Temperature-Dependent Water Redistribution from Large Pores to Fine Pores after Water Uptake in Hardened Cement Paste

Kiran, Rohith; Samouh, Hamza; Igarashi, Go; Haji, Tatsuto; Ohkubo, Takahiro; Tomita, Sayuri; Maruyama, Ippei

doi:10.3151/jact.18.588

Cited by 20 publications

(14 citation statements)

References 42 publications

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“…In a companion paper, Kiran et al (2020) showed that the water exchange from large pores to fine pores in different temperature conditions could be monitored by 1 H-NMR relaxometry. These results could be attributed to dynamic microstructural changes in C-S-H during water absorption.…”

Section: Opc-ls-mentioning

confidence: 99%

“…In a previous study (Kiran et al 2020), the local water exchange between larger pores and fine pores was modeled by Eq.…”

Section: Local Moisture Water Exchange From Larger Pores To Fine Poresmentioning

confidence: 99%

“…Furthermore, to understand the anomalous water transport behavior that was previously reported (Martys and Ferraris 1997;Taylor et al 1999;Hall 2007Hall , 2019Biagioni et al 2012;Alderete et al 2019;Wu et al 2019;McDonald et al 2020; Zhang and Angst 2020), a simplified numerical analysis is conducted. The behavior is investigated by considering dynamic microstructural changes in calcium silicate hydrate (C-S-H) (Muller et al 2013;Gajewicz et al 2016;Zhou et al 2017;Kiran et al 2020), a major group of hydrates in cement-based materials that is influenced by variations in temperature.…”

Section: Introductionmentioning

confidence: 99%

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Water Uptake in OPC and FAC Mortars under Different Temperature Conditions

Kiran

Samouh

Matsuda

et al. 2021

ACT

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This experimental and numerical study aims to evaluate the penetration depth of contaminated water in the concrete structures involved in the Fukushima Daiichi nuclear powerplant. The influence of the mortar mixture on water absorption was investigated by varying the composition: mortars containing aggregates from river sand and crushed limestone sand were compared, and 15% of the cement in the mixture was substituted with fly ash. The effect of temperature in nuclear conditions is also significant; therefore, water uptake at temperatures of 20 and 60°C was considered. Finally, pre-drying conditions were studied by drying the sample at two different conditions: at 105°C and at 40% RH (relative humidity) and 20°C. Water uptake was monitored using x-ray computed radiography in combination with mass measurements. In all cases, anomalous sorption, or a nonlinear relationship between penetration depth and the square root of exposure time was observed, with the sorption curves showing bimodal behavior. The aggregate type had no significant effect on the water uptake results. However, the samples containing fly ash clearly had lower water uptake rates, which can be explained by the differences in the calcium silicate hydrate (C-S-H) structures. With increasing temperature, the penetration was slightly accelerated at the beginning of the experiment, with the rate of penetration then decreasing rapidly. The densification of C-S-H at higher temperatures could contribute to this phenomenon. Microstructural rearrangements can also explain why the highest uptake rates occurred for samples that were exposed to severe drying conditions (105°C). The experimental results were consistent when the microstructural rearrangement was considered, further confirming these conclusions.

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Section: Opc-ls-mentioning

confidence: 99%

“…In a previous study (Kiran et al 2020), the local water exchange between larger pores and fine pores was modeled by Eq.…”

Section: Local Moisture Water Exchange From Larger Pores To Fine Poresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Water Uptake in OPC and FAC Mortars under Different Temperature Conditions

Kiran

Samouh

Matsuda

et al. 2021

ACT

Self Cite

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“…The scarcity of such data for nuclear structures has been reported in the literature [35]. The redistribution of water from large to fine pores in hardened concrete [36] is another aspect which would be dependent on microstructure of the concrete and thus could be typical for Indian concrete. Transient creep strains in concrete when exposed to fire, particularly for member temperatures above 500°C, have been reported in the literature [37], and these factors would influence the response of concrete structures to fire.…”

Section: Generation Of Fire/elevated Temperature Test Data For Indianmentioning

confidence: 99%

Fire Resistance and Elevated Temperature in Reinforced Concrete Members: Research Needs for India

Dauji

Kulkarni

2021

J. Inst. Eng. India Ser. A

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Fire and elevated temperature are important considerations for design of concrete structures, for both normal and nuclear facilities. In India, the present design guidelines for concrete subjected to fire and elevated temperature are limited to prescriptive minimum dimension and minimum cover. The other approach suggested is fire test based, and being resource intensive, is considered only for special cases of design. The various provisions of Indian standards are discussed and compared to the international standards. Fire test data for concrete/reinforcement properties at elevated temperature for Indian materials are scarce, and hence, the calculation methods are difficult to apply for Indian concrete. Validation of such methods for India is required, which again can only happen after generation of adequate database. The article highlights the present research needs for fire design of Indian concrete, along with development of analysis methodologies/guidelines for fire design of concrete structures, assessment of fire-affected concrete structures, and combination of the fire/temperature load with other extreme loads such as impact, seismic load, or missile load using advanced approaches. This article could serve as reference for designers as well as the starting point for several research initiatives in India and thereby is expected to improve the state of the art of fire design of concrete structures in India in the long term.

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“…Ordinary Portland cement, OPC, is commonly used for cementation (Glasser and Atkins 1994) since the calcium silicate hydrate or C-S-H gel, the main hydration product of OPC, has a large surface area with many sorption and reaction sites in which the contaminants can be retained (Real et al 2002;Volchek et al 2011). Moreover, the C-S-H gel has low diffusibility and solubility due to its microstructure, which reduces the mobility of the contaminants and prevents their release (Hewlett 2003;Kiran et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Effect of Chloride and Sulfate in the Immobilization of Cs-137 in C-S-H Gel

Duque-Redondo

Yamada

Manzano

2021

ACT

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Cementitious materials are commonly used in nuclear repository sites to immobilize intermediate-level radioactive wastes. This is due to the large surface area of the calcium silicate hydrate (C-S-H) gel, the main hydration product of ordinary Portland cement, which provides many sorption sites in which the contaminants can be adsorbed. The retention capacity of these materials is strongly dependent on the composition, the water content, the pH or the presence of additives. Likewise, it is also known that the durability and performance of cement and concrete are adversely affected in chloride and/or sulfate environments. In this work, atomistic simulations have been employed to analyze the effect of the presence of chlorides and sulfates in the retention and transport of 137 Cs, one of the most hazardous radioisotopes, in calcium silicate hydrate. The simulations suggest that the presence of a moderate amount of chlorides does not alter significantly the Cs uptake in C-S-H gel, while a moderate content of sulfates enhances substantially the retention of Cs ions and reduces their migration throughout the pore. This behavior is attributed to the ability of the sulfates to pull Ca out the high-affinity sites from the C-S-H surface, allowing Cs ions to occupy them.

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Temperature-Dependent Water Redistribution from Large Pores to Fine Pores after Water Uptake in Hardened Cement Paste

Cited by 20 publications

References 42 publications

Water Uptake in OPC and FAC Mortars under Different Temperature Conditions

Water Uptake in OPC and FAC Mortars under Different Temperature Conditions

Fire Resistance and Elevated Temperature in Reinforced Concrete Members: Research Needs for India

Effect of Chloride and Sulfate in the Immobilization of Cs-137 in C-S-H Gel

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