Estimation of Water Retention Curve from Mercury Intrusion Porosimetry and van Genuchten Model

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Title: Estimation of Water Retention Curve from Mercury Intrusion Porosimetry and van Genuchten Model

Author(s): Craig Leech, David Lockington, and R. Doug Hooton

Publication: Structural Journal

Volume: 103

Issue: 2

Appears on pages(s): 291-295

Keywords: adsorption; durability; moisture; porosimetry, surface area.

Date: 3/1/2006

Abstract:
The water retention curve (WRC) is a hydraulic characteristic of concrete required for advanced modeling of water (and thus solute) transport in variably saturated, heterogeneous concrete. Unfortunately, determination by a direct experimental method (for example, measuring equilibrium moisture levels of large samples stored in constant humidity cells) is a lengthy process, taking over 2 years for large samples. A surrogate approach is presented in which the WRC is conveniently estimated from mercury intrusion porosimetry (MIP) and validated by water sorption isotherms. The well-known Barrett, Joyner, and Halenda (BJH) method of estimating the pore size distribution (PSD) from the water sorption isotherm is shown to complement the PSD derived from conventional MIP. This provides a basis for predicting the complete WRC from MIP data alone. The van Genuchten equation is used to model the combined water sorption and MIP results. It is a convenient tool for describing water retention characteristics over the full moisture content range. The van Genuchten parameter estimation based solely on MIP is shown to give a satisfactory approximation to the WRC, with a simple restriction on one of the parameters.