A Novel Methodology for Service Life Projection of Black and Corrosion Resistant Reinforcement Exposed to Chlorides

A Novel Methodology for Service Life Projection of Black and Corrosion Resistant Reinforcement Exposed to Chlorides

William H. Hartt

Professor Emeritus

Department of Ocean Engineering

Florida Atlantic University – SeaTech Campus

20914 Morada Court, Boca Raton, Florida, USA

(561)542-6216 (voice)

(561)883-3825 (fax)

smshwhh@bellsouth.net

ABSTRACT

        A novel approach for quantifying damage development of reinforced concrete exposed to chlorides, as occurs for pier and harbor structures, is introduced.  The methodology is based upon a first-principles based governing equation that treats all relevant variables, including 1) Cl^- diffusion coefficient, 2) Cl^- concentration ([Cl^-]) at the concrete surface, 3) concrete cover over the reinforcement (x), and 4) [Cl^-] threshold to initiate corrosion, as distributed rather than discrete, which is now known to be the case.  Consequently, the time for reinforcement corrosion initiation, T_i, time for subsequent corrosion induced concrete cracking and delamination, T_p, and, hence, total service life, T_s, are also distributed.  By inputting distribution functions for the above variables, as are now available in the literature, the evolution of corrosion related damage is projected.  The methodology is applied to both black and selected corrosion resistant reinforcements (CRR), and advantages of the latter compared to the former are quantified.  A previously undisclosed aspect of test yard type corrosion testing of CRR that causes underestimation of service life for these reinforcements is identified and explained.