Estudo das propriedades de concretos com adição de fibras vegetais e de polipropileno para uso em paredes estruturais

Abstract

The properties of concrete with and without addition of fibers was studied in this research. Different vegetal fiber contents (sisal and ramie) and polypropylene fiber were used. With the current need for nature preservation, there is a search by reducing the use of materials responsible for major environmental impacts, both in manufacturing, use and disposal. In this way, was done a performance comparison between concrete with addition of vegetal fibers and synthetic fibers, to propose a possible replacement, was done. Vegetal fibers are studied in cementitious composites but are not usually incorporated in the practice. Synthetic fibers, specifically the polypropylene fiber, are already used by construction companies to reduce cracks in the walls. For the tests performed, was evaluated the shrinkage under restrained conditions by ring test, the mechanical properties (compressive strength, tension strength by diametrical compression and static modulus of elasticity) and physical properties (density, voids, immersion and capillary absorption). The contents used were 0.25% and 0.5% for the vegetable fibers and for the polypropylene fiber only the content of 0.25%, because the 0.5% content of this fiber showed extremely low workability. In relation to the restricted retraction, it was observed that the addition of 0.25% of fibers did not result in an increase in performance compared to concrete without fiber addition, but the addition of 0.5% of vegetal fibers showed satisfactory results, being superior to the reference concrete. It was verified that the mechanical properties of the concrete with fiber addition, generally lower than the reference concrete (without addition of fibers), did not undergo major changes, except for concrete with the highest rami content, which did not present adequate dispersion, presented much lower results. On the other hand, the physical properties presented greater variations, mainly in the type of fiber used, the concrete with 0.25% ramie content presented the highest absorption and voids, among all the concretes studied. In relation to the absorption by capillarity the concretes with addition of the vegetal fibers demonstrated better performance, that is, reduction of absorption by capillarity. Thus, it is concluded that polypropylene fiber substitution by vegetal fibers, especially sisal, is possible due to the proximity of the results found, but more studies must be carried out to prove the efficiency of the two types of fibers used.