Eco-friendly, high-toughness gypsum prepared using hemihydrate phosphogypsum, fly ash, and glass fibers: Characterization and environmental impacts

Hemihydrate phosphogypsum (HPG), obtained as a cementitious material from the dewatering of phosphogypsum, can be widely used in the preparation of construction materials owing to its low cost and environmental friendliness. However, current reports on HPG mainly focus on hydration behavior, mechanical properties, and durability, and there are few studies focusing on the enhancement of HPG toughness. In this work, glass fibers (GF) and fly ash (FA), as composite reinforcement, were mixed with HPG during its preparation to obtain eco-friendly, high-toughness gypsum. The workability, mechanical, microstructural, financial and environmental properties of the HPG-based composites with different GF volume dosages (0, 0.5, 1.0, and 1.5 vol.%) and FA weight percentages (0, 10, 20, and 30 wt.%) were comparatively investigated. The results show that the addition of an appropriate amount of FA can improve the interface transition zone between GF and the matrix and effectively increase the flexural strength and toughness of the composites. For the optimal mixture containing 1.5 vol.% GF and 20 wt.% FA, the flexural strength and toughness were 50.7% and 82.2% higher, respectively, than those of the mixture without FA and 99.2% and 675.3% higher, respectively, than those of the control sample (without GF and FA). Cost-benefit and environmental impact analyses also indicated that this composite was the most economical and environmentally friendly. Thus, this work provides an effective approach to achieve the high-value utilization of two major industrial by-products.