Factors influencing the compressive strength of fly ash based geopolymers

Soutsos, Marios; Boyle, Alan P.; Vinai, Raffaele; Hadjierakleous, Anastasis; Barnett, S. J.

doi:10.1016/j.conbuildmat.2015.11.045

Cited by 227 publications

(88 citation statements)

References 29 publications

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“…It can be attributed to the hydration of Ca species and the creation of a calcium-aluminum-silicate-hydrate (C-A-S-H) gel at very rapid pace, often resulting in a very short initial setting time during the early stage of geopolymeric reaction. 45 Other researchers also indicate that excessive silicate from higher molar ratio of SiO 2 /Na 2 O may inhibit the geopolymerization due to the formation of aluminosilicate gel precipitation and further apart the aluminosilicate source and the alkali activators. [46][47][48][49][50] As shown in Figure 5b, the flexural strength of all three specimens tested increased as the curing time increased from 7 to 28 days.…”

Section: Mechanical Strength Of Geopolymer Pastementioning

confidence: 99%

Application of geopolymer paste for concrete repair

Ding

Cheng

Dai

2017

Structural Concrete

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In this study, ground granulated blast furnace slag and coal fly ash were used as raw materials to prepare geopolymer paste as repair material for concrete structure. The functional properties, such as compressive strength, fluxural strength, and bonding strength between slag/fly ash based geopolymer paste and paste substrate were investigated. The SiO2 /Na2O molar ratio of the alkali activator plays an important role on the strength of geopolymer paste. The nature of the geopolymeric reaction product was examined using FTIR and NMR. The compressive strengths and flexural strength of the geopolymer paste were 47 MPa and 16 MPa, respectively. For concrete substrate bonded with geopolymer paste, the compressive strength test shows up to 120% repairing rate can be achieved. By comparing with Portland cement, it can be proved that the slag/fly ash based geopolymer paste has very good potential for further engineering development in the future.

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Section: Mechanical Strength Of Geopolymer Pastementioning

confidence: 99%

Application of geopolymer paste for concrete repair

Ding

Cheng

Dai

2017

Structural Concrete

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“…As the definition currently stands [40,42], there is a wide range of potential precursors and activators that may be used and which would produce geopolymers of varying quality. In terms of the precursor, the most common candidates are high purity kaolin [43,44] and different types of clays [45][46][47], or waste/by-product materials, such as slags [40] and ashes [40,[48][49][50]. However, some of these materials may not be readily available across the globe or are too expensive.…”

Section: Introductionmentioning

confidence: 99%

Sulfate and acid resistance of lithomarge-based geopolymer mortars

Kwasny

Aiken

Soutsos

et al. 2018

Construction and Building Materials

107

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2018). Sulfate and acid resistance of lithomarge-based geopolymer mortars. Construction and Building Materials, 166,[537][538][539][540][541][542][543][544][545][546][547][548][549][550][551][552][553] ABSTRACTThe resistance of room temperature cured geopolymer mortars (GPM) against chemical attacks, i.e. sodium and magnesium sulfate solutions, and sulfuric and hydrochloric acid solutions, was evaluated. GPMs were formulated using a lithomarge precursor (low-purity kaolin) to achieve 28-day characteristic compressive strengths of 37.5 and 60 MPa. Their performance was compared with those of equivalent Portland cement mortars (PCMs) having the same paste volume and strength grade. GPMs with both strength grades showed superior performance against sulfate attack when compared to PCMs. No visual deterioration was observed in GPMs, the mass and length changes were relatively small, and no changes to the microstructure were detected -in contrast to severely deteriorated PCMs.As confirmed by visual observations and lower mass loss, GPMs showed better resistance to attack by both acids than PCMs. GPMs provided a better quality (lower permeability) of an acid-degraded layer, lowering the degree of further deterioration. The main mechanisms of the matrix deterioration of GPMs in both acids was dealumination of the hardened binder, with a higher degree of changes detected for sulfuric acid.

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“…Studies on pure FA AAMs (paste [30], mortar [31][32][33] or concrete [34]) indicated that FA geopolymer presents low reactivity compared with MK geopolymer and a thermal treatment is usually necessary to achieve reasonable properties (setting time and early age mechanical properties) [33]. Under ambient conditions, pure FA AAMs initial setting time is very long (more than 24 h) because of the low reactivity of the FA but good mechanical properties can be achieved if the FA AAMs are thermally cured [30,32,34].…”

Section: Introductionmentioning

confidence: 99%

Formulation and characterization of blended alkali-activated materials based on flash-calcined metakaolin, fly ash and GGBS

Samson

Cyr

Gao

2017

Construction and Building Materials

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Highlights AAMs initial setting time, shrinkage, mass loss, compressive strength were studied. Low activation leads to high drying shrinkage because of important mass loss. Very low shrinkage values were found for MK-GGBS compared to the other AAMs. High early strength compressive strength was observed for MK-GGBS blends. Graphical abstract 2 AbstractStudies performed on alkali-activated materials (AAMs) in recent years reveal that they could be an alternative to ordinary Portland cement (OPC). The main precursors used are flash-calcined metakaolin (MK), fly ash (FA), and ground granulated blast furnace slag (GGBS). Usually, only one precursor is used to produce an AAM. The aims of this study were to measure and compare the performances of pure (one precursor) and blended AAMs (two precursors). Alkaline solution is added to activate the precursors and the influence of the activation rate was also investigated by changing the activator amount (15% and 25% of alkaline solution dry extract). Twenty-six different mixes were studied and are presented in a ternary representation. The mixtures were characterized in the fresh state (initial setting time) and the main properties useful for building applications (shrinkage, mass loss, and compressive strength) were recorded and analysed. In contrast to the situation in OPC systems, shrinkage and mass loss in AAMs were not directly correlated. The high shrinkage values observed for pure MK AAMs and pure GGBS AAMs were significantly reduced when they were associated in appropriate proportions. The association of MK and GGBS also proved very interesting regarding early age compressive strength.Keywords: Alkali-activated material (AAM), metakaolin (MK), fly ash (FA), ground granulated blast furnace slag (GGBS), compressive strength, shrinkage 3 IntroductionThe building sector is faced with the gradual exhaustion of natural resources and/or increasing difficulty in accessing them. 27°C, the reaction of alkali-activated GGBS-FA blend paste is dominated by the GGBS activation (dissolution and precipitation of C-A-S-H) while at 60°C the reaction is due to combined interaction of FA and GGBS, which indicates that FA has lower reactivity than GGBS under ambient conditions. There is only small interaction of fly ash and GGBS probably due to different kinetics of dissolution process and distribution of species. Puligulla et al.[39] studied GGBS-FA blend pastes. They found that the calcium that dissolves from slag significantly influences both early and late age properties. The availability of free Ca ions seems to prolong FA dissolution and enhance geopolymer gel formation. It is proposed that the hardening process is initiated by the precipitation of C-A-S-H and that rapid hardening continues due to accelerated geopolymerization. Liu et al. 5The studies mentioned above reveal that, under particular conditions, mixing two different precursors cangive very interesting results. However, these studies have usually focused on the identification of a particular property under particu...

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Factors influencing the compressive strength of fly ash based geopolymers

Cited by 227 publications

References 29 publications

Application of geopolymer paste for concrete repair

Application of geopolymer paste for concrete repair

Sulfate and acid resistance of lithomarge-based geopolymer mortars

Formulation and characterization of blended alkali-activated materials based on flash-calcined metakaolin, fly ash and GGBS

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