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to cracking. Corrosion may also reduce the Steel elongation at maximum load, affectingfsubseąuentiy the structure ducfility On the other hand, the composite gction of concrete and Steel in reinforced concrete structure is based on the bond between them, and this is also affected by corrosion through several mechanisms:

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k t ęof    a) increasing of hoop stresses due to pressure of rust, producing concrete cracking,

b)    change of properties of the interface concrete-steel,

c)    the corrosion of stirrups.

STEEL    CONCRETE

Figurę 6. Conseąuences of the corrosion in the structural performance.

Accordingly, reduction of structural capacity of reinforced concrete ełements affected by rebar corrosion is mainly due to the following three phenomena, which are direct conseąuence of corrosion:

-    reduction of rebar section

-    reduction of bond strength

-    loss of concrete integrity due to cover cracking.

7. Gravimetric Techniąue (Weight Loss Method)

This techniąue is a destructive method which consists of weighing the specimen bars before and afiter being introduced in the concrete that is to be tested. The difference in weight (gravimetric loss) is a quantitative average of the attack. The average corrosion ratę may be obtained as folio ws:

CR = WL * &,

& = 365/1000*D WL -W/ (A *T)

where CR is corrosion ratę [mm/year],

WL is the mass loss [g/m²*day],

W is the mass difference [g],

D is the density ofthe corroding metal [g/crrf ],

A is the surface area [m²]

T is the exposure time [day].

No instantaneous corrosion rates can be measured by this techniąue, but only a main during the period of test Obviousły, the gravimetric method is the most accurate method to ąuantify corrosion attack in laboratory experiments. Although this method is very time-consuming and only applicable to the laboratory studies, it is a useful tool to check the accuracy of the electrochemical techniąues that are able to measure the corrosion ratę quantitatively, such as the Linear Polarization and AC Impedance techniąues.