2021 Volume 19 Issue 1 Pages 53-66
This paper analyzes field experimental data obtained on about 30 concrete structures, both new (age up to 1 year) and old (age up to 60 years). The data include in situ non-destructive tests (NDT) of air-permeability kT, electrical resistivity ρ and surface moisture m, as well as tests conducted on drilled cores: O2-permeability kO, water sorptivity a24, MIP, carbonation rate Kc and chloride content Cl at 10 to 20 mm depth. The main conclusions are that in situ kT of new structures is a good indicator of both kO and a24. Regarding old structures, high values of kT and kO are accompanied by low a24 values and by tight MIP pore structure. This phenomenon is attributed to microcracks, with strong effect on permeation but not so much on capillary suction. Similarly, high values of kT are not always accompanied by deep carbonation depths. The chloride content did not show correlation with either kT or ρ. In situ measurements of ρ, under the testing conditions, did not correlate with any other durability test. Finally, the spread of kT values for old structures is significantly wider than for young structures, suggesting that age improves durable concrete but weathering and damage impair non-durable concrete.