Basic properties, durability and microstructure of alkali-activated hemihydrate phosphogypsum incorporating with ground granulated blast furnace slag (GGBFS)

Cement production has generated substantial greenhouse gas emissions, contributing to environmental pollution. This study investigates eco-friendly alkali-activated materials using hemihydrate phosphogypsum and ground granulated blast furnace slag (GGBFS), combining basic properties and durability with microstructure. The basic properties were evaluated, including fluidity and consistency, mechanical strength under different cured times, and drying shrinkage. The durability included freeze-thaw cycles, sulfate corrosion, and chloride-ion permeation tests. Furthermore, the microstructure and mechanism of modified alkali-activated materials were analysed using X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy techniques. The results showed that the binary system created better properties including the enhanced mechanical strength, the compensatory fluidity and consistency, and the optimised durability. The incorporation of GGBFS led to a reduction in fluidity and consistency. Due to the suitable contents of GGBFS, the hydration products in the binary system were dominated by C-S-H, and gypsum, which influenced changes in the properties of the binary system. A 40% slag contents facilitated process of the hydration gels of the system. The use of those solid wastes, such as hemihydrate phosphogypsum and slag, provided a sustainable development for cementitious materials and environmental conservation.