Relation between Chemical Composition and Physical Properties of C-S-H Generated from Cementitious Materials

Suda, Yuya; Saeki, Tatsuhiko; Saito, Tsuyoshi

doi:10.3151/jact.13.275

Cited by 53 publications

(22 citation statements)

References 41 publications

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“…In this study we used an upper estimate for the surface area of C-S-H 1.5 which was based on experiments at Ca/Si = 1.4. (Suda et al, 2015). The surfacenormalized mean K d value seems to increase with increasing Ca/Si ratio of the C-S-H phases but the trend is statistically not significant.…”

Section: Fe Sorption On C-s-hmentioning

confidence: 79%

Fe(III) uptake by calcium silicate hydrates

Mancini

Wieland

Geng

et al. 2020

Applied Geochemistry

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Section: Fe Sorption On C-s-hmentioning

confidence: 79%

Fe(III) uptake by calcium silicate hydrates

Mancini

Wieland

Geng

et al. 2020

Applied Geochemistry

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“…The more complex scenario for pore structure and local densities emerging from our study suggests a different origin of the S sp values. Recent studies (8,46) point to differences in the drying conditions and have shown that, only in oven-dried C-S-H at 100°C under vacuum, the water of all C-S-H pores (gel and capillary) is completely removed, leaving only water molecules in the nanotexture. In these conditions, the measured specific surface area of C-S-H (using water as an adsorption probe) is S H2O sp = 200 − 300 m 2 =g.…”

Section: Resultsmentioning

confidence: 99%

Mesoscale texture of cement hydrates

Ioannidou

Krakowiak

Bauchy

et al. 2016

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

207

146

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Strength and other mechanical properties of cement and concrete rely upon the formation of calcium-silicate-hydrates (C-S-H) during cement hydration. Controlling structure and properties of the C-S-H phase is a challenge, due to the complexity of this hydration product and of the mechanisms that drive its precipitation from the ionic solution upon dissolution of cement grains in water.Departing from traditional models mostly focused on length scales above the micrometer, recent research addressed the molecular structure of C-S-H. However, small-angle neutron scattering, electron-microscopy imaging, and nanoindentation experiments suggest that its mesoscale organization, extending over hundreds of nanometers, may be more important. Here we unveil the C-S-H mesoscale texture, a crucial step to connect the fundamental scales to the macroscale of engineering properties. We use simulations that combine information of the nanoscale building units of C-S-H and their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles. We compute small-angle scattering intensities, pore size distributions, specific surface area, local densities, indentation modulus, and hardness of the material, providing quantitative understanding of different experimental investigations. Our results provide insight into how the heterogeneities developed during the early stages of hydration persist in the structure of C-S-H and impact the mechanical performance of the hardened cement paste. Unraveling such links in cement hydrates can be groundbreaking and controlling them can be the key to smarter mix designs of cementitious materials.U pon dissolution of cement powder in water, calcium-silicate-hydrates (C-S-H) precipitate and assemble into a cohesive gel that fills the pore space in the cement paste over hundreds of nanometers and binds the different components of concrete together (1). The mechanics and microstructure are key to concrete performance and durability, but the level of understanding needed to design new, more performant cements and have an impact on the CO 2 footprint of the material is far from being reached (2).Most of the experimental characterization and models used to predict and design cement performance have been developed at a macroscopic level and hardly include any material heterogeneity over length scales smaller than micrometers (3). However, EM imaging, nanoindentation tests, X-rays and neutron scattering, and NMR analysis as well as atomistic simulations have now elucidated several structural and mechanical features concentrated within a few nanometers (4-8). The hygrothermal behavior of cement suggests a hierarchical and complex pore structure that develops during hydration and continues to evolve (1, 9-11). NMR and small-angle neutron scattering (SANS) studies of hardened C-S-H identified distinctive features of the complex pore network and detected significant structural heterogeneities spanning length scales between tens and hu...

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“…(1) Validity of the phase composition For the purposes of verifying the validity of the phase composition determined in the present study, the amount of combined water was estimated from the phase composition by referring to the previous researches (Maruyama and Igarashi 2014; Suda et al 2015). Using the molar weight of combined water, which is shown in Table 4, and the amount of each hydration product determined by Rietveld analysis, the amount of combined water contained in each hydration product contained in the 11% RH dried sample in this study was calculated.…”

Section: Effect Of Phase Composition On Expansion Characteristicsmentioning

confidence: 91%

Relationship Between Expansion Characteristics of Heat-Cured Mortars During Water Curing and Origins of Ettringite Formation

Sato

Saito

Kikuchi

et al. 2019

ACT

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Delayed ettringite formation (DEF) is known as the deterioration phenomenon that occurs in mortar or concrete cured at high temperature. It has been proposed that DEF expansion is affected by calcium-silicate-hydrates (C-S-H), although the mechanism has not yet been clarified. The present study experimentally examined the relationship between the expansion characteristics of heat-cured mortar specimens used cement, anhydrite and supplementary cementitious materials (SCMs) during water curing and the origins of ettringite formation. The proportional change in length and the phase compositions of the heat-cured specimens were acquired. The respective amounts of ettringite generated from cement and SCMs were determined. The expansion of the mortar specimens using cement, anhydrite, silica fume and fly ash occurred continuously during water curing, while the continuous expansion did not occur in the mortar specimens using cement, anhydrite and blast furnace slag. These expansion characteristics could not be explained solely by the change in the amounts of ettringite. There was a certain correlation between the amount of ettringite generated from cement and the expansion characteristics of the specimens. It is one of the evident that origins of ettringite formation or coexisting materials such as C-S-H phase can affect expansion characteristics due to DEF.

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Relation between Chemical Composition and Physical Properties of C-S-H Generated from Cementitious Materials

Cited by 53 publications

References 41 publications

Fe(III) uptake by calcium silicate hydrates

Fe(III) uptake by calcium silicate hydrates

Mesoscale texture of cement hydrates

Relationship Between Expansion Characteristics of Heat-Cured Mortars During Water Curing and Origins of Ettringite Formation

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