Análise da penetração de cloretos em concretos com adições de sílica ativa e metacaulim

Abstract

Reinforced concrete structures are susceptible to deleterious agents, especially if located in aggressive environments. Coastal regions have high concentrations of chloride ions (Cl-), a compound that initiates steel deterioration through corrosion. The ion penetration through the concrete occurs by diffusion, thus, concrete with high permeability facilitate the deleterious agent entry and, consequently, accelerate steel deterioration. Aiming structure protection from chloride ions attack, this work used pozzolanic additions (silica fume and metakaolin) to reduce concrete permeability. Three proportions were analyzed, 5/5, 3/7 and 7/3 (named S5M5, S3M7 and S7M3, respectively), in percentage of additions in relation to cement mass, totaling 10% of addition. The measurement of chloride penetration was performed according to ASTM C1202/19 and NT BUILD 492/99 methods. The X-ray diffraction test (XRD) was used to prove chloride compounds absence in concrete specimens before carrying out penetration tests. The axial compressive strength test, standardized by ABNT NBR 5739/18, evaluated the mechanical behavior of the mixtures. In order to analyze the concrete workability, the slump test (ABNT NM 67/98) was performed. The obtained results showed gains in concrete performance in terms of compressive strength and chloride penetration, but losses in workability, compared to a reference mix (without additions). The best performance was seen in the S7M3 mix, showing good results in terms of compressive strength and excellent in chloride penetration.