Influence of slag chemistry on the hydration of alkali-activated blast-furnace slag — Part II: Effect of Al2O3

Haha, Mohsen Ben; Lothenbach, Barbara; Saoût, Gwenn Le; Winnefeld, Frank

doi:10.1016/j.cemconres.2011.08.005

Cited by 462 publications

(185 citation statements)

References 49 publications

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“…Many papers can now be found in the literature that confirm the presence of Q 3 (nAl) units in the C-A-S-H gels forming during slag alkaline activation (53,63,69,70). One prominent article, authored by Puertas et al (69), reported that in C-A-S-H gels forming in slag activated with a NaOH solution, the existence of tetrahedral Al in bridging positions in the silicate chains goes hand-in-hand with a considerable increase in the number of Q 2 (1Al) units, as well as with a small amount of Q 3 (nAl) units.…”

Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 99%

“…A number of secondary products may form, including hydrotalcite, calcite and bases such as AFm, depending on activator type and concentration, slag structure and composition, and the curing conditions under which the paste hardens (11,(31)(32)(33)(34)(55)(56)(57)(58). The microstructure of the gels formed during slag activation has been explored by several authors (53,55,(59)(60)(61)(62)(63)(64)(65).…”

Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 99%

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A review on alkaline activation: new analytical perspectives

et al. 2014

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For many years now the idea of including alkalis in a Portland cement matrix has been regarded as a daft or inexcusably erroneous proposition: despite its absurdity, that opinion has been widely accepted as a basic premise by the scientific and technical community working in the area of the chemistry of cement. In 1957 Glukhovsky proposed a working hypothesis in which he established a close relationship between alkalis and cementitious materials. That hypothesis has become consolidated and has served as a basis for developing a new type of binders, initially called "alkaline cements". The present paper reviews the most significant theoretical interpretations of the role played by alkalis in the formation of the "stony" structure of cement. It ends with a broad overview of the versatility of this type of materials for industrial applications and a discussion of the possibility of building on the existing legislation to meet the need for the future regulation of alkaline cement and concrete manufacture. RESUMEN: Activación alcalina: Revisión y nuevas perspectivas de análisis.Hace algunos años, la sola idea de la presencia de álcalis en una matriz de cemento Portland se consideraba casi como una aberración, o como un error imperdonable; convirtiéndose en un postulado básico (absurdo) ampliamente aceptado por la comunidad científica y técnica vinculada a la química de los cementos. En 1957 Glukhovsky propuso una hipótesis en la que se establecía una estrecha relación entre los álcalis y los materiales cementantes. Hoy día nadie duda de que dicha hipótesis ha servido de base para el desarrollo de una nueva clase de materiales cementantes: "cementos alcalinos". En el presente trabajo se hace una revisión sobre los aspectos teóricos más relevantes del papel de los álcalis en la formación de estos conglomerantes. También se da una visión genérica de su versatilidad, desarrollo industrial y estado de la normativa actual para regular en el futuro la fabricación de cementos y hormigones alcalinos.

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Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 99%

Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 99%

A review on alkaline activation: new analytical perspectives

et al. 2014

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“…2C). The complex accretionary ash microstructures obstruct debonding of scoriae, not necessarily through the interfacial densification process noted for cement pastes with blast-furnace slag, silica fume, and limestone admixtures (26,(42)(43)(44), but rather through interconnectivity of dense bundles of strätlingite plates among microscoriae that attach to irregular scoria surfaces and the cementitious matrix.…”

Section: Role Of Pyroclastic Rock In Concrete Durabilitymentioning

confidence: 99%

“…The crystals show no corrosion: Their smooth (0001) surfaces indicate longterm stability, similar to strätlingite that persists in the geological record for hundreds of thousands of years (23). Laboratory syntheses of strätlingite in cement pastes at ambient temperatures are accelerated by alkali activators, principally sodium silicate solution or zeolite particles (26)(27)(28). Dissolution of alkali-rich Pozzolane Rosse volcanic glass and natural halloysite and zeolite textures in microscoriae accretions along scoria perimeters (8) produced high concentrations of alkali cations and a favorable environment for strätlingite crystallization (Fig.…”

Section: Role Of Pyroclastic Rock In Concrete Durabilitymentioning

confidence: 99%

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Jackson¹,

Landis

Brune

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

178

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The pyroclastic aggregate concrete of Trajan's Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime-volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium-aluminum-silicate-hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8-0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strät-lingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45-0.75. Dense clusters of 2-to 30-μm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clastsupported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.Roman concrete | volcanic ash mortar | fracture toughness | interfacial zone | strätlingite

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“…That is why, dehydration processes overlap. For example, according to data given by authors of [61], synthesised C-S-H phase can dehydrate up to about 600°C, while the main mass loss occurs up to 200°C (extremum on DTG at about 100°C). The observed effects in Figs.…”

Section: Early Hydration Of Non-activated Mixtures Containing High Anmentioning

confidence: 99%

Influence of selected activating methods on hydration processes of mixtures containing high and very high amount of fly ash

Wilińska

Pacewska

2018

J Therm Anal Calorim

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Binders containing fly ash as cement substitute have been used for many years. Typical amount of fly ash in cement composite does not exceed 35% of mass of binder. Replacement of substantial amount of cement mass by fly ash results in retardation of hydration of binder and deterioration of some concrete properties, e.g. delay in setting time and reduction in early compressive strength. These inconveniences may be reduced using proper method of activation. In this paper, possibilities to activate binding mixtures containing high and very high amount of fly ash and low amount of Portland cement were discussed basing on the literature reports as well as on our own research results. Several activating methods were described, such as mechanical activation, exchanging of part of components of binder (cement, fly ash or both of them) by more reactive fine-grained material, chemical activation by the use of alkaline activators as well as combined methods. Possibilities of using these methods were discussed in relation to amount of fly ash introduced as replacement of cement and kind of fly ash used. Usefulness of calorimetry and thermal analysis methods was also presented.

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Influence of slag chemistry on the hydration of alkali-activated blast-furnace slag — Part II: Effect of Al2O3

Cited by 462 publications

References 49 publications

A review on alkaline activation: new analytical perspectives

A review on alkaline activation: new analytical perspectives

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Influence of selected activating methods on hydration processes of mixtures containing high and very high amount of fly ash

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