TEMPERATURE CALCULATIONS DURING HARDENING

To evaluate the risk of thermal cracking in concrete or to decide when formwork can be removed, it is useful to be able to determine early-age heat development and heat loss. This article discusses a commercially-available, finite element program that can predict early-age heat development in a concrete member as well as the member's maturity. The program is used to define a cross section for a member and to solve the heat equation in the plane of the defined section. The temperature calculation performed by the program can include consideration of the initial temperature of the fresh concrete, the casting rate, the heat of hydration of the concrete, ambient wind and temperature effects, the type of formwork, the type of insulation, the time of stripping and the use of cooling pipes, heating wires and heating mats. Calculations convert the time and temperature history to an equivalent time, applying the maturity concept based on the Arrhenius equation. To demonstrate the program, a case study is presented for a concrete bridge deck constructed under cold weather conditions using two different concrete mixtures.