FAQs

Macro synthetic fibres are fibres made from plastic (mostly polypropylene) usually by extruding plastic pellets to a yarn which is then cut into short lengths. Special manufacturing techniques have allowed these fibres to be manufactured to an extremely high performance so that they can be used as reinforcement in structural concrete applications.

A more precise definition of polymer fibres for concrete can be found in BS EN 14889 -2006 Part 2 Polymer fibres Definitions specifications and conformity.  http://shop.bsigroup.com/

Macro fibres have been used to reinforce concrete of all types for the last 25 years and can replace old technologies like steel fibre which has durability concerns.

No. Manufacturing techniques vary between products and thus fibres offered by different manufacturers will look different, have different technical characteristics and perform differently in concrete. The Association recommends that customers evaluate a particular fibre on its merits by testing prior for a specific application.

No. These fibres are used for different non-structural applications such as to reduce the formation of plastic-shrinkage and settlements cracks at the concrete’s surface and anti-spalling where a concrete element is subjected to a high intensity fire. The only similarity between the two products is that they are manufactured from the same raw material polypropylene. A further definition of micro plastic fibres can be found in BS EN 14889 Part 2. .  http://shop.bsigroup.com/

MSFC is a composite material made of hydraulic cements, water, fine and

coarse aggregate, and a dispersion of discontinuous fibres. It may also contain pozzolans and admixtures commonly used with conventional concrete. All admixtures meeting ASTM specifications for use in concrete are suitable for use in MSFC.

Unlike welded wire reinforcement or rebar, which is specifically located in a single plane, macro synthetic fibres are distributed uniformly throughout the concrete matrix. The primary function of macro synthetic fibres is to modify micro and macro cracking. By intercepting cracks at their origin, macro synthetic fibres inhibit crack growth. For this reason, MSFC can be used to replace welded wire reinforcement or rebar which is used to control temperature or shrinkage cracks.

Although steel fibres and wwf have been used in recent years MSFs offer significant advantages over steel not least of which is because they do not corrode. Many concrete structures will often crack after construction as concrete is a brittle material and this allows moisture to attack the reinforcement and thus corrode the reinforcement. As MSF are manufactured from polypropylene this cannot happen and so can give the asset a much longer life therefore significantly reducing the long-term cost of an asset.

Other advantages include faster and lighter to handle for the same performance and premixed into the concrete so there is no need for site handing.

Macro synthetic fibres have been used in a wide variety of concrete applications including reinforcement for shotcrete in underground construction, poured in place concrete for secondary linings and slabs on grade and precast applications.

Refer to our gallery for more information on uses.

MSF can be added to the concrete either at the batching plant or at the project site. To get the best of what we call a premixed reinforcement it is better for them to be mixed at the batching plant in a controlled environment.

Pumping has been used to transport MSFC on many projects. In general a mixture that will pump satisfactorily without fibres will pump with fibres. In pumping MSFC, the chute from the readymix truck should be 200 mm above the grate on the hopper. This will prevent the fibre from bridging the gaps in the grate and ensure a steady flow of concrete to the pump. Note that the grate should never be removed from the hopper.

Yes MSF can be used in a self-compacting concrete. There are many MSF being used for SCC poured in place or for precast elements.

Generally the longer and thinner a fibre is the more chance of it balling there is. Today many manufacturers undertake rigorous testing to ensure that the fibre is suitable for the market by ensuring a low balling possibility and they can also assist in the dosing process so as to minimise any balls.

Collation of some of the thinner fibres also prevents balling when they are mixed into the concrete.

Using a quality fibre that is well used in the construction industry will help to ensure that the fibre will be distributed in the concrete. Generally a fibre that is probably added to the concrete when it is batched will allow the fibres to be evenly distributed throughout the concrete.

The addition of any type of fibre to a concrete mix will have an affect on its workability but this is dependent on the quantity of fibre and the type of fibre used. Mostly where a mix is used for pumping the affect will be minimal but prior testing should be undertaken to gauge the affect where required.

The fibre dosage rate is defined by a project specification in order to meet a required performance level. This performance level might be as required in a plate test (mostly used for tunnelling shotcrete applications and defined as Joules) or a beam test (mostly used for civil applications such as precast items and defined as residual strength MPa). Testing is then undertaken to see what fibre dosage rate of a particular fibre is required to meet that performance level.

What are the benefits of high strength premium fibres?

Using a high strength premium fibre will ensure that the long term benefits of its performance are retained. It is more likely that a lower dosage of fibre will be needed compared to a lower quality fibre and thus this will help to reduce overall costs such as concrete admixtures.

No. MSF cannot replace traditional reinforcement in any application. Any replacement has to be well designed and approved by an engineer.

Loose fibres are usually delivered in bags whereas collated or pucked fibres are wrapped in a dissolvable wrapping. Collated fibres can be used in an automatic dosing machine. Loose fibres are able to distribute throughout the concrete immediately whereas the collated fibres disburse in the concrete after their wrapping has dissolved or broken down.