Non-destructive tests are used to find the strength of existing concrete elements.
- Half-cell electrical potential method to detect the corrosion potential of reinforcing bars in concrete.
- Schmidt/Rebound hammer test to evaluate the surface hardness of concrete.
- Carbonation depth measurement test to determine whether moisture has reached the depth of the reinforcing bars, thereby leading to corrosion.
- Permeability test to measure the flow of water through the concrete.
- Penetration resistance or Windsor probe test to measure the surface hardness and hence the strength of the surface and near-surface layers of the concrete.
- Covermeter test to measure the distance of steel reinforcing bars beneath the surface of the concrete and the diameter of the reinforcing bars.
- Radiographic test to detect voids in the concrete and the position of prestressing ducts.
- Ultrasonic pulse velocity test mainly to measure the time travel of ultrasonic pulse passing through the concrete and hence concrete quality.
- Sonic Methods which use an instrumented hammer providing both sonic echo and transmission methods, to predict the integrity of piles and bridge decks.
- Tomographic modelling which uses the data from ultrasonic transmission tests in two or more directions to detect voids in concrete.
- Impact echo testing to detect voids, delamination and other anomalies in concrete.
- Ground penetrating radar or impulse radar testing to detect the position of reinforcing bars or stressing ducts.
- Infrared thermography to detect voids, delamination and other anomalies on concrete and also to detect water entry points to buildings.
The details of these tests may be found in ACI 228.1R-03 manual.