pulp fibers with the matrix. This also leads to the improved freeze-thaw resistance and negligible warping deformation. Furthermore, compared to traditional fiber cement board (TFCB), CSFCB exhibits added benefits of carbon absorption and solid waste valorization by the ecologic assessment. The results of the pilot production of CSFCB show that the pro-duction and utilization of CSFCB will significantly reduce environmental pollution.