Performance Characteristics of Concrete Produced with Fluidized Bed Combustion Ash Residue
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PERFORMANCE CHARACTERISTICS OF CONCRETE PRODUCED WITH FLUIDIZED BED COMBUSTION ASH RESIDUE A.E. BLAND,a* C.E. JONES,at J.G. ROSEb and J.L. HARNESSc§ a. Kentucky Energy Cabinet Laboratory, P.O. Box 13015, Lexington, KY 40512 b. Dept. Civil Engineering, University of Kentucky, Lexington, KY 40506 c. Tennessee Valley Authority, 3N 54A Missionary Ridge P1., Chattanooga, TN 37402-2801 Received 27 October,1988; refereed ABSTRACT Over the last five years, the Kentucky Energy Cabinet (KEC) and the Tennessee Valley Authority (TVA) have developed and demonstrated the production of concrete from atmospheric fluidized bed combustion (AFBC) spent bed (SB) ash, and pulverized fuel ash (PFA). This AFBC concrete contains no cement and relies on the reaction of residual lime in the SB ash to react with the pozzolan PFA to form cementitious products. The SB ash is prehydrated in order to reduce exothermic lime hydration reactions and minimize molar volume expansion. Laboratory tests were conducted to establish the performance characteristics of AFBC concretes relative to conventional concrete. AFBC concretes exhibit slower strength gain characteristics, but long term (60 day), unconfined compressive strengths of 5,000 psi have been documented. This slow strength development is typical of pozzolanic concretes. AFBC concrete is more flexible and less brittle than conventional Portland cement concrete, as evidenced by its much lower modulus of elasticity. Setting times for AFBC concretes are extended, requiring the use of accelerators under certain applications. Field demonstrations of the AFBC concretes in ready mix concrete, masonry units, and road base applications have indicated excellent workability and finishing characteristics and confirm the laboratory performance characteristics. The paper describes the results of the testing program with emphasis on the ash chemistry/conditioning, the performance characteristics and field demonstrations.
INTRODUCTION Nearly 65% of the electricity produced in the United States is by coal-fired units, and nearly 85% of the coal produced in the U.S. is used for electrical power generation. This extensive use of coal results in the generation of very large quantities of ash. In 1985, conventional pulverized coal combustion processes in the U.S. generated 48.3-million tons of fly ash or pulverized fuel ash (PFA), and 13.2-million tons of bottom ash [1]. In addition, the use of scrubber technology to control sulfur reduction also generates large quantities of sludge annually. A wide range of uses for these ashes has been considered. For example, PFA has traditionally been used as a partial replacement for cement in commercial concrete applications [2,3]. However, only 23% of the total PFA generated in the U.S. is utilized, with the majority of this utilization being in concrete applications. Ash not utilized must be disposed of in landfills or ponds, resulting in additional costs to the electric power industry. In addition to conventional technologies, atmospheric fluidized bed combustion (AFBC) s
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