Avaliação da resistência à corrosão de barras de aço galvanizados em grampos para obras de contenção

Abstract

The soil nail in recent years has been increasingly used in slope stabilization and excavation works. Until the beginning of 2020 there was no Brazilian standard for the design and execution of stapled soil structures. There were also no technical recommendations in relation to the injection material (cement paste) or the bar to be used and its respective durability, it was common agreement to use manuals or international standards. The durability of a structure is determined by several factors and when this structure involves metallic components, one of the main ones is corrosion. For this reason, the steel bars currently used in the market have a galvanizing layer, and, in addition to the galvanic protection, the second protection layer is made by cement paste, which needs to be fluid for better injection execution, which ends up by raising the water/cement ratio (w/c) of the mixture. Thus, in this work, ways to mitigate the intrinsic characteristics of the pastes that could somehow accelerate the corrosion process were studied. Fresh, hardened and electrochemical tests were carried out on two pastes with similar fluidity, but with different w/c ratios (0.50 and 0.35) with different types of cure and exposed or not to an aggressive environment with the presence of chlorides. Thus, it was possible to see that the pastes with w/c 0.35 presented more satisfactory results for porosity, less absorption and cracking and greater strength than the pastes with w/c 0.50. When the pulps were compared in relation to chloride penetration, an average penetration rate was seven times higher for the pulp with a relation w/c 0.50, compared to the pulp with a relation w/c 0.35 and additive.