The measurement of the intrinsic permeability of concrete is described. The tests developed are rapid and reliable. It is shown that the intrinsic permeability of concrete can be characterised using the air permeability test. Hydraulic permeability data can also be derived if required. The permeability of concrete in the surface layer (that comprising the cover to reinforcement) is greatly affected by both the water/cement ratio and curing. Concrete quality should not be estimated from strength data alone.

Synopsis The British Standard initial surface absorption test (ISAT), Figg hypodermic methods (air and water), and a new test, the covercrete absorption test (CAT), have been used to study the permeation properties of the near-surface of concrete. The test methods are critically appraised. It is shown that the moisture condition of the concrete can greatly alter the results obtained. Data on the surface quality of concrete and its dependence on mix proportions and degree of moist curing are presented.

The relationship between the intrinsic permeability and the Carbonation of concrete is examined. It is shown that the Figg air index test, which is portable, cheap and simple to operate, can be used to predict directly the potential resistance of concrete to carbonation. The water/cement ratio and degree of moist curing are the main factors influencing the quality of concrete in terms of its carbonation resistance.