Uploaded by User52104

Tugas 1 - Pemeliharaan Struktur - Silmi Kaffah - Struktur - 03111950020019

advertisement
Maintenance of Civil Engineering Structure
Repairing Method for Corrosion-damaged Reinforced
Concrete Structures
Silmi Kaffah and Asdam Tambusay
Civil Engineering Department, Faculty of Civil, Planning, and Geo Engineering, Sepuluh Nopember Institut of Technology
Abstract
Corrosion of reinforcement concrete structures are becoming well understood. The
continuous corrosion process does not only affect in structural serviceability by
racking or even spalling the concrete cover. The physical effects of corrosion
includes loss of bond strength between steel reinforcing bars and concrete, loss of
steel area, and due to cracking reduce of concrete strength. In this paper, details
of corrosion mechanisms, which include initation and propagation, and the
parameters which contribute to the corrosion process are described. This paper
also proposed non-destructive test to know the status corrosion in reinforced
concrete, such as hammer tests, half-cell potential tests, and chloride level tests.
Furthermore, this paper proposed repair strategies, e.g. patch repair, coating
systems, cathodic protection, and paint reinforcement.
Keywords: corrosion, reinforced concrete, corrosion mechanism, non-destructive tests,
appropiate techniques
comparatively new. One of the most
causes of the failures of concrete
structures is either the structures were
not durable enough or appropiate in
concrete. Since then, chloride-induced
corrosion has become more important
for structures exposed to chloridecontaining
environments
(FrancoLujan, Maldonado-Garcia, MendozaRangel, & Montes-Garcia, 2019).
This study reviews the corrosion
of
reinforcement
concrete.
The
following sections give fundamental
information on the corrosion process of
steel in concrete. There are three steps
will be described. First, determine the
process of corrosion which the
reinforcement concrete member will
exhibit signs of corrosion in the
reinforcement. After that, propose
potential
methods
to
further
investigate the current condition of the
structure. And the last is delivery
appropiate techniques of monitoring
and maintenance will be analyzed.
1. Introduction
The reinforced concrete is one of
the most important construction
materials, which has been mostly used
in
infrastructure
construction.
However, the durability problem which
causing premature deterioration in
reinforced concrete is increasing. The
steel rebar corrosion has been one of the
most important concrete durability
deterioration and decrease of bearing
capacity of the infrastrutures. To
ensure the reliable service, it is
significance to develop the affective
monitoring techniques. It is known that
electrochemical
corrosion
process
usually causes the corrosion of
reinforcing steel..
Corrosion of steel in reinforced
concrete structures are becoming well
understood. However, many existing
concrete structures show significant
corrosion. The structure is needing
expensive repair although it is
1
Maintenance of Civil Engineering Structure
reaches a critical concentration values
required to damage the protective layer
on the surface of steel reinforcement.
There will be a process of corrosion
when oxygen (O2) and water (H2O) on
the metal surface is in sufficient
quantity. There is no decline in the
strength of concrete structures during
the initiation of corrosion as rebar
corrosion has not started yet.
The next phase is corrosion
propagiation. Corrososion propagiation
is the process of reducing crosssectional area of reinforcement steel.
The decrease of strength of reinforced
concrete structures begins at this stage.
The whole stage of corrosion can be seen
in Figure 2.
2. Research Significance
Since reinforced concrete has
been the mostly used because
reinforcement helps concrete in tension,
the durability and longevity of the
concrete due to the corrosion potential
of the reinforcement are be a concern
using this practice. Corrosion of steel in
reinforced concrete is the number one
cause of failure. Many existing concrete
structures show significant corrosion
which need expensive repair. In most
cases, either the structures were not
durable enough or the appropiate
maintenance had been neglected.
Corrosion of the reinforcement concrete
embedded in concrete causes most of
the failures of concrete structures. Here
is the example of reinforced concrete
beam which having damage due to
corrosion (Figure 1).
Figure 2. The Whole Stage of Corrosion
The high alkalinity of the
concrete pore water (pH over 12.5) that
reduces the corrosion attack to
negligible values leads to a passive
layer forming on the steel. Corrosion
will not occur as long as this passive
layer is sustained. Two processes which
may destroy this protection layer are:
 Carbonation of concrete
 Chloride attack
Corrosion of the reinforcing steel
can show different forms. General
corrosion which mostly in cases of
carbonated concrete, leads to early
cracking and spalling of the concrete,
often
with
comparatively
little
reduction of the cross-section of the
steel reinforcement (Figure 3a and b).
Figure 1. Reinforced Concrete Beam which Having
Damage due to Corrosion
3. Work Flow Description
3.1 Corrosion Mechanism in
Concrete
Corrosion of reinforced concrete
structures can be devided into two
phases, they are corrosion initiation
and corrosion propagation. Corrosion
initiation starts when chloride (Cl)
penetrates into concrete reaches the
reinforcing steel (rebar) position. The
concentration of chloride on reinforcing
steel increases with time, until it
2
Maintenance of Civil Engineering Structure
Whereas due to chloride ions, the
localized corrosion results in pits may
be large before signs of deterioration of
the concrete surface can be seen.
per unit of time or as current density
(current per unit area).
3.2 The Cause of Damage
The main consequences of
corrosion in reinforcement steel include
loss of corrosion section of rebar area,
spalling and delaminating concrete
cover. Thus, the bond strength between
the steel reinforcing bar and concrete is
reduced, and the strength of the
structure is deteriorated.
Several factors which influence
the corrosion potential of steel
reinforcement
such
as moisture
intrusion, quality of the concrete and
construction materials, lowered pH
values over time, initial curing
conditions and the formation of cracks
in the concrete, and proper concrete
coverage of steel reinforcement.
Because of these factors, chloride
movement can speed up into the
concrete, disrupting the protective
oxide film around the reinforcing steel
and leading to rusting. This corrosion
can reduce tensile capacity and lead to
spalling and delamination of the
concrete structure.
In any type of concrete, including
ordinary,
self-compacting
or
lightweight concrete, chloride attacks
are the most detrimental to rebar.
Recently, in the last 10 to 15 years, the
use of lightweight concrete in
construction has increased. One of the
major causes of damage in reinforced
concrete consider chloride-induced
corrosion.
(a)
(b)
Figure 3. Corrosion of Reinforced Concrete. (a) Spalling
Concrete due to Carbonation and Chloride Ions; (b)
Heaviliy Corroded and Cracked due to ChlorideInduced Corrosion
Corrosion is an electrochemical
process (Bohni, 2005). For steel in
concrete, the following reactions occur:
Anodic reaction:
2Fe → 2Fe2+ + 4e(1)
Cathodic reaction:
O2 + 2H2O + 4e- → 4OH(2)
Sum of the reaction:
2Fe + 2H2O + O2 → 2Fe(OH)2
(3)
The anodic reaction represents
the dissolution of the metal (Hans
Bohni, 2005). The flux of ions and
electrons respectively can be taken as a
measure of the corrosion rate. This can
be given as mass lost per unit of time
and area, as reduction of the thickness
3.3 Evaluate the Damage
When corrosion of reinforcing
steel
develops
significantly,
the
corrosive section expand continuously
around the steel bar and generate
3
Maintenance of Civil Engineering Structure
internal pressure to concrete. The
continuous
corrosion
process
of
reinforcing steel does not only affect in
structural serviceability by cracking or
even spalling the concrete cover. By
decreasing the loss-bearing capacity,
corrosion of reinforcing steel also give
serious impact on the structural safety.
Besides, the physical effects of corrosion
include loss of bond strength between
steel reinforcing bars and concrete, loss
of steel area, and due to cracking reduce
of concrete strength.
Therefore, evaluation the cause of
damage is needed. It aims to find out
how much damage occurs in reinforced
concrete and how this damage affects
the structure.
duration
for
measurement,
not
destructive)
one
non-
4.1 Visual Observation
Visual observation is the easiest
and most effective method because it
involves the simple inspections of
wheter or not the steel corrodes in a
structure to observatios damage in a
concrete specimen. A detailed analysis
is almost always destructive as the steel
reinforcement must be removed from its
environment. Visual observation was
carried out to record any damages that
occurred in the existing structures such
as crack, delamination, and any rust
stains should be noted (Bentur,
Diamond, & Berke, 2005). In order to
check for the presence of cracks, visual
and microscopic observations were
made.
The cracks formed were not only
caused by rebar corrosion, but also the
dimention of the structure such as
length and thickness. Due to the
restraining effect of the adjacent
elements, the cracks may form. Lower
concrete quality may affect the
formation of cracks. Cracks have
formed at the weakest location by
indicating the crack mapping of the
structure.
4. Potential Methods
It is necessary to know the exact
place and the extent of corrosion
attacks at the reinforcement in order to
estimate the necessity of repair work.
Corrosion sites have to be identified
rapidly, non-destructively, and over the
entire surface. Potential mapping is
used during three stages of bridge
maintenance:
 During inspection (basis for
the repair concept)
 During repair work
 After repair work (quality
assurance, monitoring)
With the different methods for
corrosion
monitoring
one
can
differentiate
between
local
measurements and cover-all. Local
information can be derived from the
following:
 Built-in
the
structure
(sensors, reference electrodes)
 Mobil structures, but these
however are not suitable for
cover-all measurements (high
4.2 Non-Destructive Testing (NDT)
The status of corrosion in
reinforced concrete member by using
Non-Destructive Test (NDT). Those
zones where the reinforcement is
actively
corroding
should
be
determined by means of nondestructive electrochemical techniques
such as corrosion rate mapping and
corrosion potential. The use of nondestructive testing and/or analytical
4
Maintenance of Civil Engineering Structure
formulation can represent rapid and
high quality methods to evaluate the
corrosion
penetration
of
steel
reinforcement.
During the inspection, nondestructive tests were carried out. The
corrosion behaviour of the steel
reinforcement was insvestigated.
From a sructural point of view, it
is important to evaluate the reduction
of cross-sectional area of reinforcing
steel by using non-destructive tests. An
analytical model to calculate corrosion
of steel reinforcement by measuring
external crack widths was proposed, in
the case of both linear and non-linear
concrete behaviour. Usually previous
models avaliable in scientific literature
were empirical in nature and governed
by main parameters influencing the
crack opening like as bar diameter,
concrete cover, and concrete properties.
pinpointed by using this test, and the
destructive test can be directed at the
designated location (Bayuaji, et al.,
2018). The probability of corrosion in
reinforcing steel can indicate by the
potential value.
The test is limited by the fact
that a direct connection to the steel
reinforcement has to be made.
Typically, HCP readings are taken,
which is inside the concrete at a depth
varying according to the designed cover
depth (Paul & Babafemi , 2018).
4.2.3 Chloride Level Tests
Level of chloride in reinforced
concrete at the reinforcing steel
determines the time to corrosion
initiation. The corrosion is assumed to
initiate and start to reduce the crosssection of steel reinforcement. Further,
the most important finding from this
test was that the chloride level of
concrete samples at the concrete
surface at the splash and tidal zones did
not give the highest chloride level. This
is probably caused by a relatively high
compressive strength.
4.2.1 Hammer Tests
Hammer tests is a nondestructive testing method of concrete
which provide compressive strength of
the reinforced concrete. Hammer test
estimates concrete strength based on
surface hardness. The uniformity of
concrete strength and concrete quality
can be determined with ASTM
C805/C805M-13a. The hammer tests
result and compressive strength can be
correlated to get the estimate concrete
compressive stregths at hammer test
location.
5. Appropiate Techniques
In the future, the number of
reinforced concrete structures that
have online monitoring devices will
increase. This is because continuous
corrosion
of
steel
reinforcement
monitoring provides an early warning
system and accurately timed repair
measures can lead to a significant
reduction of maintenance costs.
The continuous monitoring of the
corrosion of reinforcing steel in concrete
structures has proved to be a powerful
tool for determining the state of
corrosion. Other than that, the
continuous monitoring estimates the
4.2.2 Half-Cell
Potential
Tests
(HCP Tests)
The half-cell potential (HCP) is a
standard test to determine the
corrosion
activity
of
steel
reinforcement. The possible location of
corroded reinforcing steel can be
5
Maintenance of Civil Engineering Structure
expected
lifetime
in
structure,
determines the critical period for
repairing, evaluates repair efficiency,
and prove to be a powerful tool in
testing
the
effectiveness
of
reconstruction measures.
Figure 1. shows beam which have
damage caused by spalling concrete and
exposed reinforcing steel indicate
serious deterioration. This beam is
constructed with a very thin cover
concrete, while the structure exposed to
high chloride and velocity waterflow
environment.
the same diameter either by welding 10
cm length to the existing reinforcing
steel
5.2 Coating Systems
In order to prevent or stop
corrosion in structural beams, there are
several way such as with coating which
a way of preventing these failures that
can detect and heal localized corrosion.
The best choices partly depend on the
source of the corrosion.
Water soluble particles can cause
fast deterioration problem. That means
surfaces must be free all pollutants
before coating. Before beams are
shipped, coatings are applied. This is
usually done in enclosed workshops. If
necessary, more coating materials can
be applied later. The aplication of a
hydrophobic
coating
(sometimes
referred to as penetrant pore-liners)
may be used to reduce the moisture
content of reinforecd concrete and
thereby electrolytically stifle the
corrosion reaction.
5.1 Patch Repair
Patch repair method is widely
used to restore the original conditions of
concrete structures. The patch repair
concrete must be completely chloridefree and similar in characteristics to the
concrete to be replaced.
5.1.1 Removal of Cracked and
Delaminated Concrete
By using a marker pen, delimit
the area of damage. Break the delimited
area until reaching sound steel and
concrete. Saw-cut 2 cm deep in 90°
angle the perimeter of breaking with a
jack hammer. All damaged, weak, and
easily removable concrete chipped
away. If the rebars partially exposed
after all unsound concrete is removed,
it may not be necessary to remove
additional concrete.
5.3 Cathodic Protection
Cathodic protection is the main
alternative to patch repair. It is because
although patch repairs remove the
contaminated concrete from the
deteriorating areas, they may address
other sections of hidden corrosion.
Impressed Current Cathodic Protection
(ICCP) is a technique that sends a small
electrical current through the concrete
to the reinforcing steel in order to stop
the corrosion of the steel. The benefit of
ICCP is that the extend of concrete
removal for repair is reduced vastly.
Once cathodic protection is installed, it
can control the ongoing corrosion for the
long term, with future spalling and
deterioration eliminated even in
5.1.2 Cleaning of Corroded
Reinforcement
Clean steel reinforcement with a
mechanical wire brushing or by sand
blasting. The steel reinforcement which
are corroded and have lost more than
25% of their diameter, they have to be
cut and removed. Removed rebar
should be replaced with new rebar of
6
Maintenance of Civil Engineering Structure
concrete that is severely contaminated
with carbonation or chlorides.
The anodic reaction represents
the dissolution of the metal. The flux of
ions and electrons respectively can be
taken as a measure of the corrosion
rate.
When the corrosion of reinforcing
steel
develops
significantly,
the
corrosive area expands continuously
around the steel bar and generate
internal pressure to concrete. The
physical effects of corrosion include loss
of bond strength between steel
reinforcing bars and concrete, loss of
steel area. Therefore, evaluation the
cause of damage is needed.
It it necessary to know the exact
place and the extend of corrosion at
reinforcement concrete. This paper
proposed non-destructive test to know
the status of corrosion in reinforced
concrete: (1) hammer tests which
estimates compressive strength and
concrete quality based on surface
hardness, (2) half-cell potential tests is
a standard test to determine the
corrosion
activity
of
steel
reinforcement, the possible location of
corroded reinforcing steel can be
pinpointed, (3) chloride level tests, the
chloride level of concrete at the rebar
determines the time to corrosion
initation.
Numerous repair options are
available
and
new
technologies
continue to make an impact in the field
of concrete repairs (Mackechnie &
Alexander, 2001). This paper proposed
repair strategies: (1) patch repair
includes removal of cracked and
delaminated concrete and cleaning of
corroded reinforcement, (2) coating
systems which is a way of preventing
the failures that can detect and heal
localized
corrosion,
(3)
cathodic
5.4 Paint Reinforcement
For the greatest durabilty, the
longest life to first maintenance starts
with beams that have received a
thermal metal spray or hot-fip
galvanized structural beams. The
beams would get a sealing coat of
painting. Paint the reinforcing steel
with anti-corrosion paint.
A medium to long life if
structures is delivered by high
performance paint systems. In tough
environments, paint systems based on
drying oils are appropiate for short life.
If the original finish, a thicker coating
can also extend durability. So, one or
two coats may be enough for reinforcing
steel that’s been blast-cleaned.
6. Conclusions
In this paper, details of corrosion
mechanisms, which include initiation
and propagation, and the parameters
which contribute to the corrosion
process are described. Corrosion
initiation begins and reaches the
reinforcing steel position. There will be
a process of corrosion when oxygen (O2)
and water (H2O) on the metal surface.
Whereas corrosion propagation is the
process of reducing cross-sectional area
of reinforcement steel.
The
corrosion
is
an
electrochemical process. For steel in
concrete, the following reactions occur:
Anodic reaction
: 2Fe
→ 2Fe+ + 4e(1)
Cathodic reaction
: O2 +
2H2O + 4e → 4OH
(2)
Sum of the reaction
: 2Fe +
2H2O + O2 → 2Fe(OH)2 (3)
7
Maintenance of Civil Engineering Structure
protection is a technique that sends a
small electrical current through the
concrete to the reinforcing steel, (4)
paint the reinforcing steel with anticorrosion paint.
7. References
Bayuaji, R., Darmawan, M. S., Husin,
N. A., Anugraha, R. B.,
Budipriyanto, A., & Stewart, M.
G. (2018). Corrosion Damage
Assessment of a Reinforced
Concrete Canal Structure of
Power Plant After 20 Years of
Exposure in a Marine
Environment. Engineering
Failure Analysis.
Bentur, A., Diamond, S., & Berke, N.
S. (2005). Steel Corrosion in
Concrete . London.
Bohni, H. (2005). Corrosion in
Reinforced Concrete Structures.
England.
Franco-Lujan, V. A., MaldonadoGarcia, M. A., Mendoza-Rangel,
J. M., & Montes-Garcia, P.
(2019). Chloride-induced
Reinforcing Steel Corrosion in
Ternary Concretes Containing
Fly Ash and Untreated
Sugarcane Bagasse Ash.
Construction and Building
Materials.
Mackechnie, J., & Alexander, M.
(2001). Repair Principles for
Corrosion-damaged Reinforces
Concrete Structures. Cape Town.
Paul, S. C., & Babafemi , A. J. (2018).
A Review on Reinforcement
Corrosion Mechanism. Civil
Engineering Research Journal.
8
Download
Random flashcards
Rekening Agen Resmi De Nature Indonesia

9 Cards denaturerumahsehat

sport and healty

2 Cards Nova Aulia Rahman

Nomor Rekening Asli Agen De Nature Indonesia

2 Cards denaturerumahsehat

Secuplik Kuliner Sepanjang Danau Babakan

2 Cards oauth2_google_2e219703-8a29-4353-9cf2-b8dae956302e

Create flashcards