Sorption, anomalous water transport and dynamic porosity in cement paste: A spatially localised 1H NMR relaxation study and a proposed mechanism

McDonald, Peter J.; Istók, Örs; Janota, Magdalena; Gajewicz-Jaromin, Agata M.; Faux, David A.

doi:10.1016/j.cemconres.2020.106045

Cited by 71 publications

(43 citation statements)

References 31 publications

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“…Therefore, it is concluded that the anomalous sorptivity of water in cement-based materials could be qualitatively explained by the nature of C-S-H. This conclusion is consistent with a recent discussion by McDonald et al (2020).…”

Section: Opc-ls-supporting

confidence: 90%

“…ture of C-S-H (Saeidpour and Wadsö 2015, 2016a, 2016bWu et al 2015Wu et al , 2019Gajewicz et al 2016;Zhou et al 2017;Alderete et al 2019;McDonald et al 2020;Zhang and Angst 2020). In addition, one may think that the 5-surface sealed condition will create air entrapment inside the specimen and a back-pressure cause the change in rate of penetration.…”

Section: Opc-ls-mentioning

confidence: 99%

“…It should be mentioned that shrinkage-induced visible cracks as well as cracks around aggregate has a large influence on the moisture/liquid water transport in concrete, however, as a first step research program, sev-eral factors, which are originated from the characteristics of materials used in the Fukushima Daiichi NPP buildings, including temperature, drying conditions, and mortar composition are investigated. 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: 96%

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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-supporting

confidence: 90%

Section: Opc-ls-mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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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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“…X-ray computed tomography (Smyl et al, 2016;Xue et al, 2020) has higher resolution than neutron imaging and can realize spatial detection of structures relatively faster, yet limited by the distinction between matrix and moisture. Nuclear magnetic resonance (Rucker-Gramm and Beddoe, 2010; Wyrzykowski et al, 2017;McDonald et al, 2020) is sensitive to hydrogen nucleus, however, it is limited by its parameters setting (such as the determination of surface relaxation rate) and imaging resolution. Thus, numerical methods may be an effective method for moisture distribution research.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Water Transport in Unsaturated Recycled Aggregate Concrete

et al. 2020

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The old mortar attached to recycled aggregate (RA) is the main reason for the difference in water movement between RA concrete (RAC) and natural aggregate concrete. In this study, considering the old and new interfacial transition zones, a five-phase composite model for describing the water transport and distribution in RAC is established at the mesoscale. The key parameters describing water unsaturated transport in two types of mortar, saturated hydraulic conductivity (K s) and van Genuchten model parameters (α, n), are obtained through the constant-head permeability test and isothermal adsorption test. By using the finite element method, the numerical simulations of unsaturated moisture movement in the homogeneous mortar, natural aggregate concrete, and five-phase RAC are systematically carried out. The proposed water transport model in the matrix is validated by comparison with the available experimental findings from the literature. The results show that the model can well predict unsaturated water transport in cement-based materials, including RAC. A parameter sensitivity analysis is undertaken to ascertain the main influencing factors of water transport in RAC. It is concluded that the RA replacement rate (R ra), the thickness of the old mortar (d m), and the aggregate volume fraction (F a) are the primary parameters affecting moisture movement in RAC.

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“…T 1 and T 2 depend on fluctuations in magnetic dipole–dipole interactions caused by the relative motion of pairs of spins [ 3 ]. Relaxometry (relaxation time) may extend due to the relative motion of spins in a fluid as water or oil, theoretical studies have been done by Korb [ 4 , 5 ] previously, and recent studies on cement hydrates by McDonald [ 6 , 7 , 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

1H NMR Spin-Lattice Relaxometry of Cement Pastes with Polycarboxylate Superplasticizers

Pang

Sun

et al. 2020

Materials

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1H spin-lattice relaxometry (T1, longitudinal) of cement pastes with 0 to 0.18 wt % polycarboxylate superplasticizers (PCEs) at intervals of 0.06 wt % from 10 min to 1210 min was investigated. Results showed that the main peak in T1 relaxometry of cement pastes was shorter and lower along with the hydration times. PCEs delayed and lowered this main peak in T1 relaxometry of cement pastes at 10 min, 605 min and 1210 min, which was highly correlated to its dosages. In contrast, PCEs increased the total signal intensity of T1 of cement pastes at these three times, which still correlated to its dosages. Both changes of the main peak in T1 relaxometry and the total signal intensity of T1 revealed interferences on evaporable water during cement hydration by dispersion mechanisms of PCEs. The time-dependent evolution of weighted average T1 of cement pastes with different PCEs between 10 min and 1210 min was found regular to the four-stage hydration mechanism of tricalcium silicate.

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Sorption, anomalous water transport and dynamic porosity in cement paste: A spatially localised 1H NMR relaxation study and a proposed mechanism

Cited by 71 publications

References 31 publications

Water Uptake in OPC and FAC Mortars under Different Temperature Conditions

Water Uptake in OPC and FAC Mortars under Different Temperature Conditions

Numerical Simulation of Water Transport in Unsaturated Recycled Aggregate Concrete

1H NMR Spin-Lattice Relaxometry of Cement Pastes with Polycarboxylate Superplasticizers

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