MONITORING CONCRETE TEMPERATURE DURING CONSTRUCTION OF THE CONFEDERATION BRIDGE

A short-term monitoring project on the Confederation Bridge, crossing the Northumberland Strait in Atlantic Canada, was completed to collect data on the temperatures in high performance concrete during construc tion. High temperatures in the middle of the large concrete members we re caused by cement hydration. The temperatures inside some members di d not approach ambient levels until one month after pouring. The core temperature of the large concrete members was not significantly influe nced by weather conditions or orientation. Temperature gradients exist ed between the middle of the concrete and the cooler outer surfaces. A fter the formwork was removed, the gradients suddenly increased, a phe nomenon called thermal shock. The degree of thermal shock was a functi on of weather conditions, concrete location, concrete spatial orientat ion, and the temperature difference between the concrete and the surro unding air. When new concrete was cast against hardened concrete, a la rge thermal gradient was induced across the construction joint in both the new and hardened concrete. The temperature data collected during construction will be used to calibrate a finite element model that wil l predict three-dimensional heat flow in concrete, and cracking due to the heat of hydration and varying ambient and boundary conditions.