Alkali activated metakaolin with high limestone contents – Statistical modeling of strength and environmental and cost analyses

Perez-Cortes, Pedro; Escalante-Garcı́a, J.I.

doi:10.1016/j.cemconcomp.2019.103450

Cited by 78 publications

(11 citation statements)

References 55 publications

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“…The fly ash (85-95 wt.% of the total ash) consists of fine particles which are collected by electrostatic precipitation, or mechanical capture, from the flue gas, while the coarser bottom ash falls through the air stream to the bottom of the boiler and is removed mechanically [3]. The mineral composition of coal ash is represented mainly by the glass phase, similar only due to the simple filler effect [55,59,61], but to a certain extent, through participation in the dissolution processes and geopolymer gel formation [57,60,62,63]. Moreover, it was shown that calcite and limestone themselves alkali activated with waterglass, displayed cementitious properties [60,66].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Fly Ash-Based Geopolymers: Effect of Calcite Addition and Mechanical Activation

et al. 2020

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Blends of fly ash and natural calcite, mechanically activated for 0–400 s in a planetary mill, were used to synthesize geopolymers at ambient temperature. The calcite content in the blends was 0–10 wt.%. Sodium hydroxide solution was used as an alkaline agent. Mechanical activation of the raw material considerably enhanced its reactivity with respect to the alkaline agent, as was observed using Fourier-transform infrared spectroscopy, isothermal conduction calorimetry, thermogravimetry coupled with mass spectrometry analysis of the evolved gas, and SEM/EDS. The addition of calcite to the fly ash improved the compressive strength of the geopolymers, especially during the early age of curing. For 7 d aged geopolymers based on the 90% fly ash + 10% calcite blend, the strength was 8.0-, 3.5- and 2.9-fold higher than that for the geopolymers based on the unblended fly ash for 30 s, 180 s and 400 s mechanical activation time, respectively. Using Mössbauer spectroscopy, it was revealed that iron present in the fly ash did not play a significant part in the geopolymerization process. The dominant reaction product was sodium containing aluminosilicate hydrogel (N-A-S-H gel). Calcite was found to transform, to a small extent, to vaterite and Ca(OH)2 in the course of the geopolymerization.

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Section: Introductionmentioning

confidence: 99%

Synthesis of Fly Ash-Based Geopolymers: Effect of Calcite Addition and Mechanical Activation

et al. 2020

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“…Lee and van Deventer [14] showed that small additions of laboratory-grade synthetic calcium and magnesium carbonate salts (CaCO 3 and MgCO 3 ) to a paste based on alkaliactivated fly ash resulted in an increase in the compressive strength of the geopolymer. Later, this conclusion was confirmed by studies of geopolymer composites involving widespread natural carbonate minerals, such as calcite and dolomite [15][16][17][18][19][20][21][22][23][24][25][26]. The positive effect of the addition of carbonate minerals on the physical-mechanical properties of geopolymer materials was explained mainly by the common filler effect.…”

Section: Introductionmentioning

confidence: 78%

“…In the case of calcite, after adding 5% of the carbonate mineral, the R rel C reached a plateau (Figure 6). Most likely, these trends are explained by a combination of the two factors noted above: First, the physical filler/micro-aggregate effect, and second, the leaching of Ca 2+ and Mg 2+ ions from calcite and dolomite, which can affect the release of Al and Si ions from aluminosilicate raw materials and the formation of an aluminosilicate hydrogel [20,22,23].…”

Section: Mechanical Propertiesmentioning

confidence: 99%

“…At the same time, it was also noted that calcite and dolomite were not completely chemically inert components. Due to partial dissolution, the carbonate minerals had an effect on the release of Al and Si from aluminosilicate raw materials (metakaolin or FA) and on the formation of alkaline activation products [17,20,22,23]. In addition, even 100% limestone [20,27] and dolomite [28], alkali-activated by water glass, exhibited binding properties.…”

Section: Introductionmentioning

confidence: 99%

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Geopolymers Based on Mechanically Activated Fly Ash Blended with Dolomite

et al. 2021

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This study reports the effect of natural dolomite addition to fly ash and the mechanical activation of this blend on the geopolymerization process. Dolomite was replaced with fly ash at 1, 3, 5, and 10 wt.%. Geopolymers were synthesized at ambient temperature using NaOH solution as an alkaline agent. The geopolymerization process, reactivity of the raw material, compressive strength, and microstructure were studied using X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetry, and scanning electron microscopy. It was shown that blending fly ash with dolomite and mechanical activation improved the geopolymer strength, especially during the early age of curing. For geopolymers prepared using a 90% fly ash + 10% dolomite blend cured for 7 d, the strengths were 8.2-, 2.3-, and 1.4-fold higher than those for geopolymers prepared using 100% FA for 30 s, 180 s, and 400 s milling times, respectively. A simple method for evaluating the increments of mechanical activation, carbonate additives, and the synergistic effect in the increase in the compressive strength of the composite geopolymer is proposed.

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“…On the basis of some preliminary test results, 12 test data points and the associated limits on space were adopted (Figure 1), and two categorical variables were considered ((w/b)values of 0.25 and 0.40). e analytically fitted response (12 terms) function of this DOE could be formulated for the three process variables (equation ( 1)) and replicated for each test category [20,30,37]. On the other hand, the RSD system required the formulation of a regression formula that would be used to describe the response-dependent surface (y) as a function of the independent variables [1].…”

Section: Discussionmentioning

confidence: 99%

Optimization of Arabian‐Shield‐Based Natural Pozzolan and Silica Fume for High‐Performance Concrete Using Statistical Design of Experiments

Abbas

Khan

2021

Advances in Civil Engineering

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In this study, the optimum dosages of silica fume (SF) and natural pozzolan (NP) were experimentally and statistically assessed for the best strength and durability properties of high-performance concrete (HPC). SF and NP were used as partial replacement Portland cement (PC) by up to 12 and 25 wt.%, respectively. Additionally, the prediction models based on second-level factorial (SLF) and response surface design (RSD) were formulated to estimate the HPC properties and their validation. The SLF-based model was further employed to investigate the significance and interactions of the PC, SF, and NP blends. The 28-day strength of the blended-cement HPC with a water-to-binder ratio w / b of 0.25 was generally higher than that of the control concrete. The positive synergy of PC–NP–SF was also observed in the HPC permeability. The paired t -test of the mean square error (MSE) of the SLF- and RSD-based models revealed that the MSE of the former was notably less than that of the latter. These results established the superiority of the SLF-based model over the RSD-based model. Therefore, the SLF-based model was further employed to investigate the importance of various binders.

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Alkali activated metakaolin with high limestone contents – Statistical modeling of strength and environmental and cost analyses

Cited by 78 publications

References 55 publications

Synthesis of Fly Ash-Based Geopolymers: Effect of Calcite Addition and Mechanical Activation

Synthesis of Fly Ash-Based Geopolymers: Effect of Calcite Addition and Mechanical Activation

Geopolymers Based on Mechanically Activated Fly Ash Blended with Dolomite

Optimization of Arabian‐Shield‐Based Natural Pozzolan and Silica Fume for High‐Performance Concrete Using Statistical Design of Experiments

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