Early age temperature distributions in reinforced concrete box girder

The analysis of bridge temperatures during the early age of concrete is a complicated problem. At early ages, cement hydration produces an internal heat, which depends mainly on the chemical composition of cement. This heat is added to the permanent and fluctuated time-dependent heat gained from or lost to the surrounding atmosphere. The effect of the daily temperature change andtheseasonal movement of the sun can leads to serious thermal movements or stresses along the span of the bridge.In this research, an experimental program was used to study the temperature distribution in concrete bridge superstructures during the early age of construction. For this aim, a full-scale experimental box-girder bridge segment was constructed in Gaziantep University. Thermocouples were installed in the slabs and the walls to monitor the temperature changes of concrete. Moreover,pyranometer and anemometer were used to record the solar radiation and wind speed, respectively. In addition, a temperature probe with solar radiation shield was installed to monitor the ambient air temperature.The results showed that concrete temperature was mainly related to the location of thermocouples. Interior thermocouples were much influenced by hydration heat, while the temperatures of the near surface thermocouples showed higher dependency on air temperature than on hydration heat. A maximum temperature gradient of approximately 25℃ was recorded between the interior and the exterior thermocouples of the south web. Keywords: air temperature, box-girder, hydration heat, temperature gradient, solar radiation