Role of slag in microstructural development and hardening of fly ash-slag geopolymer

Puligilla, Sravanthi; Mondal, Paramita

doi:10.1016/j.cemconres.2012.10.004

Cited by 462 publications

(152 citation statements)

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“…This is in line with the findings of Provis et al (22) who found that the use of BFS instead of fly ash in geopolymers leads to a decrease in porosity, possibly due to the different chemistry existing in fly ash and BFS geopolymers. Puligilla and Mondal (48) proposed that the simultaneous formation of the geopolymeric gel and the calcium aluminium silicate hydrate gel (formed in presence of Ca) may help to fill the gaps between the different hydrated phases and the unreacted particles, resulting in a more dense and homogeneous matrix. However, there are no thorough conclusions about the contribution of the different gels, so other parameters should probably be taken into account.…”

Section: Porositymentioning

confidence: 99%

Contributions to the study of porosity in fly ash-based geopolymers. Relationship between degree of reaction, porosity and compressive strength

2016

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ABSTRACT:The main contribution of this paper relates to the development of a systematic study involving a set of parameters which could potentially have an impact on geopolymer properties: curing temperature, type of activating solution, alkali metal in solution, incorporation of slag (Ca source) and type of slag used. The microstructures, degrees of reaction, porosities and compressive strengths of geopolymers have been evaluated. Geopolymers prepared with soluble silicate presented a more compacted and closed structure, a larger amount of gel, lower porosity and greater compressive strength than those prepared with hydroxides. On the other hand, Na-geopolymers were more porous but more resistant than K-geopolymers. Although there is an inverse relation between degree of reaction and porosity, between compressive strength and porosity it is not always inversely proportional and could, in some cases, be masked by changes produced in other influencing parameters. RESUMEN: Contribuciones al estudio de la porosidad de geopolímeros basados en cenizas volantes. Relación entre grado de reacción, porosidad y resistencia a compresión.La principal contribución de este documento es el desarrollo de un estudio sistemático implicando una serie de parámetros que podrían afectar a las propiedades de los geopolímeros: temperatura de curado, solución activadora, metal alcalino de la solución, incorporación de escorias (fuente de calcio) y tipo de escorias. Se han evaluado: microestructura, grado de reacción, porosidad y resistencia a compresión. Los geopolímeros preparados con silicatos presentaron un microestructura más densa y compacta, una mayor cantidad del gel geopolimérico, menor porosidad y mejores propiedades mecánicas que los preparados con hidróxidos. Los geopolímeros preparados con sales de sodio fueron más porosos pero más resistentes que los preparados con sales potasio. Aunque existe una relación inversa entre el grado de reacción y la porosidad, en algunos casos, la relación entre resistencia y porosidad es inexistente ya que puede estar enmascarada por cambios producidos por otros parámetros que afecten a la reacción.

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Section: Porositymentioning

confidence: 99%

Contributions to the study of porosity in fly ash-based geopolymers. Relationship between degree of reaction, porosity and compressive strength

2016

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“…According to Puligilla and Mondal [39], GGBS also enhances long-term polymerization because the medium is more basic. The fast initial setting observed for pure GGBS AAMs can also be explained by the fineness of the GGBS (Figure 1).…”

Section: Initial Setting Timementioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

“…GGBS-FA AAMs (paste [38][39][40][41][42][43], mortar [16,43,44] or concrete [45]) were also investigated. Kumar et al [38] revealed that at 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.…”

Section: Introductionmentioning

confidence: 99%

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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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“…This conditions limit the application of geopolymer for precast purposes whilst for normal concrete, the binder should be able to set in room temperature. Addition of calcium to produce ambient cured geopolymer binder has been conducted elsewhere [8][9][10][11][12][13]. …”

Section: Introductionmentioning

confidence: 99%

The Effect of Lime Addition on the Setting Time and Strength of Ambient Cured Fly Ash Based Geopolymer Binder

Adam

Amiri

Suarnita

et al. 2016

MATEC Web of Conferences

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Abstract.One of the limitations of geopolymer as the alternative binders in concrete is the necessity of heat curing. This study aimed to produce fly ash geopolymer binder subjected to ambient curing by adding a small proportion of lime and varying the activator dosage. The Class F fly ash from Mpanau coal-fired power plant was mixed with alkaline solution consists of sodium silicate and sodium hydroxide with Na2O dosage of 5%, 7%, and 9%. To achieve ambient cured paste, 8%, 9%, and 10% slaked lime was added as the substitute for the fly ash. The setting time test was conducted for each mix and the compressive strength was performed at age of 7, 14 and 28 days. The test result shows that the setting time of the fly ash based geopolymer paste can be controlled by adding a small proportion of slaked lime. The addition of lime increased strength but decreased the setting time.

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Role of slag in microstructural development and hardening of fly ash-slag geopolymer

Cited by 462 publications

References 40 publications

Contributions to the study of porosity in fly ash-based geopolymers. Relationship between degree of reaction, porosity and compressive strength

Contributions to the study of porosity in fly ash-based geopolymers. Relationship between degree of reaction, porosity and compressive strength

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

The Effect of Lime Addition on the Setting Time and Strength of Ambient Cured Fly Ash Based Geopolymer Binder

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