Effect of mineral additions incorporated in concrete on thermodynamic and kinetic parameters of chloride-induced reinforcement corrosion

Abstract

In this article, the beneficial effects of pozzolanic mineral additions incorporated in concrete under the attack of chlorides are evaluated. Three different mineral additions incorporated in binary combinations with Portland cement (silica fume, metakaolin and fly ash) were studied. By monitoring and analyzing thermodynamic and kinetic parameters, the corrosion performances of reinforced test specimens were evaluated over an extended period of chloride attack (44 weekly cycles of wetting in a solution of NaCl and air drying, equivalent to 308 days of attack). The electrochemical techniques (Ecorr, Rp and EIS)1Electrical resistivity (ER), corrosion potential (Ecorr), polarization resistance (Rp), electrochemical impedance spectroscopy (EIS), corrosion rate (icorr), control concrete (C), concrete with silica fume (SF), concrete with fly ash (FA), concrete with metakaolin (MK).1, added to the electrical resistivity technique (ER), are allowed to evaluate the protection capacity of the concretes under study, in relation to this strong attack on the reinforcement. They also allowed the production of subsidies capable of generating scientific discussion about the mechanisms of protection, imparted to concrete by mineral additions, in this specific aggressive medium rich in chlorides. The results showed that the used mineral additions produced significant increases in the resistivity of concretes, which is probably due to physical changes in the pore structure of cement paste, besides the improvement of paste-aggregate interface and the changes in the conductivity of pore solution. This higher resistivity certainly delayed the transport of chlorides and their attack on the reinforcement, seen by small changes in the values of Ecorr, Rp and icorr in concretes with pozzolans. The EIS results showed that there was little change in the impedance values at the steel-concrete interface in these systems with mineral additions, in spite of the strong and prolonged attack.