Near surface characteristics of concrete: intrinsic permeability

Dhir, Ravindra K.; Hewlett, P. C.; Chan, Y. N.

doi:10.1680/macr.1989.41.147.87

Cited by 109 publications

(55 citation statements)

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“…Relative humidity (RH) provides direct information about the content and distribution of moisture in the concrete sample and is considered a useful parameter in checking the reliability of an air permeability measurements; particularly when distinguishing between pore structure and moisture affects [14,16,20,21]. In this study, RH measurements were carried out on sample surfaces and within drilled 20 mm deep holes using an RH probe, which is shown in Figure 2.…”

Section: Relative Humidity On the Surface And In The 20mm Drilled Holementioning

confidence: 99%

“…Not affecting the results in Figure 4 was physically bonded or adsorbed moisture on gel surfaces, which is typically lost at temperature around 105 o C [14,23,27,44]. In this element of the study, therefore, both capillary and the gel porosities were determined on the basis of the moisture of 40 o C and 105 o C respectively.…”

Section: Porosity and Sorptivitymentioning

confidence: 99%

“…In addition, the sorptivity reflect the near-surface properties, while most current studies focus on measuring the permeation properties of the whole sample [13,14,29]. The difference between the nearsurface zone and core section may be another factor contributing the observed trend.…”

Section: Porosity and Sorptivitymentioning

confidence: 99%

“…Prior to all permeation testing, initial conditions of samples must satisfy certain requirements as specified in classical theories [14,15]. Drying is an unavoidable preconditioning procedure for gas permeability [11,16], gas adsorption [17], gas diffusion [18] and water absorption [19,20].…”

Section: Introductionmentioning

confidence: 99%

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Establishment of a preconditioning regime for air permeability and sorptivity of alkali-activated slag concrete

Yang

Chen

Magee

et al. 2016

Cement and Concrete Composites

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This study reports an experimental investigation designed to assess the influence of near-surface moisture contents on permeation properties of alkali-activated slag concrete (AASC). Five different drying periods (5, 10, 15, 20 and 25 days) and three AASC and normal concretes with compressive strength grades ranging from C30 to C60 were considered. Assessment of moisture distribution was achieved using 100 mm diameter cores with drilled cavities. Results indicate that air permeability of AASC is very sensitive to the moisture content and its spatial distribution, especially at relative humidity above 65%. To control the influence of moisture on permeation testing, the recommendation of this paper is that AASC specimens should be dried in controlled conditions at 40 o C for 10 days prior to testing. It was also concluded from this study that AASC tends to perform less well, in terms of air permeability and sorptivity, than normal concrete for a given strength grade. This conclusion reinforces the need to further examine AASC properties prior to its widespread practical use.

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Section: Relative Humidity On the Surface And In The 20mm Drilled Holementioning

confidence: 99%

Section: Porosity and Sorptivitymentioning

confidence: 99%

Section: Porosity and Sorptivitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Establishment of a preconditioning regime for air permeability and sorptivity of alkali-activated slag concrete

Yang

Chen

Magee

et al. 2016

Cement and Concrete Composites

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“…where ρ is the fluid density, and g is the acceleration due to gravity. For water at 20° C, Several hypotheses have been advanced to try and explain the broad range of measured permeability values in cement-based materials including: gas slippage on the surface of the pores [5]; microcracks induced by sample drying prior to gas permeability measurements [13]; delayed cement hydration [6,14]; swelling of cement hydrates in contact with water [14] and dissolution and migration of fine elements [6,9,14,15]. However, careful examination shows that none of these is sufficient to explain fully the wide variation of results.…”

Section: Introductionmentioning

confidence: 99%

A 3D lattice Boltzmann effective media study: understanding the role of C-S-H and water saturation on the permeability of cement paste

Zalzale

McDonald

Scrivener

2013

Modelling Simul. Mater. Sci. Eng.

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A 3D lattice Boltzmann model is developed and used to calculate the water and gas permeabilities of model cement pastes at different degrees of water saturation. In addition to permeable micron-sized capillary pores and impermeable solid inclusions, the lattice Boltzmann model comprises weakly-permeable nano-porous calcium silicate hydrate (C-S-H).The multi-scale problem is addressed by using an effective media approach based on the idea of partial bounce-back. The model cement paste microstructures are generated with the platform µic. The critical parameters, C-S-H density and capillary porosity, are taken from 1 H nuclear magnetic resonance relaxation analysis. The distribution of water and air is defined according to the Kelvin-Laplace law. It is found that when the capillary porosity is completely saturated with a fluid (either water or gas), the calculated intrinsic permeability is in good agreement with measurements of gas permeability on dried samples (10 -17 -10 -16 m 2 ).However, as the water saturation is reduced, the calculated apparent water permeability decreases and spans the full range of experimentally measured values (10 -16 -10 -22 m 2 ). It is concluded that the degree of capillary water saturation is the major cause for variation in experimental permeability measurements. It is further concluded that the role of the weaklypermeable C-S-H, omitted in earlier modelling studies, is critical for determining the permeability at low capillary saturation. Keywords

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Modeling of multiphase flow with phase change in porous media - a case study

Šelih

Sousa

2005

Mat.-wiss. u. Werkstofftech.

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A general numerical model developed to simulate the time-dependent changes of moisture content, temperature and pore pressures is proposed for a porous material. The model is based on a coupled heat and mass transfer mathematical formulation. The model's validation is conducted using experimental data for concrete. The gravimetric technique is used to obtain the experimental data on moisture content in cylinders made up of fully saturated concrete exposed to drying. Further to demonstrate the applicability of the model, it is also studied the moisture migration, temperature development and thermal stresses in a concrete element exposed to fire. The obtained results indicate that during fire, several degradation phenomena are taking place at the same time. Thermal stresses developed by the temperature differential, especially when temperature-dependent material properties are taken into the account, along with the increase of pore pressures, may contribute to structural failure.

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Near surface characteristics of concrete: intrinsic permeability

Cited by 109 publications

References 0 publications

Establishment of a preconditioning regime for air permeability and sorptivity of alkali-activated slag concrete

Establishment of a preconditioning regime for air permeability and sorptivity of alkali-activated slag concrete

A 3D lattice Boltzmann effective media study: understanding the role of C-S-H and water saturation on the permeability of cement paste

Modeling of multiphase flow with phase change in porous media - a case study

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