The objective of this study is to evaluate the protective capacity of concretes produced with metakaolin in relation to the transportation and penetration of chlorides. Thus, from a commercial concrete of fck equal to 30 MPa, more two other concretes were produced by replacing 10% of cement by metakaolin, by weight. In one of them, it was kept the same water/binder of the initial reference mix design (w/b = 0.60), and in the other concrete the compressive strength remained fixed. In all three mixes, the same range of concrete consistency was maintained, with a slump equal to (100 + 10) mm. The front of chlorides in the cement matrix was evaluated by spraying a solution of silver nitrate, after an attack of 8 weekly cycles of wetting and drying using a solution containing chlorides. To obtain an indicative of the internal structure of the concretes, it was carried out the test of water absorption by immersion, which permitted an evaluation of the concrete open porosity, as well as it was performed the analysis of concrete samples by means of XRD and SEM. These studies aimed to verify the potential of metakaolin in fixing chlorides in the form of Friedel's salt, besides providing microstructural analysis of the concretes. It was concluded with this work that the incorporation of metakaolin decreases the diffusivity of chlorides to the extent that this mineral addition produces refinement of the concrete pore structure and also because it induces the formation of Friedel's salt, which becomes it an effective agent in preventing the corrosion of reinforcement in chloride-rich environments.
metakaolin; concrete; chlorides; Friedel's salt; durability
