Thermal Integrity Profiler (TIP) testing was performed by means of Thermal Wire® cables and Thermal Acquisition Ports (TAPs). The TIP system, manufactured by Pile Dynamics, Inc (PDI) in association with FGE, reads concrete temperatures during curing using cables embedded in the concrete.
The Thermal Wire cables consist of temperature sensors spaced every one foot along the length of a wire. For this D-Wall panel, six Thermal Wire Cables were attached along the full length of one of the reinforcement cages prior to placement within panel. Once the cage was installed to agreed depth, a TAP box was attached to each wire, and data acquisition began prior to concrete placement.
During curing of the concrete, the hydrating cement generates heat, increasing the temperature in the shaft. Every 15 minutes, the TAP units automatically record the measured temperature at each sensor location along the length of the wire, generating a profile of temperature versus depth at each increment of time. After the concrete peak temperature has been achieved, each TAP was connected to a TIP processing unit and the data was downloaded for further interpretation in the office.
The TIP results may be evaluated for concrete quality and for location of the reinforcing cages. The overall average temperature for all Thermal Wire readings over the embedded depths can be directly related to the overall volume of concrete installed. Panel integrity may be assessed based on the average temperature measurements from each Thermal Wire at each depth increment. If the measured average temperature versus depth is consistent, the panel is considered to be uniform in shape and quality. Bulges can be identified as localised increases in average temperature, while insufficient concrete quality or section reductions can be identified as localized decreases in average temperature. Anomalies present over more than ten percent of the effective cross-sectional area are normally seen in multiple Thermal Wires at the same depth. Because soil and/or slurry pockets produce no heat, areas of soil intrusion or inclusion are indicated by lower local temperatures.
Reinforcement cage location can be estimated based on the relative temperature difference between an individual Thermal Wire and the average of all wires. Higher individual Thermal Wire temperatures indicate the wire is closer to the center of the shaft, or near a local bulge, while lower individual Thermal Wire temperatures indicate the wire is closer to the soil-pile interface, or a local defect. By viewing diametrically opposite Thermal Wires, instances where a lateral shift of the reinforcing cage has occurred can be determined, if one wire temperature is higher than average and the diametrically opposite wire temperature is lower than average.