Stirred Grinding of Coal Bottom Ash to Be Evaluated as a Cement Additive

Abstract

By-product generation from coal combustion in coal-fired thermal power plants has been increasing worldwide and reached to 125 million tons in the U.S. and 100 million tons in Europe. Coal-fired thermal power plants have a share of about 20% in Turkey's electricity production. Almost 57 million tons of coal with varying ash content of 20–55% was consumed in those plants. Uranium and thorium radioactivity of ashes of low rank coals limits the use of ashes. Consuming local bituminous coals, Catalagzi Thermal Power Station has been producing 0.65 million tons of ash including fly ash (80%) and bottom ash (20%), which have a potential use in civil engineering. The majority of the fly ash has already been used in cement or directly in concrete mortars. This study was aimed to evaluate the bottom ash of the CATES. For this purpose, bottom ash was ground in a pilot scale set including a vertical stirring mill. The set had the controlled feeding, separation, and collection facilities to represent industrial scale grinding. Compressive strength tests were carried out on the ground bottom ash samples by mixing in varying amounts of Portland cement for curing times of 2, 7, 28, and 90 days. It was found that with a 25% ash containing cement a strength value of 48.86 Mpa which corresponds to 93.82% of strength of reference was obtained at 90 days curing time.