Title: Service Life Model for Concrete Structures in Chloride Laden Environments

Author(s): Richard E. Weyers

Publication: Materials Journal

Volume: 95

Issue: 4

Appears on pages(s): 445-453

Keywords: chloride; concrete bridges; corrosion; corrosion rate; diffusion; service life; time-to-cracking;

DOI: 10.14359/387

Date: 7/1/1998

Abstract:
Bridges are a major element in ground transportation networks. Of the present 70 billion dollar backlog of bridge rehabilitation needs, 28 billion dollars is attributed to the corrosion of steel in concrete. The chloride corrosion of steel in concrete structures is not confined to bridges; but also reduces the service life of parking garages and sea and coastal structures. The service life model for reinforced concrete structures in chloride laden environments consists of the following serial phases: diffusion to the depth of the steel that would precipitate first maintenance actions; corrosion of the steel at the first maintenance depth until cracking and spalling occurs; continuation of spalling until a damage level is reached that is defined as the end-of-functional service life for an element or structure. The diffusion phase is described by Fick's Law and the boundary conditions define the solution form. The time-to-cracking model is dependent upon factors as concrete strength properties, cover depth, and corrosion rate. Corrosion rate has a significant influence on the time-to-cracking that typically occurs in three to seven years after initiation.