Using alumina-rich sludge and phosphogypsum manufactures low-CO2 cement

Journal article, 2021

Calcium sulfoaluminate-belite (CŜAB) cement has been proposed as a low-CO cement for substituting ordinary Portland cement (OPC). The aim of this work was to study synthesis of CŜAB cement from two industrial wastes, namely Alumina-rich sludge (AS) and phosphogypsum (PG). The main phases of the synthesized cement were ye'elimite, larnite, ternesite and anhydrite. The properties of CŜAB cement were investigated through the test of compressive strength, setting time and hydration products. We found that the optimal procedure was burning at 1150 °C for 1 h which needs much lower energy than traditional production. CŜAB cement could reach 39.4 MPa at 28 d hydration, when basicity factor, the ratio of aluminum to sulfur and aluminum to silicon ratio were 0.8, 2.5 and 3 respectively. Blending phosphogypsum into clinker, made paste get a much higher compressive strength (53.2 MPa at 28 d). Adding phosphogypsum to CŜAB cement hindered hydration process of cement and decreased hydration products except for ettringite. Production of this cement is beneficial to recycle industrial wastes and reduce CO emission. This is meaningful for further development of cement industry. 2 2