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.

A preliminary study on the effect of fine aggregate replacement with metakaolin on strength and abrasion resistance of concrete

“…Although some authors [19][20][21] used bottom ash (BA), after grinding or melting, as pozzolanic material in which cement was partially replaced; others employed it as fine aggregate replacement. The usage of BA as sand replacement can be summarized as following: Ghafoori et al [22] carried out investigations on a series of laboratory-made roller compacted concretes (RCC) containing high-calcium dry BA as a fine aggregate.…”

Prediction of unburned carbon in bottom ash in terms of moisture content and sieve analysis of coal

“…The source, type, and fineness of the fuel, and the operating conditions of the power plant have important role on the physical and chemical properties of fly ash and BA [21]. Researches carried out on mixtures containing fly ash, BA, Portland cement and water was used as components for road construction and it was found out that only mixtures containing BA with lower carbon level had the desired conditions [17].…”

A review on improvement of coal-fired power plants and environmental benefits of ash utilisation

“…The Federal Highway Administration (USA) reports that using coal ash concrete reduces the need to produce new concrete, which consequently means further reductions in future greenhouse gas emissions, energy use and natural resources (EPA-530-K-05-002, 2005;Kizgut et al, 2010). The BA is used as a sand replacement, aggregate for lightweight blocks, a road-base component, for agricultural drainage mediums and as an engineered bulk fill.…”

“…The source, type and fineness of the fuel and the operating conditions of the power plant have an important role on the physical and chemical properties of FA and BA. The recycling of these materials are of increasing interest worldwide, due to the high environmental impact of the cement and concrete industries (Kizgut et al, 2010).…”

“…The lignitic coal industry produces over 24 million tons/year of coal combustion waste, which consists of roughly about 18 million tons of FA and six million tons of BA. The power station produces on average approximately 650.000 tons of ash by burning 1.6 million tons of bituminous coal per annual (Kizgut et al, 2010;EUAS, 2010). The source, type and fineness of the fuel and the operating conditions of the power plant have an important role on the physical and chemical properties of FA and BA.…”