Investigation into the effect of calcium on the existence form of geopolymerized gel product of fly ash based geopolymers

Zhao, Xianhui; Liu, Chunyuan; Zuo, Liming; Wang, Li; Zhu, Qin; Wang, Mengke

doi:10.1016/j.cemconcomp.2018.11.019

Cited by 150 publications

(74 citation statements)

References 42 publications

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“…Significance of the results and key outcomesThe investigation described in this paper allowed to link the mechanical behaviour of alkali activated mortars with the microstructure of the binding matrix, and contributed towards the understanding of a number of key aspects related to activation of fly ash and fly ash/GGBS based binders. The mechanisms governing the reaction of low-blended systems is still under investigation[56,57]. The research provided insights into the following: Silicate content in the activating solution: compressive strength results suggested that the silicate content in the activating solution has a direct influence on the strength development of neat fly ash samples.…”

mentioning

confidence: 99%

Effects of slag substitution on physical and mechanical properties of fly ash-based alkali activated binders (AABs)

Rafeet

Vinai

Soutsos

et al. 2019

Cement and Concrete Research

158

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Neat fly ash-based alkali activated binders require high activator dosages and high temperature curing in order to develop satisfactory mechanical properties. Blending ground granulated blast furnace slag (GGBS) with fly ash can give medium to high strengths without the need for high temperature oven curing. An extensive investigation was carried out for understanding the effects of GGBS substitution of fly ash in mortar. GGBS substitution in the mix has an impact on mix proportions, fresh and hardened properties, and microstructure of reaction products. The strength of fly ash/GGBS blends cured at room temperature increased with the increase of GGBS content, whilst setting time showed an opposite trend. Fly ash/GGBS blends required lower activator dosages for obtaining high compressive strength, which has cost and environmental benefits. XRD, FTIR, TGA, and SEM/EDX results confirmed the presence of C-AS -H gel as a reaction product with as low as 20% GGBS content.

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mentioning

confidence: 99%

Effects of slag substitution on physical and mechanical properties of fly ash-based alkali activated binders (AABs)

Rafeet

Vinai

Soutsos

et al. 2019

Cement and Concrete Research

158

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“…The filler effect of FA provides additional nucleation sites for cement hydration, increasing the packing density of the cementitious system, and refining the pore structure [ 40 , 68 , 69 ]. Under the influence of the alkaline environment, active FA particles participate in hydration to form C–S–H/C–A–S–H, improving strength development during and after the curing stage [ 44 , 70 ]. When adding large amounts of FA to a blended binder, mineral accelerators (e.g., CṠA and quicklime) are essential to improve the initial strength performance of the hardened backfill.…”

Section: Resultsmentioning

confidence: 99%

Quicklime and Calcium Sulfoaluminate Cement Used as Mineral Accelerators to Improve the Properties of Cemented Paste Backfill with a High Volume of Fly Ash

Ding

Zhang

2020

Materials

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In order to reduce the CO2 emission and cost of binders used in cemented paste backfill (CPB) technology, new blended binders with a large amount of fly ash (FA) were fabricated. Different doses of quicklime and calcium sulfoaluminate cement (CṠA) were used as mineral accelerators to improve the early workability of CPB. The effects of CṠA and quicklime on flowability, compressive strength, pore structure, hydration heat, and hydration evolution were investigated experimentally. The results showed that the addition of quicklime and CṠA reduced the spread diameter of the fresh backfill and improved the mechanical performance of the hardened CPB. With increasing quicklime and CṠA, the cumulative hydration heat of the blended binder distinctly increased in the first 6 h. CṠA improved the initial hydration by increasing the reactivity, and quicklime increased the hydration rate by activating FA. The blended binder (15% quicklime + 10% CṠA) with the lowest CO2 emission and cost had potential application in filling technology.

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“…To fit the GB/T 21144-2007 It was found in alkali activation related researches that an excessive amount of CaO will lead to decreased efficiency of the alkali activation system and result in an incomplete hydration reaction, which further affects strength development in the slurry [23]. In addition, the literature indicates that also in the alkali-activated or GEOPOLYMER system excessive Ca(OH) 2 has a negative impact on the development of compressive strength [24]. One of the probable reasons was that parts of chloride salts dissolved in the water during curing, forming many pores in the bricks and reducing the strength of the bricks.…”

Section: Effects Of Fbfa Addition On the Characteristics Of The Alkalmentioning

confidence: 99%

Microstructure and Strength of Alkali-Activated Bricks Containing Municipal Solid Waste Incineration (MSWI) Fly Ash Developed as Construction Materials

Zhao

Qiu

et al. 2019

Sustainability

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Alkali-activated materials (AAM) are widely applied in the field of building materials and civil engineering to substitute cement materials. This study used two types of municipal solid waste incineration fly ash (MSWI-FA): grate-firing fly ash (GFFA) and fluidized bed fly ash (FBFA) as brick raw materials. Various weight ratio of 20%, 30%, and 40% GFFA and FBFA were added to coal fly ash (CFA), GGBFs (Ground Granulated Blast-Furnace Slag), and an alkali-activating reagent to produce alkali-activated bricks. Microstructure and crystalline phase composition were observed to analyze their compressive strength, and a leaching test was used to prove the material’s safety for the environment. It can be seen from the results of this study that the alkali-activated bricks containing FBFA had higher compressive strength than those containing GFFA in the same amount. Considering the engineering properties, the alkali-activated bricks containing FBFA are more suitable to be used as building materials. The difference in the compressive strength resulted from the large amount of calcium compounds and chloride salts present in the GFFA. From SEM analysis, it was observed that there was a large number of pores in the microstructure. It was also found from the results of XRD that the bricks containing GFFA contained a large amount of chloride salt. From the results of the two leaching tests, it was found that the amounts of six heavy metals detected in the leachates of the bricks in this study met the corresponding regulation standards. This described MSWI-FA is suitable for use as alkali-activated material, and its products have potential to be commercially used in the future.

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Investigation into the effect of calcium on the existence form of geopolymerized gel product of fly ash based geopolymers

Cited by 150 publications

References 42 publications

Effects of slag substitution on physical and mechanical properties of fly ash-based alkali activated binders (AABs)

Effects of slag substitution on physical and mechanical properties of fly ash-based alkali activated binders (AABs)

Quicklime and Calcium Sulfoaluminate Cement Used as Mineral Accelerators to Improve the Properties of Cemented Paste Backfill with a High Volume of Fly Ash

Microstructure and Strength of Alkali-Activated Bricks Containing Municipal Solid Waste Incineration (MSWI) Fly Ash Developed as Construction Materials

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