Modelling of water vapour sorption hysteresis of cement-based materials based on pore size distribution

Jiang, Zhilu; Xi, Yunping; Gu, Xiaoqiang; Huang, Qinghua; Zhang, Weiping

doi:10.1016/j.cemconres.2018.09.015

Cited by 34 publications

(14 citation statements)

References 32 publications

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“…DVS measurements are commonly performed with drugs ( Sheokand et al, ; Wu et al, ), wood ( Patera et al, ; Simón et al, ) or construction materials ( Bui et al, ; Jiang et al, ), for analyzing, e.g ., the stability, mechanical performance, hydration kinetics and amount of water that is adsorbed or desorbed by composite materials or chemical compounds ( Suresh et al, ). For a certain T, this analytical method facilitates the detection of sample mass changes in response to RH variations, obtaining isotherms that may be useful for assessing, e.g ., the stability, hydration state, polymorphism or adsorption/ desorption of water of different materials and chemicals ( Simón et al, ; Suresh et al, ).…”

Section: Discussionmentioning

confidence: 99%

Salt hydration and drop drying of two model calcium salts: Implications for foliar nutrient absorption and deposition

Fernández

Pimentel

Bahamonde

2020

J. Plant Nutr. Soil Sci.

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Background: Hygroscopic salts are often applied as foliar fertilizers and calcium (Ca) salts have been used as model for cuticular permeability studies, with focus on their Point of Deliquescence (POD). Aim: This study was aimed at characterizing water sorption and desorption processes at 20, 30, and 40°C temperature (T), of two model Ca salts commonly used as foliar sprays. Methods: Trials were developed with pure Ca-chloride and Ca-nitrate salts in addition to 2 M and 150 mM Ca solutions. Salts were analyzed by Dynamic Vapour Sorption (DVS) and climate chamber experiments. Results: For both Ca salts, water sorption and desorption processes followed hysteresis curves which varied with T. Salt POD was T-dependent and generally decreased with increasing T. For both Ca salts, the process of efflorescence began at or below 10% RH, at a certain level of water desorption Ca-salts becoming highly concentrated solutions (HCS). Conclusions: Owing to the low point of efflorescence (POE) of both salts, drops of Ca-chloride and Ca-nitrate supplied as foliar sprays will not fully dry under normal RH and T conditions in most world areas. Both Ca salts have a similarly high foliar penetration potential despite their different POD. The significance of the results for the potential absorption of foliar fertilizers and salts by the foliage is discussed under an agronomic and eco-physiological viewpoint.

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Section: Discussionmentioning

confidence: 99%

Salt hydration and drop drying of two model calcium salts: Implications for foliar nutrient absorption and deposition

Fernández

Pimentel

Bahamonde

2020

J. Plant Nutr. Soil Sci.

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“…Previous studies suggested the total porosity of the C-S-H grains to be around 50%, 23,[47][48][49] while the evaporable water was found to account for about 25-to-37% of the total interlayer water. 29,30 The number of water layers that can be adsorbed within the C-S-H particles is largely controlled by the size of the interlayer space, which is smaller than 5 Å (see Figure 1 in Ref. [21]).…”

Section: C-s-h Gel Modelmentioning

confidence: 99%

“…28 Similar studies were also conducted by Burgh, Jiang, and Huang, wherein the pore size distribution and the contribution of the interlayer C-S-H spacing to the sorption isotherm were empirically described without explicitly considering the detailed micro-and mesoscale structure of cement pastes. [29][30][31] Moreover, atomistic simulations offer an accurate description of water sorption within the C-S-H layers, but, in turn, are intrinsically unable to describe the multiscale structure of cement pastes due to the limited number of atoms they can account for. 32 Overall, a unifying model describing accurately describing the role of each pore scale in governing the water sorption behavior of cementitious materials is still lacking.…”

Section: Introductionmentioning

confidence: 99%

Deconstructing water sorption isotherms in cement pastes by lattice density functional theory simulations

et al. 2021

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The moisture content in cement pastes influences their mechanical properties and durability. However, the complex, multiscale nature of cement pastes makes it challenging to isolate the contributions of each scale to their macroscopic water sorption isotherms. In particular, the contribution of the calcium-silicate-hydrate gel (the binding phase of cement pastes) remains only partially understood. Here, we introduce a density functional theory lattice model describing water sorption in calciumsilicate-hydrate, which properly reproduces experimental water sorption isotherms in cement pastes. Based on this model, we deconstruct the contribution of each pore scale (interlayer spacing, gel pores, and capillary pores) to the total sorption isotherm.We show that, when the relative humidity is below 80%, the calcium-silicate-hydrate gel accounts for more than 90% of the moisture content adsorbed in cement pastes. In turn, we find that the contribution of the interlayer space within the calcium-silicatehydrate grains is governed by the competition between the rate of interlayer space opening and the increasing propensity for water to fill larger pores upon increasing relative humidity. Overall, our results highlight the key role played by the calciumsilicate-hydrate in governing the sorption isotherms of cement pastes.

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“…The desorption process displays a significantly hysteretic nature compared to the absorption process, which implies that the gas-liquid equilibrium in pores is nonhomogeneous. The hysteresis represents the "ink bottle effect," which refers to the effect that a small pore (bottleneck) exerts stress upon the water in a connected large pore (bottle) [25]. Larger concrete capillary pores require a higher RH to reach equilibrium saturation than small pores.…”

Section: Rh-saturation Equilibriummentioning

confidence: 99%

“…Transport coefficient D(S) of Equation (25) in absorption and desorption processes are then represented as Equations (26) and (27), respectively.…”

Section: Moisture Transport Modelmentioning

confidence: 99%

Influence of Temperature on the Moisture Transport in Concrete

et al. 2020

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Moisture with harmful ions penetrates into the interior of concrete, which causes deterioration of the concrete structure. In this study, a moisture saturation equilibrium relationship of concrete was tested under different temperatures and relative humidity conditions to develop moisture absorption and desorption curves. Based on experimental data and numerical simulation, a model of moisture transport in concrete was established. The results from the model indicate that the moisture absorption rate was lower at higher temperatures and largely dependent on the saturation gradient, while the desorption was increased at higher temperatures and mostly affected by the saturation gradient. The proposed model was highly in agreement with the experimental data.

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Modelling of water vapour sorption hysteresis of cement-based materials based on pore size distribution

Cited by 34 publications

References 32 publications

Salt hydration and drop drying of two model calcium salts: Implications for foliar nutrient absorption and deposition

Salt hydration and drop drying of two model calcium salts: Implications for foliar nutrient absorption and deposition

Deconstructing water sorption isotherms in cement pastes by lattice density functional theory simulations

Influence of Temperature on the Moisture Transport in Concrete

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