GRL Engineers recently highlighted a collection of case studies using Thermal Integrity Profiling, or TIP, for drilled shafts and other cast-in-place concrete foundations. TIP uses the heat generated as concrete cures to evaluate shaft shape and integrity. Relatively cool zones can indicate reduced section, poor-quality concrete, or soil or slurry inclusions, while warmer zones can indicate a bulge.
I have not used TIP on one of my projects yet, but I have reviewed a lot of Crosshole Sonic Logging results where debonding and other possible anomalies complicated the interpretation. CSL measures the concrete between access tubes. TIP sensors are attached to the reinforcing cage and provide temperature profiles around the shaft, which can also be used to evaluate concrete cover and cage alignment.
The Central 70 case study is a useful example because the testing program used both TIP and CSL on more than 50 drilled caissons. The thermal data were collected automatically and transmitted for review, allowing potential anomalies to be discussed within roughly 24 to 48 hours after concrete placement. CSL followed after its normal waiting period.
I don’t think the takeaway is that one method replaces the other. FHWA guidance treats integrity testing as a supplement to good construction observation and inspection, not the sole basis for accepting a foundation element. But where the results are complicated, having two different views of the concrete can be valuable.
Read GRL’s Central 70 case study
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