Research on the incorporation of untreated flue gas desulfurization gypsum into magnesium oxysulfate cement

The growing concern of low-carbon economy and sustainable development has obliged the researchers to investigate green building materials through utilizing industrial by-products. In this study, the industrial waste material, flue gas desulfurization gypsum (FGDG), is incorporated into the magnesium oxysulfate cement (MOSC). The performance of FGDG-incorporated MOSC is evaluated by testing the setting time, compressive strength, density, water absorption, water resistance, volume stability and SO42- releasing. The hydration products are detected by X-ray diffraction, while microstructure is observed by optical microscope and scanning electron microscope. Increasing the proportion of FGDG retards the initial and final setting times of paste. Compressive strength for MOSC mixtures varies from 52.4 to 62.4 MPa at hydration age of 3 days. The water absorption and the release of SO42- increase when increasing the FGDG content. The FGDG-incorporated MOSC presents a superior water resistance and volume stability in contrast with the FGDG-free MOSC. The main hydration products of the paste are Mg(OH)(2) and 5 Mg(OH)(2)center dot MgSO4 center dot 7H(2)O (5.1.7) phase. The microstructure analysis is in agreement with the results of mechanical properties. Finally, the FGDG-incorporated MOSC is identified as a promising building material by the evaluation of economic and environmental sustainability. (C) 2020 Elsevier Ltd. All rights reserved.