A constitutive model for drying of a partially saturated porous material

Vlahinić, Ivan; Jennings, Hamlin M.; Thomas, Jeffrey J.

doi:10.1016/j.mechmat.2008.10.011

Cited by 55 publications

(27 citation statements)

References 44 publications

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“…Several continuum models of deformations induced by RH changes have been proposed [1][2][3]. Typically, these models are based on poromechanics and relate the volumetric strain to the Laplace pressure generated by liquidvapor interfaces in the pore system (also known as capillary stress) [30,52,53].…”

Section: Continuum Modeling Of Reversible Drying Shrinkagementioning

confidence: 99%

“…Evaporable water in cement paste influences important mechanical properties such as drying shrinkage [1][2][3] and creep [4][5][6][7][8][9][10][11]. These influences are due to forces that water and dissolved ions exert from within the complex, multiscale pore system that develops during hydration, i.e., after dry cement powder (mostly calcium silicate minerals) reacts with water.…”

Section: Introductionmentioning

confidence: 99%

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Hysteresis from Multiscale Porosity: Modeling Water Sorption and Shrinkage in Cement Paste

et al. 2015

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Cement paste has a complex distribution of pores and molecular-scale spaces. This distribution controls the hysteresis of water sorption isotherms and associated bulk dimensional changes (shrinkage). We focus on two locations of evaporable water within the fine structure of pastes, each having unique properties, and we present applied physics models that capture the hysteresis by dividing drying and rewetting into two related regimes based on relative humidity (RH). We show that a continuum model, incorporating a poreblocking mechanism for desorption and equilibrium thermodynamics for adsorption, explains well the sorption hysteresis for a paste that remains above approximately 20% RH. In addition, we show with molecular models and experiments that water in spaces of ≲1 nm width evaporates below approximately 20% RH but reenters throughout the entire RH range. This water is responsible for a drying shrinkage hysteresis similar to that of clays but opposite in direction to typical mesoporous glass. Combining the models of these two regimes allows the entire drying and rewetting hysteresis to be reproduced accurately and provides parameters to predict the corresponding dimensional changes. The resulting model can improve the engineering predictions of long-term drying shrinkage accounting also for the history dependence of strain induced by hysteresis. Alternative strategies for quantitative analyses of the * Corresponding author. hmj@mit.edu PHYSICAL REVIEW APPLIED 3, 064009 (2015) 2331-7019=15=3(6)=064009 (17) 064009-1

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Section: Continuum Modeling Of Reversible Drying Shrinkagementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hysteresis from Multiscale Porosity: Modeling Water Sorption and Shrinkage in Cement Paste

et al. 2015

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“…The role of the solid and of the solid plus pores is explicitly accounted for, and the pressure is reduced by a factor S, which has the effect of averaging the pressure over all of the pores, filled or not. These equations can provide insight and are the subject of continuing research (Vlahinic et al 2008). Understanding porosity is central to understanding volume changes on drying, and if models that predict porosity are developed then properties can be designed from first principles.…”

Section: 3mentioning

confidence: 99%

Characterization and Modeling of Pores and Surfaces in Cement Paste

Jennings

Bullard

Thomas

et al. 2008

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Cement-based materials have complex multi-component, multiscale structures that first form through chemical reaction and then continue to change with time. As with most classes of materials, the porosity of cement paste strongly influences its properties, including strength, shrinkage, creep, permeability and diffusion. Pores in cement paste range in size from nanometers to millimeters, and numerous investigations and models have been reported in the literature. This paper reviews some key concepts and models related to our understanding of the pore system and surface area. A major reason for the complexity of cement-based materials is that the principal reaction product, calcium silicate hydrate (C-S-H), forms with a significant volume fraction of internal, nanometer-scale pores. This gel pore system contains water that is also adsorbed to the solid surfaces, blurring the distinction between the solid phase and pores. The gel pore system changes not only with the chemical composition and extent of reaction, but also with changes in relative humidity, temperature, and applied load. Pores can be characterized by their surface area, size, volume fraction, saturation, and connectivity, but precise quantitative models are still not available. A useful approach for characterizing the structure of cement paste is to document the influence of time and external factors on structural changes. Scientific progress will be facilitated by the development of models that accurately describe the structure and use that structure to predict properties. This is particularly important because the composition and chemistry of commercial concretes is changing more rapidly than laboratory experimentation can document long-term properties such as durability. Some of the possible models are discussed.

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“…Many researchers have reported that, in this interval, the shrinkage depends on the thickness of the adsorbed water layer on the solid surface (Bentz et al 1998;Feldman and Sereda 1968;Bazant 1988;Vlahinic et al 2009). The shrinkage driving force caused by the increase of surface free energy is dominant while the effect of capillary pressure may be small; the negligible effect of SRA on shrinkage of AAC in this range of RH (Fig.…”

Section: Water Content and Shrinkage Behavior Of Aacsmentioning

confidence: 99%

Microstructure and Shrinkage Behavior of Autoclaved Aerated Con-crete(AAC) -Comparison of Vietnamese and Japanese AACs-

Lam

Asamoto

Matsui

2018

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We investigated the microstructure and shrinkage behavior of autoclaved aerated concrete (AAC) from several manufacturers in Vietnam comparing with Japanese AAC. Three types of Vietnamese AAC and one type of Japanese AAC were used for powder X-ray diffraction, scanning electron microscopy, mercury intrusion porosimetry, and shrinkage tests. The experimental results show that the main hydration products of AAC that used fly ash as silica materials is semi-crystalline calcium silicate hydrate, while the ones of others are tobermorite; but the tobermorite crystals of AACs from some manufacturers in Vietnam are disordered structures and lack of interlocking among tobermorite crystals. The pore size distribution of all Vietnamese AAC are single peak, whereas Japanese AAC is bimodal. The pore distribution characteristics of AACs significantly influenced their shrinkage behavior and the shrinkage of Vietnamese AAC is higher than that of Japanese AAC at intermediate relative humidity (RH). The capillary tension is the principle shrinkage mechanism for AAC materials at high RH (above about 65%) to cause local minimum shrinkage of Japanese AAC at high RHs, while the change in surface free energy is dominant at low RH conditions.

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A constitutive model for drying of a partially saturated porous material

Cited by 55 publications

References 44 publications

Hysteresis from Multiscale Porosity: Modeling Water Sorption and Shrinkage in Cement Paste

Hysteresis from Multiscale Porosity: Modeling Water Sorption and Shrinkage in Cement Paste

Characterization and Modeling of Pores and Surfaces in Cement Paste

Microstructure and Shrinkage Behavior of Autoclaved Aerated Con-crete(AAC) -Comparison of Vietnamese and Japanese AACs-

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