Valorization of phosphogypsum in cement-based materials: Limits and potential in eco-efficient construction

Phosphogypsum (PG) is a type of synthetic gypsum generated during the production of phosphoric acid. Each ton of phosphoric acid generates 5 tons of phosphogypsum. This industrial process has caused significant environmental problems worldwide. After an extensive literature review, it has been possible to verify that both sedimentary and igneous PG can be used as materials building components. The use of PG up to 50% meets the limits required for index I, with a radioactivity equivalent to radio-226 and a concentration of radon-222. The data found on bricks (0,11-0,41 Bq m-2 h-1) and plate (0,16-0,41 Bq m-2 h-1) show a lower exhalation rate. It is also found that calcination contributes to the reduction of PG impurities, and the mechanical strength increase. Mortars and concretes produced with PG-based cementitious systems achieve high compressive strength levels (60 MPa, 70 MPa, 80 MPa) and accomplish the requirements of the European standards EN 998-1, EN 998-2, EN 13813, Eurocode 1992 and the American standard ASTM C270. The mineral phase of PG influences the setting time. It is concluded that cementitious materials produced from phosphogypsum are technically viable and achieve satisfactory performance in some building areas. The following open research lines have been detected: PG-based concrete with high performance, PG-based hydration cement, stabilized mortar, PG-based concrete with high workability, and studies on durability (e.g. chloride ingress, carbonation, sulphate attack and acid attack in PG-based concrete).