Development of a Process for the Production of Lightweight Aggregate and Pozzolan From Lakeview Generating Station Fly Ash

CIM Bulletin, 1970

J. F. BOUX, President, Enercon Limited, Toronto, Ont

The study of the total utilization of fly ash has involved all of the known technology in the processing of this waste material into useful products. In addition, a complete knowledge of all the possible uses of fly ash and its products in the market area was probably the most important factor in evaluating the theory and practical feasibility of the total utilization of fly ash from a single large supply. Laboratory tests carried out on the separation of fly ash into different fractions were shown to improve its value and utilization. Four main fractions were studied: a fine pozzolanic low-carbon fraction; a coarse fraction for lightweight aggregate production by pelletizing and sintering; a high-iron fraction; and a carbon-rich fraction. The term "beneficiation" here refers to a process of separating fly ash into more useful components. Laboratory and pilot sinter strand tests were employed to optimize the sintering capability and the quality of the heat-hardened pellets through a study of the agglomeration cycle in four principal heat zones, under controlled conditions of air flow, temperature and atmosphere, and including the controlled sizing of pellets. The suitability of the heat-hardened pellets as lightweight aggregate was evaluated in test batches of concrete, which were compared with concrete containing commercial lightweight aggregate of established quality. A study of beneficiated fly ash pozzolan as a partial cementitious binder component in normal and high-temperature cured concrete was reported in a paper at the recent Second International Fly Ash Symposium. Samples of raw and beneficiated Lakeview ash were compared with samples of other established high-quality fly ash pozzolans. The evaluation indicated the usefulness of beneficiated Lakeview ash as a pozzolan. Economic studies indicated that to accomplish the primary objective of total utilization of any single source of fly ash (in this case. fly ash from the Lakeview Generating Station, producing approximately 400,000 tons per year), a broad knowledge of the technology of various mineral processes was essential. The design of the fly ash processing plant had to be based on the disposal of all the raw fly ash produced by the generating station. This is contrary to the normal design of a processing plant in which raw materials are supplied and produced according to product demand. The design, therefore, had to be of such flexibility as to produce as wide a variety of products as possible, and the ability to market them had to be well researched and understood
Keywords: Aggregate, Aggregates, Concrete, Enercon Limited, fly ash, Portland cement, pozzolan, Stirling Sintering Company., Fines, fly ash, Pellets, Process, Processes, Strength, Utilization