Service Life Projection for Chloride-Exposed Concrete Reinforced with Black and Corrosion-Resistant Bars

Abstract

Corrosion-induced deterioration of reinforced concrete is a pervasive problem internationally. In response to this, an equation has been derived whereby the fraction of electrochemically independent reinforced concrete elements within which corrosion-caused damage has resulted after a given exposure time is calculated. The approach considers that all relevant variables conform to some distribution rather than being discrete, as is now known to be the case. These variables are (1) surface Cl− concentration, (2) the effective Cl− diffusion coefficient, (3) concrete cover, and (4) the critical Cl− concentration threshold to initiate corrosion. Upon inputting (1) distribution parameters for the above variables, (2) the critical reinforcement corrosion loss to cause concrete damage, and (3) the average corrosion rate over the exposure period and numerically integrating, the fraction of elements that has experienced cracking/delamination after the selected time was determined. Upon repeating the calculation for incremental times, a cumulative distribution function plot for the occurrence of (1) corrosion initiation and (2) cracking/delamination was constructed. Example results are provided for concrete reinforced with both black bar and select corrosion-resistant reinforcements. The approach provides an improved tool for materials selection, service life projection, and maintenance planning.