Abstract
Eco-cement is a new type of Portland cement being developed not only to solve the municipal and industrial waste problem caused by limited availability of landfill sites, but also to contribute to the protection of the environment by providing a complete recycling system of wastes that would otherwise be dumped. This new cement is designed to use municipal waste incinerator ash as up to 50% of raw materials. Combustible wastes like waste oil, plastics, RDF (refuse-derived fuel) also can be used as fuel. Eco-cement consists of the same main components as normal Portland cement (NPC); alite(C3S), belite(C2S), calcium aluminate (C3A), calcium alumino-ferrite (C4AF) and calcium sulfate. The manufacturing process of Eco-cement is also mostly the same as NPC. Incinerator ash generally contains substances undesirable for cement, such as Cl and a small amount of heavy metals. The metals vaporize in the form of chlorides through the sintering process and are caught as kiln dust in the bag filter. The heavy metals, then, are extracted from the dust through the metal recovery process and delivered to a smelter for refining. This makes the Eco-cement process a complete recycle system for municipal and industrial wastes. Another type of Eco-cement featuring rapid hardening in one hour was also designed. This cement contains 20% of calcium chloro-aluminate (C11A7･CaCl2), instead of C3A. Other main components of this type are C3S, C2S, C4AF and calcium sulfate. This cement is suitable for concrete blocks, wood-fiber board and other non-rebar concrete products.
