Research on the influencing factors on the corrosion resistance of rebars in concrete

This paper aims to study the influence of NaNO2 contents, water-cement ratios, mineral admixtures (fly ash and fine mineral powder) on the corrosion resistance of rebars in concrete. Electrical resistance and the corrosion current were established in order to research the anti-corrosive performances of the steel reinforced concrete. In this study, the mixing dosages of NaNO2 are increased from 0% to 2.0% by mass ratio of the total mixtures. Moreover, water-cement ratio (w/c) applied in this research ranged from 0.3 to 0.5. Fly ash and slag powder ranged from 10% to 30%, meanwhile assembly unit of fly ash (10% similar to 20%) and slag powder(10% similar to 20%) were used to improve the corrosion resistance of rebars. The research results indicated that electrical resistance increased initially and then decreased with the increase of NaNO2 contents and water-cement ratios. When the dosage of NaNO2 was 1.0% and water-cement ratio was 0.4 respectively, steel reinforced concrete presented the maximum electrical resistance. Additionally, electrical resistance was increased by the addition of fly ash and slag powder. Resistances of steel reinforced concrete with assembly unit of fly ash (10% similar to 20%) and slag powder (10% similar to 20%) was higher than that with single unit of fly ash or slag powder. Moreover, the corrosion resistance coefficient (R-p) of steel reinforced concrete firstly increased and then decreased with the increase of NaNO2 content. However, the decreasing w/c and the increased amount of mineral admixtures led to an increase of R-p. Steel reinforced concrete with 30% fly ash manifested the highest R-p.