Solidification/stabilization of toxic metals in calcium aluminate cement matrices

•Reliable encapsulation and effective sorption of Pb, Zn and Cu on CAC was proved.•Cu and Pb were fully retained in the CAC mortar, while Zn was retained in 99.99%.•A maximum sorption capacity ca. 60mg/g CAC was attained for Cu.•Three different PSD patterns were established as a function of XRD phase assemblage.•Some metal-loaded mortars achieved suitable mechanical strengths for landfilling. The ability of calcium aluminate cement (CAC) to encapsulate toxic metals (Pb, Zn and Cu) was assessed under two curing conditions. Changes in the consistency and in the setting time were found upon the addition of the nitrates of the target metals. Both Pb and Cu caused a delay in CAC hydration, while Zn accelerated the stiffening of the mortar. Compressive strengths of the metal-doped mortars, when initially cured at 60°C/100% RH, were comparable with that of the free-metal mortar. Three different pore size distribution patterns were identified and related to the compounds identified by XRD and SEM. Sorbent capacities of CAC for the toxic metals were excellent: a total uptake was achieved for up to 3wt.% loading of the three metals. In this way, CAC mortars were perfectly able to encapsulate the toxic metals, allowing the use of CAC for waste management as proved by the leaching tests.