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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.

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It is well chronicled that coal fly ash can mitigate the risk of alkali-silica reaction (ASR) in concrete structures. However, the efficacy of individual fly ashes is highly dependent on their chemical composition. Prescriptive requirements for ASR mitigation have largely focused on whether the fly ash is classified as Class F or Class C per ASTM C618, Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete, whereas performance requirements may require extensive testing to satisfactorily demonstrate mitigation potential of a fly ash. Previous research established the need for an accurate model to predict required fly ash replacement rates for ASR mitigation based on the chemical constituents of cement and fly ash. Therefore, a new model is proposed to account for the availability of each chemical constituent from cement and fly ash separately, utilizing ASTM C1260, Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method), and ASTM C1567, Standard Test Method for Determining the Potential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate (Accelerated Mortar Bar Method), test data. The successful development of models based on 14-day and 28-day expansion data from these tests is presented in this article.