A probability model of steel corrosion in concrete

Abstract

Competition between chloride and hydroxyl ions in portland cement concrete sometimes results in corrosion of embedded steel if oxygen is available for cathodic reaction. This article describes a Monte Carlo probability model that simulates the competing corrosion and passivation reactions as functions of Cl - /OH ratio and oxygen availability. Probabilities of corrosion predicted by the model agree well with those determined by tests of bare steel rods in high-pH solutions containing oxygen bubbles. Reduced oxygen availability is predicted to increase the Cl - /OH ratio at threshold of corrosion. Threshold ratios from 0.66 to 1.4 are suggested for most reinforced concrete.