Water Retention and Gas Migration of Two High-Performance Concretes after Damage

Abstract

In the context of long-term repository of high-level and long-lived nuclear waste, authors investigate different concrete properties related to fluid transport, in order to determine which is able to detect damage earliest. To this purpose, different protocols are tested, which impose progressive damage to two different Andra high-performance concretes (HPCs), based on pure portland (CEMI) or composed cement (CEMV)-type cements. The properties investigated are pore size distributions and porosity [by mercury intrusion porosimetry (MIP)], water retention curves, relative gas permeability, and gas migration properties (gas breakthrough pressure). Gas breakthrough pressure (GBP) is assessed rather than gas entry, by accurately measuring gas presence on the downstream side of a confined sample subjected to slowly increasing gas pressure on its upstream side. From MIP data, authors show that CEMI concrete has smaller porosity but greater pore sizes than CEMV. For CEMI concrete, all damage procedures significantly affect water retention curves and gas breakthrough pressures, yet they have no effect upon the relationship between relative gas permeability and water saturation. For CEMV concrete subjected to low damage levels, gas breakthrough measurements detect damage, whereas water retention and gas permeability do not.