TRANSACTIONS OF THE JAPANESE SOCIETY OF IRRIGATION, DRAINAGE AND RECLAMATION ENGINEERING, Volume 183, Page 31-39 (1996)

Proposal of Empirical Equation for Adiabatic Temperature Rise in Concrete in the Case of Low Ambient Temperature

Takefumi NAKAZONO*, Masato KUNITAKE** Hidehiko OGATA*, Takao NAKAZAWA*** and Tadayosi KIKUMURA****

* United Graduated School of Agricultural Sciences, Kagoshima University
** Faculty of Agriculture, Miyazaki University
*** Faculty of Engineering, Miyazaki University
**** Ready-Mixed Concrete Association of Miyazaki

Abstract

　In order to predict and control thermal cracks in concrete structures, it is necessary to understand the hysteresis of temperatures calculated from the precise adiabatic temperature rise curve. Therefore, temperatures at the center points of concrete specimens placed and cured in the laboratory were measured at constant temperature and humidity. The constants of the adiabatic temperature rise curve were determined by back-analysis using the measured temperatures, and analysis of heat conduction using these constants was carried out by the three-dimensional finite element method. For an ambient temperature of 30℃, the estimated temperatures fitted well, but for an ambient temperature of 5℃, a considerable difference between the measured and calculated temperatures was demonstrated as the temperature rose. Furthermore, for an ambient temperature of 5℃, analysis of heat conduction was performed, taking into account the effects of the thermal conductivity of concrete and the convection heat transfer coefficient, but the calculated temperatures did not agree well with the measured ones. Therefore, an adiabatic temperature rise curve for a low ambient temperature, to which the function form of the autocatalytic equation could be applied, was adopted, and analysis of heat conduction was carried out using this new empirical equation. It was found that the temperatures calculated using the new empirical equation approximated the measured ones. Since the hysteresis of the calculated and measured temperatures after the peak point expected to generate thermal cracks showed particularly good agreement, it was possible to apply the new empirical equation for predicting interior concrete temperatures at low ambient temperature.