Impact Echo is a non-destructive test system for examining and assessing concrete elements in structures. Impact Echo is used for:
- Location voids and honeycombing in concrete structures (depth of defects in elements)
- Locating delamination (at reinforcement) in concrete structures
- Determining voids in post-tensioning ducts
- Structural thickness of elements.
Infrastruct uses the Germann Instruments DOCter Impact Echo system.
Impact Echo uses a sharp mechanical impact on the concrete surface to generate stress waves that penetrates through the concrete. The stress waves travels into the concrete and are reflected from the back wall of the element or from an anomaly within the element, for example a void. The reflected stress wavesare picked up using a sensitive displacement transducer placed about 50mm from the impact point.
Impact echo is an expert system requiring a detailed knowledge of its use, the technique and knowledge of the concrete element under test.
Examples of Use:
- Locating Voids in Post-Tensioning Ducts
The team in Infrastruct were requested to non-destructively examine post-tensioned downstand concrete beams and determine the location and condition of the ducts.
We used high frequency GPR to locate the duct profile within each concrete beam and we used the DOCter Impact Echo system at small intervals to assess and record the void condition within the ducts. This was very successful at locating voids in post-tensioning ducts.
Selected duct and tendon exposures were made to confirm the findings of the DOCter Impact Echo system.
Figure 1 shows the DOCter Impact Echo system in use on the Bridge and Figure 2 shows a voided post-tensioning duct located using the DOCterImpact Echo system.
- Locating Piles under Existing Floor Slab
The team in Infrastruct were asked to determine, non-destructively, the depth of a concrete slab and to locate buried piles under the concrete slab.
We used a combination of test systemsincluding the impact echo which was particularly useful in areas of congested reinforcement. The piles were located and marked up on the concrete surface and a detailed report prepared for the Client.
Figure 3 shows the DOCter Impact Echo system in use on the floor slab to locate changes in the thickness of the floor.
