Bond after fire

Abstract

Bond between concrete and reinforcement is investigated in this project after a thermal cycle at high temperature to measure bond residual properties. Six mixes were prepared with either quartzitic gravel or expanded-clay aggregates, and two types of fibers were adopted as well. Cubes were cast to measure the residual compressive strength of the various mixes and specimens reinforced with a single bar were prepared, to study the residual bond properties. The results show that the higher the maximum temperature attained during the thermal cycle, the greater the decrease of both the compressive and bond strength. The latter, however, is more affected by the temperature than the former. A relationship was also found between the decreasing bond strength and the decreasing compressive strength in residual conditions. This relationship was instrumental in modelling bond behavior in order to describe its response in terms of applied pull-out load versus bar slip (at the unloaded end of the bonded bar), and to make comparisons with the experimental results.