Fluid transfer through the concrete cover is the main factor affecting the durability of concrete structures. All deterioration mechanisms (e.g. carbonation, corrosion or freeze-thaw attack) involve the movement of gas, liquid and/or aggressive ions into the concrete leading to irreversible changes in the chemical/physical structure of the cement paste matrix which can eventually lead to failure. This study examined various tests for assessing the permeation and durability characteristics of cover concrete.
The fluid transfer tests ( e.g. ISAT, CAT, API and intrinsic air and water permeability) were found to be sensitive to the properties of concrete (e.g. concrete type, design strength, curing, mix constituents .. etc.). However, difficulties with the application of such tests in-situ were highlighted. These included complicated or destructive set-up procedures, time consuming test processes or the lack of theoretical understanding of the way the tests work. Yet the most serious of these is the absence of moisture standardization prior to testing as it can yield misleading results.
A new drying technique, utilizing a vacuum, is proposed. The effectiveness of the technique was verified experimentally, and theoretically using the finite element technique. In addition a new test for assessing the air permeability of concrete is described. The test incorporates a preconditioning |
