Concret Damage Due to Corrosion
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Transcript of Concret Damage Due to Corrosion
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UNIVERSITY OF GAZIANTEP FACULTY OF ENGINEERING CIVIL DEPARTMENT
CE-547
Corrosion of Plain &Reinforced concrete
Report # 3:
(Concrete damage due to corrosion of
reinforcement )
Submitted to:
Do.Dr. Mehmet GESOLU
Prepared by:
Chalak Ahmed Mohammed [email protected]
2014 45056
Date : 17.03. 2015
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Corrosion of reinforcing steel is a major deterioration process affecting
reinforced concrete structures worldwide. Corrosion causes cracking and
spalling of the concrete cover, loss of load bearing capacity and ultimately
structural collapse.
Fig.(1)
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Cracking of the cover is often a critical limit state and this can be modelled as a two-stage process consisting of an initiation phase, defined as
the time taken for corrosion to commence, and a propagation phase, where
the formation of corrosion products induces expansive stresses and damage.
Until recently, most research has focused on the time up to corrosion
initiation, while the propagation phase leading to failure remains poorly
understood. One important aspect that lacks understanding is the amount of
corrosion products that must form to cause damage. It is likely that not all
corrosion products contribute to cracking because some are soluble species
that dissolve in the pore solution and migrate into adjacent cement paste
away from the sites of corrosion.
Fig.(2)
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Observations
Corrosion products can migrate through the aggregate-paste interface as
well as the bulk paste. They can be deposited in cracks, air voids, inner &
outer hydration products, and relicts of reacted slag. A distinct boundary
between the affected and unaffected paste can be seen, indicating the extent
of the rust penetration (Fig 3).
Fig 3: BSE
montage of samples with different degrees of corrosion, showing rust accumulating at the steel-
concrete interface and migrating into the cement paste, cracks and air voids
EDX microanalyses show that the affected paste has higher analysis totals,
and Fe and O contents, but is depleted in Ca (Fig 4
Subsequent corrosion products are forced to accumulate at the steel-
concrete interface, inducing expansive pressure that leads to bond failure
and cracking.
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Fig 4: BSE
images and EDX element maps indicating the extent of rust penetration and decalcification.
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Image analysis found that only a small amount of corrosion product,
approximately 100m thick covering about 20% of the rebar perimeter, is
needed to generate the first visible cover crack (~0.05mm width). Once
cracking has initiated, the rust preferentially deposits in large cracks rather
than pore spaces in the cement paste. Hence, the extent of rust penetration into the cement paste does not increase much with corrosion (Fig 5b).
Fig 5: Effect of corrosion degree on the amount of damage and area of the rust layer (CL) and rust
penetrated paste (RP).
Regards...