04b Concrete Repair Methods
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Transcript of 04b Concrete Repair Methods
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1
RECO2006 Construction IV
Concrete Repair
Edward CY YIU
Department of Real Estate and Construction
January 2007
2
Intended Learning Outcomes
How to repair concrete?
What are the commonconcrete repair
methods?
How to determine
which repair methodsto be used?
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Anatomy of Concrete Repairs
Emmons, 1993, p.99
4
Repair Strategy
Materialselection
Methodselection
SupportDesign
SafetyPrecaution
Costs
Logistics
Emmons, 1993, p.98
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Process
Re-bars Undercutting Cleaning Repair Protect
Concrete Surface
preparation
Bonding Apply newmaterial
Emmons, 1993, p.98
6
Performance Requirements ofConcrete Repair
Protection of Rebars
Aesthetics
Integrity and Compatibility (with substrate)
Carry loads
Waterproofing
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Repair Systems Selection
Criteria Stability of element
Cost
Disturbance to users
Existing concrete condition
Exposure condition
Compatibility of repair material to
substrate
8
Concrete Repair Methods
Buildings Department (1998) lists the following
common repair techniques for concrete:
Patch Repair
Recasting/Partial Recasting
Sprayed Concrete
Micro-concrete
Pre-packed concrete Non-shrinkage grout
Sealing system
Protective Coating
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Traditional Repair Methods
Patch Repair
Cementitious mortars
Resin-based mortars
Recasting/Partial Recasting
Sprayed Concrete
Dry process spray
Wet process spray
10
Preparation Before Work
Preparation of concrete surface
Cleaning of reinforcement
Coating reinforcement
Bond Coat
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Preparation
Marking out, Hack back to 10-20mm behind re-bars,ensure concrete cover
Saw cut the edge, Brush/grind the re-bar
Prime coat for re-bar, bond coat for substrate
Batching of repair mortar and apply.
Dowel bars:
Holes drilled with rotary-percussive drills to providekeys
Air blown by pneumatic device
Required length of insertion Give it a 1/2 turn and then turn back to original position
Give 2 hrs initial set off time
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Cleaning of reinforcement
For cleaning of reinforcement rust, high pressure water-abrasiveblasting should be the best ways of ensuring a chloride-free surfacefor the reinforcement. Probably, it is the only way of removingchlorides from the pits in rusting reinforcement.
If the damage is caused by carbonation, it is less critical to removerust from the reinforcement. Coating with a layer of firmly adheringcement paste will be sufficient to prevent further deterioration. Othermaterial for coating can be used if the repair is not in a cementitiousone.
http://www.sadgrovesquay.com.au
/abrasive/sandblast1.jpg
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1. Patch Repair
It is most suitable for small-volume repairs as torestore concretes durability. The damaged concreteshould be removed and patched up with appropriaterepair mortars.
In general, there are two common repair mortars usedfor repairing works:
Cementitious mortars Resin-based mortars
i. Cementitious mortars: Cementitious mortars is one type of repair mortars for
patch repair on small-volume repairs. It is used to
restore durability of the structure. The damagedconcrete is removed and these areas will be patchedup with appropriate repair mortars.
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1. Patch Repair
Emmons, 1993
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1. Patch Repair (Contd)
Mailvaganam and Taylor (1994) prefers resin based mortars. It isbecause the resin based mortars have an elastic modulus of aboutone-tenth of concrete.
The coefficient of thermal expansion is five times more than that ofconcrete.
It has the strongest compressive strength than the other type ofcementitious based mortars.
Recently, polymer is added into the mortar in order to increase theirstrength.
However, there are some limitations in polymer repair materials e.g.it may cause delamination or blistering when applied on the dampedareas; and
It is not recommended to be applied in areas where fire resistance is
required. It has poor fire resisting property and it has thermalincompatibility with substrate concrete.
16
Properties of typical concrete repairmaterials
(Mays, G. and Wilkinson, W., 1987)
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Emaco S66
Emaco S88C; Emaco
S88C with MCI
For repair load-bearing concreteSilica fume-modified repair
mortar
Silica fume-modified
Lanko 731For repair of spalling, honeycombing,
stair nosing, ramp etc.
Fibre-reinforced, non-
shrinkage mortar
Renderoc GP;
Renderoc HB40
(with higher
performance)
For area where superior resistance is
required to chlorides and carbon
dioxide.
For general purpose concrete
reinstatement.
Medium-weight
cementitious mortar
ReferenceSuitabilityTypes of cementitious
mortars
Types of Mortar
18
Types of Mortar (Contd)
Unicell 25; Unicell 40,
and unicell ultra rapid.
Suitable for concrete repair. It can be
applied in thick section and is suitable for
structural and non-structural application.
Polymer modified repair
mortar for high build with
different classes of strength
Barra Mortar HL;
Nitomortar HB;Renderoc HB; HB25
For high build, vertical and overhead
repairs (rather low compressive strengthwill be developed)
Polymer modified repair
mortar, feature lightweight
Emaco R740Restore concrete and inhibit further
deterioration before significant structural
damage occurs.
Polymer modified repair
mortars, feature shrinkage
compensating properties
Barra 80; Barrafill;
Renderoc S; Ronafix
Mix A; Ronafix Mix D
For locations where required high
compressive strength, and reinstatement of
concrete.
Polymer modified repair
mortar suitable for different
degree of exposure
Polymer modified
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Renderoc Plug 1;
Renderoc Plug 20
(20mins setting)
Rapid patching and plugging of concrete
segments.
Rapid setting waterstopping
mortar
Emaco S90UWSpecifically developed for underwater
repair and restoration work.
Rapid setting underwater
mortar
Rapid Setting
Types of Mortar (Contd)
20
Nitomortar PEFor fast and emergency reinstatement
of concrete, bedding, jointing and
reprofiling of concrete
(cannot be applied to damp or wet
surface)
Polyester resin mortars
with high strength
jointing and multi-
purpose repair
compounds
Polyester resin mortars
Nitomortar SFor fast and permanent reinstatement
of concrete
High strength, abrasion-
resistant epoxy
reinstatement mortar
Expocrete UAFor use in exceptionally wet
conditions and for underwater
applications
Expocrete GPLow slump for general repair workTwo-part epoxy resin
mortars (possesses
outstanding strength
and adhesive powers)
Expoxy resin mortars
ReferenceSuitabilityTypes of resin-based
mortars
Types of Mortar (Contd)
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8 tests on Repair Mortar:
compressive strength (28 days) 30-60 MPa Tensile strength (7 days) 2 MPa Mod of Elasticity (28 days) 15-25 kN/mm2
Bond Strength (7days) 2.0 MPa Shrinkage Cracking (7 days) Coutinho ring test Permeability Workability Chemical Analysis Open-up inspection: 1 / 25sm patch repair Pull-off test (bond coat adhesion strength): 1/ 50sm patch repair
Pass if 1/2 fracture in substrate or pull-off stress > 1/4 of the 7-day
bond str Core a 75mm dia. Full thick of the repair with 7days age.
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Bond Strength of Patch Repairtested by pull-off test Pull-off test on the
adhesion strength of the
bond between the repair
mortar and the substrate
concrete, aided by any
bond coat
identify re-bar position
Repair area shall have a
minimum age of 7 days
Re-bar sensor to identify
the location of
reinforcement bars
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Core
A 75mm dia. Core
containing the full
thickness of the repair
was produced
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Detail of the core
Repair Mortar
Substrate
Cored hole
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Dummy
A suitable metal plate
was glued to the
cored hole and let it
dry for one hour;
this attachment was
pulled with increasing
tensile force using a
calibrated device until
failure occurs.
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Result 1
Criteria:
fracture shall be at least
half in the substrate
concrete, unless
the pull-off stress is not
less than 1/4 (i.e. 0.5 MPa)
of the minimum 7 days
bond strength of the repair
mortar (2.0 MPa).
Result 1
Fracture at bond surface,
bond strength = 27psi (0.9
MPa) - PASS
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Result 2
Half of the fracture at
substrate, bond
strength = 18psi (0.6
MPa) - PASS
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Results 3 & 4
Result 3: less than
half of the fracture at
substrate, bond
strength = 12psi
(0.4MPa) - FAIL
Result 4: fracture at
surface material,bond strength = 9psi
(0.3 MPa) - FAIL
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2. Recasting In this method, the damaged part of the structural element will be
demolished, replace corroded reinforcement and recast it with same oreven better grade concrete in order to restore its structural strength.
Considerations for practical uses Pay attention to the discontinuity which causes any instability to the
linked structural elements due to demolition.
Dowel bars and/or replacement steel bars should be placed on thecleaned reinforcement bars.
For recasting of slabs, evacuation may be required for flats above orbelow the element.
The joint between old and new concrete should be paid with specialattention. Poor joints will result easy seepage of water and causes of
corrosion. Shear key is required for large areas of recasting. Pre-soaking of substrate is necessary Avoid air trapping by thorough compaction of repair mortar.
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Recasting by form and pump
Applicat ion ranges
When defective
depth is ranges from
75mm to 100mm.
Also for vertical
members e.g. wall
and column. When structural
restoration is
required.
Emmons, 1993, p.168
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Full Depth Recast
Emmons, 1993, p.168
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3. Sprayed Concrete
Sprayed concrete is a technique which is widely
used in high-volume concrete repair work.
The concrete mix will be sprayed with or without
admixture or polymers to the defected areas
under high air pressure. This process can be
done by means of nozzle gun.
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Dry Spray Concrete
There are two different methods of spraying: Dry process spraying Wet process spraying
Dry process spraying is the process which the mixture of damp sand and cement ispassed through the delivery hose to the nozzle and the water is mixed at that time.
This process is often used for repair work. It is because of its fast application process and restoration of structural strength at an
early stage.
The performance characteristics of dry sprayed concrete are they have good densityand high strength.
It has very good bond to a suitable substrate. These advantages make it more variable than conventional concrete and wet process
sprayed concrete. (SCA, 1999)
(SCA, 1999)
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Wet Spray Concrete
Wet process spraying means all the ingredientsincluding water are mixed together beforetransporting to the site for repairing works.
It is not normally applied for building repairssince the size of equipment is much larger thanthat of dry process spraying.
(SCA, 1999)
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Cracks prevention
Concrete surface must be reinforced withsmall-mesh small diameter reinforcement
before carrying out sprayed concrete. This
can prevent developments of cracks when
the concrete shrinks.
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Spray Concrete Considerations fo r practical uses
The process should be in a continuous process. Concrete mixed should be complied with acceptable standard and quality. The operation should be carried by experienced nozzleman. Acceptance test should be carried out to test the skill of the nozzleman.
The process should be held at right angle to and at one meter from thesurface of the repair areas.
Min. spray concrete thickness should be considered before sprayingprocess.
Reference should be made to Code of Practice for Structural Use ofConcrete.
Good surface preparation should be done. Sufficient safety precautions must be taken.
Appl ication ranges Large areas of repairs with thickness > 50mm
In vacant flats and/or public areas, this can minimize the nuisance topeoples.
Partial strength is to be restored.
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Sika Mono Top-612;
Optimix RM770
General concrete repair
work
Wet Spary
Sika Rock 30Specially prepared for use in dry
shotcrete applications.
(compressive strength: 30-40 N/mm2)
Gunite mortar
(cementitious based)
Renderoc DS
(aggregates used
are classified as
non-reactive.);
Renderoc SC;
Optimix RM770
For large area repairs (rather low
compressive strength developed)
Should not be used when the
temperature is
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1. Micro-concrete
By applying this method, the contaminated or damaged concrete are removed andreplaced by fluid micro-concrete.
It is used to re-form desired concrete profiles. Usually, prescribed mixes are available in the market with shrinkage compensators to
control shrinkage in plastic and hardened states.
Considerations for practical uses
It needs special design by the supplier and specialist advice is required. Formwork with leakproof is required. Pre-soaking of the formwork and substrate is required. Aggregates used should not be greater than 10mm. In order to improve workability, aggregates should be rounded in size. Good curing of the repair is essential.
App licat ion ranges
For use in area with limited working space or congested reinforcement For use in thin sections where the use of normal concrete is impractical
40
Renderoc LA27Low alkali, non-reactive
micro-concrete
Renderoc LA55High performance
shrinkage compensated
Renderoc LAFor area where access to the repair
zone is restricted or where
reinforcement is congested which
unable to carry out compaction
and vibration.
Difficult access which make
hand/trowel-applied mortars
impractical.
Shrinkage compensated
ReferenceSuitabilityTypes of micro-concrete
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2. Pre-packed Concrete
Graded aggregates similar to the substrate concrete willbe placed firstly in the formwork.
After the placement of graded aggregates, cement groutwill be injected into the formwork from THE BOTTOM.
The resulting concrete will be in excellent quality inproper implication.
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Considerations for practical use
All loose and spalled concrete should be repaired prior to the application. Target compressive strength of the pre-packed concrete should be compatible with
that of the substrate.
Trials on compressive strength before operation are recommended. Careful design on aggregate size and grading is recommended.
Aggregate size shouldnt be too fine in order to avoid blockage of grout patch. Similar to micro-concrete, formwork with leakproof is required. Pre-soaking of the substrate with water is necessary. Aggregate should be clean and free from silt before application.
App licat ion ranges For use at areas where concrete placing is difficult, e.g. at beam soffits. For areas with congested reinforcement or depth of repair is greater than 75mm
where patch repair is not suitable.
For where the structural strength have to be restored.
Advantages Compare to sprayed concrete, it has greater density, greater uniformity, lesserpermeability, lower shrinkage, less dependence on personal skills of equipmentoperators, less dust, less clean-up work, and more economical.
Limitations All works in vertical surfaces require formwork. At least 3 to 4 inches of space is
required for replacement.
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3. Non-shrink grout
cementitious, epoxy resin or polyesterresin based
In repair works, non-shrink grout is used incrack injection repair.
Also, it is used to repair porous concreteand in those areas with very congestedreinforcement.
Usually, it has a very high workability, itcan be applied either flowable or in fluid.
If mixtures are according to specifiedinstruction, the compressive strength of
non-shrink grout can be higher than 50N/mm2 although it has high workability.
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Non-shrink grout
Considerations for practical use
Please refer to micro-concrete
Applicat ion ranges
used in crack injection repair,
To repair porous concrete,
Very congested reinforcement or in limitedworking spaces,
Thickness of repair is thin.
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Conbextra GP; ConbextraConbextra HES;
Conbextra HF; Conbextra
UW; Calgrout No 1
For general purpose of crack injection.Different kinds of cementitious
grout are available such as, rapid
set, high strength, high
performance or specifically for
underwater application
Non-shrink cementitiousgrout
Cementitious based
Ronabond EP 22UWCapable of restoring structural integrity
and can be used under water
Epoxy resin suitable for
structural element
(suitable for use
underwater)
Ronabond EP 22S;High strength resin and capable of
restoring structural integrity
Epoxy resin suitable for
structural element
Nitofil THFor injection of cracks of about 0.5-
9mm wide.
Permits injection of open-ended cracks
Thixotropic epoxy resin
injection grout
Ronabond EP 21SLV;
Ronabond EP 21 FLV
(more flexible)
As resin binder in flooring screeds or
for repair of cracks subject to
movement.
Ultra low viscosity expoxy
resin injection
Nitofil LV; Sikadur 752; HI-
Crete 85; Conbextra EP;
Expocrete S
For injection of cracks of about 0.25-
9mm wide.
Permits maximum resin penetration
Low viscosity epoxy resin
injection grout
Epoxy resin based
ReferenceSuitabilityTypes of non-shrink grout
46
4. Joint Sealing System
This system is generally applied for repairing activecracks.
The crack must be widened and sealed as joints if anymeasurements or circumstances suggested that it is livecrack.
When those live cracks cannot successfully be gluedtogether with resin injection, the joints must be widenedat the surface and sealed as a joint.
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ERTOBLOC 224;
Ronabond PU 10;
Ronabond PU 20
(High strength);
Ronabond PU
Sealing of waterways
Fast setting,
Used underwater
High resistance to pressure. Some of
the products are with different
properties, such as, high strength,flexible and elastic for use in
different situation.
Instant-setting
hydraulic
mortar/grout
Sikaflex-11FCAs an elastic adhesive and elastic joint
sealant.
One component
polyurethane
sealant/adhesive
Sikaflex PRO 2HPPermanent elastic one-compound joint
sealing compound
Joint sealing
compound
(Polyurethane base)
Sikadur CombiflexFor joints and cracks subject tonormal or large movements
Versatile sealingsystem
ReferenceSuitabilityTypes of joint sealing
system
48
Protection Methods
Protective Coating
Apply Cathodic Protection
Provide Additional Concrete Cover
Realkalization or Desalination
Overcladding and Insulation
Protection with Corrosion Inhibitors
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5. Protective Coating
The protective coating is a thin outer layer which used toprotect the substrate concrete by acting as animpermeable barrier or slowing the rate of penetration ofactive components from the surrounding environment.
Three main functions of protective coating are: Change appearance;
Improve surface properties;
Barrier against the penetration of aggressive gases, liquids andvapours.
Good protective coating should allow water vapour to
pass out through it in order to stop the building up ofvapour pressure in the substrate concrete which causesblistering. (BSIS)
50
Considerations for practical use Good surface preparation before application of the coating, such as
completed repairing of concrete and removal of surfacecontaminations and voids.
Remove all loose part of existing painting and check thecompatibility of the existing paints before application.
If a solvent based protective coating is selected, it should be in anopen space with good ventilation for coating to evaporate.
Appl ication ranges
It should be applied on repaired concrete substrate to preventfurther deterioration. In those areas where frequent wetting of concrete surface is
unavoidable.
On surfaces where exposed to aggressive surroundings.
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SikaTop Seal 107;
Ronabond Joltec
Finish; Ronabond
Jotec Transparent;Ronabond Nigatex
Provides an effective barrier against
the transmission of liquid water.
It should be applied on concrete,
brickwork and blockwork.
Waterproof protective
coating
Sikagard-62; Ronabond
Cover Plus 150
As a barrier to resist chemical
resistance, such as carbon ion.
Protective coating with
moderate chemical
resistance
Sikagard 680 S-Concrete
Cosmetic
Protection and enhancement of
concrete and asbestos cement
building elements, especially
facades.
Acrylic resin protective
coating for concrete
Nitoprime Zincrich;Frianzinc EPE
As an anti-corrosion primer forexposed steel reinforcement for
use with concrete repair mortars
Single component epoxyzinc primer
(corrosion protection)
ReferenceSuitabilityTypes of protective
coating
52
6. Cathodic Protection
The purpose of applying cathodicprotection is to stop the setting up of
anodes on the reinforcement by applying a
low voltage electric current or by a
sacrificial anode.
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Sacrif icial Anode System
There are two main systems ofcathodic protection:
Sacrificial Anode System
Impressed Current System
In sacrificial anode system, the steelis connected to a metal which is lessstable in electro-chemical series, e.g.zinc. Since zinc is more anodic thansteel, the current will flow from zinc
to steel and zinc will be corrodedinstead of steel.
Sacrificial anodes fixed to the rebar with
tie wires. (Fosroc: Galvashield XP)
54
Impressed Current System
In impressed current system, an externalcurrent with sufficient intensity is applied to
over-ride the corrosion current.
Discrete impressed current cathodic
protection (ICCP) anode. (Fosroc: Ebonex)
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Pros and Cons
Advantages:
The only way to completely stop steel
corrosion
Permanent solution
Disadvantages:
Ongoing cost to maintain
Many structures not suitable (access, non-
continuous reinforcement, pre-stressing steel,
etc.)
56
Cathodic Protection Considerations for practical use Installation and maintenance costs for the systems are much higher
than other repair methods.
It needs special design by the supplier and specialist advice isrequired.
Defects must be repaired before implication of cathodic protection. Electrical continuity has to be assessed before implication.
Appl ication ranges In area where corrosion is active or chloride content is high.
Recasting or large scale patch repair is not feasible. Corrosion of steel reinforcement is not that serious while application.
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EbonexFor protection of steel corrosion
in reinforced concretestructures and steel framed
buildings
Discrete cathodic protection
anodes
Impressed Current System
Galvashield XPTo be embedded within repairs
performed in chloride
contaminated concrete to
protect adjacent steel from the
onset of corrosion.
Embedded zinc anode which
acts to prevent corrosion
of reinforcing steel in
concrete:
Galvashield CC45,
Galvashield CC65
For pre-stressed/post tensioned
structures (Not for use with
epoxy and polyester repair
mortars or primers.
Drilled in sacrificial anode for
reinforced concrete
structures
Sacrificial Anode System
ReferenceSuitabilityTypes of cathodic
protection
58
Realkalization
Advantages: Based on reversing the principles of cathodic
protection
Limited concrete removal
No ongoing maintenance
Disadvantages:
Very high installation cost Not all structures are suitable
Environmentally unsound
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Overcladding
Advantages: Greatly improves appearance
Provides the additional benefit of insulation
Provides a long-term solution
Disadvantages: Very expensive
Can hide latent defects
Extended contract period The Jardine House case
60
Corrosion Inhibitors
See Sika FerroGard-903 CorrosionInhibitor or Tyfo CIS Inhibitor
Tyfo CIS Inhibitor Layer 2DESCRIPTION
Tyfo CIS Layer 2 is a single-component, clear, waterbasedliquid with a mild odor. It may beapplied by roller or spray following the application of Tyfo CIS Layer 1. Layer 2 controls the pH,
purges and encapsulates water-soluble chlorides, fills voids in the concrete, and inhibits furtherpenetration of moisture. Layer 2 also acts as a contact corrosion inhibitor on the reinforcing steel.
After receiving both Layers 1 & 2, the exposed surfaces are cleaned by washing with fresh water or
by abrasive blasting. All exposed steel is then treated with the Tyfo CB material and the concretesection is restored using Tyfo P or Tyfo PF as required.
USE
Tyfo CIS Layer 2 is used with the TyfoConcrete Repair System on new or old concrete surfacesto seal porosity, increase compression strength, maintain pH, protect f rom acid and alkali attack,
pacify and extract chlorides, and inhibit embedded steel corrosion.
ADVANTAGES
Ease of application
Can be applied to horizontal, vertical or overhead surfaces Restores properties of deteriorating Portland concrete cement
Can penetrate concrete 2 to 3 inches, depending upon existing porosity Dramatically improves condition of substrate prior to repairs
Protects new concrete
For new and old structures Non-toxic
14%C-418New concrete
Hardness Increase
Increases 2,000 psi
(13.8 MPa)C-42
Compression
Strength
50% reduced voltagein 14 days
(400 to 200mV)
C-876Corrosion Inhibition
Typical Test Value*ASTM MethodProperty
MATERIAL PROPERTIES
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European Standards for Repair
and Protection of Concrete The standards related to the repair and
protection of concrete of concrete currently
available as standards or under
development by CEN TC104 SC8-
Protection an Repair an Repair of
Concrete. It was updated on 6 November
2001.
62
State-of-the-art Repair andProtection Methods
Concrete Patch repair with phosphate-based
Cathodic protection
Chloride extraction
Concrete re-alkalization
Concrete strengthening plates/sheets
Surface-applied penetrating sealer and coating
Re-bar Fusion-boned epoxy bar coatings
Inhibitive primer
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1) Patch Repair: Magnesium
phosphate-based It is a unique, two-component with rapid setting
concrete repair and grouting system. It curesfaster than concrete and it has a very goodbonding with new and old concrete. The repairsystem can be applied at any temperaturewithout shrinkage and is freeze/thaw and deicingsalt resistant since it does not require water asan additive.
loctite.com.hk.
64
2) Concrete strengthening
An advanced technology of concretestrengthening techniques which do not need torecast the concrete structure for strengthening.
This technique apply the use of placing anbonding CIFIRP (Fibre Reinforced Polymer)plates or sheets to surfaces of structuralconcrete members.
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Examples of Concrete
Strengthening Materials
Ronacrete FRP systemFor structural strengthening
for post-reinforcement of
structural members, such
as beams, columns, slabs)
Fibre reinforced
polymer (FRP)
system
SikaWrapShear strengthening in a
building beam and slab
Flexural strengthening of slab
Composite fabrics for
structural and
seismic
strengthening
ReferenceSuitabilityTypes of concrete
strengthening
66
3) Chloride Extraction
If there is a presence of chloride ion, the concrete willdeteriorate at a faster rate. It is mainly due to thedepassivating effect of chloride ions. Usually, a value of0.8% (a critical acceptance value) is adopted forpractical use.
In this method, chloride ions are removed from concreteby dissolving in electrolyte and drawing it to an externalelectrode by an electrical potential. The external
electrode being used in this method is a titanium wiremesh which is embedded in electrolytic paste ofcellulose fibre. The paste is adhered onto the surface ofconcrete.
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4) Concrete Re-alkalization
Alkaline is a substance which can protectreinforcement from corrosion. When concrete iscarbonated, its alkalinity decreases and hencethe protection of reinforcement is decreased.This method is used by diffusing alkalinechemicals like metallic hydroxides into concretefor increasing pH value and cause re-passivation.
Recently, this technique is still under testing andnot yet been developed for field test. Therefore,
it is difficult to find this service in the market.
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5) Surface-applied PenetrationSeal
Aquron CPT-2000 is a highly reactive catalyticagent which reacts with free alkali and/oralkaline hydrates by internally producing a silicahydro-gel which fills the pore spaces and thevoids around aggregate. Furthermore, alkali isconverted to a neutral compound structure,reducing the potential for internal chemical
reactions. More density is added, additionalbonding strength is provided and concrete ispermanently hydrostatically sealed from within.
http://www.aquron.com/2000_tech_sheet.htm
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prevents ingress and migration of moisture and
damaging corrosive
Deplete soluble chlorides in concrete and inhibitcorrosion of imbedded reinforcing steel
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6) Corrosion Inhibitor
With the addition of calcium nitrite, thestandard threshold of corrosion is elevated
i.e. the protective passivity layer cantolerate a higher level of chloride ions.
http://www.na.graceconstruction.com/conc
rete/
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Reading
Rostam, Steen. (1996) High performance
concrete cover why it is needed, andhow to achieve it in practice, Construction
and Building Materials, 10(5), 407-421.
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References Buildings Department, (1998), Interim Technical Guidelines on The Inspection,
Assessment and Repair of Buildings for The Building Safety Inspection Scheme, TheGovernment of the Hong Kong SAR.
Mays, G. and Wilkinson, W., Polymer Repairs to Concrete: Their Influence onStructural Performance, ACI-SP 100-22 Katherine and Bryant Mather InternationalConference 1987, pp.351-338.
Mailvaganam, N.P. and Taylor, D.A., Compatibility of Repair Systems for ConcreteStructures, CANMET/IRC Symposium on Advanced Materials, Ottawa, 1994, 11 p.
Pullar-Strecker, P., (1988). Corrosion Damaged Concrete: Assessment and Repair.London: Butterworths, 1988.
Buildings Department, (1998), Interim Technical Guidelines on The Inspection, Assessment and Repair of Buildings for The Building Safety Inspection Scheme, Highway Department, HKSAR Govt (2002) Guidance Note on the Repairof Spalled
Concrete Road Joints, GN028. The Government of the Hong Kong SAR.
Currie, R. J. (1994). Repair and Maintenance of Reinforced Concrete. Building
Research Establishment Report. Watford: BRE publication. Schmick, Bonnie L. Pollington, Annette. (2002) Concrete repair manual
Amer ican Concrete Ins ti tute. Imprint Farmington Hills, Mich. : ACI International,[2002?] 2nd ed.[HKU 624.18340288 C7 S]
The Australian Corrosion Association and The Asian Pacific Materials and CorrosionAssociation, (2001). Fosroc galvashield: New ways to repair and protect reinforcedconcrete, Corrosion & Materials, vol 26 (4), 6-7.
The Sprayed Concrete Association, (1999), Introduction to Sprayed Concrete, TheSprayed Concrete Association.
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The End
For enquir ies, please send email to
Edward CY YIUDepartment of Real Estate and Construction
The University of Hong Kong