Impact des matériaux locaux sur la portance des bâtiments en béton arme post-incendie au Burundi

Abstract

Burundi has just recorded several cases of fires setting ablaze to reinforced concrete structures. The central market of Bujumbura is an example of unforgettable fire in the memory of Burundians. This should lead everyone to be more vigilant, to think about the different components of fires and, surely, to ask questions about the resistance of structures to fire.This research work based on an experimental approach, analyzes the impact of local materials on the thermomechanical behavior of concrete subjected to high temperature. Given that in Burundi the concretes can be either river gravel or crushed gravel from quarries, two categories of ordinary concrete (25 MPa) formulated with two gravels [river gravel (GC) and crushed gravel from quarries ( GC)] undergo heating / cooling cycles at a rate of 5 ° C / min at 250 ° C, 350 ° C, 450 ° C, 600 ° C and 900 ° C. We are studying the evolution of cracking and two main mechanical properties of these concretes (compressive strength and elastic modulus) as a function of the temperatures applied to coat the average of this evolution. The analysis proved that the local concrete manufacturing materials have properties required by the standard (granulometry and mechanical strength). Several scales of observation carried out have shown that our local materials follow the normal course of the reduction in the characteristic compressive strength of concrete defined by Euro code 2-annex 1-2. The average difference in the resistance reduction factor is estimated at 7.76% (2.75% at 450 ° C, -5.6% at 600 ° C and 26.12% at 900 ° C). The comparison of the results at different heating scales showed that the change in elasticity modulus is similar for the two concretes BO_GR and BO_GC.