Pozzolanic Processes

These lime-based stabilization processes depend on the reaction of lime with a fine-grained siliceous material and water to produce a hardened material. The most common pozzolanic materials used in waste treatment are fly ash, ground blast-furnace slag, and cement-kiln dust. As all these materials are waste products to be disposed of, the fixation process can reduce contamination from several wastes. Other additives, generally proprietary, are often added to the sludge to enhance material strength or to help limit migration of problem contaminants from the sludge mass.

Lime and Portland cement are the setting agents, but gypsum, calcium carbonate, and other compounds may also be used. Lime-based and cement-based processes are better suited for stabilizing inorganic wastes rather than organic wastes. Decomposition of organic material in sludge after curing can result in increased permeability and decreased strength of the material.

Certain processes fall in the category of cement-poz-zolanic processes. In this case both cement and lime-siliceous materials are combined to give the best and most economical containment for waste.

0 0

Post a comment