ing bar. The second period encompasses the time in which
the stress builds-up, Tstress, as corrosion products, having
filled the porous zone, exert an expansive pressure on the
surrounding concrete. The model assumes that this pressure increases linearly as the volume of corrosion products
increases until the internal tensile stresses exceed the tensile
Nomenclature
a internal radius of the cylinder
as surface area of the steel reinforcing bar
b exterior radius of the cylinder
Ab original cross-sectional area of the steel reinforcing bar
C clear concrete cover (mm)
D diameter of steel reinforcing bar (mm)
Ec elastic modulus of concrete
Eef effective elastic modulus of concrete
f
0
c
compressive strength of concrete
f
ct tensile strength of concrete
F Faraday’s constant
i
cor corrosion rate
i current density
I current (A)
k hole flexibility
M atomic mass of metal
P internal radial pressure
Pcor internal radial pressure caused by corrosion
Pcr
internal radial pressure that causes cracking of
concrete
T time
Tcr time from corrosion initiation to corrosion
cracking
Tfree time required for corrosion products to fill a
porous zone around a steel reinforcing bar
T0 time required for CO2or Cl
ions to diffuse to
the steel-to-concrete interface and activate corrosion
Tstress time through which the stress builds-up
ml percentage steel mass loss
Ml mass of steel lost in timeT
Mloss
mass of steel per unit length consumed to produceMr
Mr mass of rust per unit length
Mst
original mass of steel per unit length before corrosion damage
z ionic charge (2 for Fe!Fe
2+
+2e
)
d internal radial displacement
dc displacement in concrete
dl
thickness of steel lost to form rust
d0 thickness of porous zone
dr
thickness of rust
c ratio of molecular mass of steel to molecular
mass of rust
/cr
concrete creep coefficient (2.35)
m Poisson’s ratio (0.18 for concrete)
qs
mass density of steel
qr
mass density of rust
w factor depends on D, Candd0
Fig. 1. Service life model of corroded structures[2].
T. El Maaddawy, K. Soudki / Cement & Concrete Composites 29 (2007) 168–175 169
strength of concrete at which time cracking of concrete
cover occurs. It should be noted that this assumption is
valid up to the point of cracking, after which time pressure
distribution is not uniform. Cover cracking marks the end
of functional service life of a corroded structure where
structural rehabilitation is needed.
ing bar. The second period encompasses the time in which
the stress builds-up, Tstress, as corrosion products, having
filled the porous zone, exert an expansive pressure on the
surrounding concrete. The model assumes that this pressure increases linearly as the volume of corrosion products
increases until the internal tensile stresses exceed the tensile
Nomenclature
a internal radius of the cylinder
as surface area of the steel reinforcing bar
b exterior radius of the cylinder
Ab original cross-sectional area of the steel reinforcing bar
C clear concrete cover (mm)
D diameter of steel reinforcing bar (mm)
Ec elastic modulus of concrete
Eef effective elastic modulus of concrete
f
0
c
compressive strength of concrete
f
ct tensile strength of concrete
F Faraday’s constant
i
cor corrosion rate
i current density
I current (A)
k hole flexibility
M atomic mass of metal
P internal radial pressure
Pcor internal radial pressure caused by corrosion
Pcr
internal radial pressure that causes cracking of
concrete
T time
Tcr time from corrosion initiation to corrosion
cracking
Tfree time required for corrosion products to fill a
porous zone around a steel reinforcing bar
T0 time required for CO2or Cl
ions to diffuse to
the steel-to-concrete interface and activate corrosion
Tstress time through which the stress builds-up
ml percentage steel mass loss
Ml mass of steel lost in timeT
Mloss
mass of steel per unit length consumed to produceMr
Mr mass of rust per unit length
Mst
original mass of steel per unit length before corrosion damage
z ionic charge (2 for Fe!Fe
2+
+2e
)
d internal radial displacement
dc displacement in concrete
dl
thickness of steel lost to form rust
d0 thickness of porous zone
dr
thickness of rust
c ratio of molecular mass of steel to molecular
mass of rust
/cr
concrete creep coefficient (2.35)
m Poisson’s ratio (0.18 for concrete)
qs
mass density of steel
qr
mass density of rust
w factor depends on D, Candd0
Fig. 1. Service life model of corroded structures[2].
T. El Maaddawy, K. Soudki / Cement & Concrete Composites 29 (2007) 168–175 169
strength of concrete at which time cracking of concrete
cover occurs. It should be noted that this assumption is
valid up to the point of cracking, after which time pressure
distribution is not uniform. Cover cracking marks the end
of functional service life of a corroded structure where
structural rehabilitation is needed.
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