The feasibility of immobilizing strontium in cement-bentonite matrices was investigated by studying the effect of mineralogical phase development on mechanical and containment performances. Within this context, the chemical composition and physical properties of bentonite were determined. Different cement-bentonite waste matrices were prepared and analyzed using XRD technique to trace the changes in phases during the curing period. The mechanical performance of these matrices was evaluated by measuring the compressive strength throughout their curing period and the containment performance was determined by conducting long-term static leaching test then the experimental results were checked against some regulatory limits. The results indicated that the presence of strontium and bentonite did not lead to formation of new hydrated phases. The mechanical performance of the matrices is acceptable and the enhanced compressive strength was attributed to the progression in the formation of cement hydrated phases and the pozzolanic reaction between bentonite and lime in cement-bentonite matrices. The speciation data and phase structures analysis indicated that Sr2+ containment in cement might be due to Ca substitution in Ettringite structure and cations exchange on Montmorillonite lattice. The mathematical analysis of the long-term leaching results indicated that strontium leaching resulted from a combination of first order reaction and diffusion mechanisms. (C) 2013 Elsevier B.V. All rights reserved.