Civil Engineering Reference
In-Depth Information
Introduction
1.1 BACKGROUND
Plain concrete is strong in compression, but weak in tension. For this reason,
it was originally used for simple, massive structures, such as foundations,
bridge piers, and heavy walls. Over the second half of the nineteenth
century, designers and builders developed the technique of embedding steel
bars into concrete members in order to provide additional capacity to resist
tensile stresses. This pioneering effort has resulted in what we now call
reinforced concrete (RC).
Until a few decades ago, steel bars were practically the only option for
reinforcement of concrete structures. The combination of steel bars and
concrete is mutually beneficial. Steel bars provide the capacity to resist ten-
sile stresses. Concrete resists compression well and provides a high degree
of protection to the reinforcing steel against corrosion as a result of its
alkalinity.
Combinations of chlorides (depassivation of steel) and CO
2
(carbon-
ation of concrete) in presence of moisture produce corrosion of the steel
reinforcement. This phenomenon causes the deterioration of the concrete
and, ultimately, the loss of the usability of the structure [1]. Over the
second half of the 1900s, the deterioration of several RC structures due
to the chloride-ion induced corrosion of the internal steel reinforcement
became a major concern. Various solutions were investigated for applica-
tions in aggressive corrosion environments [2]. These included galvanized
coatings, electrostatic spray fusion-bonded (powder resin) coatings, and
polymer-impregnated concrete epoxy coatings. Eventually, iber-reinforced
polymer (FRP) reinforcing bars were considered as an alternative to steel
bars [3,4].
The FRP reinforcing bar became a commercially available viable solution
as internal reinforcement for concrete structures in the late 1980s, when
the market demand for electromagnetic-transparent (therefore nonferrous)
reinforcing bars increased.
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