Quality with FransWhat the test is
A small two-chamber vacuum cell is pressed against the concrete surface. The device pulls a vacuum and measures how fast air flows back through the near-surface concrete. Tight, well-cured cover lets very little air through; porous, badly cured or poorly compacted cover lets more through. The result is the air-permeability coefficient kT, which can range over about six orders of magnitude, so differences between good and poor cover show up clearly.
The method is not new in itself: it was developed in the early 1990s and has been a Swiss standard method (SIA 262/1) since 2003, where limiting kT values are linked to exposure classes. What is new is a dedicated ASTM test method, which makes it easier to write into specifications outside Europe.
Before and now
| Topic | Typical site practice | With an air-permeability test |
|---|---|---|
| What is checked | Strength (cubes/cylinders), cover depth (cover meter) | Quality of the cover concrete itself, on the real element |
| Damage | Cores for in-situ checks | Non-destructive, surface test |
| Time | Lab results in days or weeks | A few minutes per test point |
| Standard | Swiss SIA 262/1 (Annex E) mainly in Europe | Now also ASTM C1963-26 |
Sources agree the test correlates well with other durability tests such as chloride and water-absorption tests. They also agree on the main limitation: moisture changes the reading, so the near-surface moisture (or electrical resistivity) has to be measured alongside it. It is not meant for cracked areas or very porous concretes such as pervious concrete.
Why this matters for QA/QC
Most durability problems I see start in the cover: poor curing on a hot, windy day, honeycombing at the bottom of a wall, or a slab that was left uncovered. The cubes from the same truck still pass, because they were cured in a tank. A cover test gives you evidence about the concrete the client actually gets, which is exactly where carbonation and chlorides attack the steel.
It is also a useful tool when there is a dispute: instead of arguing about curing records, you can test the suspect area and a well-cured reference area side by side. Remember it is one piece of evidence, not a pass/fail on its own, unless your specification sets kT limits.
Check on your site tomorrow
- Look at your curing records for the last exposed elements (slabs, walls facing weather or sea air). Are they complete, with start time and method?
- Check whether your project specification asks for any in-situ durability test (permeability, resistivity, cover). If not, raise it for future high-exposure elements.
- Walk recently stripped elements for signs of poor cover: dusting, honeycombing, bleeding marks, early cracks.
- If a curing failure is suspected, plan a comparison: suspect area vs a well-cured area, tested the same way and at a similar moisture state.
The 31-point checklist I use before every pour: bar sizes, spacing, cover and laps against the approved drawing.
Download the checklist
Sources: ASTM C1963-26 (scope and summary) · Ebensperger & Torrent: Concrete air permeability in-situ test, status quo · Torrent et al. (EPFL): Specification and site control of the permeability of the cover concrete, the Swiss approach · ACI: Suitability of the Torrent permeability tester for covercrete · Screening Eagle: Torrent permeability tester (manufacturer data). Summary in my own words; your project specification and the responsible engineer decide acceptance.