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FAQs Schöck Combar®

Approvals and certificates

How has Schöck Combar® been proven fit for purpose?

There is no standard governing the use of Schöck Combar®. Planning certainty is, however, offered by the general technical approval, issued by

  • DIBt (German Institute for Construction Technology):
    General technical approval (no.: Z-1.6-238) Schöck Combar® reinforcing bar

For further approvals and certificates for other countries, please refer to www.schoeck-combar.com

Planning / Design

Which standard can be used for Schöck Combar® designs?

Schöck Combar® designs can be based on EC2 and ACI. As EC2 does not deal with glass fibre reinforcement, some deviating rules apply and are laid out in the general technical approval for Combar®.

I normally base designs on EC, and use ACI for glass fibre reinforcement in the absence of a suitable European standard. Is that possible?

Schöck Combar® is regulated by the general technical approval (GTA no.: Z-1.6-238) issued by DIBt (German Institute for Construction Technology). The provisions governing design and calculation, and the rules governing construction that are specified in this GTA are derived from EC2. The GTA also contains some regulations that deviate from EC2 to take account of the special material properties of Schöck Combar®. The design concept for Schöck Combar® is aligned to EC2 / fib, which is a more recent and modern set of rules compared to ACI that also addresses the issue of durability, which is scarcely mentioned in ACI.

I have created a steel design. How much glass fibre would that equate to?

The main difference between Schöck Combar® and reinforcement steel is the much lower modulus of elasticity of Schöck Combar®, whereas the long-term tensile strength of both Schöck Combar® and reinforcement steel is virtually the same (Combar® 445 N/mm², reinforcement steel 435 N/mm²). This produces the following differences:

Elements where the load is key:

  • approximately the same cross section as reinforcement steel

Elements where the crack width is key:

  • provided the same boundary conditions apply, approximately twice the reinforcement cross section is needed for Schöck Combar®

Elements where the deflection is key:

  • provided the same boundary conditions apply, approximately three times the reinforcement cross section is needed for Schöck Combar®

An accurate design process does, however, determine the exact reinforcement needs.

Where are the differences when designing with Schöck Combar® compared to reinforcement steel?

The main differences when designing with Schöck Combar® compared to reinforcement steel are

  • the lower modulus of elasticity (60,000 N/mm²)
  • the structure of the material (one-directional fibre pattern) and thus
    • the design of the shear forces
    • the limitation of deflection
    • the limitation of crack width

Design tools

for

  • Design and construction
  • Structural calculations
  • Drawing creation
  • Execution

are available in our Download area

Installation

For detailed information on how to handle and install Schöck Combar®, please refer to our Handling and Safety Tips. Particular care must be taken to avoid any contact between Schöck Combar® bars and sharp edged objects.

How much time and effort should I calculate when installing Schöck Combar®?

The work involved is similar to the installation of reinforcement steel bars.

  • The bars are cut to length with an iron saw or angle grinder (don't use a bolt cutter or the bars will fray)
  • The usual spacers are needed to observe clearance to the concrete cover (possibly less than with reinforcement steel)

Note:
Installation price quotes are often based on kg.
Attention! 1 kg of Schöck Combar® is equivalent to three times the length in meters of reinforcement steel.

How are Schöck Combar® bars joined together?

  • Tie wire is commonly used
  • Cable ties (non-metallic connection)
  • Special clips for joining same-diameter bars (8 and 12 mm) to each other
  • Cable clamps developed by Schöck are available for joining Schöck Combar® with steel rebars of more than 32 mm diameter.

Can Schöck Combar® be bonded into construction materials (timber, concrete, etc.)?

The material is not harmed by any type of adhesive (regardless of whether it contains solvents or not, or is single- or multi-component)!
As such, all common adhesives are suitable in principle, although the load bearing capacity of the bonds should first be determined by a specialist on a case by case basis.

Is there a nut to fit the outer thread on Schöck Combar® bars?

No.
The ribs on the bar are designed for optimum composite construction in concrete.

Installation in civil engineering projects

If you have questions relating to installation in civil engineering projects (e.g. tunnels), please contact our Schöck Combar® design support colleagues directly (+49 7223 967449).

Material costs

What does Schöck Combar® cost?

The material cost is determined by the type and volume of material, which must be based on information provided by the structural engineer.

What is the price ratio of Schöck Combar® to reinforcement steel?

Price / Kg
Schöck Combar® : Rebar
15-20 : 1

but ! Weight
Schöck Combar® : Rebar
1 : 3

=> Price
Schöck Combar® : Rebar
5-7 : 1

Detailed design is, however, necessary to determine whether less, the same amount, or more Schöck Combar® is needed compared to reinforcement steel.

How much more does a slab reinforced with Schöck Combar® cost compared to the use of reinforcement steel?

This would cost at least 50 – 100 €/m² more.

Where can I buy Schöck Combar®?

Schöck Combar® glass fibre reinforcement can be purchased directly from Schöck or from our partner SIG (UK only). In Ireland Schöck Combar® is supplied exclusively by Contech Accessories.

Costs for (planning) works to design Schöck Combar® glass fibre reinforcement

What does a structural calculation using Schöck Combar® cost?

A design using Schöck Combar® must be created by a structural engineer/stress analyst. Please ask your architect or stress analyst about the cost of such design creation.

The free service offered by Schöck includes:

  • Technical product and design advice:
    • When converting reinforcement steel designs to Schöck Combar®
    • When designing with Schöck Combar® from the start
    • Schöck offers to perform structural calculations. Please address enquiries to design@schoeck.co.uk
  • For design tools, please look here

Material

What is Schöck Combar® made of?

  • E-CR glass fibres (75% volume, 88% weight proportion)
    Particularly corrosion resistant glass fibre
  • Vinyl ester resin (25% volume, 12% weight proportion)
    Synthetic thermosetting resin that, when hardened, is extremely strong with good resistance to chemicals

Schöck Combar® is designed and approved for a service life of more than 100 years, even in warm and moist concrete (alkaline surroundings).

Schöck Combar® is particularly resistant to:

  • Chlorides, fluorides
  • Saline solutions (de-icing salt, sea salt, fertilisers, etc.)
  • Alcohol, aldehydes, oil, fuels and most acids, lyes and organic solvents

What can you say about the energy used in manufacturing Schöck Combar® compared to reinforcement steel?

  • Glass fibre production:
    Melted at 1,200°C – 1,600°C
  • Steel production:
    Energy-intensive chemical reaction that produces CO2
    Temperature > 2,600° C

Is glass fibre dust hazardous?

As with any work that involves the production of dust particles (e.g. when processing timber and metal), suitable protective equipment (mask, goggles) should always be worn.

Suspended dust particles that can be inhaled < 10 μm
Fine dust particles that can get into the lungs < 2.5 μm. They can penetrate as far as the alveoli.
[Ulrike Koller, GSF-Forschungszentrum für Umwelt und Gesundheit, ÖA-FLUGS Scientific advisor: Prof.Dr.Dr.H.-E.Wichmann, Director, GSF-Institut für Epidemiologie]

The diameters of the continuous glass fibres used in Schöck Combar® range between 20 and 30 μm. As such, they cannot get into the lungs and the risk of chronic effects on the lungs is very slight. Possible irritation caused by these fibres is of a simple mechanical nature and can be minimised with good hygiene to avoid dust and by wearing suitable protective equipment.
[APFE, European Glass Fibre Producers Association Continuous Filament Glass Fibre and Human Health July 2003]

Is the resin harmful to health?

Schöck Combar® bars contain resin that has fully hardened, with no further chemical reactions taking place. Accordingly, the material is immune to most acids, lyes, solvents and microorganisms.
Schöck Combar® can be disposed of as household waste.
[Dr. Vogt chemical laboratory, Karlsruhe: "Examination of Schöck Combar® glass fibre reinforcing bars", 2005 (LAGA) is available in our Download area]

What happens to Schöck Combar® in a fire?

Schöck Combar® is surrounded by concrete. It therefore takes longer for higher temperatures to reach Schöck Combar®.
Depending on the concrete cover / fireproofing and fire impact, a concrete element loses load bearing capacity after about 30 to 90 minutes.

For details on the restrictions on load bearing capacity in fires, please refer to "Schöck Combar® Technical Information".

Schöck Combar® bars are flame retardant. Once the resin near the surface has burned away, the flames extinguish.
Schöck Combar® has a very low calorific value of 0.93 kWh/kg (as measured by IBMB Braunschweig)
The comparable value of heating oil is about 9.5 kWh/kg, while most plastics range between 6 and 12 kWh/kg.

Has Schöck Combar® been examined from an environmental perspective?

In 2011, IBR examined Schöck Combar® for radioactivity, biocides, PBC, pyrethroids, phthalates, VOC (solvents and aromatics), heavy metals and fine dust, and awarded its "Tested and recommended" seal.
The "Tested and recommended" seal issued by the Institut für Baubiologie Rosenheim GmbH (IBR) is awarded to products with a structural biology that poses no risks in respect of residential housing, and protects the environment at the same time.
[Institut für Baubiologie Rosenheim GmbH: Expert opinion no. 3011-451, 2011]

Schöck Combar® has been examined by the regional waste organisation LAGA (Länderarbeitsgemeinschaft Abfall). Their installation classes govern the options for further use of the material (unrestricted installation Z0 through Z5  hazardous waste landfill).
The analysis of Schöck Combar® resulted in classification Z0, which means that installation of Schöck Combar® is not subject to any restrictions.
[Dr. Vogt chemical laboratory, Karlsruhe: "Examination of Schöck Combar® glass fibre reinforcing bars, 2005" is available in our Download area]

Structural biology

What advantages does Schöck Combar® offer over reinforcement steel from a structural biology perspective?

Schöck Combar® is not electroconductive. It therefore does not:

  • cause unwarranted current flows in concrete elements
  • connect and drag electromagnetic fields across the reinforcement

Schöck Combar® is not magnetisable. Its magnetic permeability is 1.001 (compared to air, vacuum =1.000, reinforcement steel, depending on condition, >>100). It therefore does not:

  • cause any changes to the natural geomagnetic field

[Luber, B., Dr. Moldan, D.: "Glass fibre reinforcement in concrete elements for undisrupted geomagnetic fields in residential housing", 2013, conference proceedings from the 7th EMC conference of the professional association of structural biologists in Germany (Berufsverband Deutscher Baubiologen VDB e.V.) available here]

Is Schöck Combar® electroconductive?

No
Schöck Combar® is an isolator.

Is Schöck Combar® magnetic or magnetisable?

No

Does Schöck Combar® shield against electrosmog?

No
No interaction with electromagnetic fields

Which elements can be reinforced with Schöck Combar®?

Depending on the structural conditions, most concrete elements can be reinforced with Schöck Combar®.

  • Foundations
  • Floor slabs
  • Ceilings
  • Walls
  • Slab joists
  • Lintels
  • Ring beams
  • ...

Where and in which elements is the use of Schöck Combar® recommended?

Structural biologists generally recommend avoiding the use of steel in the immediate vicinity (distances of up to 1.50 m) of areas where people spend a lot of time, e.g. in bedrooms.

Can Schöck Combar® be combined with steel?

Yes
Parts of a ceiling can be reinforced with Schöck Combar® and the remainder with reinforcement steel.
So just using Schöck Combar® to reinforce the bedroom ceiling would be conceivable, for example.