Transformation of Wastes into Complementary Cementing Materials

摘要

This paper shows how wastes can be converted into useful complementary cementing materials instead of being landfilled. Two examples are presented. The first one deals with paper sludge, the residue coming either from deinking of old papers or water treatment. When calcined under 650°C, paper sludge is transformed into a mixture of metakaolin and calcium carbonate which consumes calcium hydroxide very quickly and can be considered as a very reactive pozzolan. When calcined over 700°C, the calcium carbonate contained in paper sludge starts to decarbonate and yields calcium oxide and calcium hydroxide. A hydraulic product is obtained, which can be used for partial replacement of portland cement, in backfilling mortars or as a viscosity agent in self-leveling concrete. The second example is the development of synthetic slag from different wastes. These wastes are mixed with a source of calcium and molten at 1450°C, then cooled and granulated with water. The resulting vitreous product, once milled, presents very effective hydraulic properties.