Effect of internal alkali activation on pozzolanic reaction of low-calcium fly ash cement paste

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

doi:10.1617/s11527-015-0703-6

Cited by 16 publications

(16 citation statements)

References 22 publications

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“…When compared with Reference, IWC and IAA-Ca(OH) 2 showed a decrease in the volume proportion of pores in the 0.02-0.33 lm range and an increase in that of pores in the 0.003-0.02 lm range in the Fa40 specimens at 24 months. Similar findings were reported in previous studies [16,17]. The changes in the volume ratios in the Fa40 specimens imply that the pozzolanic reaction of fly ash was accelerated by IAA-Ca(OH) 2 and IWC.…”

Section: Volume Of Pores Related To Pozzolanic Reactionsupporting

confidence: 90%

“…The pastes were mixed in a mechanical mixer and cast in 40-mm-per-side cube-shaped molds. Similar to the experimental method of previous studies [16,17], a needle with an internal diameter of 0.395 mm was inserted into the center of the specimen. The surfaces were then sealed with aluminum adhesive tape to prevent water loss and carbonation.…”

Section: Mixture Proportionmentioning

confidence: 99%

“…5 for a comprehensive evaluation of the effect of IAA-Ca(OH) 2 on the Ca(OH) 2 content in both Fa0 and Fa40 specimens. Previous studies suggested that the Ca(OH) 2 content at a depth of 16-20 mm from the tip of the needle could be influenced by a wall effect because of the mold and aluminum adhesive tape [16,17]. Therefore, the Ca(OH) 2 content of the entire specimen was calculated as average values at four depths (i.e., at depths of 0-16 mm from the tip of the needle in increments of 4 mm).…”

Section: Within a Depth Of 0-16 MM From The Tip Of The Needlementioning

confidence: 99%

“…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%

“…IAA from the age of 3 months has been also investigated to limit the negative effect of IAA from the age of 1 month on the production of Ca(OH) 2 from the cement hydration in pastes at an early age. It was concluded that IAA from the age of 3 months was more effective in accelerating the pozzolanic reaction of fly ash (up to 12 months) in hardened cement-based paste than IWC from the age of 3 months [17].…”

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: Volume Of Pores Related To Pozzolanic Reactionsupporting

confidence: 90%

Section: Mixture Proportionmentioning

confidence: 99%

Section: Within a Depth Of 0-16 MM From The Tip Of The Needlementioning

confidence: 99%