On-Site VaRTM Steel Repair and Reinforcement Method

The Vacuum-assisted Resin Transfer Molding method (VaRTM), which is used in the manufacturing of FRP structural components for wind turbine blades and the aircraft field, is applied to the repair and reinforcement of steel structures.

This is a new repair and reinforcement technique that uses vacuum pressure to inject resin, enabling the easy molding of multiple layers of carbon fiber sheets and the rapid production of high-quality CFRP reinforcement materials. It can be used not only for repairing cross-sectional losses due to steel corrosion but also for reinforcing joints in steel structures.

※ The On-site VaRTM method is a patented technology developed by Toray Industries, Inc.

Outline of the On-Site VaRTM Method

Merits of Use

①

It is possible to form high-quality and stable CFRP reinforcement materials on-site while conforming to the shape of the structure.
②

Construction can be completed in a short period regardless of the number of layers applied. (Basically within 3 days)
③

This method does not require fire, welding, or heavy machinery, making repairs possible even in explosion-proof areas.
④

Reinforcement materials for three-dimensional cross-sections (e.g., stiffening ribs) can be formed on-site.
⑤

There is almost no risk of curing defects caused by condensation during the curing process.

Fields of Application

Factory
Transmission Tower
Highway Facility

Materials and Equipment Used

Reinforcement Materials

Materials	Product Name	Specification
TORAYCA® Cloth	UM46-40P	UM46-40P Unidirectional CF sheet with particles, weight: 400g/m² Tensile Strength: 2400 MPa or higher, Tensile Modulus: 440 Gpa
Adhesive Layer Sheet	G-Flow	G-Flow GF Mesh Sheet, weight: 500g/m²
Adhesive Layer Sheet	MC300A	MC300A Chopped Strand Mat, weight: 300g/m²
Impregnation Adhesive Resin	AUP40T1	AUP40T1 Room temperature curing epoxy resin, low viscosity
Primer	E258R	E258R Room temperature curing epoxy resin, high viscosity (putty-like)

※ TORAYCA® is a registered trademark of Toray Industries, Inc.

Main Equipment Used

Vacuum Pump	Digital Vacuum Gauge	Vacuum Can

Standard Construction Procedure

STEP 1

Surface Preparation

Grind the bonding surface, remove any corroded areas, and expose the sound steel surface.
STEP 2

Primer Coating

Apply the primer and allowing it to fully cure.
STEP 3

Reinforcement Material Installation

Apply the fiber sheet materials, starting with the adhesive layer sheet, followed by the TORAYCA® cloth.
STEP 4

Auxiliary Materials Layout

Place sealant tape around the perimeter of the sheet. Apply the peel ply and flow media in that order on top of the TORAYCA® cloth. Install plastic tubes for air intake and resin injection, cover with bagging film, and seal the vacuum area.
STEP 5

Vacuum Suction

Operate the vacuum pump to create a vacuum inside the bagging film. Use the vacuum gauge to ensure the appropriate level of vacuum is reached and confirm that there are no air leaks.
STEP 6

Resin Injection

Mix the impregnation resin and begin injecting it into the CF sheet.
STEP 7

Curing

Allow the impregnation resin to cure until it is fully hardened.
STEP 8

Removal of Auxiliary Materials

Remove the auxiliary materials.
STEP 9

Finishing

Apply coating to the CFRP repair area.

STEP.3 - Reinforcement Material Installation

STEP.6 - Resin Injection

Comparison with Other Methods

Methods	Steel Plate Attachment	CF Sheet Bonding （Hand Lay-Up）	On-Site VaRTM Method
Picture
Strong points	Conventional technology Generous technology, data, and past construction projects	Low initial investment in construction No heavy machinery required Simple construction process	High-quality reinforcement can be achieved Shortened construction period No need for weatherproofing 3D reinforcement materials can be formed on-site
Weak points	Concerns about the reduction in base material performance due to the installation of bolt holes Possibility of re-corrosion	In case of multi-layering, long construction periods are required Rain and moisture protection is required during construction and curing proses	Initial investment in tools is required Professional construction skills are required Currently, there is limited reinforcement data

Methods	On-Site VaRTM Method
Picture
Strong points	High-quality reinforcement can be achieved Shortened construction period No need for weatherproofing 3D reinforcement materials can be formed on-site
Weak points	Initial investment in tools is required Professional construction skills are required Currently, there is limited reinforcement data