Comparaison des résistances mécaniques des bétons renforcés de fibres synthétiques et de fibres naturelles soumis à des agressions chimiques.

Abstract

Concrete structures are often exposed to aggressive environments because of the air pollution to which they are exposed or that of the land on which they are built. Such pollution can be natural, such as construction on gypsum soils, or industrial, such as the release of chemicals into the atmosphere or into rivers and land, as is the case with sulphates, which can cause concrete structures to expand, crack and ruin. Different fibers have been incorporated into concrete to improve its mechanical performance and thus give it greater durability. In recent years, researchers and industrialists have shown renewed interest in the use of natural fibers, particularly those of plant origin, for the reinforcement of concrete because of their economic, social and environmental advantages. The aim of this work is to study the mechanical behavior of concrete reinforced with plant fibers, in this case alfa and hemp fibers, in the face of external sulphate attacks. We have formulated and manufactured test specimens of different types of concrete reinforced with alfa and hemp fibers with different amount, comparing them with two control concretes, one ordinary and the other reinforced with polypropylene fibers. In order to evaluate the effect of external sulphate attacks, all the concretes were subjected to two ageing protocols: 1) complete immersion in two different sulphate solutions dosed at 12.5% sulphate, 2) an accelerated ageing protocol in the form of immersion/drying at 60°C in the same sulphate solutions. Two sulphates were used, sodium sulphates (Na2SO4) and magnesium sulphates (Mg2SO4). The different tests used showed that concretes reinforced with 1% alfa fibers and those reinforced with 0.25% hemp fibers have shown results similar to those of ordinary concrete and polypropylene..