Investigation of the usage of fly ash containing a high amount of sulfate as a clinker replacement material

Abstract

Tons of fly ash are released every year due to the coal burned in thermal power plants that meet 80% of Turkiye's electrical energy needs. Especially considering the low-quality lignite reserves in Turkiye, the recycling rate of the high sulfate fly ash is relatively low. In concrete production, the use of ash containing high SO3 is not allowed due to the limitation of SO3 ratios of fly ash by regulations. Herein, the usability of fly ash, which has a high sulfate content due to the low-quality lignite reserves in Turkiye, and is therefore wholly waste, as a clinker replacement material was investigated. Fly ash, which has been used as a clinker replacement material, was obtained from Afsin Elbistan thermal power plant. Binders were obtained by grinding together the high sulfate fly ash, clinker and gypsum at different rates. The setting times of the mixtures in the fresh cement paste were determined, and the compressive strengths of the hardened samples were examined. As a result of the study, it was concluded that although the high sulfate fly ash extended the setting time by approximately 29% compared to the reference specimen, it increased the 28-day compressive strength of the hardened specimens up to 14%