A study on pozzolanic reaction of fly ash cement paste activated by an injection of alkali solution

Bùi, Phương Trinh; Ogawa, Yuko; Nakarai, Kenichiro; Kawai, Kenji

doi:10.1016/j.conbuildmat.2015.06.046

Cited by 37 publications

(29 citation statements)

References 15 publications

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“…The effect of IWC on the reduction of Ca(OH) 2 content at the tip of the needle was not shown clearly. The pore structures at the age of 2 months also confirmed the effectiveness of IAA from the age of 1 month [16]. Meanwhile, IAA from the age of 1 month limited the production of Ca(OH) 2 in the cement paste containing no fly ash at 2 months.…”

Section: Introductionmentioning

confidence: 53%

“…Several methods have been suggested to overcome these drawbacks, including alkali activation, hightemperature curing, a reduction of the water-tocementitious materials ratio (w/cm), internal water curing, and internal alkali activation [1,[8][9][10][11][12][13][14][15][16][17]. Alkali activation on fly ash particles is a chemical procedure in which fly ash is mixed directly with certain alkali activators (alkali solutions), and the mixture is cured at higher-than-ambient temperatures (usually 40-100°C) to accelerate the strength development [10,11].…”

Section: Introductionmentioning

confidence: 99%

“…Bui et al [16] suggested the use of internal alkali activation (IAA) based on a combined method of alkali activation and internal curing: IAA was carried out at 20°C by the natural injection of alkali solution [e.g., NaOH or saturated Ca(OH) 2 solution] into cement-based pastes with 0 and 40% replacements by fly ash from the age of 1 month. To inject the alkali solution, the tip of a syringe needle was inserted into the center of 40-mm cubic paste specimens as an original model for IAA.…”

Section: Introductionmentioning

confidence: 99%

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Long-term pozzolanic reaction of fly ash in hardened cement-based paste internally activated by natural injection of saturated Ca(OH)2 solution

2018

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The pozzolanic reaction of fly ash in hardened cement-based paste internally activated by a natural injection of saturated Ca(OH) 2 solution from the age of 1 month was investigated. This investigation was conducted with the aim of comprehensively evaluating the long-term effectiveness of this technique. The Ca(OH) 2 content, degree of the fly-ash reaction, and pore structure were measured using thermal gravimetric analysis, selective dissolution, and mercury intrusion porosimetry, respectively. The Ca(OH) 2 consumption was calculated from the Ca(OH) 2 content in the pastes with 0 and 40% replacements of cement by fly ash. The cement hydration and pozzolanic reactions of fly ash in the pastes proceeded gradually up to 12 months, but were negligible from 12 to 24 months regardless of whether solution was injected. An injection of alkali solution increased both the Ca(OH) 2 consumption and the degree of the fly-ash reaction after aging for 12 months. The relationship between the Ca(OH) 2 consumption and degree of the fly-ash reaction indicated that the injection of alkali solution activated the surface of the fly-ash particles at early ages, whereas the injection of water did not activate these particles but accelerated the cement hydration, which promoted the pozzolanic reaction. The refinement of the pore structure in the pastes confirmed the effectiveness of the solution injection. Consequently, the injection of saturated Ca(OH) 2 solution from the age of 1 month directly activated fly-ash particles and accelerated the long-term pozzolanic reaction (i.e., up to 24 months) in hardened cement paste with 40% replacement by fly ash, although it was not effective in further enhancing the pozzolanic reaction from 12 to 24 months. Keywords Internal alkali activation Á Ca(OH) 2 content Á Degree of fly-ash reaction Á Pore structure Á Selective dissolution The original version of this article was revised due to a retrospective Open Access order.

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Section: Introductionmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Long-term pozzolanic reaction of fly ash in hardened cement-based paste internally activated by natural injection of saturated Ca(OH)2 solution

2018

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“…1. It was tested that median particle size d 50 Similarly, for the cementitious specimens, when pseudo colored images were transformed from FE-SEM images then Calcium Silicate Hydrate (CSH), Portlandite (CH), unreacted cement particles of Alite and Belite, and glassy alumina-silicate particles of fly ashes were observed. 3.…”

Section: Discussionmentioning

confidence: 99%

“…This shows that all these samples contain higher contents of either Al or Si due to the presence of phases of Silicates, Calcium-Silicate, Calcium-Aluminum-Silicate as identified by [49] for fly ashes. In the pozzolanic reaction of the fly ash cement paste, a chemical reaction between the reactive silica from the fly ash and excess calcium hydroxide from cement hydration forms additional C-S-H gel [50]. The C-S-H formed by this pozzolanic reaction may have wider variation in composition particularly Si/Ca ratio which tends to be higher.…”

Section: Chemical Properties 331 Box and Whisker Plotsmentioning

confidence: 99%

Effects of Wet Separated and High Speed Milling Fly Ash Added in High Volume to Cementitious Materials

Haider

Alit²,

Bittnar

et al. 2020

Period. Polytech. Civil Eng.

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In this research high speed milling was carried out on particles of brown coal raw fly ash, on second layer, and on third layer particles obtained from wet separation of brown coal raw fly ash. Due to milling process, median particle size d50 of raw fly ash, second layer, and third layer reduced by 46 %, 23 %, and 77 %, densities reduced by 11 %, 17 %, and 8 % respectively. Due to milling process, formation of agglomerations was observed, the standard deviation of the chemical composition of each element from the mean value reduced. After milling, high volume cementitious paste mixes were prepared with 60 % cement replacement. Due to the milling process the increase in compressive strength at 28 and 90 days was observed for raw fly ash is 59 % and 16 %, for second layer is 12 % and 15 %, for third layer and milled third layer is 78 % and 75 %. Flexural strength testing showed that due to the milling process the deflections at maximum loads have reduced considerably leading to brittle behavior of milled cementitious specimens. The testing for Mercury Intrusion Porosimetry showed that the cementitious specimens of third layer have maximum concentration of large capillary pores between 0.05 and 10 µm, whereas, all others have maximum concentration of medium capillary pores between 0.01 and 0.05 µm. Autogenous shrinkage of cementitious specimens was measured for first sixteen hours after mixing which showed that the second layer particles have the least shrinkage as compared to all other specimens.

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Historical Development of Construction Materials – From Stone Age to Modern Age

Samal

Panigrahi

Ganguly

et al. 2023

Development of Geopolymer From Pond Ash‐Thermal Power Plant Waste

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A study on pozzolanic reaction of fly ash cement paste activated by an injection of alkali solution

Cited by 37 publications

References 15 publications

Long-term pozzolanic reaction of fly ash in hardened cement-based paste internally activated by natural injection of saturated Ca(OH)2 solution

Long-term pozzolanic reaction of fly ash in hardened cement-based paste internally activated by natural injection of saturated Ca(OH)2 solution

Effects of Wet Separated and High Speed Milling Fly Ash Added in High Volume to Cementitious Materials

Historical Development of Construction Materials – From Stone Age to Modern Age

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