The advantages of the synthetic macro fibres in concrete

Fibre-reinforced concrete has become one of the most widely used materials in the manufacture of industrial floors.  Numerous standards and guidelines around the world acknowledge its function for structural purposes.  With the introduction of synthetic macro fibres in concrete, traditional steel reinforcement can be either reduced or completely replaced in industrial floors, bringing benefits such as lower costs and more practical installation, as well as considerable reduction in CO2 emissions. The use of fibres also makes concrete, which is essentially a brittle material, significantly more ductile and tougher.

Synthetic macro fibres

The use of macro fibres in industrial floors is rapidly increasing globally, thanks to the growing number of designers and construction companies that acknowledge its capacity to meet design requirements.

Macro fibres provide three-dimensional reinforcement within the matrix and a structural contribution to the concrete, in compliance with European standard EN 14889-2:2006, “Fibres for concrete. Polymer fibres. Definitions, specifications and conformity”, which defines them as “for structural use”.  When they are used to improve the load-bearing properties of concrete, synthetic macro fibres undergo testing according to European standard EN 14651, which contains the test method for measuring the toughness class of fibre-reinforced concrete and, therefore, the residual performance properties of concrete after cracking.  Not only does the use of fibre-reinforced concrete enable traditional steel reinforcement to be reduced to a minimum or replaced completely, it also speeds up construction times on site, improves the level of safety in the workplace and minimises the impact of transporting materials.

There are currently two associations: MSFA (Macro Synthetic Fibres Association) in Europe and FRCA (Fibre Reinforced Concrete Association) in the USA, through which Mapei and other manufacturers from the construction materials sector work with designers and leading universities to promote this innovative technology and its numerous advantages in the market.

Reducing environmental impact

What makes synthetic fibres sustainable technology may be easily identified during both the manufacturing phase and the application phase of the product itself.

Synthetic fibres are manufactured by melting granules of different types of polymers together and then extruding filaments in differing forms and with different mechanical characteristics. All waste material from the manufacturing process is constantly collected and recycled, classifying the production of synthetic fibres as a ‘zero-waste’ process according to Circular Economy principles.

Another aspect that makes synthetic fibres a sustainable technology relates to its application, which is far more cost-effective compared with traditional steel reinforcement. Eliminating the transport and application/positioning of steel mesh also leads to a significant reduction in the amount of construction materials consumed and, as a result, a reduction in equivalent CO2 emissions.

Using synthetic fibres as a replacement for traditional steel mesh and eliminating contraction joints can result in CO2 reductions of up to 49.5%, for example, in the case study below this equates to a CO2 reduction of 139,250kg for the 25,000m2 of concrete flooring.

Design support

With such a modern and increasingly sustainable approach, designers play a key role in choosing to opt for materials with low impact on the environment. This means they have to calculate the analysis of a building’s life cycle and identify construction techniques and processes that would reduce time required for their construction.

In line with this approach, the Concrete Flooring Solutions line by Mapei provides support for floor designers proposing sustainable and innovative solutions, through the use of fibre reinforced concrete containing Mapei macro fibres for structural use.

Case study:

New 25,000 m2 logistic hub – Cordys Capital, Szirmabesenyő, northern Hungary.

High-strength polymer fibres to withstand high volumes of goods-handling traffic

In addition to erecting 192 columns to support the roof structure, the main contractor – Perfect Construct Ltd - wanted to install a floor that would guarantee excellent performance properties, mechanical characteristics and durability, in line with the overall build quality.  The floor also needed to withstand the high volume of traffic expected for handling and moving goods.

An innovative and functional solution needed to be found and Perfect Construct Ltd turned to Mapei, who proposed a complete system for the construction of fibre-reinforced concrete floors.  Rather than using steel fibres, as specified in the original project, Mapei proposed the use of high strength polymer fibres - MAPEFIBRE ST 50 TWISTED - which were added during the mixing phase of the concrete, along with DYNAMON SR31 super-plasticising admixture and MAPECURE SRA curing admixture. The fibres enabled the steel reinforcement to be eliminated, whilst guaranteeing a high level of ductility and toughness for the concrete.  The admixtures enabled the concrete to maintain its workability over an extended period, made it easier to pour and helped maintain its high mechanical performance properties and, at the same time, reduced hydraulic shrinkage and the risk of the formation of micro-cracks.

Once the concrete floor had been poured, the surface was finished with MAPETOP N AR6 – a ready-to-use, pre-blended dry shake hardener that creates high strength and abrasion resistant anti-wear layers for concrete floors in industrial and commercial environments. Once the surfaces had been treated, the final step was to prevent evaporation taking place too quickly by applying MAPECURE E30, a film-forming curing agent in water solution that helps provide more resistance to wear and reduces surface dust formation.

The Mapei system was used to create a jointless floor within several bays, each measuring 500 m². It enabled the flooring contractor to create a surface free of cracks, without having to move joints, despite the extensive bay areas.  Following the successful application, the same system was also used for the construction of external concrete floors.