When looking at fibres and fibre reinforced concrete, a great deal of attention is focused on “Industrial Ground Floors” for applications such as warehouses and factories.
For these projects, most solutions concentrate on optimising joint spacing, slab thickness and the ability of the floor to carry the heavy point loadings associated with racking systems placed thereon. The “buildability” of the floor is also critical to enable the benefit of laser screed technology to increase the efficiency of the floor laying process. In such applications FCS can offer our APEX steel fibres together with detailed design support to help engineers and contractors optimise their solutions.
However, less attention has historically been given to the external pavements and hard standings that generally surround or are adjacent to the “building”. The construction of these areas is typically more traditional, adopting “long strip” construction to suit drainage and level changes. Also, the challenges of laying concrete externally do not normally allow for the large area construction methods, which can be achieved in the relatively “controlled” environment of an internal pour, to be easily replicated outside the building envelope.
Many engineers will propose an external concrete design with a single layer of mesh – however the position of the mesh and area of reinforcement provided can vary between projects with little explanation or reason.
If the mesh is positioned in the top face, the mesh provides control to cracking – but will not contribute any enhancement to load carrying capability of the slab. Alternatively, if the mesh is positioned in the bottom face, the slab will have enhanced load carrying and structural performance – but will not contribute to resisting the propagation of cracks at the surface of the concrete.
Adopting a structural fibre concrete solution, where the fibres enhances the load carrying capability of an external pavement and provide a crack control function, enable many benefits to both the design and construction of the slab, in comparison to traditional mesh fabric reinforcement construction, to be realised.
Fibres are proven to increase the durability of the concrete, through improving the impact and abrasion resistance. Permeability of the concrete is reduced enhancing the ability of the concrete to withstand repeated freeze / thaw cycles, in addition to withstanding the dramatic thermal effects when de-icing salts are spread onto frozen concrete surfaces, further increasing the robustness of the slab.
In such applications, FCS would recommend our Nexus 85 macro synthetic fibre which can be used at a market leading dosage rate of 2.5kg/m3, in full compliance with EN14889-2 and CE certified, to enhance the load bearing capacity of the concrete slab – providing an alternative to typical mesh reinforcement.
FCS can provide detailed design calculations demonstrating the load carrying performance of a fibre reinforced concrete slab, when subjected to heavy goods vehicles (HGV) and other loads typically considered for external pavements.
By removing mesh reinforcement, the contractor can pour the fibre reinforced concrete without concerns about the placement and location of reinforcement, thereby improving the efficiency of the construction process. Access to pour areas are improved, as the delivery of concrete by the ready-mixed truck is not restricted by previously fixed reinforcement.
Replacement of the mesh with Nexus 85, also avoids future corrosion and spalling of steel reinforcement so frequently seen on external concrete applications, further enhancing the long-term durability and surface functionality of fibre reinforced concrete slabs.
FCS can also advise on the spacing, type and detailing of joints. By considering the fibre, design and construction methodology, together we can optimize the solution offered for a specific project.
For further information on how you could replace traditional mesh reinforcement with a structural fibre solution, please contact us.
