Future Concrete Road Use of Sustainable Macro Synthetic Reinforcement Fibre

Mr. Manoj Didwania (B.E Civil, PGDCTM-CEPT, MBA-OM, IGBC-AP, CIPP) Senior Manager, Adani Total Gas Ltd

Manoj Didwania is a Construction Professional with more than 18 years’ experience in all phases of Project Life Cycle having expertise in Estimation, Procurement, Procurement, Contract Management and Planning. His research interest includes Supplementary cementitious Material (SCM), Sustainable and Green Buildings, Cost effective and durableconstruction Material.

For further details kindly contact: manojdidwania1984@gmail.com

The article is talks about to the use of Macro Synthetic Reinforcement Fibre (MSRF) as the full/Partial replacement of Steel Reinforcement for Concrete Pavement and Floor. This article starts by reviewing the conventional way of Concreting of Pavement and floor with Steel reinforcement with its advantage and disadvantage. This Articles later talk about the Case study where 100% replacement of steel reinforcement was done by Macro Synthetic reinforcement fibre (MSRF) for the Concrete Pavement where the Load requirement was 12 T/m2. Article will suggest about the process, steps, practical application, limitation, advantages of using MSRF for Concrete pavement which was experience and observe during the Case Study. In today’s world where sustainability in construction is core issue, the MSRF plays important role to reduce the embodied carbon and Co2 Emission.


Synthetic fibers are manufactured from materials such as acrylic, aramid, carbon, nylon, polyester, polyethylene, or polypropylene. The use of synthetic fibers has been increasing at a steady rate in the past couple of decades. Fibres have been used for thousands of years in mortar construction. With the latest manufacturing techniques, we can take modern synthetic materials and turn them into highly engineered short fibres which act like small reinforcement bars in concrete. Dependent on the application these fibres range in length.

Classification of Micro and Macro Synthetic fibres

 a) Micro Synthetic fibre b) Macro Synthetic fibre

Macro synthetic fibres are defined in EN 14889 – Part 2 Fibres for concrete – Definitions, specifications and conformity and are broadly classified into two Classes.

Class I: Micro Fibre <0.30mm in diameter are fine hair like fibres typically between 6mm and 12mm in length. Micro synthetic fibres do not provide any post crack ductility. They do not control cracking of hardened concrete and cannot be used in lieu of other reinforcement. They cannot be considered in the structural design of concrete.

Class II: Macro Fibre >0.30mm in diameter are short discreet elements (like a tooth pick) and typically between 30mm and 65mm long. Macro synthetic fibres increase the ductility of concrete, improving the post-cracking capacity and can be used as the sole reinforcement in many concrete structures

However, macro synthetic fibres can be used to provide the concrete with significant post-cracking capacity and hence can be used in some designs based on plastic analysis, such as for ground-supported slabs and for rock support using sprayed concrete. Design approaches are not as well developed as for steel fibres (see separate entry Design/Approach/Steel-fibre-reinforced concrete), though in many cases the same methods are used, making allowance for the differences in the stress:strain behaviour and in the long-term performance.


In the beginning, steel fibres were mostly used as a substitute for secondary reinforcement or for crack control in less critical parts of the construction. However, over time, SFRC came to be applied in many different construction applications, such as in tunnel linings, ground support in mines, floors on grade, floors on piles and prefabricated elements, to the point where, nowadays, steel fibres are widely used 'as the main and unique reinforcement for industrial floor slabs, shotcrete and prefabricated concrete products. Steel fibres are also now being considered for many structural purposes contributing to the construction 's strength, stability and durability.

Macro-synthetic fibers, have lower tensile strengths and Modulus of Elasticities than steel fibers but will have a much higher fiber count across a potential crack. In effect, the total strength across a crack should be equivalent. This strength is also dependent on the ability of the fiber to bond to the concrete matrix itself. MSF is non-magnetic and non-corrosive making it a very attractive option for exterior paving projects where aesthetics and safety may be a concern. As MSF is mixed, it also becomes somewhat pliable and will not be as abrasive or harmful to pumping lines and equipment.

Synthetic fibres are usually much cheaper than steel fibres, in direct cost comparisons and also because a far lower density of synthetic fibres than steel are required in the concrete mix.

For example, for container combi slabs the density of synthetic fibres required in concrete is around maximum ranges to 3 kg/m3 compared with 35 kg/m3 for steel fibres. So, if the synthetic fibres cost Rs 1500 /m3 and steel fibres cost Rs 3500/m3, there’s a whopping saving of Rs 2000/m3.


In this project which we are referring, we used Macro Synthetic fibre for the Concrete Pavement where we replace the steel reinforcement 100% with MSF. The first thing we did as the procedural work is to get the Load calculation being done to identify right dosage for the applied Load. Most important aspect for any project we want to apply the MSF is that the design calculation shall be vetted by structural consultant.

All quality checks and test certificate from recognised Institute were reviewed prior to selection of right kind of Macro Synthetic fibre and their past projects feedbacks were taken to build confidence within the team for surety of Execution

Batching and Mixing of Concrete Containing MSF

MSFs can be added to the concrete at a ready-mix plant during batching and mixing, or it can be added to the ready mix transit concrete truck at arrival on site. In either case, checks should be made to ensure proper fibre dispersion throughout the concrete. If the fibres are mixed at site, the concrete mix should be mixed for at least five minutes at maximum mixing speed of the transit mixer to disperse the fibres throughout the load of concrete.

Most challenging task for the project execution team was mixing the fibre in the 1 bag Mixer, as using the mixer in the batching plant the perspective was it will be more controlled and quality Concrete.