A new analytical method to predict permeability properties of cementitious mortars: The impacts of pore structure evolutions and relative humidity variations

Xiong, Qing Xiang; Tong, Liang-yu; Zhang, Zhidong; Shi, Caijun; Liu, Qingfeng

doi:10.1016/j.cemconcomp.2022.104912

Cited by 29 publications

(5 citation statements)

References 68 publications

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“…The results are interesting, as they show a clear difference with traditional PC. Specifically, we know that for PC the hydraulic conductivity drops when the relative humidity goes from 100 to 50%, slowing the drying process itself [ 41 , 88 ]. In addition, the water vapour transport is the main conductivity mechanism only when the RH is lower than 50% [ 41 ].…”

Section: Results and Discussionmentioning

confidence: 99%

New Insights into Pore Structure and Hydraulic Conductivity of Sodium Hydroxide Alkali-Activated Slag through Advanced Modelling

Sirotti,

Carette,

Staquet

2024

Materials

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The study of alkali-activated slag (AAS) is motivated by the need for more sustainable alternatives to Portland cement (PC) within the construction industry. Specifically, AAS offers good mechanical and chemical properties. However, the influence of the activator on its pore structure and hydraulic conductivity remains unclear. Both pore structure and hydraulic conductivity are key parameters in understanding the drying process and could potentially explain the high drying shrinkage observed so far. The present study aims to investigate the pore size distribution and hydraulic conductivity of six distinct AAS/sodium hydroxide mortar compositions, with a particular emphasis on the effect of varying the activator’s molarity and the solution-to-binder ratio (s/b). This research uses the mass variation in different relative humidity (RH) conditions from experimental tests to model the pore surface area, the pore size distribution, and the hydraulic conductivity. From the results, it emerges that increasing the molarity from 0.5 to 8 M reduces the open porosity and refines the pore structure, while increasing the s/b from 0.5 to 0.8 increases the open porosity while refining the pore structure. In addition, high molarity compositions are not suitable for testing in high RH and natural carbonation conditions due to the occurrence of deliquescence. Moreover, the main drying mechanism in AAS is water vapour transport even at high relative humidity, contrary to what was observed in the literature for PC. Finally, the hydraulic conductivity of alkali-activated slag presents a minimum of around 85% RH against the 60–70% RH for PC, causing AAS to dry faster when the relative humidity decreases from 85 to 50%.

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Section: Results and Discussionmentioning

confidence: 99%

New Insights into Pore Structure and Hydraulic Conductivity of Sodium Hydroxide Alkali-Activated Slag through Advanced Modelling

Sirotti,

Carette,

Staquet

2024

Materials

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“…At present, some well-developed theoretical or empirical formulas are usually used to assess the chloride diffusion coefficient [41]. In this study, the relationship between the chloride diffusion coefficient and porosity of cement mortars is established by using the generalized effective medium theory [42,43], as follows:…”

Section: Porositymentioning

confidence: 99%

Influence of coarse aggregate settlement induced by vibration on long-term chloride transport in concrete: a numerical study

et al. 2022

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High-frequency vibration helps to improve the compactness of concrete, but also causes the settlement of coarse aggregates (CAs) and then affects the durability of hardened concrete. In this paper, a numerical study combining multi-phase CA settlement model and multi-component ionic transport model is performed to understand the influence of vibration-induced settlement on long-term chloride transport in concrete. Through parametric analysis, the influence mechanism of relevant factors on both chloride profile distribution and reinforcement corrosion initiation is discussed in detail. The results indicate that with the increase of vibration time, a decrease of chloride concentration appears in the bottom part of concrete specimen and a significant increase in the top part, because more CAs deposit in the bottom layer. Due to sedimentation, a more obvious fluctuation of chloride concentration along the height direction can be observed in the concrete mixed with a larger density and particle size of CAs. According to the model prediction, the corrosion of the top steel bar initiates 1.03-1.80 years earlier than that of the bottom steel bar under the same parameters. In practical engineering, special attention should be paid on the stability of fresh concrete and vibrating procedures to avoid obvious CA settlement.

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“…Some multi-phase numerical models are proposed for comprehensively investigating the coupled process of concrete cracks, chloride transport, freeze-thaw cycles, and chemical process, where the entire process from concrete cracking up to repairing can be successfully reproduced and digitally visualized Li et al 2021;Meng, et al 2022). The validity of those models was verified against third-party experiments (Liu et al 2023a(Liu et al , 2023bXiong et al 2023). The chloride diffusivity of mesoscopic concrete with compressive and tensile-induced damage was systematically predicted and compared to experimental results (Xiong et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, micro-pore structure was modelled in the work of Liu et al (2021) using the CEMHYD3D model (Bentz et al 2005), where the permeability in cementitious materials was predicted. Furthermore, in addition to mechanical damage, the chloride transport of practical cementitious materials is moisture-dependent (Liu et al 2023a(Liu et al , 2023bXiong et al 2023). The effect of mechanical damage on transport properties remains poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Modelling of Damage Spatiotemporal Distribution in Saturated Cementitious Materials and its Chloride Transport Evolution

Rusheng

Gao

et al. 2023

ACT

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Crack-induced damage significantly affects the chloride transport mechanism in cementitious materials. To quantitatively evaluate the crack effects, a coupled model was proposed in this paper for saturated cement paste with various uniaxial tensile damage. First, the 3D microstructure of hydrating cement paste was simulated based on a voxel-based hydration model, and its damaged spatiotemporal distribution under uniaxial tensile stress was simulated using a finite-element model. Based on the damaged cement paste, an electrical Modelling framework was presented to simulate the chloride transport. The results show that the damage spatiotemporal distribution in saturated cementitious materials with uniaxial tensile and its chloride transport evolution can be successfully modelled using the self-created model and coupled method. the damage of cementitious material is an accumulation process of cracks spread over the main crack. During the process, the crack connectivity and crack width affect chloride transport and its fracture-volume threshold value is 1.40%. Compared to studies published, the coupled model could well simulate chloride transport in saturated cementitious materials with uniaxial tensile damage.

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A new analytical method to predict permeability properties of cementitious mortars: The impacts of pore structure evolutions and relative humidity variations

Cited by 29 publications

References 68 publications

New Insights into Pore Structure and Hydraulic Conductivity of Sodium Hydroxide Alkali-Activated Slag through Advanced Modelling

New Insights into Pore Structure and Hydraulic Conductivity of Sodium Hydroxide Alkali-Activated Slag through Advanced Modelling

Influence of coarse aggregate settlement induced by vibration on long-term chloride transport in concrete: a numerical study

Modelling of Damage Spatiotemporal Distribution in Saturated Cementitious Materials and its Chloride Transport Evolution

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