04b Concrete Repair Methods

5/26/2018 04b Concrete Repair Methods

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RECO2006 Construction IV

Concrete Repair

Edward CY YIU

Department of Real Estate and Construction

January 2007

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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

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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

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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

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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

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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.

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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

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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)


mortar, feature lightweight

Emaco R740Restore concrete and inhibit further

deterioration before significant structural

damage occurs.


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.


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


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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



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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

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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

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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

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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)

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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

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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)

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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.)

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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


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

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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

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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.

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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.

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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

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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.

72

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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For enquir ies, please send email to

Edward CY YIUDepartment of Real Estate and Construction

The University of Hong Kong

[email protected]

04b Concrete Repair Methods

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