Abstract
Uptake of water (and therefore ions) by unsaturated, hardened concrete may be characterised by the sorptivity. This is a simple parameter to determine and is increasingly being used as a measure of concrete resistance to exposure in aggressive environments. The complete process is described by a nonlinear diffusion equation, with the hydraulic diffusivity a strongly nonlinear function of the degree of saturation of the concrete. Accurate analytical approximations to the solution of this equation, as well as numerical solutions for general conditions, exist when the diffusivity function is known. Unfortunately, it is not an easy function to determine, requiring accurate information on the water penetration profile. A simple alternative which estimates the diffusivity from sorptivity and porosity measurements is presented for an assumed exponential dependence of diffusivity on water saturation. Predicted water penetration profiles corresponding to this estimated diffusivity are shown to be accurate by comparison with published experimental results.
Résumé
L'entrée de l'eau (et par conséquent, des ions) dans le béton non saturé peut être caractérisée par la sorptivité. C'est un paramètre simple à déterminer, utilisé souvent pour décrire la résistance du béton à un environnement corrosif. Le phénomène est décrit par l'équation de diffusion non linéaire, où la diffusivité de l'eau est une fonction non linéaire de la teneur en eau du béton. Des approximations analytiques précises existent pour résoudre cette équation, ainsi que des solutions numériques pour des conditions aux limites générales, quand la diffusivité est une fonction connue. Malheureusement cette fonction est difficile à déterminer et nécessite des mesures précises de profils de pénétration de l'eau. Une autre alternative simple consiste à estimer la diffusivité à partir de mesures de sorptivité et de porosité, en partant d'une relation exponentielle de la diffusivité avec l'eau de saturation. La prévision des profils de teneur en eau utilisant cette diffusivité est en accord avec les profils expérimentaux publiés.
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References
Gummerson, R. J., Hall, C., and Hoff, W. D., ‘Water movement in porous building materials—3 A sorptivity procedure for chemical injection damp proofing,’Building and Environment 16 (1981) 193–199.
Hall, C., ‘Water sorptivity of mortars and concretes: a review’,Magazine of Concrete Research 41 (1989) 51–61.
Ho, D. W. S. and Lewis, R. K., ‘The water sorptivity of concretes: the influence of constituents under continuous curing’,Durability of Building Materials 4 (1987) 241–252.
McCarter, W. J., Ezirim, H. and Emerson, M., ‘Properties of concrete in the cover zone: water penetration, sorptivity and ionic ingress’,Magazine of Concrete Research 48 (1996) 149–156.
Bear, J “Dynamics of Fluids in Porous Media’. (Elsevier, New York, 1972).
Carpenter, T. A., Davies, E. S., Hall, L. D., Hoff, W. D. and Wilson, M. A., ‘Capillary water migration in rock: process and material properties examined by NMR imaging’,Mater. Struct. 26 (1993) 286–292.
Kutilek, M. and Valentova, J., ‘Sorptivity approximations’,Transport in Porous Media 1 (1986) 57–62.
Campbell, G. S., ‘A simple method for determining unsaturated conductivity from moisture retention data’,Soil Science 117 (1974) 311–314.
Gummerson, R. J., Hall, C., Hoff, W., Hawkes, R., Holland, G. and Moore, W., ‘Unsaturated water flow within porous materials observed by NMR imaging’,Nature 281 (1979) 56–57.
Daian, J.-F., ‘Condensation and isothermal water transfer in cement mortar. Part 1: Pore size distribution, equilibrium water condensation and imbibition’,Transport in Porous Media 3 (1988) 563–589.
Parlange, M. B., Prasad, S. N., Parlange J.-Y. and Romkens, M. J. M., ‘Extension of the Heaslet-Alksne technique to arbitrary soil-water diffusivities’,Water Resources Research 28 (1992) 2793–2797.
Lockington, D., ‘Estimating the sorptivity for a wide range of diffusivity dependence on water content’,Transport in Porous Media 10 (1993) 95–101.
Spiegel M. R., ‘Mathematical Handbook of Formulas and Tables’ (Schaum's Outline Series, McGraw-Hill, NY, 1968).
Link, J., Kaufmann, J. and Schenker, K., ‘Water transport in concrete’,Magnetic Resonance Imaging 12 (1994) 203–205.
Elrick, D. E. and Robin, M. J., ‘Estimating the sorptivity of soils’,Soil Science 132 (1981) 127–133.
Hall, C., Hoff, W. D. and Wilson, M. A., ‘Effect of non-sorptive inclusions on capillary absorption by a porous material’,Journal of Physics D: Applied Physics 26 (1993) 31–34.
Lockington, D., Hara, M., Hogarth, W. and Parlange, J.-Y., ‘Flow through porous media from a pressurized spherical cavity’,Water Resources Research 25 (1989) 303–309.
Lockington, D., ‘Falling-rate evaporation and desorption estimates’,Ibid. Water Resources Research (1994) 1071–1074.
Lockington, D. and Parlange, J.-Y., ‘Approximate formulae for the wetting front position and boundary water content during horizontal infiltration’,Transport in Porous Media 18 (1995) 95–105.
Parlange, J.-Y., Hogarth, W., Fuentes, C., Sprintal, J., Haverkamp, R., Elrick, D., Parlange, M. B., Braddock, R. D. and Lockington, D. A., ‘Interaction of wetting fronts with an impervious surface-longer-term behaviour,17 (1994) 249–256.
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Lockington, D., Parlange, J.Y. & Dux, P. Sorptivity and the estimation of water penetration into unsaturated concrete. Mat. Struct. 32, 342–347 (1999). https://doi.org/10.1007/BF02479625
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DOI: https://doi.org/10.1007/BF02479625