Nano-structural Changes of C-S-H in Hardened Cement Paste during Drying at 50°C

Aono, Yoshimichi; Matsushita, Fumiaki; Shibata, Sumio; Hama, Yukio

doi:10.3151/jact.5.313

Cited by 81 publications

(33 citation statements)

References 26 publications

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“…Whatever the considered paste, heating led to the coarsening of the pore structure: that is to say the increase of both capillary porosity and critical pore radius (corresponding to the sudden slope change in the MIP results). As suggested by Brue et al [14] ettringite dissolution [62,63] as well as C-S-H alteration [64][65][66] can be considered as the major causes of the pore structure modifications.…”

Section: Porosity and Microstructurementioning

confidence: 98%

Temperature influence on water transport in hardened cement pastes

Drouet

Poyet

Torrenti³

2015

Cement and Concrete Research

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International audienceDescribing water transport in concrete is an important issue for the durability assessment of radioactive wastemanagement reinforced concrete structures. Due to the waste thermal output such structures would besubmitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature onwater transport within hardened cement pastes of four different formulations. Using a simplified approach(describing only the permeation of liquid water) we characterized the properties needed to describe watertransport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presentedand discussed

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Section: Porosity and Microstructurementioning

confidence: 98%

Temperature influence on water transport in hardened cement pastes

Drouet

Poyet

Torrenti³

2015

Cement and Concrete Research

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“…It is evident that drying at elevated temperatures makes the water loss faster but may result in more severe microstructural alterations. For the hardened cement paste oven-dried at 50°C after 4 weeks, the pores larger than 8 nm were found to be increased and the pores smaller than 8 nm decreased, while the total pore volume remained unchanged [42]. 50°C is recommended as the most efficient drying temperature for cementitious materials, because it costs the least time meanwhile the minimum microstructural alterations [43].…”

Section: Effect Of Temperature On Microstructurementioning

confidence: 99%

Influence of moisture condition on chloride diffusion in partially saturated ordinary Portland cement mortar

Zhang

2018

Mater Struct

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Experiments have been carried out to study the influence of moisture condition, including moisture content and its distribution, on the chloride diffusion in partially saturated ordinary Portland cement mortar. The mortar samples with water-tocement (w/c) ratios of 0.4, 0.5 and 0.6, cured for 1 year, were preconditioned to uniform water saturations ranging from 18 to 100%. The interior relative humidities of these partially saturated cement mortars, i.e. water vapour desorption isotherm (WVDI), were measured. The WVDI results in relation to the pore structures obtained from the mercury intrusion porosimetry tests of paste samples with the same w/ c ratios were analyzed, which provided a basic insight into the moisture distribution in the non-saturated cement mortars. The relative chloride diffusion coefficients of cement mortars at various water saturations were determined based on the Nernst-Einstein equation and conductivity technique. It is found that the relative chloride diffusion coefficient D rc depends on the degree of water saturation S w and WVDI. At a given S w level, the D rc is larger for a higher w/c ratio. The role of the w/c ratio in the D rc -S w relation, however, becomes less pronounced with increasing w/ c ratio. There exists a critical saturation, below which the water-filled capillary pores are discontinuous and the D rc -value tends towards infinitely small. An increase of the w/c ratio results in a decrease of the critical saturation level.

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“…15. Polymerization of silicate anions inside of C-S-H at a temperature as low as 50°C and associated irreversible volume changes are also inferred by Aono et al (2007) using 29 Si NMR MAS and true density measurement. Thus, the main reaction re- W/C=0.40 Fig.…”

Section: Sorption Desorption and Hysteresismentioning

confidence: 99%

Origin of Drying Shrinkage of Hardened Cement Paste: Hydration Pressure

Maruyama

2010

ACT

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The driving force of drying shrinkage of hardened cement paste has been attributed to RTln(h)/v with external relative humidity h and water molar volume v in theories of capillary tension and disjoining pressure. However, these theories fail to explain the considerable hysteresis observed in length-change isotherms. In this study, the sorption isotherm and length-change isotherm of cement pastes were determined with different water-to-cement ratios and cement types, and internal pressure of shrinkage Π was calculated using the measured strain and elastic modulus of the skeleton. This internal pressure is a kind of disjoining pressure originated from hydration force and built up within adsorbed water films as a result of interactions between the hydrophilic solid surface and water molecules. Changes in internal surface energies of hardened cement pastes due to hydration, drying and temperature history result in a different statistical thickness of the adsorbed water layer under the same equilibrium relative humidity. The proposed model gives a rational explanation for the hysteresis in length-change isotherm.

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Nano-structural Changes of C-S-H in Hardened Cement Paste during Drying at 50°C

Cited by 81 publications

References 26 publications

Temperature influence on water transport in hardened cement pastes

Temperature influence on water transport in hardened cement pastes

Influence of moisture condition on chloride diffusion in partially saturated ordinary Portland cement mortar

Origin of Drying Shrinkage of Hardened Cement Paste: Hydration Pressure

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