Estudio de aditivos inhibidores de corrosión para estructuras de hormigón armado. Análisis cualitativo y cuantitativo de penetración de cloruros

The study of systems or substances that prevent the steel corrosion are of great importance in structures exposed to marine environments that suffer corrosion of steel in reinforced concrete, since the repair costs exceed significantly the prevention systems. Calcium nitrite and microsilica were studied in this research as inhibitor of steel corrosion additives for concrete. The specimens were prepared with Pozzolanic Portland cement, w/c 0,55, A44 - 28H steel 8 mm diameter, 15 cm long, leaving 3,5 cm externally to monitor corrosion potential. The cubic specimens of 15 cm diameter each were previously contaminated in an accelerated system with dissolution of sodium chloride in cycles of semi-immersion and dried. Chloride ions penetration analyses were performed qualitatively after cutting cubic specimens in halves, spraying the interior surface with two dissolutions: silver nitrate and potassium chromate. The results of chlorides penetration were recorded photographically. On the other hand, the results of quantitative analyses of chloride ions were compared with qualitative analyses results. It was deduced that the possibility of using qualitative analysis in real structures to obtain a preliminary diagnosis of the presence of chloride ions in the concrete exists. Measurements of corrosion potential registered demonstrated that calcium nitrite was more effective additive as corrosion inhibitor, when compared to microsilica. Even though microsilica minimizes the size of concrete pore it does not avoid the chloride ions diffusion into the steel evidenced in potential values. For calcium nitrite potential values were maintained in steel passivity range, while microsilica values were similar to those of concrete without additives. This condition it is maintained after three year old of the specimens.