MATERIALS FOR RCC REPAIRS AND REHABILITATION

AVINASH KUMAR GUPTA

EE TRAINING CCW AIR

SOOCHNA BHAWAN , NEW DELHI

14/04/2017

1.0 Repair/ Rehabilitation Strategies

• Reduction of dead/ live loads• Repair/ strengthening of columns, beams

and slabs• Improving the compressive strength of

concrete• Attending to cracks and joints• Improving masonry structure to resist

earthquake forces• Providing protective cover against the

aggressive deteriorating chemicals.

2.0 Stress Reduction

• Reducing of dead/ live loads• Replacing heavy solid partitions with light

weight partitions• Enlarging penning by removing filler wlls• Reducing number of stories• Changing the building use• Span reduction of beam by props

Materials for Repairs (Function Wise)

1)Materials for surface preparation2)Chemical rust removers for corroded

reinforcements3)Passivators for reinforcement protection4)Bonding agents5)Structural repair materials6)Non structural repair material 7)Injection grouts8)Joint sealants9)Surface coating for RCC

Selection of Materials

Essential Parameters•Low shrinkage properties•Requisite setting/ hardening properties•Workability•Good bond strength (equal)•Compatible coefficient of thermal expansion, compatible, mechanical properties & strength to that of the sub strata•Allow relative movement in case of sealant•Minimal or no curing requirement •Alkaline character•Low air & water permeability•Aesthetics•Cost•Durable, non degradable or non bio degradable•Non hazardous/ non polluting

Materials

A.Premixed cement mortar modified with non polymeric admixtures

B.Polymers/ latex modified cement addition for mortar/ concrete

C.Styrene butadiene rubber latex( SBR)D.PVDC (Poly Vinylidene Chloride)E.Epoxy ResinsF. Acrylics and modified acrylicsG.Chemicals for corrosion inhibitor, removal

of rust.

Premixed cement concrete/ Mortars

• High drying shrinkage• Slow setting• Low workability• Curing requirement• Permeable- .

Polymer modified mortars/ concrete (PMM/ PMC)

Polymers (Latex) are in the dispersed form. First added to water than cement mortar/

concrete. OPC + Aggregate + fibers + polymers. Polymers forms continuous films on drying Improved properties.

Physical and mechanical properties of polymer modified mortars

• Good workability• Improved water retention• Better flowability. Reduced bleeding/ segregation• Films gap the crack and hence better resistance to crack

propagation• Increased tensile and flexure strength. But not

improvement in compressive strength.• Attacked by acids/ sulphates/ organic solvents• Better resistance to alkalis & salts• Strength reduction with increase in temperature• More polymer lesser shrinkage• Good water proofing quality• Better abrasion resistance• Bio nondegradable

Mix Proportioning, polymer modified mortar

Cement mortar (1:2 to 1:3)Polymer latex - .05 to .2 of cement by wtw/c ratio .3 to .6

Toughness test. Without polymer modification (left), the patch flashes off very quickly and breaks like a potato chip. Notice the

residual mortar on the concrete substrate. The 10% polymer-modified patch (right) could not be moved.

Generals Guidelines1. It adheres to metal. Trowels to be

washed immediately

2. Surface to be saturated dry

3. Not to be placed below 50C & above 300C

4. Protect from rainfall

5. Joint after every 3-4 meter

6. Moist cured

7. Non toxic

8. Not to be stored in open

Fields of Application of polymer modified mortar

1) Structural repairs to RCC PMM/ PMC2) Ultra Rapid Hardening Polymer Modified Shotcrete Polymerisable monomer for leaking & flowing water Rapid hardening cement + SBR for urgent construction &

repair works.3) Polymer ferrocements Steel & carbon fibers in latex modified mortar Impact resistance4) Anti washout under water concrete Anti wash out, segregation resistance, flow ability, self

leveling ability and bleeding control. Water soluble polymers MC & HEC Water becomes viscous (Hydrogen bond with polymers and

disperses in water)

Polymer modified mortars5) Protective anticorrosive and water proofing

coatings• Polymer modified pastes & slurries• Very high polymer content 50%• OPC + silica sand + water + polymer latexes• 0.2 mm to 4mm• SBR, PAE, EVA, SAE• Elongation & water resistance, crack bridging

capacity6) Bond Coats• PM CM paste & slurries • Bond coats/ grouts• Very good adhesive qualities on cementitious as

well on metallic surface.

APPLICATIONS

POLYMER MODIFIED MORTARS

EPOXIESEpoxies• Polymerisation takes place when epoxy resin &

hardener come in contactAdvantages• Good machanical strength• Chemical resistance• Ease of workingApplications• High performance coatings• Adhesives• Injection grouting• High performance systems• Industrial flouring • Grouting

EPOXIES• Materials

A. Epoxy resins :-• DGEBA(Di Glycidyl Ether of Bisphenol – A)

• High viscosity

B. Epoxy Hardner :-• Polyamide• Amine adduct• Polyamide• Low viscosity polyamide• Aromatic amine adduct

EPOXIES

Mix A with B

PROCESS Epoxy resin + Hardner Liquid state (Pot life usable) Gels (thick, not usable) Soft solid Hard solid

Epoxy Resin A

Hardner B

Liquid

Usable or pot life

Too thick to use

Soft Solid

GELS Hardens

Hard Solid

EPOXY FLOOR

High Build Epoxy system

Modified Epoxy system• Diluents• Coal tax epoxy system• Rubber modified epoxy system• Epoxy phenolic Inter Penetrating

Polymer Network System (IPN)• Epoxy mortar/ concrete• Composite fiber system

Modified Epoxy system

A. Diluents• Used for lowering viscosity• Improving handling charactersticsB. Coal tar Epoxy system• Coal tar epoxy resin• Polyamine hardner• Water resistant protective coatings, ships

marine structures• 40:60 ratio

Modified Epoxy system

C. Rubber modified epoxy systemImproves drawbacks of • Brittleness• Low elongationD. IPNs

• Coatings for concrete structures• Steel reinforcement bars against corrosion

REHABILITATION AND RETROFITTING E. Epoxy mortar/ concrete• Epoxy + silica sand (aggregate)• Structural repairs• Industrial flooring• Foundation granting• Roads• Optimum resin sand 1:7

F. Composite fiber system• Fiber reinforced layer wrapped to exterior

surface

EPOXIESPRECAUTIONS• Toxic – care to handle• Use rubber gloves• Utensils to be cleaned immediately• Pot life (usable life) ½ to 2 hours• Not to be used in exposed environment• Costlier

.

EPOXIES

FIELD OF APPLICATIONS• Anticorrosive & water proofing protective

coatings FBEC (Fusion bonded epoxy power

coatings) as well as IPN coatings for bars against corrosion. Provides tough film.

Epoxy coating in conjunction with epoxy grouting and polyurethane coatings.

• Bond coats• Structural repairs

APPLICATIONS

APPLICATIONS

CONCRTE INJECTION