Moisture diffusivity in mortars of different water–cement ratios and in narrow ranges of air humidity changes

Garbalińska, H.; Kowalski, Stefan Jan; Staszak, Maciej

doi:10.1016/j.ijheatmasstransfer.2012.09.026

Cited by 18 publications

(10 citation statements)

References 31 publications

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“…8. Perfect agreement is obtained for the measured mass changes and the modeling results, and the agreement seems better than the moisture transport modeling results in (Garbalinska et al 2013). This agreement confirms that the desorption process of vapor from pore surface adopts second-order kinetics.…”

Section: Desorption Phasementioning

confidence: 59%

Kinetics and Equilibrium Isotherms of Water Vapor Adsorption/Desorption in Cement-Based Porous Materials

Zeng

Zhang

2015

Transp Porous Med

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The kinetics and equilibrium of water vapor adsorption/desorption isotherm (WVSI) are fundamental information for solid-moisture interaction in the microstructure of cement-based porous materials (CBPM). This paper presents firstly the experimental data for WVSI of CBPM with a ternary binder. Mass changes in specimen are recorded in sorption tests for materials with different aggregate contents and water-to-binder (w/b) ratios under controlled ambient relative humidity. Both the sorption equilibrium and sorption kinetics are investigated through some established physical models, and the corresponding intrinsic parameters of moisture sorption are determined. For sorption kinetics, the mass change during sorption is interpreted through Elovich model, power model and pseudofirst-order and pseudo-second-order models. The mass change in sorption occurs mainly in the first 40 days, and the pseudo-second-order model shows the best adaption to all adsorption/desorption processes. For sorption equilibrium, Guggenheim-Anderson-de Boer (GAB), modified Halsey and Oswin models are used to interpret the moisture sorption capacity. The hysteresis between adsorption and desorption processes is attributed, respectively, to the mechanisms of snap-through, energy instability and pore constrictivity for low, middle and high relative humidity ranges. From the analysis, it is found that (1) through the interpretation of pseudo-second-order model the moisture sorption kinetics can be controlled by the sorption between the water molecules and the pore wall in addition to vapor diffusion; (2) the sorption capacity is sensitive to aggregate content and w/b ratio; incorporating aggregates, decreasing w/b ratio and increasing humidity gradient tend to decrease the sorption capacity of CBPMs; (3) the sorption isotherm hysteresis is well described by GAB-H model, both the extent of hysteresis and the energy constant related to pore surface tension showing clear correlation with the aggregate content and w/b ratio of CBPMs. Electronic supplementary materialThe online version of this article (

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Section: Desorption Phasementioning

confidence: 59%

Kinetics and Equilibrium Isotherms of Water Vapor Adsorption/Desorption in Cement-Based Porous Materials

Zeng

Zhang

2015

Transp Porous Med

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“…The sorption of pastes examined in the present paper was also the subject of articles by the authors of [14][15][16][17]. In turn, works [18][19][20][21][22][23] studied cement mortars with w/c ratio = 0.50, 0.65, 0.80 in the processes of sorption and desorption. Different methods of calculation were used based on the inverse problem so that, having recorded the kinetics of the sorption and desorption processes, the diffusion coefficient variability of the tested mortars in a wide range of humidity could be determined.…”

Section: Introductionmentioning

confidence: 92%

Sorptive testing of mortars with varying water-cement ratios

Stolarska

Ciborowski

2018

E3S Web Conf.

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The article presents the results of studies on sorption performed on three samples of mortars with similar density of about 2,000 kg/m 3 . The tested mortars differed in their water-to-cement ratio. Three levels of w/c ratio were adopted that were respectively: 0.5; 0.55 and 0.6. The prepared mortars were cut into samples with a thickness of 1 cm, dried to constant weight at a temperature of 105°C and insulated on the side surface with silicone. The experiment was carried out at a temperature of 25°C and at six different levels of relative humidity ϕ ≈ 12, 33, 54, 76, 85, 98%. Relative humidity was provided by saturated solutions of the appropriate salts: LiCl (ϕ ≈ 12%), MgCl 2 (ϕ ≈ 33%), Mg(NO 3 ) 2 (ϕ ≈ 53%), NaCl (ϕ ≈ 76%), KCl (ϕ ≈ 85%), K 2 SO 4 (ϕ ≈ 98%). The adopted level of temperature and range of relative humidity meet the hygrothermal conditions which tend to affect the cement mortar in real life. The long-term measurement results were used to assess the behaviour of the tested mortars under various conditions of moisture and to determine the equilibrium sorptive humidity.

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“…Unlike the bulk mass transfer, the mass flux near the interface is induced mainly by adsorption of surface active component. Applying appropriate mass transfer approach, expressed in modification either in diffusion coefficients or model equations themselves, is typical to describe the mass transfer in any media, where concentration gradients do not generate dominant driving force (e.g., ions flux in presence of electric field) or in cases where molecular diffusion coefficients are not known and are substituted by effective diffusivities [69][70][71]. Calculating adsorptive near-interface mass transfer creates the need for effective diffusion coefficient estimation.…”

Section: The Near-interface Adsorptive Flux Computationmentioning

confidence: 99%

Superficial transportation model using finite volume method

Staszak

2018

Theor. Comput. Fluid Dyn.

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The work presents a new modeling technique designed for transporting selected property while simultaneously tracking particular value of certain field variable. The model addresses the problem of transportation of superficial properties according to fluid/fluid interface evolution. Such problem arises when some superficial variable needs to be attached to the evolving interface or front defined. Several multiphase models in CFD technique lack such ability. The model proposed is illustrated by the experimental two phase system of toluene/water with surfactant specie (sodium dodecylsulfate SDS). The selected superficial property that is important to be tracked according to interface evolution is Gibbs surface excess. The computation was performed using Ansys/Fluent software with proposed models created and attached using C programming language. Keywords Interface mass transfer · Adsorption · Liquid-liquid interfaces · Fluid dynamics List of symbols

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Moisture diffusivity in mortars of different water–cement ratios and in narrow ranges of air humidity changes

Cited by 18 publications

References 31 publications

Kinetics and Equilibrium Isotherms of Water Vapor Adsorption/Desorption in Cement-Based Porous Materials

Kinetics and Equilibrium Isotherms of Water Vapor Adsorption/Desorption in Cement-Based Porous Materials

Sorptive testing of mortars with varying water-cement ratios

Superficial transportation model using finite volume method

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