Glass fiber reinforcement

Armored concrete is a generally applied building material. Although concrete has a high compressive strength, the tensile strength is minor. To work around this limitation, reinforcement is used on the side of the elements that are subjected to traction.

Glass fiber reinforcement

Steel rods are an effective and cost-efficient armor of concrete, but unfortunately are often subjected to corrosion, for instance through the impact of chloride ions.

This often occurs when concrete comes in contact with sea salt or thaw salt or even where contaminated aggregates are (were) used in the concrete mix.

If the steel reinforcement rods are well-isolated from the source of corrosion, or are surrounded by concrete with a high pH-value, they could hold out for decades, without any visible form of decay of concrete. Unfortunately, it is not always possible to provide sufficient protection from corrosion.

Insufficient cover, a poor design, a faulty concrete composition and the presence of large quantities of aggressive components may all result in cracks occurring in the concrete and corrosion of the steel reinforcement rods.

Developing methods to combat reinforcement corrosion

To combat corrosion of reinforced steel it is possible to use reinforced steel protected with epoxy resin.

However, recent studies have shown that this solution does not suffice, even if the coating is applied correctly and the rods have been treated and installed professionally (studies from Ken Clear (1992), Sagues (1998) and Pyc & Weyers (2000)).

Other solutions are being tried out. For instance, stainless steel has excellent corrosion resistant properties but due to its cost price, large-scale use is limited.

Another solution was to improve the concrete composition and increase the concrete topping so the chloride ions would take much longer before reaching the steel. This is a good solution on paper, but in practice it will be hard to realize, because of the circumstances during production and processing: pressure of time and the quality / the level of education of the deployed personnel.

The development of cathodic protection methods or the application of low-voltage current has provided a new solution which, although technically sound, is also expensive and requires expertise from the designer in the field of chemistry and electricity.

Glasvezelwapening Glasvezelwapening

Corrosion-resistant glass fiber reinforcement
Ervas glass fiber reinforcement rods do not have the disadvantages mentioned earlier and are appealing in terms of costs/benefit proportions

Ervas glass fiber reinforcement rods are made of a bundle of clamped up glass fibers that are impregnated in a thermo-hardening resin. This resin ensures the fibers are held together and operate as 1 rod. The end result is a rod that is fully inert, non-corrosive and alkali-resistant. In order to improve the adhesion, the outer side has been reformed and sanded in. Glass fiber reinforcement rods are known as gfrp – reinforcement rods (glass fiber reinforced plastic or polymer rebars). Gfrp - rods are produced in a factory through pultrusion, and they are available in various diameters from 6 mm to 32 mm. They may be used instead of stainless steel or coated reinforcement steel (epoxy, zinc).

In theory, glass fiber reinforcement may be used in common reinforced concrete (without pre- or post-stressing) in components that are subjected to bending, compression and shifting.


The advantages of glass fiber reinforcement

  • Fully inert, non-corrosive and alkali-resistant
  • Fully resistant against chloride ions
  • The tensile strength is 1½ to 2 times that of steel
  • Is 4 times as light as steel and may therefore be easily transported and installed without special lifting equipment.
  • Considerably extends the life-span of concrete structures in aggressive environments
  • Requires no maintenance
  • Transparent for magnetic fields and radio frequencies.
  • Not conductive: neither electrically, nor  thermally.
  • Good resistance against impact: resists sudden and high concentrated loads.
  • Excellent wear-resistance with cyclical load conditions.
  • Dimensionally stable in fluctuations of temperature: the expansion/shrinkage of glass fiber reinforcement rods fits in closely with that of concrete.

Use: Where can glass fiber be used?
Wherever there is concern for serious corrosion of concrete reinforcement through chemical affection or for instance by chlorides. In short, anywhere where stainless steel, galvanized steel or epoxy-coated steel is currently used: where there is minor concrete topping, for instance like in architectural concrete; where reinforced steel may give cause for electro-magnetic interferences.

  1. Concrete subject to thaw salts
    • Bridge decks
    • New -jerseys
    • Parking garages
    • Salt storage repositories
  2. Concrete subject to sea salt
    • Riverside walls, seawalls
    • Buildings and artworks in the vicinity of the sea
    • Special constructions like aquariums, amusement parks
    • Artificial reefs, wave breakers
    • Floating docks
    • Piers, jetties
  3. Concrete subject to other aggressive elements
    • Chemical factories (collection zones for tank leakages)
    • Concrete around pipelines and tanks for fossil fuels
    • Pulp and paper industry
    • Water purification stations
    • Petro-chemical factories
    • Cooling towers
    • Fireplaces
    • Nuclear installations
    • Agri concrete
    • Brine tanks
    • Chemical cisterns and pits
    • Mining applications: rock anchors, electrolysis tanks, metal extraction tanks
    • Concrete around indoor swimming pools
  4. Concrete with minor Topping
    • Imitation natural stone elements
    • Architectural prefabricated concrete, cornices
    • Façade panels, façade elements
    • Balconies
  5. Application where low conduction or an electromagnetic neutrality is required
    • MRI-wards in hospitals
    • Buildings for the calibration of instruments
    • Radar and compass buildings
    • Control towers
    • Military installations which must remain undetected by radar
    • Manholes for electric and telephone equipment and wiring
    • Electrical transformer stations
    • Concrete in the vicinity of power current cables and stations
    • Railroad crossings
    • Laboratories
    • Aluminum and copper melting ovens
  6. Applications in case of drillings when concrete temporarily requires reinforcement which may not damage the cutter head
    • Tunnels
    • Supporting walls in mining
    • Subway works
    • Vertical shafts
  7. Other applications
    • Structural repair of wood
    • Polymer concrete

Some preconceptions
There are some preconceptions against glass fiber reinforcement, which we would like to discuss further here:

  1. Glass fiber was argued to not be alkali-resistant (concrete with pH > 10). This is not an issue the glass fibers are fully embedded in the epoxy matrix and therefore do not directly come in contact with the concrete, except for at the outer edges. However, these need not to be specially protected because the alkalis will only penetrate just a few millimeters.
  2. Ervas glass fiber rods cannot be bended at the building site itself. They must be pre-shaped in the factory, with the right measurements and bends. However, this is often also the case for common reinforcement rods, which then must be transported to another location to receive an epoxy coat. Besides, this coating will damage easily during transportation and installation, which in turn will lead to the problem of pit corrosion on the spot where the steel is not covered by the epoxy protection over a relatively small surface. Stainless steel may also be bent at the wharf but it should be done with a machine that does not use common carbon steel at the same time. Because of the enormous forces that are exerted in bending, particles of common steel may be pressed into the stainless steel and damage the passivation layer. This will also lead to pit corrosion. Besides, stainless steel is more expensive. In general, the supplier of glass fiber reinforcement has standard brackets and corner brackets available, which make it possible to achieve the desired result, without extra pre-treatments.
  3. Although glass fiber reinforcement weighs only a quarter of steel and therefore provides great advantages regarding handling and applying, it has a tendency to come to the surface when the concrete trembles. This must be prevented by tying the reinforcement firmly to the spacer blocks and spacer lugs, with plasticized iron wire or nylon thread. This work will in any case be less strenuous on the steel bender and fits well in the framework of the new labor legislation which aims to protect the health of builders by restrictions on the amount of weight allowed to be lifted.
  4. Ervas glass fiber reinforcement steel has other physical properties compared to common steel: a lower elasticity modulus and lower stiffness. This may be neutralized by designing concrete elements with a larger proportion of reinforcement steel or by designing deeper elements. Glass fiber reinforcement steel is often used where these properties are of less influence, like in the upper reinforcement layer of a bridge deck. It is obvious that the glass fiber reinforcement is no direct replacement of common reinforced steel, but it has certain advantages which, if used sensibly in specific applications, will provide effective and cost-efficient solutions for the designer, contractor and client.

Technical data
For technical details and download of this, go to Technical data Ervas Adhesive Reinforcement.