Paper discusses the current approach for specifying concrete durability in structures. The shortcomings of the use of bulk parameters such as strength, water-binder ratio, and binder content to specify durability are discussed. Studies carried out over the last 10 years at Dundee University, using simple permeation tests, which are sensitive to curing, cement type, and concrete grade, have shown close association between permeation properties and concrete durability. Paper deals with the measurement of concrete durability by the Dundee-modified initial surface absorption test (ISAT). A wide range of concrete mixes made with ordinary portland cement and blends with pulverized fuel ash (PFA) and ground granulated blast furnace slag were designed. The duration of moist-curing was varied from 0 to 28 days, and the maximum aggregate size ranged from 5 to 40 mm. All mixes were tested for absorptivity and durability, including freeze-thaw resistance, carbonation, chloride ingress, and mechanical wear. Results show that the absorptivity of concrete, measured with the ISAT, can be used as an accurate specification for concrete durability, irrespective of curing, grade, or mix constituents. A tentative surface absorptivity classification for durability has been proposed. |
