Concrete desorption isotherms and permeability determination: effects of the sample geometry

Abstract

The isotherm sorption curve is a first-order parameter used in the Finite Element modelling of concrete moisture transport, shrinkage and creep behaviour. An original experimental campaign was developed by EDF R&D in order to characterise the first desorption isotherm at room temperature of a laboratory concrete. Long-term drying tests were carried out on three sample geometries: radial and axial one-dimensional drying on thin discs and multi-dimensional drying on representative elementary volumes (REV), in order to evaluate the possibility of accelerating the tests. Porosity, densities and mass loss curves are measured and the first-desorption isotherms obtained for the three different configurations are compared. Several analyses of these results are proposed including the assessment of a criterion for the determination of the moisture content final balance (estimation of the asymptotic mass loss) and the back analysis of equivalent permeability. The tests results show the significant time gain using thin (2.5 mm) concrete half samples drying in radial direction compared to the REV samples.

Validation of drying simulations by in-situ RH measurements in concrete in a variable temperature environment

“…The characterization of the drying behavior of VER-CORS concrete has been performed with two main different kinds of tests. First, the desorption isotherms have been measured at EDF R&D MMC using a testing protocol described in [11,2]. Second, weighing of full samples of the same dimensions as samples of creep test campaigns is also performed.…”

The Use of Sorption Balance for the Characterization of the Water Retention Curve of Cement-Based Materials

“…This information proves to be hard to acquire experimentally mainly because the time required for the onset of water balance is too long (Baroghel-Bouny et al 1999;Baroghel-Bouny 2007;Trabelsi et al 2011;Poyet 2009;Poyet et al 2011;Sémété et al 2016). Many authors have attempted to gain time by diminishing the dimension of the tested samples (fine disks, powders, shreds) (Radjy et al 2003;Daïan 1988;BaroghelBouny et al 1999;Tada and Watanabe 2005;Espinosa and Franke 2006;Baroghel-Bouny 2007;Ishida et al 2007;Trabelsi et al 2011;Q.…”

“…Many authors have attempted to gain time by diminishing the dimension of the tested samples (fine disks, powders, shreds) (Radjy et al 2003;Daïan 1988;BaroghelBouny et al 1999;Tada and Watanabe 2005;Espinosa and Franke 2006;Baroghel-Bouny 2007;Ishida et al 2007;Trabelsi et al 2011;Q. Wu et al 2014;Rougelot et al 2009;Sémété et al 2016). Nevertheless, this approach does pose a problem of parasitic carbonation during the tests and calls for particular precaution: injection of inert gas for instance (Ranaivomanana et al 2011;Brue et al 2012;Q.…”