EVOLUTION OF CEMENTED PASTE BACKFILL SATURATED HYDRAULIC CONDUCTIVITY AT EARLY CURING TIME

* Chaire Industrielle CRSNG Polytechnique-UQAT en environnement et gestion des rejets miniers One interesting management approach to reduce environmental impacts related to sulphide mine tailings storage consists in using them as a component of cemented paste backfill (CPB). CPB consists of a mixture of tailings, binder agent, and water. Binder hydration in CPB leads to an evolution of the porous matrix and entails a change in hydrogeotechnical properties of the backfill. Key property to investigate for an efficient management of tailings is the saturated hydraulic conductivity (ksat). In this study, results of permeability tests performed on cemented paste backfill samples at different curing times are presented. Results show that the addition of 4.5 % wt of binder can reduce ksat by a factor of more than ten after 28 days of curing. The kinetic is also different depending on the binder used. Typically, a binder made of Portland cement and slag has a greater impact on the reduction of ksat than a binder made of Portland cement and fly ash. Finally, a simple equation to predict ksat of the studied CPB is proposed. Results show a relatively good correlation between predicted and measured values. RÉSUMÉ Une approche intéressante pour réduire les impacts environnementaux liés à l’entreposage des rejets de concentrateur sulfureux est de les entreposer sous forme de remblai en pâte cimenté (RPC). Le RPC consiste en un mélange d