Potential of Blast Furnace Slags to Immobilize Toxic Wastes

Waste disposal has become a major concern in most industrial countries because of limited sites and strict environmental standards for landfilling. The common cementing materials, widely available and used, are normal portland cement, lime and high-calcium fly ashes from coal combustion. Ground granulated blast-furnace slag is also a component in binder formulation of general interest because of its potential for metal immobilization, based on its physical and chemical properties. The present work analyzes the immobilization of toxic wastes containing cadmium, lead and chromium in portland cement matrices with 80% of blast-furnace slag in comparison with plain portland cement matrices. The results show that lower levels of toxic ions in pore solution are obtained for blast-furnace blended cements due to differences in phases formed and the reduction of species to less toxic ones that occurs at the redox potential of slags. Differences in porosity may also cause a reduction in metal leaching from slag-blended cements.