Utilization of wet-handled and dry-handled coal bottom ashes in portland cement based composites

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2021-9-7

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Tirkeş, Sera

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Coal bottom ash (BA) is a coarse, granular, incombustible by-product collected from the bottom of coal-burning furnaces. Traditionally, it has been handled by wet-handling systems (WHS) that use large amounts of water for cooling and conveying BA. WHS relies on established technologies such as impounded hoppers or submerged scraper conveyors. However, the need for water treatment, environmental concerns such as contaminated water, and high operational costs caused a necessary shift from WHS to more sustainable dry-handling systems (DHS) that do not need water and water treatment. Furthermore, returning heat energy to the boiler from the DHS result in lower coal usage. Currently, both handling systems are actively used in thermal power plants. This research focuses on the performance of wet-handled (WH) and dry-handled (DH) BAs in Portland cement-based systems when used as supplementary cementitious material (SCM) or fine aggregate (FA). BAs were collected from two different thermal power units with similar burning systems and operating conditions which burn the same coal. One unit was equipped with WHS and the other with DHS allowing a controlled comparison of the ash handling systems. Both BAs were highly amorphous and had similar chemical compositions; albeit, AHBA was lighter, coarser, more porous, and more grindable. When ground and used as an SCM or sieved and used as FA, both BAs showed comparable compressive and flexural strengths, heat of hydration, and alkali-silica reaction resistivity. Results show that BAs from both ash-handling systems can be efficiently utilized in Portland cement-based systems.

Subject Keywords

Dry-Handled Bottom Ash, Wet-Handled Bottom Ash, Supplementary Cementitious Material, Fine Aggregate, Sustainability

URI

https://hdl.handle.net/11511/94324

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

S. Tirkeş, “Utilization of wet-handled and dry-handled coal bottom ashes in portland cement based composites,” M.S. - Master of Science, Middle East Technical University, 2021.