FREQUENTLY ASKED QUESTIONS CONCERNING CONCRETE REINFORCEMENT WITH
GLASS FIBRE AND REPLACEMENT OF STEEL MESH IN BUILDING GROUND BASED SLABS
1. CAN ANY GLASS FIBRE BE USED FOR REINFORCING CONCRETE?
NO. Only alkali resistant glass fibres (AR) can be used with concrete. The Zirconium content must be higher than 16% according the European Norms. The rest of glass fibres will get chemically destroyed as the time passes inside the concrete, until it disappears. Depending on the concentration, this can take places in weeks or months. The highest Zirconia content glass fibre in the world is 19,1 %, since at this level, the glass fibre is already immune to the chemical reactions against alkalinity. There are 4 AR glass fibre manufacturers in the world. FIBRATEC contains 19,1 % Zirconia and is NUMBER 1 in the World in Zirconia content.
2. CAN POLYPROPYLENE FIBER REPLACE STEEL MESHES IN GROUND BASED SLABS WITH CONCRETE?
No. Polypropylene fibers do not poses any mechanical property that can improve significantly the flexural strength. It only can avoid cracking on the external layer of concrete by slowing down the drying process of concrete, since it retains water and releases this water slowly afterwards.
3. WHAT IS THE DIFFERENCE BETWEEN REINFORCING CONCRETE WITH STEEL FIBERS AND DOING IT WITH AR GLASS FIBRES?
The steel fibers will cause oxidations as time passes. They also can block concrete pumps by forming balls. The dosage is typically very high with steel fibers (over 20 kg per m³ of concrete)
It is not recommendable to use steel fibers on concrete floors where thickness is less than 10 cm.
Steel fibers' density is 8 kg/cm3 compared to 2,4 of concrete. Therefore they go to the bottom of the floor when the slab is vibrated and as a result, they are not evenly distributed. (Glass fibres' density is 2,7 kg/cm3 very similar to concrete’s density and therefore disperse homogenously)
4. WHAT ARE THE BASIC ADVANTAGES OF GLASS FIBRES COMPARED TO STEEL MESHES?
There are many advantages. Manipulation, productivity during execution, security for workers, excellent quality in finishing of the floors are only some of them. AR glass fibres literally can sew any mm³ of concrete together and thus provide protection against cracking in the whole slab. Some additional advantages of AR glass fibres compared to steel meshes are: Avoids labor cost of placing steel mesh on the floor, avoids cutting and unifying steel meshes to suit floor’s shape, avoids cost of concrete pump. We also avoid transportation cost using AR glass fibres. Usually, using AR glass fibres will improve costs around 20%, it additionally will improve the execution time.
5. ARE THERE ALREADY IMPORTANT PROJECTS WHERE STEEL MESH HAS BEEN REPLACED BY AR GLASS FIBRES?
Yes. There are many big projects that can be visited in our website. The number of projects is growing each day, especially in Spain. We currently export our fibers to Swizerland too and we are opening new markets soon like UK, Portugal, Venezuela, Ecuador, Brazil and others.
6. IS FIBRATEC CERTIFIED BY ANY INTERNATIONAL LABORATORY?
YES. Fibratec posseses Bureau Veritas flexural test results where it´s efficiency compared to steel fibres has been demonstrated. You can download above mentioned certificates in our website.
7. WHERE CAN I GET A DOSAGE CALCULATION FOR MY SLAB?
Most of slabs are very simple to calculate. We have some standard calculations for pedestrian or parking pavements for example. With 2 or 3 kg AR glass fibres /m3 concrete, most of these can be built. For heavier applications like industrial floors where high point loads will exist, Fibratec cooperates with some specializaed engineering companies. We can recommend you some of these companies upon request so they can make requested calculations for your projects.
8. IS IT EXPENSIVE TO HIRE AN ENGINEERING COMPANY'S SERVICES IN ORDER TO CALCULATE THE DOSAGE FOR A SLAB?
Engineers usually charge based on the size of the project and the amount of AR glass fibre to be applied. You will get important savings using FIBRATEC AR glass fibres instead of steel fibres and steel meshes. It will be worth paying to these project engineers.
9. ARE AR GLASS FIBRES VISIBLE ON THE SURFACE OF THE PAVEMENT?
No, never. This typically happens when you use multifilament polypropylene fibres. In those cases where you use macro fibres or steel fibres, it is even worse, since you have real problems to poolish those surfaces.
10. DOES AR GLASS FIBRE MAKE BALLS OF CONCRETE, DOES IT BLOCK CONCRETE PUMPS?
No, NEVER. AR glass fibres are dispersed in the concrete evenly. We have never had any bad experience with AR glass fibres usage concerning blocking pumps or making any concrete balls or similar. It's dispersion is incredibly even in only a few minutes. You have to consider that the density of AR glass fibres is similar to that of concrete. Thanks to this fact, AR glass fibres will not go down the concrete slab as happens when you vibrate concrete with steel fibres in it.
11. HOW CAN YOU EXPLAIN ITS HOMOGENIOUS, TRIDIMENTIONAL DISPERSION IN CONCRETE?
First of all, its similar density to concrete makes it mix homogeniously. Secondly, there are over 200.000.000 of filaments in 1 kg of AR glass fibre that will cover all the concrete mass tridimentionally
12. CAN ANY STEEL MESH BE REPLACED WITH AR GLASS FIBRES?
It depends on the dosage calculation. It can never replace structural, steel like vertical elements or Steel bars between floors... In many cases, we have been able to reduce slab's thikness, thus saving money for our customers.
13. IS IT POSSIBLE TO AVOID IRON BARS IN BALCONIES OR CANTILEVER STRUCTURES USING AR GLASS FIBRES?
No. Those are structural elements, therefore should remain. AR glass fibres can replace steel meshes whenever the floor has already its structure and the slab over it is simply the pavement we will walk or drive on. With ARG glass fibers we aim to avoid cracks due to either plastic shrinkage or light mechanical deformation of the pavements that are already built on compacted ground based floors that are acting as structures.
14. DOES AR GLASS FIBRE ACCELERATE DRYING OR CURING PROCESS OF CONCRETE SLAB?
No. It does not absorb water in fact. Polypropylene fibres however do retain water. In fact, glass fibres can retain water for some longer time in order to improve hydration of the concrete slab, avoiding partially the evaporation of water. Concrete slabs can dry quickly if you don't place polyehtylene membranes between the concrete slab and grain layer. Also quick drying may occur if wind and sun is directly acting on the concrete slab.
15. HOW DOES AR GLASS FIBRES AFFECT WORKABILITY OF CONCRETE?
It makes concrete in fact better manageable since glass fibres increases ductility of concrete.
16. CAN I ADD MORE AR GLASS FIBRE TO MAKE THE CONCRETE STRONGER?
Adding more glass fibre does not necessarily mean that it will be better. You have to add what is suggested to each application. If you exceed, workability of concrete could start getting more difficult for that particular concrete application that you projected.
17. DO I NEED TO ADD ANY PLASTISIZER IN THE CONCRETE WHEN I USE AR GLASS FIBRES?
No. Typically steel fibres do require this, but not AR glass fibres.
18. ARE GLASS FIBRES COMPATIBLE WITH OTHER ADDITIVES FOR CONCRETES?
Yes. You can add any additive to concrete. This won't have any kind of reaction or interference with glass fibres.
19. CAN I USE A BLENDER IN STEAD OF A MIXER TO MIX AR GLASS FIBRES WITH MORTARS FOR RENDERS?
Any method that can guaranty a homogenious dispersion is ok for mixing. When mixed with paints or chlorinated rubbers, make sure glass fibres are dispersed until they are not visible. Although you might not be able to see the fibres, they will bond paint particles together.