Strength development of alkali-activated fly ash produced with combined NaOH and Ca(OH) 2 activators

Vargas, Alexandre Silva de; Molin, Denise Carpena Coitinho Dal; Masuero, Ângela Borges; Vilela, Antônio Cezar Faria; Castro-Gomes, João; Gutiérrez, Ruby Mejía-de

doi:10.1016/j.cemconcomp.2014.06.012

Cited by 99 publications

(37 citation statements)

References 31 publications

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“…The peak at a wavenumber of 1052 cm −1 in the raw fly ash shifts to a final position at approximately 1006 cm −1 in conjunction with a soaking duration of 336 h and approximately 1018 cm −1 in conjunction with NaOH solution concentration of 2 M, indicating a progressive reaction that is rich in silica gel. This shift is consistent with the formation of a sodium aluminosilicate-type gel (Zhang et al 2012a;Vargas et al 2014;Ismail et al 2014;Nadziri et al 2017). Alkali activation of low-calcium fly ash promotes the formation of more cross-linking in an aluminosilicate-type gel, which can be seen from the vibration in the band between 400 and 800 cm −1 .…”

Section: Changes In the Functional Groups Of The Fly Ash Residuessupporting

confidence: 80%

Analysis of Active Ion-Leaching Behavior and the Reaction Mechanism During Alkali Activation of Low-Calcium Fly Ash

Yin

Kang

et al. 2018

Int J Concr Struct Mater

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The dissolution and release of active ions, such as Si 4+ , Al 3+ and Ca 2+ , from fly ash directly affect the rate and extent of reaction product formation, which in turn affect the physical and mechanical properties of fly ash filling materials. In this study, low-calcium fly ash was soaked and activated in NaOH solutions with different concentrations (approximating the optimum dose range) for different lengths of time. The amounts of active ions leached and the changes in the mineral composition, chemical functional groups and surface morphology were tested and analyzed via ICP-OES, XRD, FTIR and SEM/EDS techniques. Based on these analyses, the reaction mechanism of alkali activation of low-calcium fly ash was further investigated. The results showed that the NaOH activation effect can significantly increase the amount of active ions leached from low-calcium fly ash. Notably, the amount of Si 4+ and Al 3+ leached clearly increased with increases in both NaOH concentration and soaking time. The plausible reaction mechanism is discussed in detail, which is that the alkali activator principally affected the surface of the vitreous particles of lowcalcium fly ash and induced differing surface modifications in the dissolution stage, depolymerization stage, polycondensation and polymer gel stage and diffusion stage. It was observed that the progress of the reaction is controlled by dissolution in the early stages, whereas activation is governed by diffusion when the surfaces of the fly ash particles are covered by precipitates.

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Section: Changes In the Functional Groups Of The Fly Ash Residuessupporting

confidence: 80%

Analysis of Active Ion-Leaching Behavior and the Reaction Mechanism During Alkali Activation of Low-Calcium Fly Ash

Yin

Kang

et al. 2018

Int J Concr Struct Mater

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“…When an alkaline solution at a certain pH is applied to FA, the Si\ \O bonds and Al\ \O bonds deteriorate, and a network structure of C-A-S-H or N-A-S-H is generated [39,40]. This process is always used in the preparation of geopolymers [41]. During the course of FBR-VD, the NaOH solution drops are laid onto the surface of the FA, and the alkalinity in the drops is far higher than that in the cement paste.…”

Section: Naohmentioning

confidence: 99%

Pozzolanic reaction of fly ash modified by fluidized bed reactor-vapor deposition

He-hua

et al. 2017

Cement and Concrete Research

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“…On the other hand, about 50% of flyash is used in bound form in concrete products while 27% is utilized as loose form in structural fills and embankments [12]. More so, several studies have been reported on the improvement of mechanical characteristics of soils using alkali activated flyash-based geopolymers [13][14][15][16][17][18][19][20][21][22][23][24]. Such studies have proven that the flyash content is vital for the geopolymerization process while the unconfined compressive strength (UCS) of the soil-mixtures increased with increase in flyash content at an optimum of 30% content [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Soil-Geopolymer Mixtures Using Recycled Concrete Aggregates for Base and Subbase Layers

et al. 2019

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The recycling of concrete aggregates has become a viable venture to investigate particularly its application in road construction. This study was conducted to proffer the feasibility of using recycled concrete aggregate (RCA) mixed with soil, flyash and alkali activator as an alternative to soil-cement in road base or subbase applications. The resulting product known as Soil-RCA geopolymer was made by varied mix constituents of flyash, RCA, sodium silicate, and sodium hydroxide. The influence of mixture variables on the mechanical properties of Soil-RCA geopolymer was investigated through an experiment design using two different flyash. Models to predict the unconfined compressive strengths based on mixture parameters were also established for the sensitivity analysis and selection of final mixtures. The results and analysis showed that the Soil-RCA geopolymer mixture exhibited sound strength, stiffness and durability characteristics.

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Strength development of alkali-activated fly ash produced with combined NaOH and Ca(OH) 2 activators

Cited by 99 publications

References 31 publications

Analysis of Active Ion-Leaching Behavior and the Reaction Mechanism During Alkali Activation of Low-Calcium Fly Ash

Analysis of Active Ion-Leaching Behavior and the Reaction Mechanism During Alkali Activation of Low-Calcium Fly Ash

Pozzolanic reaction of fly ash modified by fluidized bed reactor-vapor deposition

Soil-Geopolymer Mixtures Using Recycled Concrete Aggregates for Base and Subbase Layers

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