Comparing thermal integrity test data with as-built conditions-Paper

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The paper compares thermistor-based thermal integrity test data with the as-built conditions of diaphragm wall panels used to construct two deep shafts in London. Thermal testing offers rapid results during construction and avoids instrumentation inside reinforcement cages, but temperature variations can be misinterpreted if assessed without design and construction information.<br /><br />The study found that temperature profiles reflect not only concrete-section changes but also construction details and heat loss. Secondary panels had higher average peak temperatures than primary panels, partly because they bordered previously cast concrete. Temporary steel formwork caused lower temperatures near the tops of primary panels by dissipating heat. Couplers were associated with small local temperature reductions, while a section lacking aggregate showed an increased temperature, likely due to its higher cement content. A panel with reinforcement-cage movement and reduced cover showed lower temperatures on one face. Lower temperatures at panel toes may reflect normal heat loss, but can also indicate debris, poor base cleaning, or mixing of bentonite and concrete.<br /><br />The authors recommend reviewing thermal results alongside reinforcement details, ground conditions, construction methodology, and accurate concreting records. Reports should provide temperature-versus-depth graphs, flag changes exceeding 5°C, deliver preliminary results within 24 hours of peak temperature, and issue a full report within seven days of construction completion. Time-lapse profiles and downloadable data should also be available. Construction records—including concrete volumes and levels, tremie-pipe movements, bentonite properties, excavation timing, and overbreak—help investigate anomalies and improve subsequent work. A consistent reporting approach and review of both tested and untested elements can strengthen quality assurance.

Keywords

diaphragm wall

thermal integrity testing

thermistor data

deep shafts

London construction

concrete temperature profile

reinforcement cage

construction quality assurance

temperature anomalies

thermal testing report