FREQUENTLY ASKED QUESTIONS

QUESTIONS AND ANSWERS ON STEEL
MESH AND ITS REPLACEMENT WITHGLASS FIBRES

1. CAN ANY GLASS FIBRES BE USED?

No. Only AR glass fibres (resistant to the alkalis in concrete) with a zirconium content of over 16% are suitable for use as concrete reinforcement. All other glass fibres degrade over time. In fact, the higher the zirconium content, the longer it lasts. The manufacturer of AR glass fibre with the highest zirconium content and the only one which complies with EN 15422:2008 standards is Fibratec, manufactured in Japan.

2. DOES POLYPROPYLENE FIBRE REINFORCE CONCRETE?

No, polypropylene does not have any mechanical properties which improve the flexural strength of concrete. It only prevents micro-cracking in the external layer of the concrete and it does this by stopping it from drying out too quickly. And this does not always work as its distribution is not homogenous, due to the big difference between its specific weight and the specific weight of concrete (0.9 compared to 2.5).

3.WHAT IS THE DIFFERENCE BETWEEN STEEL FIBRE AND GLASS FIBRE REINFORCEMENT??

The main difference is usage. Steel may lead to rusting on floors built outside.Also, when adding steel fibre into the concrete mixer, it often causes hedgehog-like clumps to form, blocking the nozzles of concrete pumps. Dosage starts at 20kg/m3.

The use of steel fibre is not advisable for floors that are less than 10cm thick.

Steel fibres create spikes on the floor surface, meaning that you are forced to lay an additional wearing course, increasing material and labour costs as a result.

With AR glass fibre, you have none of the aforementioned disadvantages.

4. WHAT ARE THE MAIN ADVANTAGES OF AR GLASS FIBRE COMPARED TO WELDED STEEL MESH?

There are many varied advantages. Using Fibratec will reduce construction time by about 60%. You will not need to pump concrete over steel mesh as the floor will no longer be need it.

You will not have to position steel mesh , or lift it onto separators, or bind it together, or cut it to adapt it to nooks in the area to be concreted, or go around columns or manholes. There will be no problems with levelling mesh on sloping ground. There is no need for stockpiling areas in which it will begin to rust (in breach of regulations) and no cranes will be needed for loading it onto trucks and unloading it at the site.

In the majority of cases, a truck won’t be needed as sacks of glass fibre can be transported in any vehicle. For example: in a 20m2 application, instead of a truck-load of mesh, one plastic supermarket bag with 4kg of Fibratec V12-AM will sufficient and this can be put on the passenger seat. No circular saws or shears will be needed for cutting steel mesh.

You will have the peace of mind that the mesh is not lying on the ground inside the flooring (where it serves no purpose). Every cubic centimetre is protected and bound together by millions of glass fibres which are 50-60% stronger than steel and perfectly distributed.AR glass fibre and concrete have very similar specific weights (2.68 and 2.5 respectively) and the tensile strength of Fibratec AR fibre is 1620N/mm2 while the strength of steel varies between 1000 and 1200 N/mm2.

5. ARE THERE EXAMPLES OF WORKS IN WHICH STEEL MESH WAS REPLACED BY AR GLASS FIBRE?

Yes, many. And in Spain.Visit the Fibratec page to see just a small selection.In fact, there are hundreds of successfully completed projects.

6. IS FIBRATEC CERTIFIED BY A RECOGNISED LABORATORY?

Yes. Fibratec is identical to the fibre used by various universities in their studies of reinforced concrete and therefore any of said studies can certify the effectiveness of AR glass fibre.We also have Bureau Veritas laboratory testing certificates comparing the resistance of 3kg of glass fibre with 20kg of 50mm corrugated steel fibre.

In these tests, the glass fibres provide more flexural strength to the concrete than the steel fibres. Similarly, tests from the BOMA IMPASA testing lab have demonstrated that Fibratec is a fibre with reinforcement characteristics similar to those of structural macro-fibres (which are not necessary in the construction of floors as the latter are not structural elements).

Mallazo

7. HOW DO I FIND OUT THE RIGHT DOSAGE FOR MY PROJECT?

Fibratec can prepare a dosing report for you, taking into consideration the specific conditions of your floor, in order to recommend the correct dosage.To do this, we will need information such as the type of concrete you are going to use in the works, the condition of the ground in terms of load-bearing capacity, the desired thickness of the floor and the and the type and amount of exceptional loads to which it will be subjected. This report is free.

8. IS IT EXPENSIVE TO PRODUCE ACERTIFIED ENGINEERING STUDY OF THE DOSAGE FOR A SIGNIFICANT WORK?

The cost of these types of study depends on the size of the works. Usually, even when paying for a fibre calculation study, you will save a significant amount by using FIBRATEC in your floors. We can recommend a number of engineers that specialise in this type of calculation, given that there are very few that can do them.

9. DO ‘HAIRS’ PROTRUDE FROM THE SURFACE OF A FLOOR MADE WITH GLASS FIBRE?

No, never. Floors made with Fibratec can be polished with absolute peace of mind.Not a single thread will break the surface of the floor. It is also ideal for concrete with imprinted patterns.

10. DO GLASS FIBRES CLUMP TOGETHER, SINK TO THE BOTTOM OR FLOAT TO THE TOP OF CONCRETE?

No, we have never experienced fibre clumping or even anything less than a perfectly homogenous distribution throughout the concrete, seeing as it spreads randomly and in three dimensions through the mass in a matter of minutes.

It must be born in mind that the density of glass fibre is almost the same as that of concrete and therefore the vibration of the latter does not, for example, cause the fibres to sink to the bottom of the slab.

11. HOW DO YOU EXPLAIN THE EVEN DISTRIBUTION OF THE FIBRES THROUGH THE CONCRETE?

Firstly, it is due to its physical properties (its density is almost equal to that of concrete) and secondly, it is the number of filaments per cubic metre: there are around 200,000,000 in 1kg of fibre.

12. CAN IT REPLACE ANY TYPE OF STEEL MESH?

It can replace the majority of steel meshes, as long as they perform no structural function and in some cases the thickness of the floor can even be reduced.

Mallazo
Mallazo

13. CAN THE INSTALLATION OF STEEL GIRDERS BE AVOIDED BY REPLACING THEM WITH AR GLASS FIBRE?

The steel reinforcements of structural elements should never be replaced. Adding Fibratec to compression layers cannot replace the use of steel reinforcements but it does save on the subsequent screeding and the surface can be left as is and polished, for example.

This was done in the construction of the multi-story car parks of the new Courthouses of Las Palmas in Gran Canaria, saving on an 8cm layer of concrete, 15 x 15 x 6 steel mesh and all the transport and labour needed for thousands of square metres of screeding.

14. DOES GLASS FIBRE DRY OUT THE CONCRETE, MAKING IT SET MORE QUICKLY?

No. It does not absorb water. This occurs on any floor when polyethylene plastics are not laidon the ground underneath it or when it is exposed to the sun or wind. The cracks produced during concrete shrinkage are basically caused by four factors.

Neither steel mesh nor fibre can avoid cracking if the following situations occur:

  1. Making cuts that are spaced further apart than the recommended distance and shallower than 33% of the thickness of the floor.
  2. NOT forming contraction joints within the first 24 hours.
  3. NOT respecting the recommended pattern of cuts made around columns, manholes, etc.
  4. NOT protecting the floor from the sun and wind in the first 7 days; i.e. not hydrating it frequently to control its temperature and not covering it to maintain its humidity and keep it as cool as possible.

15. HOW DOES THE USE OF GLASS FIBRE AFFECT THE WORKABILITY OF THE CONCRETE?

It makes it easier to mould and increases workability. It makes the concrete more cohesive as soon as it is mixed in.

16. IF I AM ON SITE, HOW DO I CALCULATE THE RIGHT AMOUNT TO THE CONCRETE?

First consult the site management for the correct dosage and then add the fibre in 1kg bags or 20kg sacks depending on the capacity of the concrete mixer.

You can order a 6 litre capacity plastic recipient which, when filled to 2cm from its upper lip, will give you about 1kg of fibre.

17. CAN I ADD A MUCH LARGER AMOUNT OF FIBRE TO MAKE THE CONCRETE EVEN STRONGER?

Greater quantity does not mean better quality: you should only use the recommended dosage.

Adding less or more fibre would be detrimental to the handling, the results and the resistance of the concrete.

18. DO I NEED TO ADD ANY TYPE OF ADDITIVES SUCH AS PLASTICIZERS WHEN USING GLASS FIBRE IN CONCRETE?

No, additives are usually used with steel fibres but not with glass fibre.

19. IS GLASS FIBRE COMPATIBLE WITH OTHER SUBSTANCES THAT I CAN ADD TO CONCRETE?

It is compatible. There are no compatibility issues with other chemical substances that can be added to concrete. Not even the most aggressive acids.

20. CAN I USE A HAND-HELD MIXER TO PREPARE THE CONCRETE AND GLASS FIBRE MIX?

Yes. Any method which guarantees a good mix until the fibres are correctly dispersed throughout the mass is valid. The mixing process takes one minute in a bucket. In fact, with chlorinated rubber, paint or micro-cement, using a hand-held mixer is highly recommended (for Fibratec V13-MO which is specially designed for these products).

In general terms,2 to 3kg can be mixed per minute in a cement mixer.