Use of Two-Pressure-Head Method to Assess Water Permeability of Structural Concrete

Determining the water permeability of concrete in structures remains a conundrum because of difficulties in removing the influences of moisture. This study describes the extended flow-net theory developed on the basis of the two-pressure-head concept, which provides a means of measuring permeability under the partially saturated condition. Surface-mounted tests and standard laboratory water penetration tests were carried out to verify this approach. Before determining the water permeability, steady-state flow rates at two different pressure levels were evaluated and the effects of initial moisture conditions on flow behavior were investigated. The results indicate that the proposed approach does offer a useful means of determining the water permeability of structural concrete, although it cannot be claimed tobe universally applicable for all moisture conditions likely to be encountered in practice. Keywords: extended flow-net theory; in-place water permeability; two-pressure-head test; unsaturated flow.