Pile/Pier Repairing Using CFRP

METHODOLOGY FOR REPAIR OF DAMAGED PIERS/PILES/GIRDERS USING CFRP

IMPORTANT LINKS

Chappergram Bridge (Before Repair)

Chappergram Bridge (After Repair using CFRP)

STEPS:

Any weak spots, disintegrated concrete or honey combed area must be chipped off, until sound surface is achieved
The cracks will be cleaned with wire brush on the concrete surface to remove any dust or dirt.
The surface of the cracks is then grinded to make a good bonding surface for epoxy adhesive.
As per ratio the two component of epoxy adhesive Chemdur 31 (or equivalent), will be mixed together. It is important that mixed epoxy must be applied within the pot life.
Injection nozzles will be fixed on the prepared crack surface with mixed epoxy at specified locations.
The remaining cracks surface will be sealed off with epoxy adhesive with the help of scrapper to make the crack leakage free.
After at least 24 hours of nozzles fixing, injection procedure will be initiated.
Mixed two components of epoxy Chemdur 52 (or equivalent) will be fed in to the injection pump.
Out let pipe of the injection pump will be inserted into one of the nozzle, preferably the lowest one.
Compressed air (without moisture) will be pumped into the injection pump via inlet.
The epoxy will be injected against the gravity into the nozzle at a pressure of 100psi (0.69Mpa), until it seeps out of the nozzle above. The lower nozzle will be corked.
Now injection outlet pipe will be inserted into the seeped out nozzle, and epoxy will be injected again. When it will seep out from above nozzle this inlet nozzle will be corked. All the nozzles will be fed with epoxy unless these are filled completely.
In case of through cracks in a structural component, the nozzles will be fixed on both sides, and if epoxy seeps from other side it will also be corked.
Whole length of the crack will be injected in this manner. The injected cracks will be left to cure for 24 hours.
The nozzles will be flushed off, and the sealed crack surface will be grinded again, to make a uniform surface.
All the cracks will be injected in the same manner.
The surface of application will be primed with Chemdur 300-impregnation epoxy (or equivalent), via roller.
CFRP CFW-600 fabric will be cut as per desired length, and will be placed on table
fixed with polythene sheet.
The impregnation epoxy will be applied with roller on fabric as well as on the piles/piers/girders.
The saturated fabric will be applied on the surface, and will be pressed with hands.
The special roller will be pressed hard on the applied fabric to remove any voids/kinks and gaps.
The applied fabric will leave for curing, for one day.
For application of the 2nd layer of CFRP (Carbon fiber reinforced polymer or equivalent) the steps 17 to 22 will be repeated.

Cracks Repair by Epoxy Injection

Filling cracks by injection is necessary to join the de-bonded concrete, and bring the structure to stronger state. Injection epoxy is widely used and recommended procedure for structural strengthening.

Epoxy injection consists of mainly two components.

Chemical epoxy for sealing in the crack. The material should be low viscosity with high compressive strength, more than concrete, with good bond and tensile strength so that the repair crack must not reappear.
High strength epoxy for sealing cracks on concrete surface, and to bond the injection nozzles, so that it can withstand the under pressure epoxy from injection pump.

CHEMDUR 52 (or equivalent), is two component low viscosity (density 1.1 kg/l), injection epoxy used for sealing of cracks in structural components such as bridges, industrial structures, columns, beams foundations, walls, floor slabs, based on epoxy resins. It complies with ASTM C 881-78, Type I, Grade 1 Class B+C. It not only forms an effective barrier against water infiltration of corrosion promoting media, but also structurally bonds the concrete section together.

CHEMDUR 31 (or equivalent), is a thixotropic epoxy resin adhesive. It is a multipurpose adhesive and can be used as the crack and surface sealing. It complies with ASTM C 881-78 Type I, Grade 3 Class B+C.

CFRP Wrap CFW-600 is a unidirectional Woven Carbon Fiber Fabric the wet application process for Structural Strengthening having Tensile strength: 4900 N/mm2 (nominal), Tensile E-modulus: 230, 000 N/mm2, Elongation at break: 1.5 % (nominal) and Laminate thickness is 1.4 mm per layer (impregnated with Chemdur 300).

CHEMDUR 300 is a two part, epoxy based impregnating resin for CFRP Wrap fabric reinforcement for the wet application method and primer resin for the wet application system. Easy mix and application by trowel and impregnation roller, manufactured for manual or mechanical saturation methods, good adhesion to many substrates, High mechanical properties, extra long pot life.

The PDF Drawings of Proposed Rehabilitation of Damaged Bridge using CFRP is as follows:

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Pile/Pier Repairing Using CFRP

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