Performance Characteristics of Concrete Produced with Fluidized Bed Combustion Ash Residue

Abstract

ABSTRACTOver 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.