Effects of modified materials prepared from wastes on the performance of flue gas desulfurization gypsum-based composite wall materials

Abstract The utilisation of industrial wastes and straw fibre to prepare building materials is a green alternative that saves natural resources and protects the environment. This study investigates the effect of cement, inorganic wastes, and straw fibre on the properties of flue gas desulfurization (FGD) gypsum. Response surface methodology was adapted to study the mechanical and water resistance properties of the samples. The results indicate that the properties of gypsum-based composites improved upon addition of cement and wastes due to the synergistic effect between them, which resulted in formation of calcium silicate hydrates (C-S-H) and ettringite (AFt). The addition of 3 wt% of sorghum straw fibre (SSF) significantly improved the flexural strength, decreased the apparent density and thermal conductivity of samples at a length to diameter ratio (LDR) of 7.5. The SSF successively treated with alkali, enzyme, and waterproofing agent removed the non-toughening compounds of the fibre, resulting in better mechanical properties and thermal conductivity. This outcome occurred because the non-toughening compounds of SSF, especially protein, pectin, and hemicellulose, negatively impact the studied properties. This work provides a theoretical basis to improve the overall properties and prepare a lightweight high-strength thermal insulation FGD gypsum-based composite for wall materials.