Reinforcement of the flexural strength of a beam or slab
RELATED MATERIALS
MEGAPLATE: carbon plates for structural strengthening
EPOMAX-PL: two-component epoxy adhesive paste for composite plates
MEGAWRAP-200: carbon fabric for structural strengthening
EPOMAX-LD: two-component epoxy impregnation adhesive for composite fabrics
EPOMAX-EK: two-component epoxy putty
MEGACRET-40: high-strength fibre-reinforced repairing mortar
I. NATURE OF THE PROBLEM – REQUIREMENTS
Increasing the flexural strength of concrete beams or slabs may be needed when:
- Loads increase or the use of the structure changes.
- An existing building must be upgraded to meet new codes.
- Construction materials have aged, reinforcement has corroded, or defects are present.
- Elements require repair after earthquake damage.
A strengthening system should increase flexural capacity and stiffness while limiting cracking and fatigue.
II. SOLUTION
Flexural strength is increased by externally bonding carbon composite materials to the tension face. Carbon plates (MEGAPLATE) or carbon fabrics (MEGAWRAP-200) are adhered with epoxy adhesives and fibres aligned along the stress direction. This reinforcement:
- Increases flexural strength and stiffness.
- Reduces cracking and improves fatigue behaviour.
Carbon plates are lighter, easy to cut and install, durable, corrosion resistant and thin compared with steel plate strengthening.
III. APPLICATION
1. Prepare the substrate: remove loose parts, plaster, paint, oil or grease. Clean with a hard brush and make the surface flat. Fill imperfections with MEGACRET-40 mortar or EPOMAX-EK epoxy putty.
2. Remove the protective tape from one side of the MEGAPLATE and apply EPOMAX-PL adhesive with a trowel. Spread the adhesive so that most excess paste is along the centre of the plate, not at the edges.
3. Place the carbon plate on the dry, clean surface and press with a plastic roller until paste overflows at the edges and trapped air is removed. After pressing, the adhesive layer should be roughly 0.5 to 2 mm thick.
4. Tap the plate gently to detect voids. If extra anchorage at the beam ends is required, wrap carbon fibre strips (MEGAWRAP-200) around the plate to provide shear reinforcement.
IV. REMARKS
- Reinforced elements should be unloaded as much as possible since composite reinforcement becomes effective after deformation increases.
- Ensure good substrate preparation and anchorage beyond the strengthened region.
- Avoid splicing MEGAPLATE; crossing of fibres or plates is allowed.
- The substrate strength can be tested by the pull-off method. Extra plates can be installed for quality control tests.
- The open time of epoxy systems decreases with higher temperatures.
- High temperatures, such as during a fire, reduce the efficiency of composite reinforcement; protect plates from heat and sunlight.
- Apply fibre reinforced polymer systems only when the concrete surface temperature is above 5 degrees Celsius.
RELATED MATERIALS
MEGAPLATE: carbon plates for structural strengthening
EPOMAX-PL: two-component epoxy adhesive paste for composite plates
MEGAWRAP-200: carbon fabric for structural strengthening
EPOMAX-LD: two-component epoxy impregnation adhesive for composite fabrics
EPOMAX-EK: two-component epoxy putty
MEGACRET-40: high-strength fibre-reinforced repairing mortar
I. NATURE OF THE PROBLEM – REQUIREMENTS
Increasing the flexural strength of concrete beams or slabs may be needed when:
- Loads increase or the use of the structure changes.
- An existing building must be upgraded to meet new codes.
- Construction materials have aged, reinforcement has corroded, or defects are present.
- Elements require repair after earthquake damage.
A strengthening system should increase flexural capacity and stiffness while limiting cracking and fatigue.
II. SOLUTION
Flexural strength is increased by externally bonding carbon composite materials to the tension face. Carbon plates (MEGAPLATE) or carbon fabrics (MEGAWRAP-200) are adhered with epoxy adhesives and fibres aligned along the stress direction. This reinforcement:
- Increases flexural strength and stiffness.
- Reduces cracking and improves fatigue behaviour.
Carbon plates are lighter, easy to cut and install, durable, corrosion resistant and thin compared with steel plate strengthening.
III. APPLICATION
1. Prepare the substrate: remove loose parts, plaster, paint, oil or grease. Clean with a hard brush and make the surface flat. Fill imperfections with MEGACRET-40 mortar or EPOMAX-EK epoxy putty.
2. Remove the protective tape from one side of the MEGAPLATE and apply EPOMAX-PL adhesive with a trowel. Spread the adhesive so that most excess paste is along the centre of the plate, not at the edges.
3. Place the carbon plate on the dry, clean surface and press with a plastic roller until paste overflows at the edges and trapped air is removed. After pressing, the adhesive layer should be roughly 0.5 to 2 mm thick.
4. Tap the plate gently to detect voids. If extra anchorage at the beam ends is required, wrap carbon fibre strips (MEGAWRAP-200) around the plate to provide shear reinforcement.
IV. REMARKS
- Reinforced elements should be unloaded as much as possible since composite reinforcement becomes effective after deformation increases.
- Ensure good substrate preparation and anchorage beyond the strengthened region.
- Avoid splicing MEGAPLATE; crossing of fibres or plates is allowed.
- The substrate strength can be tested by the pull-off method. Extra plates can be installed for quality control tests.
- The open time of epoxy systems decreases with higher temperatures.
- High temperatures, such as during a fire, reduce the efficiency of composite reinforcement; protect plates from heat and sunlight.
- Apply fibre reinforced polymer systems only when the concrete surface temperature is above 5 degrees Celsius.
