Both class F and class C Fly Ash (FA) as precursors have been extensively used for the development of geopolymers [19], [20], [21]. The class C FA contains high calcium oxide (CaO) and is designated as a self-cementing FA. The Class C Fly ash has been used for making concrete and soil stabilization without cement [22], [23], [24]. The reaction ...
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In Thailand, most fly ash is obtained from burning lignite coal, which contains a large amount of calcium, or high-calcium fly ash (HCF). The content of the calcium compound is one …
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Cementitious mixtures with so-called high calcium fly ash show better strength parameters as compared to the ones with conventional siliceous fly ash. This practical feature is the consequence of improved hydraulic activity. Differential thermal analysis and thermogravimetry were used, together with the other methods, to evaluate the reactivity of …
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Table 1 Chemical composition of starting materials Fig. 1 Setting time of mix formulations at 22 °C Fig. 2 XRD patterns of raw fly ash and geopolymer paste with different additives at final setting under ambient conditions. a fly ash, b …
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The major constituent is fly ash occupying 76.4%-80.3% by the total mass of the constituents, while calcium oxide, nanosilica, and the minimum amounts of sodium-based activators are added to induce the early-age strength development.
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High-calcium fly ashes, classified as Cla ss C by ASTM International (ASTM) C618 definition, are often excluded as a means to mitigate alkali silica reactions (ASR) in concrete. This is because a relationshi p between high-calcium content and expansion was often documented when Class C fly ash was used at a 10% to 15% replacement
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At 28 days, non-evaporative water content of sample with 20% fly ash (20FA3NS) is the highest, suggesting nano-silica significantly accelerate hydration and results in generation of more Ca(OH) 2 which provides high pH condition for fly ash hydration. Once its dosage exceeds 20%, non-evaporative water content shows decrease trend.
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Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. ASTM International, Pennsylvania, United States. doi:10.1520/C0618-22. Sarıdemir, M., & Çelikten, S. (2023). Effects of MS modulus, NA concentration and fly ash content on properties of vapour-cured geopolymer mortars exposed to high temperatures.
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In this study, high-calcium FA based geopolymer concretes modified with high-silica source by-products and physical, mechanical and microstructural investigations were performed. According to the experiments conducted and their results, the following conclusions can be made: i-In general, the use of GP and SF slightly increased the fresh and ...
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A high-calcium fly ash (FH, 23% total CaO–5% free CaO), ... In this case of tested fly ash, similar strengths are observed due to almost equal active silica content. (3) The reaction of FH in hydrating cement is followed from high water binding and, thus, lower porosity is created. This behavior is due to the high content of reactive calcium ...
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Additionally, due to the high content of CaO (≥10%), Class C fly ash can raise pH and accordingly has been applied at absurdly high rates. On the other hand, Class F ashes …
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A study on the effect of nano silica on compressive strength of high volume fly ash mortars and concretes. Mater. Des. 2014;60:433–442. doi: 10.1016/j.matdes.2014.04.025. [Google Scholar] 158. Supit S.W.M., Shaikh F.U.A., Sarker P.K. Effect of nano silica and ultrafine fly ash on compressive strength of high volume fly ash mortar. Appl. Mech.
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The Afşin-Elbistan thermal power plant, which is located in Turkey, is a lignite burning thermal power plant with a capacity of eight units in two plants and an installed capacity of 2795 MW, which are the most FA generating plants in country [5].These thermal power plants generate more than 3 million tons of fly ash (FA) every year [6].The Afşin-Elbistan FA is of high …
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To understand the formation mechanism of high-calcium fly ashes, the mineralogical, physical, and chemical properties of several high calcium fly ashes and their different density fractions (<1.0, 1.0−2.5, 2.5−2.89, and >2.89 g/cm3) from a coal-fired power plant were characterized by X-ray diffractometry (XRD), field scanning electron microscopy equipped with energy dispersive …
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The Silica-alumina ratio of the developed geopolymer paste ranges from 2.75-3.0 with a ratio of 2.87 appeared to be the best in this work. Alumina emanates from the source materials of fly …
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This study investigates the effect of silica and alumina contents on setting, phase development, and physical properties of high calcium fly ash …
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High-calcium fly ashes, classified as Class C by ASTM International (ASTM) C618 definition, are often excluded as a means to mitigate alkali–silica reactions (ASR) in concrete. This is …
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Fly ashes are broadly classified worldwide into two chemical types for their industrial applications, mostly in cement industries, namely class C and class F. Class C fly ash, with its …
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The mechanisms underlying the effects of nano-calcium carbonate (NC) on the strength of high volume fly ash (FA) mortar are discussed. Two NCs are used as 2%, 4%, 6%, and 8% by weight of ...
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Thus, silica fume showed the greatest efficiency of all tested additives as an inhibitor of the high-calcium fly ash expansion. Silica fume at a content of 42.9% by weight of fly ash provided crack resistance and no expansion during air curing, but did not impart water resistance to the mix.
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Small amounts of silica fume were used to partially replace high calcium fly ash at 3–9% by weight to increase the strength of alkali-activated mortar. ... The optimum content of silica fume was ...
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Japan Atomic Energy Agency (JAEA) research on the degradation of high content fly ash silica fume cement (HFSC) provides a good working example that highlights the need to develop a C(-A)-S-H gel ...
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In general, high-calcium Class C fly ash is produced from the burning of younger lignite or sub-bituminous coal, whereas the burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. ... High content of silica and alumina in fly ash potential uses for zeolite synthesis [33]. The range of CaO content extends ...
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[36] The increase in fineness (% 45 retained on sieve #325) reflecting the reactivity of fly ash was found to improve the strength of mortar. 46 [36] [37][38] The calcium-bearing glass by its ...
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Cementless slag ash concrete may be manufactured using high-calcium fly ash and silica fume as replacements for a binder and a microfiller, and incorporating slag sand from thermal power plants (TPP) as an aggregate. This concrete consists of waste products from TPP (fly ash and slag) and ferro-alloy plants (silica fume) and contains neither natural nor artificial aggregates for …
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In this study, the Afşin-Elbistan fly ash (FA), which is high in calcium content (≈43%) and which does not meet the standards to be used in concrete, was used as a geopolymer raw material. In order to increase the utilization of this high-calcium FA as a geopolymer raw material, two high-silica source industrial by-products, namely silica ...
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Conversely, low-calcium AAM systems employ precursors generally deficient in CaO, such as metakaolin or coal fly ash. Due to the paucity of calcium ions in these systems, the geopolymerization products are predominantly composed of N(K)-A-S-H. ... ASW with high silica content can serve as a silica source, leading to a reduction in production ...
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The main ingredients of bituminous coal fly ash are silica, alumina, iron oxide & calcium, with varying amounts of carbon, as measured by the loss on ignition (LOI). ... it is evident that lignite and sub-bituminous coal fly ash have …
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The strength loss was from the high calcium content of FBC fly ash and incorporation of silica fume thus increased the durability of the composite. View Show abstract
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