A CASE STUDY ON MEASUREMENT OF TEMPERATURE RISE IN CONCRETE AND ASSESSMENT OF PROBABILITY OF CRACKING DUE TO HEAT OF HYDRATION

Abstract

Experimental study 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 3 thermo couples (TC’s) 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. The derived temperature rise equations with strong correlation coefficient “r” values could be used to predict the early age temperature rise in structures with similar geometry, concrete, weather conditions, curing and form removal. Another purpose of this study is to know the probability of cracking based on the existing cracking assessment based on Korean methods as Indian specifications are non-existent and also to find the crack index for internally restraint cases based on temperature difference, both the elastic; hypoelastic models. The study indicated that the existing provisions based on crack index appear to be very conservative which tend to overestimate the probability of crack occurrence compared with construction observations on prototype structures.