Concreto reforçado com fibras de carbono submetido a ataque por ácido clorídrico

Abstract

Artificial metallic or synthetic fibers used to reinforce concrete in construction has been increasingly widespread. Durability tests have shown that fiber-reinforced concrete can present smaller variations in mass, good appearance and good mechanical strength. In this context, carbon fibers have stood out among the new generation of reinforced em entitious composites because this type of fiber has low density, low coefficient of expansion, high tensile strength, good chemical stability and excellent durability. This study aims to evaluate the mechanical resistance, microstructure and durability of special concrete with the addition of carbon fibers in specific tests and exposure to an aggressive acidic environment. In order to explain the relationship of structure and property of the new composite, images of the fibers and fractured surfaces of the concrete were evaluated by scanning electron microscopy (SEM). The addition of carbon fibers resulted in statistically significant increases in the compressive and tensile strengths of concrete and did not result in significant changes in its modulus of elasticity. The carbon fiber acts directly on the concrete cracking mechanism at the moment of rupture, restraining the formation of large cracks from microcracks and maintaining the transition zone of the coarse aggregate adhered to the matrix. The performance of this innovative composite material under exposure to aggressive environments was determined by a 7-day chloride acid (HCl(aq) 10%) attack experiment. The mechanical properties, assessed before and after the chemical attack, indicated that, both before and after an acid exposure, the concrete added with carbon fibers presented a compressive strength superior to the minimum value for concrete structures (20MPa), which was not reached by conventional concrete. The research concludes that the addition of carbon fiber waste into the concrete is positive, providing mechanical improvements and performance improvements when subjected to acid attack, when compared to conventional concrete, increasing the durability and consequently the service life of the structures.