Author(s): C. Andrade
on of steel reinforcement
Institute of Construction Science ‘Eduardo Torroja’, CSIC,
1 Principles of corrosion
Concrete is the most widely used construction material in the world.
Many kinds of
materials, elements and structures are fabricated with cement-based mixes.
concrete was industrially developed at the beginning of the 20th century,
and it has stimulated tremendous developments in housing and infrastructures.
Reinforced and prestressed concrete represents a very successful combination
of materials, not only from a mechanical point of view but also from a chemical
perspective, because the hydrated cement is able to provide to the steel an excellent
protection against corrosion.
This chemical compatibility allows for the composite
behaviour of reinforced concrete and is the basis of its high durability.
The composite action occurring in the steel–concrete bond may be unlimited
in time while steel remains passive.
The study of the conditions leading to reinforcement
corrosion is then of high importance because corrosion may significantly
affect the load-bearing capacity of reinforced or prestressed concrete.
The natural state of metals is their oxidized state.
Metals can be found in nature
in the form of oxides, carbonates, sulphates, etc.
In a pure state only
the so-called ‘noble’ metals can persist in contact with the environment without
For the practical use of a metal, a certain energy is invested
in its reduction from the natural mineral state.
The metal then presents the tendency
to liberate this energy to attain its lower energy state.
The process by which a
metal returns to its mineral state is known as ‘corrosion’.
Corrosion is therefore the
process by which the metal passes from its metallic state at ‘zero’ valence to its
oxidized state liberating electrons.
For iron it can be simply written as:
Fe → Fe2+ + 2e−
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Paper DOI: 10.2495/978-1-84564-032-3/06
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