Corrosion resistance behavior of enhanced passivation Cr-modified rebars and their service life prediction based on Monte Carlo simulation

Abstract

This work investigates enhanced passivation and corrosion resistance of various Cr-modified rebars compared to carbon rebar. It also evaluates their service life through time-varying probability analysis based on Monte Carlo simulation, combined with the parameters obtained from sampling and testing reinforced concrete mortar samples exposed to various marine conditions over 5 years. The results show that the free energy required for oxide thickening of rebar decreases from 20.12 kJ/mol to 9.25 kJ/mol as the Cr content increases from 5 % to 11 % (wt.), which facilitates the developed Cr-modified rebars rapidly form a passive film, exhibiting a chloride threshold level 6–14 times higher than that of carbon rebar. In the harshest marine splash zone, sea sand concrete with Cr11 rebar ensures a theoretical 50-year service life, contrasting sharply with the much shorter lifespan estimated at 5–6 years for carbon rebar. The corrosion rate of Cr-modified rebars was notably lower than that of the carbon rebar, and the Cr oxides/hydroxides facilitate the transformation of FeO(OH) with larger volume expansion to Fe3O4 with smaller volume expansion, reducing from 130 μm in HRB to 70 μm in the case of the thinnest Cr11 rebar. The thin and dense rust layer of the developed rebars is advantageous in blocking Cl- and guarantees a smaller volume expansion of structure even if the rebars are corroded. This study underscores the suitability of Cr-modified rebars for sea sand concrete structures and sheds new light on rebar-reinforced concrete structure developments toward eco-efficient and sustainable infrastructures.