ORIGINAL ARTICLE Parameters controlling the release of hazardous waste (Ni 2+ , Pb 2+ and Cr 3+ ) solidified/stabilized by cement-CEM I Ch. Belebchouche • K. Moussaceb • A. Tahakourt • A. Aı ¨t-Mokhtar Received: 4 March 2013 / Accepted: 23 April 2014 Ó RILEM 2014 Abstract In this article, first, we present the charac- terization and the process of solidification/stabiliza- tion (S/S) of hazardous waste, industrial rejections of Algeria, by hydraulic binder CEM I, Second, we present the study on the influence of leaching tests and the amount of waste on the release of solidified/ stabilized waste to the surrounding environment. S/S was performed at the laboratory using two types of formulations. The mechanical strength was evaluated at 7 days then at 28 days of cure. The results of mechanical strength show an increasing up to a maximum threshold, then a decrease due to the increasing of the amount of waste in the S/S materials. pH-dependence test showed two types of solubiliza- tion; chemical species that depends on pH (Ni 2? , Pb 2? , Cr 3? , Ca 2? ) and others which are independent from pH (Na ? ,K ? , Cl - ). It was observed that the amounts of heavy metals released into the pH depen- dence, PW and MMF tests were very large compared to the amount released into the MLT test. XRD and SEM–EDX analysis show the presence of heavy metals within the structure of S/S materials which explains the effectiveness of the S/S process. Mortar showed better efficiency in trapping pollutants com- pared to cement paste. Keywords Hazardous waste  Solidification/ stabilization  Hydraulic binder  Amount of waste  Leaching tests  Morphology 1 Introduction Industrial activities of human being in various fields such as chemical, mechanical, metallurgical and other industries produce each year large quantities of residual waste such as: heavy metals. The contamina- tion of groundwater by heavy metals has become a problem on public health and environment, as water is considered as the main vector that carries the transfer of pollutants in the environment. The geochemical mobility of heavy metals along with their toxicity poses a serious threat to the humans’ health and that of animals and it requires an immediate solution [9]. These threats have triggered attention to find appro- priate technologies in order to remediate polluted soil. One of the powerful techniques is the precipitation of these toxic pollutants such as hydroxides [22, 32]. However, this technique induces large amounts of hazardous waste with high concentrations of heavy Ch. Belebchouche (&)  K. Moussaceb  A. Tahakourt Laboratoire de Technologie des Mate ´riaux et de Ge ´nie des Proce ´de ´s (LTMGP), Faculte ´ de Technologie, Universite ´ A/MIRA Bejaia, Route Targa-Ouzemour, 06000 Bejaı ¨a, Algeria e-mail: belebchouche_c@hotmail.fr A. Aı ¨t-Mokhtar Universite ´ de La Rochelle, CNRS, LaSIE UMR7356, Avenue Michel Cre ´peau, 17042 La Rochelle Cedex 1, France Materials and Structures DOI 10.1617/s11527-014-0315-6