Abstract
Knowledge of the behavior of concrete at high temperature and its residual performance is of great interest for the safety evaluation of civil engineering structures. Several studies have investigated the behavior of concrete at high temperatures but few researches have focused on the residual behavior of concrete. The latter has been studied experimentally on Tunisian concretes formulated with the aggregates of the quarries of Djebel Ressas and Borj Hfaiedh. Thermogravimetric (TGA) and differential thermal (DTA) analyzes allowed the determination of different physicochemical processes occurring within the cement paste. The rate of rise in temperature is chosen according to the RILEM recommendations (0.50 degrees C/min). This rate showed the presence of chemical kinetics. Four temperature steps (corresponding to the temperature peaks obtained during the ATG/ATD tests) were applied, with three different durations (4, 8 and 24 hours), to study the effect of duration of heating on the properties of the concrete. These heating-cooling cycles allowed the study of mechanical (residual compressive strength) and physical (loss of residual mass) properties on cylindrical specimens (100 x 300 mm). Compression tests have shown that the various properties of the concrete mentioned above decrease as a function of temperature.