COMPARISON OF TEMPERATURE RISE PREDICTION METHODS WITH MEASURED TEMPERATURES DUE TO HYDRATION OF CEMENTITIOUS MATERIALS IN CONCRETE

The paper deals with the experimental study which was carried out to investigate the temperature rise characteristics of the concrete used in a prototype component of foundation for Interchange station of Nagpur Metro Rail Project, Nagpur, Maharashtra State. The actual temperature rise was measured by embedding Thermo Couples – Resistance temperature detector (RTD) in the prototype structure during concreting. The measurements were taken at 5 locations in the component – a pile cap by inserting thermo couples (TC’s) in 3 layers at each location totaling to 15 in all. The monitoring of temperature recorded by thermocouples was done by digital recorder manually on hourly basis up to 13 days and then once in 3 hrs. up to next 21 days and beyond but restricted to 14 days in this reporting. The temperature at the time of insertion i.e. initial/starting temperature was noted and maximum temperature reached, the time to reach peak temperatures was recorded. The plot of time-temperature demonstrated the actual temperature rise, its trend both increasing and decreasing wherein all the thermal effects in and on the concrete such as effects of exothermic reaction of hydration of cement, conduction, convection and thermal properties of concrete such as specific heat, thermal conductivity, diffusivity and so also the external factors such as ambient temperature, humidity, wind speed, solar radiation, curing and form removal have played their role and the resultant was the actual temperature reached at that point where the measurements have been recorded by embedded TC’s. The comparison of the actual measured temperatures made with the various methods available to predict maximum concrete temperatures by empirical formulas such as PCA method, adiabatic temperature rise curves as published in ACI committee reports and ASCE method showed that the actual measured temperatures vary on plus as well as minus side over predicted.