Permeability and sorption properties of mature near-surface concrete

Measurements of the permeation or sorption characteristics of concrete are increasingly being used as indexes of durability or resistance to chemical attack of new concrete. This investigation was intended to find if these relatively simple, inexpensive tests can be used to assess the condition of the concrete in mature structures that may have deteriorated during their service life. Such structures may be nearing the end of their design life, but it may be necessary to extend their service life. In such cases the state of the concrete needs to be assessed. The paper explores the profiles of oxygen permeability and water sorption, with distance from the surface, of concrete taken from in-service structures typically in the 20 to 30 year age range and hence proposes generalized permeability and sorption profiles. However, as the two types of measurement, permeability and sorption, do not, for concrete from in-service structures, correlate one with the other or with carbonation depth or strength, it is unlikely that either parameter is a valid index of the overall state of concrete from a mature structure.