ABSORPTION AND SORPTIVITY OF COVER CONCRETE

The absorption characteristics and sorptivity of cover concrete obtain ed by the initial surface absorption test (ISAT), the covercrete absor ption test (CAT), and the sorptivity test have been studied and compar ed. Two types of concrete, namely ordinary portland cement (OPC) contr ol and low water concrete (LWC) of grade 35 have been tested. The labo ratory work has shown close agreement between the ISAT and sorption re sults but the CAT yields higher results. An analytical model has been developed based on the mechanisms of capillary suction and pressure-dr iven flow, In this model water entering concrete during the tests is a ssumed to be concentrated in a well-defined volume. This volume is ful ly saturated and is separated from the surrounding concrete by a wetti ng front at which capillary suction occurs. By applying the physical e quations for capillary suction pressures and permeability the experime ntal. results are explained in terms of the basic properties of the co ncrete. The model gives good agreement with the experimental results.