High Volume Utilization of Fly Ash Containing Mercury-Impregnated Activated Carbon

In March of 2005, the EPA published final regulations to control mercury emissions from coal-fired electric utilities. The most mature retrofit technology available for mercury collection is the injection of a sorbent such as powdered activated carbon. Unfortunately, carbon injection technology is accompanied by high concentrations of mercury in the fly ash, (an important by-product that is used in concrete), which renders the fly ash unacceptable for concrete use. This project will develop reaction-bonded, castable ceramic materials, made with high carbon/mercury content fly ash, that can replace concrete in commercially viable applications. In Phase I, it was demonstrated that various types of fly ash, containing excess activated carbon and mercury could be made into strong reaction-bonded, castable ceramic materials through the selection of activators, water content, and curing temperature. The reaction not only generated strong bonding materials, but effectively encapsulated both the mercury and activated carbon, rendering the new cement composition environmentally benign and suitable for use in various concrete applications. Phase II will further characterize and optimize the engineering properties of the materials, including compressive strength, workability, freeze-thaw resistance, indirect tensile strength, elastic constants, etc. These properties will be compared against the standards developed for current fly ash concrete and Portland cement based concrete. Commercial Applications and other Benefits as described by the awardee: The new materials would allow fly ash to remain useful and marketable, even after the adoption of mercury control technologies by coal-fired power plants. The use of this reaction-bonded material also would minimize emissions of greenhouse gases by minimizing the demand for Portland cement-based concrete.