Fundamental understanding of the setting behaviour of the alkali activated binders based on ground granulated blast furnace slag and fly ash

Nedunuri, Aparna Sai Surya Sree; Muhammad, Salman

doi:10.1016/j.conbuildmat.2021.123243

Cited by 43 publications

(14 citation statements)

References 36 publications

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“…A higher proportion of fly ash in the alkali-activated slag/fly ash mixtures led to a slower setting due to the lower reactivity of the ash. The content of reactive CaO, the main chemical component of slag, decreased with the higher addition of the fly ash, leading to a lower amount of dissolved Ca 2+ ions in the medium and a deceleration of the activation reaction [ 19 , 43 , 44 ]. Thus, the decelerated formation of C–A–S–H gel may lengthen the setting time of alkali-activated slag/fly ash pastes.…”

Section: Resultsmentioning

confidence: 99%

Influence of the Fly Ash Content on the Fresh and Hardened Properties of Alkali-Activated Slag Pastes with Admixtures

Hita

Criado

2022

Materials

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A study on the influence of the inclusion of slag or fly ash and five types of superplasticizers on the fresh and hardened properties of alkali-activated cements is presented. Three alkali-activated slag formulations with different fly ash content (0, 15, and 30%) in the presence of five admixtures (vinyl copolymer, melamine, and three polycarboxylates with different chain lengths) were assessed for fluidity control and setting adjustment without loss of mechanical properties. Solid sodium metasilicate was used as an alkaline activator. Their fresh and hardened properties were studied through slump, setting time, isothermal calorimetry, mechanical strengths, and porosity tests. The results showed that the increase of fly ash content delayed the reaction and improved workability but reduced compressive strengths. Concerning the admixtures, these maintained fluidity especially for the one based on polycarboxylate with very long chains. The melamine and polycarboxylate with very long chain admixtures did not have a drastic impact on mechanical properties at early ages; even a gain of flexural and compressive strength was noted.

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Section: Resultsmentioning

confidence: 99%

Influence of the Fly Ash Content on the Fresh and Hardened Properties of Alkali-Activated Slag Pastes with Admixtures

Hita

Criado

2022

Materials

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“…Therefore, the early strength of PC grouting materials developed slowly. The reaction process of alkali-activated grouting materials can only be completed through the depolymerization and repolycondensation of active substances in a highly alkaline environment [ 41 ]. Therefore, the application of alkali-activated materials in grouting materials can fully utilize its early strength advantage.…”

Section: Resultsmentioning

confidence: 99%

Coagulation Mechanism and Compressive Strength Characteristics Analysis of High-Strength Alkali-Activated Slag Grouting Material

Huang

Cui

et al. 2022

Polymers

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In deep coal mining, grouting reinforcement and water blockage are the most effective means for reinforcing the rock mass of extremely broken coal. However, traditional cement grouting materials are not suitable for use in complex strata because of their insufficient early mechanical strength and slow setting time. This study innovatively proposes using alkali-activated grouting material to compensate for the shortcomings of traditional grouting materials and strengthen the reinforcement of extremely unstable broken coal and rock mass. The alkali-activated grouting material was prepared using slag as raw material combined with sodium hydroxide and liquid sodium silicate activation. The compressive strength of specimens cured for 1 d, 3 d, and 28 d was regularly measured and the condensation behavior was analyzed. Using X-ray diffraction and scanning electron microscopy, formation behavior of mineral crystals and microstructure characteristics were further analyzed. The results showed that alkali-activated slag grouting material features prompt and high strength and offers the advantages of rapid setting and adjustable setting time. With an increase in sodium hydroxide content, the compressive strength first increased (maximum increase was 21.1%) and then decreased, while the setting time continued to shorten. With an increase in liquid sodium silicate level, the compressive strength increased significantly (and remained unchanged, maximum increase was 35.9%), while the setting time decreased significantly (and remained unchanged). X-ray diffraction analysis identified the formation of aluminosilicate minerals as the main reason for the excellent mechanical properties and accelerated coagulation rate.

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“…In addition, the formation of C–S–H gels due to the presence of Ca 2+ from both GGBFS and FA or SW and readily available [SiO 4 ] 4− from the alkaline activator could also lead to some heat release in the very early age 17 . The second peak, marked as “2,” stretching from 12 to 36 h, is associated with the acceleration period of the reaction 43,45 . Between the peaks “1” and “2,” there is an induction period (also known as a dormant period) that can be explained by the following reasons.…”

Section: Resultsmentioning

confidence: 99%

“…17 The second peak, marked as "2," stretching from 12 to 36 h, is associated with the acceleration period of the reaction. 43,45 Between the peaks "1" and "2," there is an induction period (also known as a dormant period) that can be explained by the following reasons. The first one is that a certain period of time is required before certain ionic species in solution reach a critical concentration for the formation of main reaction products.…”

Section: Reaction Kineticsmentioning

confidence: 99%

A comparison between alkali‐activated slag/fly ash binders prepared with natural seawater and deionized water

Ren

Sun

et al. 2022

J Am Ceram Soc.

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In this research, the effects of natural seawater (SW) on the properties of alkali‐activated slag/fly ash (AASF) are studied. AASF prepared with deionized water is set as the reference mixture. The results showed that the use of natural SW resulted in a prolonged setting time and lower heat release, but no obvious impact on the flowability of AASF specimens. The long‐term compressive strength became higher when SW was used, whereas the corresponding flexural strength and fractural toughness turned lower. The use of SW induced the formation of new products that were not identified in the reference mixture, such as Cl–hydrocalumite and gypsum. In addition, it is evidenced that the dissolution of fly ash (FA) particles was significantly delayed with the incorporation of SW. All these results were related to the various ions introduced by the natural SW and their interactions with the alkaline activator as well as the precipitation of salts on slag and FA surfaces or in the matrix.

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Fundamental understanding of the setting behaviour of the alkali activated binders based on ground granulated blast furnace slag and fly ash

Cited by 43 publications

References 36 publications

Influence of the Fly Ash Content on the Fresh and Hardened Properties of Alkali-Activated Slag Pastes with Admixtures

Influence of the Fly Ash Content on the Fresh and Hardened Properties of Alkali-Activated Slag Pastes with Admixtures

Coagulation Mechanism and Compressive Strength Characteristics Analysis of High-Strength Alkali-Activated Slag Grouting Material

A comparison between alkali‐activated slag/fly ash binders prepared with natural seawater and deionized water

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