Chapter One

Stephen R. Yeomans University of New South Wales, Canberra, Australia

1.1. Introduction

Reinforced concrete is one of the most widely used modern materials of construction. It is comparatively cheap and readily available and has a range of attractive properties and characteristics that makes it suitable for a variety of building and construction applications. It is also used in a range of exposure conditions. The long-term performance of reinforced concrete is usually assessed against two main criteria, serviceability and durability. Serviceability relates to structural integrity, i.e. the ability of the element to sustain loads safely throughout its life and to perform its intended function. Durability, on the other hand, refers to the ability of the concrete to resist changes in its microstructure and properties, particularly where such changes may adversely affect the serviceability of the element. Perhaps the most obvious consequence of a lack of durability in reinforced concrete is the corrosion of the steel reinforcement, a topic that has been widely studied and reported.

Steel embedded in concrete (or cement mortar) is normally protected from corrosion due to the presence of a passive film on the surface of the metal. This film forms in the highly alkaline environment of hydrated cement, with a pH in excess of about 13 and, as long as the passive state is maintained, the steel will not corrode. To ensure long-term corrosion protection to the steel, the concrete mass must be sufficiently impermeable so as to limit the transport of species such as water, chloride