Phosphogypsum leachate cleaning waste as partial cement replacement in mortars

• LDW-mortars increased the compressive strength at 2.5–10% replacement compared to the reference. • LDW-mortars were able to immobilise potential contaminants. • The gamma index ( I ) was < 1 for LDW-mortars. This study presents the first valorisation of a waste generated from the cleaning process of phosphogypsum leachate. Leachate decontamination waste (LDW), which contains non-negligible concentrations of heavy metals, radionuclides and fluorine, was used as a partial cement replacement in mortars at varying proportions. New cements and mortars were produced from mixtures of a commercial Portland cement (CEM I 52.5) with different concentrations of this waste (2.5, 5, 7.5, 10, 25 and 35 wt.%). The physical-chemical properties, mechanical behaviour, and environmental impact of these LDW-cement mortars were evaluated. The results revealed that incorporating LDW at levels of up to 10% not only maintained but even enhanced the mechanical properties compared to the reference mortar. Furthermore, the cement matrix effectively immobilized potential contaminants in all cases, contributing to environmental safety.