repair and strengthening

8/7/2019 Repair and Strengthening

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Repair and Strengthening of Repair and Strengthening of Reinforced Concrete StructuresReinforced Concrete Structures

By :-

Dixit Bhardwaj



Definitions:-Definitions:-Repair involves re-establishing thestrength

and function of the damagedelements.

Strengthening involves upgradingof the

strength and/or the stiffness of astructural



Damage of concreteDamag

e of concrete

Concrete structures can be damaged due to

different environmental effects:-

• Freezing and thawing

• Abrasion

• Corrosion

• Overloading



Freezing and thawingFreezing

and thawing

ØExposing damp concrete to freezingand

thawing cycles results in poor qualityconcrete.

ØGood quality concrete withsufficient

air-entrained will resist cyclic freezing

for years.



AbrasionAbrasion

• Abrasion of concrete floors may resultfrom

foot or vehicular traffic.

• Wind or waterborne particles can alsoabrade

concrete surfaces.



CorrosionCorrosion

• Concrete can be damaged when exposedto

aggressive chemical environments.

• Sulphate chemicals attacks concrete. It isfound

naturally in some soils and sewer treatmentfacilities.

• Concrete can be made to performsatisfactorily in various atmospheric



Types of DamageTypes of Damage:-:-•

Non-Structural damage•

•-Doors, windows, partitions• Do not affect the integrity of • the structure.

•

Structural damage• -Beams, columns, slabs etc.• Can affect the integrity of the

building.



Examples of ConcreteExamples of Concrete

Damages:-Damages:-

Freeze-Thaw

Deterioration



Corrosion, abrasion &Corrosion, abrasion &

deteriorationdeterioration



Corrosion of steelCorrosion of steel

With improper cover or

protection.

Steel starts to corrode;

Pushes concrete cover away;

Deterioration progresses.



Spalling of concreteSpalling of concrete



Spalling of concrete-Spalling of concrete-insufficient coverinsufficient cover



Severe Damage:- Earthquake;Severe Damage:- Earthquake;

Blasting & ExplosionsBlasting & Explosions

Damaged columnsEarthquake



ExplosionExplosion

D a m a g e d

w a ll

D a m a g e d

b u ild in g



RepairingRepairing

concreteconcretestructuresstructures



Repairing concreteRepairing concrete

structuresstructures

Repairing concrete structures requiresspecial

training and skills.

Each structure is a unique system anddamage

in one building is usually differentfrom that of

other buildings.



Before the repair :-Before the repair :-

• Initial investigation of the damage.

• Assessment of the condition of thebuilding.

• Emergency protection plan.

• Thorough study of the damage to define:

• Significance of the damaged elements;

•Level of damage;

• Cause of damage.



Selecting the repair schemeSelecting the repair scheme

In selecting the repairing scheme, thefollowing aspects need to be considered:

• Type and age of the structure;

• Importance of the structure;

• Type and degree of the damage;

• Available materials;• Cost and feasibility;

• Aesthetics.



Three main stages:-Three main stages:-

For the repair to be successful, it isvery important to carefully select:

• Materials;

• Preparation;

• Application.



MaterialMaterial

It is known that new concrete does not bond well toexisting

concrete due to volumetric changes during setting.

Selecting proper repairing material is the first and

perhaps themost important issue for a successful repair.

There are several cement and bonding agents

availablein the market…BUT you need to check carefully:

• Properties and data sheets;

•Applicability for your application and;

• Method and instructions for a lication.



PreparationPreparation

Proper preparation is also crucial for asuccessful

repair.

Preparation usually includes but is notlimited to the

following:

• Cleaning the damaged area;

• Removing all loose concrete and bond

inhibiting material.



ApplicationApplication

It Depends on :-

• Type and location of the damage.

• Material used for repair.

It is important to strictly follow the

manufacturer’sinstructions for application.



Methods of repair:Methods of repair:

Many repairing techniques are being usedin

concrete structures. The following are

somecommon techniques:

• Patching;

• Crack injection;

• Removal and replacement;

• Jacketing.



Honeycombing

Spalling – Local damage



PatchingPatching

Define the area needs to bepatched;

Chip out lose material and cleanpatch area;

Use suitable bonding agent.

Place concrete patch materialand finish.

Use appropriate curing practices.

P ti f tP

ti f t



Preparation for concretePreparation for concrete

patching:-patching:-

R i f h ll k bR

i f h ll k b



Repair of shallow crack byRepair of shallow crack bypatchingpatching

- /1 E n la rg e tra ck th e cra ck w ith a co ld

ch ise l a n d a h a m m e r

-2 C le a n th e u n d e rcu t a re a w ith a stiff

.w ire b ru sh

-3 M oiste n in g th e a re a to b e

.re p a ire d- .4 Fo rce th e co n cre te p a tch m ix in to th e a re a



Preparation - Water blastingPreparation - Water blasting

Remove loose and deteriorated concrete



Patching by ShotcretePatching by Shotcrete



Crack injectionCrack injection

Crack injection is widely used to groutshallow and deep cracks.

Polyurethane injection is used to seal

cracks in water retaining structures.Epoxy raisin is used for structuralcracks:

High viscosity for wide cracks;

Low viscosity for fine cracks.



Crack injectionCrack injection



Removal and replacementRemoval and replacement

Removal and replacement techniqueis used to

replace badly damaged portions of concrete in

columns, beams, walls or a slabs.



Repair of damaged columnRepair of damaged column

(removal & replacement)(removal & replacement)



JacketingJacketing

Jacketing is used forrepairing damaged columnsor beams.

It can also be used forstrengthening undamagedcolumns or beams to

improve strength and/orstiffness.

One or two sides jacketing



Three or four sides jacketingThree or four sides jacketing

repair and strengthening

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