cathodic protection of steel in concrete pdf

Even after the publicity surrounding the large number of structures exhibiting
acute signs of distress 25 or so years into a designed 120-year life-span, there is still a
body of engineers who believe that all that is required to achieve any specified design
life in a hostile environment is to provide a higher concrete grade with the same
design and maintenance of the structure. This contention does not correspond with
the facts and means that publications such as this book will not only be dealing with
civil engineering miscalculations of the past but also those perpetrated in the future.

The traditional use of cathodic protection has been to prevent corrosion of steel
objects in the ground or water and this is still its most common application. It is now
almost universally adopted on ships, oil rigs and oil and gas pipelines. Over the last 50
years cathodic protection has advanced from being a black art to something
approaching a science for these applications.

Over the past 30 or so years there has been a steady increase in the use of cathodic protection for the rehabilitation of reinforced concrete structures which are exhibiting signs of distress. The most common damage mechanism is chloride-induced corrosion of the steel reinforcement and this is normally what cathodic protection systems are intended to stop. Initially the cathodic protection techniques for reinforced concrete followed the practice of ‘traditional’ impressed current systems
closely but, particularly over the past decade or so, there have been significant developments which have allowed the protection of concrete structures to become a legitimate and yet distinctly different part of the cathodic protection mainstream with its own protection criteria, anode types and even power supplies.

The object of this volume is to be an introduction to the current state of the art in
cathodic protection of concrete and outline other related electrochemical techniques
for stopping corrosion of steel reinforcement. Some guidelines on what cathodic
protection is, and how and when to use it, are also discussed in order that a practising
civil engineer or owner should have an introduction into the murky world of the
cathodic protection of reinforced concrete.