Nine cubic yards of wet concrete will release the energy equivalent of 400 lb of TNT as it cures. Researchers at the University of South Florida are now partnering with industry to deliver a new device and software to monitor the heat distribution in curing cast-in-place concrete foundations, such as drilled shafts and bored piles, as a new quality-assurance tool.
The method, called Thermal Integrity Profiling (TIP), is the product of 15 years of research and recently has been taken to market by Pile Dynamics Inc. The Cleveland-based firm recently released a field-ready testing device that is cheap enough for mass distribution. The Florida Dept. of Transportation tested it during construction of the Judge S.S. Jolley bridge, Marco Island, Fla., and gave it glowing reviews.
“We’ve been impressed with the method,” says Larry Jones, geotechnical engineer for FDOT, “largely because it gives us the ability to evaluate a portion of the shaft inside the drill-shaft cage and outside as well.”
The device measures and infers the absence of intact concrete by noting cool regions—necks or inclusions—in its thermal mapping readout. The presence of additional concrete is registered by warm regions—over-pour bulging into soft-soil strata or voids—says Gray Mullins, a USF professor who helped develop the software. Anomalies both inside and outside the reinforcing cage disrupt the normal temperature signature for the entire shaft.
The TIP system can be set up in two ways. One method runs a thermal probe through standard tubes installed in the rebar cage before the pour—the same tubes used for probe tests. The other technique features thermal wiring installed in the rebar cage and embedded in the pile. Data is transmitted to the surface continuously as the concrete cools.