An optimised preconditioning procedure for gas permeability measurement

To study the permeability of cementitious materials, a procedure of drying out moisture before the actual measurement of this property, normally called preconditioning, is an unavoidable necessity. In this study, the preconditioning procedure proposed by AFREM (Association Francaise de Recherche et d'Etudes des Materiaux) and a detailed preconditioning procedure developed by the authors earlier, is used to carry out the measurement of permeability to gases of 13 concrete compositions in order to compare the different steps proposed by these procedures: these concretes have been studied in terms of durability in a "BHP2000" project. These 15 compositions include 4 ordinary concretes, 5 medium strength concretes, 4 HPCs and 2 VHPCs. We have compared die preconditioning temperatures for their possible effects on the measured value of permeability as well as its adequacy ill drying out moisture during a short period of time. Also, In addition to the practicality of the procedures, the coverage of the whole range of degrees of saturation by the permeability results is given due importance. These considerations have culminated in an optimised preconditioning procedure which is not only simple and flexible but also guarantees adequate information about the permeation characteristics of the material under study, for a whole range of concrete qualities.