Inhibition and compressive-strength performance of Na2Cr2O7 and C10H14N2Na2O8•2H2O in steel-reinforced concrete in corrosive environments

This paper studied corrosion-inhibition and compressive-strength performances of Na2Cr2O7 (sodium dichromate) and C10H14N2Na2O8 center dot 2H(2)O (ethylenediaminetetraacetic disodium salt: EDTA-Na-2) admixtures in steel-reinforced concrete immersed in NaCl and in H2SO4 corrosive environments. Electrochemical methods were used for studying corrosion responses of different concentrations of the individual admixtures and their synergies, in the model that partially replace the toxic Na2Cr2O7 by the environmentally-friendly C10H14N2Na2O8 center dot 2H(2)O, in steel-reinforced concretes. After the electrochemical experiment, the steel-reinforced concrete samples were subjected to the compressive-strength testing and analyses of ASTM C39/C39M-03 and ASTM C267-01(2012). Results showed that the use of environmentally-friendly EDTA-Na-2 for partially replacing toxic Na2Cr2O7 chemical exhibited better corrosion-inhibition and compressive-strength improvement in the NaCl-immersed concretes, than in the H2SO4-immersed concretes. The 2 g Na2Cr2O7 + 6 g EDTA-Na-2 admixture (representing partial replacement model of 6 g Na2Cr2O7 by 6 g EDTA-Na-2) exhibited optimal corrosion inhibition efficiency (eta = 99.0%) and very good compressive-strength improvement advantage in the NaCl-immersed concretes. In contrast, comparatively low compressive-strength reduction trade-off with the good inhibition effectiveness of eta = 79.9% support use of 6 g EDTA-Na-2 admixture only (i.e., without Na2Cr2O7 addition) for inhibiting reinforcing-steel corrosion in the H2SO4-immersed concretes.