Study on properties of untreated FGD gypsum-based high-strength building materials

Abstract

This paper introduces an untreated flue gas desulfurization (FGD) gypsum-based high-strength building materials prepared using the uncalcined desulfurization gypsum. The chemical compositions, physical properties and particle micromorphology of the untreated FGD gypsum were analyzed. The influence of digestion time on the mechanical properties of untreated FGD gypsum-based high-strength building materials was studied, therefor the optimal digestion time was determined to be 18h. The mechanical properties, water resistance, frost resistance and shrinkage property of the building materials were tested. The hydration reaction mechanism, hydration process, hydration products, pore structure, micromorphology of the building materials were researched by means of XRD (X-ray diffraction), MIP (Mercury Intrusion Porosimeter) and SEM (scanning electron microscope). Non-evaporable water content was used to represent the hydration degree. The results show that the untreated FGD gypsum-based high-strength building materials has good mechanical properties, water resistance, frost resistance and low shrinkage ratio, high hydration degree, dense microstructure. And its Ca/Si atom ratio is low. This study provides a new approach for the more effective use of untreated FGD gypsum, which effectively saves the natural resources.