Metakaolin-based geopolymer: Formation of new phases influencing the setting time with the use of additives

Dupuy, C.; Havette, Julien; Gharzouni, Ameni; Texier-Mandoki, Nathalie; Bourbon, Xavier; Rossignol, Sylvie

doi:10.1016/j.conbuildmat.2018.12.114

Cited by 46 publications

(20 citation statements)

References 32 publications

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“…There were no visible differences between the patterns of the samples with and without boron. This is consistent with [ 37 ], in which the presence of borax and boric acid did not lead to the appearance of new phases. It can be then concluded that boron was built into the structure of a geopolymeric N–A–S–H gel (N–A–S–H = Na 2 O·Al 2 O 3 ·SiO 2 ·H 2 O), thus forming N–B–A–S–H gel.…”

Section: Resultssupporting

confidence: 92%

“…They had similar observations that the trigonal boron dissolved and rearranged into tetrahedral boron, which was introduced in the geopolymeric cross-linked network that was made by Taveri et al [ 31 ]. The tetrahedral boron in the mixture could directly participate in the geopolymerization, resulting in enhanced polycondensation [ 37 ]. It should be noted that tetrahedra such as [AlO 4 ] and [BO 4 ] introduce additional negative charges to a structure that should play an important role in the heavy metal immobilization properties of boroaluminosilicate geopolymers.…”

Section: Resultsmentioning

confidence: 99%

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Immobilization of Heavy Metals in Boroaluminosilicate Geopolymers

et al. 2021

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Boroaluminosilicate geopolymers were used for the immobilization of heavy metals. Then, their mechanical properties, phase composition, structure, and microstructure were investigated. The addition of borax and boric acid did not induce the formation of any crystalline phases. Boron was incorporated into the geopolymeric network and caused the formation of N–B–A–S–H (hydrated sodium boroaluminosilicate) gel. In the range of a B/Al molar ratio of 0.015–0.075, the compressive strength slightly increased (from 16.1 to 18.7 MPa), while at a ratio of 0.150, the compressive strength decreased (to 12 MPa). Heavy metals (lead and nickel) were added as nitrate salts. The loss of the strength of the geopolymers induced by heavy metals was limited by the presence of boron. However, it caused an increase in heavy metal leaching. Despite this, heavy metals were almost entirely immobilized (with immobilization rates of >99.8% in the case of lead and >99.99% in the case of nickel). The lower immobilization rate of lead was due to the formation of macroscopic crystalline inclusions of PbO·xH2O, which was vulnerable to leaching.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Immobilization of Heavy Metals in Boroaluminosilicate Geopolymers

et al. 2021

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“…This will be discussed further in Section 2.4. Many chemical retarders for PC are not compatible with AAMs [60], but citric acid [61], d-gluconic acid [62], borate and phosphate [63] have all been described to give useful retardation in specific cases. However, the appropriate selection of a retarder depends critically on the role and content of calcium within the alkali-activation process; high-calcium mixes tend to be more effectively retarded by small organics that can complex Ca 2+ as it is released from the solid precursor and thus delay the precipitation of C-A-S-H type gels, whereas low-calcium mixes appear to be more amenable to the use of inorganic retarders.…”

Section: Chemical Admixturesmentioning

confidence: 99%

Recent progress in low-carbon binders

Shi

Provis

2019

Cement and Concrete Research

460

131

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The development of low-carbon binders has been recognized as a means of reducing the carbon footprint of the Portland cement industry, in response to growing global concerns over CO2 emissions from the construction sector. This paper reviews recent progress in the three most attractive low-carbon binders: alkali-activated, carbonate, and belite-ye'elimite-based binders. Alkali-activated binders/materials were reviewed at the past two ICCC congresses, so this paper focuses on some key developments of alkali-activated binders/materials since the last keynote paper was published in 2015. Recent progress on carbonate and belite-ye'elimite-based binders are also reviewed and discussed, as they are attracting more and more attention as essential alternative low-carbon cementitious materials. These classes of binders have a clear role to play in providing a sustainable future for global construction, as part of the available toolkit of cements.

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“…Alkali-activated binders can be obtained by the activation of raw materials in powder form under the action of soluble alkali silicates [ 1 ]. The materials in powder form are usually industrial by-products rich in silica and aluminum, such as fly ash [ 2 ], ground granulated blast furnace slag (GGBFS) [ 3 ], and metakaolin [ 4 ]. The alkali activation process consists of three distinct stages: The enrichment of the medium by the dissolution of aluminosilicates by reactive precursors during the reaction, restructuring by polycondensation to achieve a stable state of the precursors with the subsequent development of a gel phase, and then the final stage of gel hardening [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Preplaced Aggregate Concrete Fabricated with Alkali-Activated Slag/Fly Ash Cements

et al. 2021

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This study assesses the characteristics of preplaced aggregate concrete prepared with alkali-activated cement grout as an adhesive binder. Various binary blends of slag and fly ash without fine aggregate as a filler material were considered along with different solution-to-solid ratios. The properties of fresh and hardened grout along with the properties of hardened preplaced concrete were investigated, as were the compressive strength, ultrasonic pulse velocity, density, water absorption and total voids of the preplaced concrete. The results indicated that alkali-activated cement grout has better flowability characteristics and compressive strength than conventional cement grout. As a result, the mechanical performance of the preplaced aggregate concrete was significantly improved. The results pertaining to the water absorption and porosity revealed that the alkali-activated preplaced aggregate concrete is more resistant to water permeation. The filling capacity based on the ultrasonic pulse velocity value is discussed to comment on the wrapping ability of alkali-activated cement grout.

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Metakaolin-based geopolymer: Formation of new phases influencing the setting time with the use of additives

Cited by 46 publications

References 32 publications

Immobilization of Heavy Metals in Boroaluminosilicate Geopolymers

Immobilization of Heavy Metals in Boroaluminosilicate Geopolymers

Recent progress in low-carbon binders

Characteristics of Preplaced Aggregate Concrete Fabricated with Alkali-Activated Slag/Fly Ash Cements

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