Effect of the Type of Concrete with Mineral Additions on the Reinforcement Corrosion Induced by Chlorides - Analysis in the Same Mechanical Strength Class

Abstract

The environment in which the concrete structure is inserted has a great influence on its durability and its service life. Thus, the present work aims to study of the performance of 5 types of concretes of same compressive strength (35 MPa at the age of 28 days) and considers kinetic and thermodynamic aspects of the corrosion induced by chlorides. The 5 types of concretes studied were produced with the use of mineral additions in partial replacement on cement mass (10% of silica fume, 30% of fly ash and 20% of metakaolin), besides the control situation (without mineral addition). The water-to-cementitious materials ratio was different for the concretes ranging from 0.30 to 0.55. Specifically, for the concrete with fly ash, two water/binder ratios were studied (0.30 and 0.40) with the goal of verifying if there are or not significant differences on properties of corrosion with little change of water quantity in the mix. The chloride attack consisted by 308 days (44 weekly cycles) in immersion in aggressive solution rich in chlorides and subsequent drying in a laboratory environment. During this period, the corrosion potentials ($E_{c}orr$) and corrosion rate ($i_{c}orr$) from polarization resistance ($R_{p}$) of steel bars were monitored. As a general result, it was possible to compare the performance of concretes at the same class of compressive strength to denote which systems have the longest durability in view of attack by chloride. The results have shown that the concretes produced with mineral additions did not show steel bar corrosion, thus configuring major service life for them. Control concrete presented depassivation of reinforcing steel, $E_{c}orr$ more electronegative and higher $i_{c}orr$ over time.

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