Dacite concretes with fly ash exhibit negligible expansion regardless of the effective cement alkali content (from 0.6% up to 1% Na 2 O eq) which indicates that fly ash can mitigate ASR even when the cement alkali content is higher than 0.6% Na 2 O eq. This suggests that reactive aggregates can be used and that the cement alkali limit can be ...
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1. Introduction. Fly ash-based geopolymer is formed through the chemical reaction between the alkaline activator solutions and fly ash. Alkaline activators can be a combination of alkali hydroxide and alkali silicate, such as sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3).Geopolymer products are formed during the curing process achievable at low …
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When fly ash content is increased to 55% and 65% by weight of cement, the ultrasonic pulse velocity drops to 4287 and 4283 m/s respectively. ... The analysis of concrete microstructure revealed that fly ash particles are covered with amorphous SiO 2 and alkali reaction product. Fly ash contains 49.8% of amorphous SiO 2, which reacts with NaOH ...
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This study investigated the mechanical properties and toughness of slag/fly ash-based alkali-activated cementitious materials (AASF) by incorporating PAM with different molecular weights and dosages. ... The water-to-binder ratio was 0.45, the alkali content (Na 2 O as a percentage of the powder materials) was 8 %, and the activator modulus was ...
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This study uses fly ash to replace partial cement. NaOH is used to increase alkali content of cement to 1.0% Na 2 O eq.LiOH and LiNO 3 are added separately to obtain several Li/(Na + K) molar ratios to fabricate cement specimens cured at 38 °C in a relative humidity environment. This study aims to observe the diachronic changes of water-soluble alkali and …
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When the fly ash content or alkali dosage was too high, fly ash cannot be activated properly and excessive moisture was consumed, reducing the overall density. The internal pore structure was more susceptible to frost heave forces during freeze-thaw cycles, resulting in a faster decline in the relative dynamic modulus [ 33 ].
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The effect of alkali dosage (A/F), water-binder ratio (w/b), and modulus (Ms) on the performance of fly ash geopolymer (FAG) was reported. The rheology of Na 2 SiO 3 /NaOH …
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The addition of slag as a secondary precursor in fly ash-based alkali-activated materials contributed to the refinement of pore structure and thus restricted the transport of chloride ions in the concrete [28]. ... It meant that the chloride permeability resistance of AAFS concretes decreased with an increase in the content of fly ash.
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Fly ash and granulated blast furnace slag contain abundant volcanic ash components such as calcium oxide, silicon dioxide, and aluminum oxide. Fly ash also contains a large amount of …
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The main obstacle to advancing FA-based printable formulations is the low rate of structural build-up during curing and inadequate mechanical properties in the hardened state due to the low reactivity of fly ash (FA) [[16], [17], [18], [19]].To improve the early structural build-up of alkali-activated fly ash (AAF) mixtures, portlandite (Ca(OH)₂, CH) can be incorporated.
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The aim of the present study is to investigate the potential of sea water as a feasible alternative to produce alkali-activated fly ash material. The alkali-activated fly ash binder was fabricated by employing conventional pure water, tap water, and sea water based alkali activating solution. The characteristics of alkali-activated materials were examined by …
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The effects of SS on the bond strength and the microstructure of the interface between alkali-activated SS/fly ash (FA) lightweight mortar (ASFm) and concrete substrates was studied. The SS contents, namely, the mass ratio of SS to the summation of FA and SS, were 0 %, 20 %, 40 %, 60 %, and 80 %. ... This phenomenon is principally attributed to ...
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Alkali-activated cement (AAC), a sustainable clinker-free building material, is a promising alternative to OPC, produced by alkali-activating aluminosilicates such as fly ash (FA) and ground blast furnace slag (BFS), which reduces CO 2 emissions by 60%–80 % compared to OPC [5].Moreover, AAC exhibits better mechanical properties and stable structural integrity at high …
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The optimum alkali-equivalent content in fly ash A was AE% = 7%, with the best compressive strength 38.58 MPa at 20% slag substitution amount. The mix proportion with the second-best compressive strength occurred in fly ash C, at AE% = 8%. The compressive strength was 36.63 MPa when the slag substitution amount was 20%.
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This is due to an increase in alkali content relative to the silica-alumina ratio, which effectively promotes the hydration reactions of SHPMFG, thereby enhancing its compressive strength. ... of modulus ratio and dosage of alkali-activated solution on the properties and micro-structural characteristics of alkali-activated fly ash mortars ...
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Fly ash is a silicate glass body characterized by high silicon and aluminum content, and low calcium content, making it significantly less reactive compared to slag glass bodies with low silicon, high calcium, and moderate aluminum content. The glass network in fly ash contains a higher proportion of [SiO 4] 4-and [AlO 4] 5-ions, which ...
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The dispersion of fly ash in water results in an alkaline pH from 10 to 13. At high pH, ... 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 contain mostly low CaO content lower than 10% creating potential limitations in ...
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KEYWORDS: Class C fly ash, alkali silica reactivity, ASR ABSTRACT High-calcium fly ashes, classified as Cla ss C by ASTM International (ASTM) C618 ... reduction in expansion continued as the fly ash content increased. INTRODUCTION This project was initially designed as a 3-year study to perform a comprehensive
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Scientific Reports - Alkali and sulfate effects on mechanical properties and microscopic mechanisms of slag and fly ash geopolymers Skip to main content Thank you for visiting nature.
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Alkali-activated lime fly ash pastes with high levels of fly ash in an alkali-activated system have been described by Shi (Citation 1996a, Citation 1996b). The alkali activation catalysis of hydration reaction in slags (which contain about 50% calcium) is reported with and without fly ash (Soong et al. Citation 2006 ).
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Coal fly ash contains essential constituents for cement production, such as Ca, Si, Al, and Fe. Application of coal-fired ash to produce clinker at high doses may reduce the limestone content in the raw mix.
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This study aims to develop fly ash-clay brick alkali-activated mixtures suitable as sustainable porous building materials [15], [16], [17], [18].Clay brick waste material, rich in silicates and aluminates, will partially replace fly ash, along with alkali activators, to produce porous AAM binder systems [19].The effects of brick content on the formation of porous structure, …
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Significant environmental issues are raised by the phosphogypsum (PG) waste that is being produced. In Lithuania, about 1,500,000 tons of PG waste is generated yearly, and about 300 Mt is generated yearly worldwide. A by-product of burning wood biomass in thermal power plants is biomass fly ash (BFA). By 2035, compared to 2008 levels, industrial biomass …
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Abstract. The effects of portland cement alkali content, and replacement of portland cement with Class F fly ash, slag, or silica fume on alkali-silica reactivity (ASR) were studied by measuring the expansion of mortar bars made with Pyrex glass and stored over water at 38°C. Expansions were negligible with portland cements having alkali contents of 0.40% Na2O …
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In order to efficiently utilize industrial solid waste while minimizing the preparation cost of engineering materials and the technical difficulty of construction, this paper prepared a high fly ash content alkali-activated fly ash slag composite system at normal temperatures and conducted an in-depth investigation on it. A systematic study was conducted on the …
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Fly ash and granulated blast furnace slag are both bulk industrial solid wastes. Using these two raw materials to completely replace cement and prepare alkali-activated fly ash slag concrete (AAFSC) at room temperature can not only efficiently utilize industrial solid waste and reduce the carbon footprint, but also reduce the economic cost and technical difficulty of …
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A study on the influence of the inclusion of slag or fly ash and five types of superplasticizers on the fresh and hardened properties of alkali-activated cements is presented. Three alkali-activated slag formulations with different fly …
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Mechanical model and strength development evolution of high content fly ash–cement grouting material. Constr. Build. Mater., 398 ... early-age hydration and microstructure of alkali-activated GGBFS-Fly ash-limestone mixtures. Cem. Concr. Compos., 124 (2021), Article 104244, 10.1016/j.cemconcomp.2021.104244. View PDF View article View in ...
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To avoid the flash-setting problem and improve fluidity, three alkali-activated slag formulations with different fly ash content, together with the presence of five admixtures (vinyl copolymer, …
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The aluminum content in fly ash is primarily found within the glassy phase and various crystalline constituents, including mullite and albite. ... reflecting the reactivity of fly ash in alkali-activation processes, ranges from 4.52 to 24.90 in this work. The R value exhibits high predictive accuracy for estimating the strengths development of ...
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