Comportement physico-mécanique et durabilité du béton fibré.

Abstract

The phenomenon of fire in buildings can cause significant damage to concrete structural elements, for this the safety of users, the stability of structures depends on the thermal stability as well as the mechanical properties of concrete. Damage to concrete can be observed as a result of fires in buildings and tunnels.Various research works in the field have shed light on the phenomena observed on the behaviour of concrete subjected to high temperatures. The objective of the present manuscript is to describe the impact of polypropylene fibers on the behaviour of heated concrete subjected to heating and cooling cycles at temperatures of 200°C, 450°C and 600°C respectively for six hours, through a series of experimental tests on mass loss, water absorption, porosity, compressive and tensile strength. For this purpose, mixtures were prepared with a water/cement ratio with the incorporation of polypropylene fibers at a rate varying from 0.5% to 1.5%. These fibers were added to improve the thermal stability and to prevent the concrete from cracking. The results show that a considerable loss of strength was observed for all specimens tested. The relative compressive strengths of the concretes containing polypropylene fibers were higher than those of the concretes without fibers. Similarly, a greater loss of mass of the polypropylene fibers compared to the concrete without fibers was observed when the temperature was increased. The flexural tensile strength of the concrete was more sensitive to elevated temperatures than the compressive strength and a rapid increase in porosity was observed for the fiber-reinforced concrete compared to the reference concrete. Furthermore, the water absorption by the fibers is proportional to the fiber content of the concrete