In 2010 Insimbi recognised the potential of the fibre business, and purchased the previously known Mettaloy Fibres, this became a division within the Insimbi Group of Companies. Insimbi Fibres’ focus is to be the number 1 supplier of both steel and polypropylene fibres within South Africa. Steel and polypropylene fibres have been used in the mining industry for many years, as a support to shot crete whereby it offers support thereby giving advanced warning of rock burst.

The main purpose of the below article is to give both engineers and construction companies an insight of what fibre reinforced concrete can offer as well as some examples of applications already carried out in SA.

The use of steel or polypropylene fibres for the reinforcement of concrete used for highways, floor slabs and heavy-duty or well-trafficked floors is almost a standard practice in the UK and other parts of Europe, but this practice is relatively unknown in South Africa.

Already in use by major contractors for road building and flooring, these specialist fibres are provided in the correct length and size to meet the requirements of individual projects, enabling hardworking and totally jointless floors to be provided as required.

The benefits of fibre-reinforced concrete floors are legion. The use of proven design methods, the mastering of concrete behaviour, the understanding of the technology and the constant monitoring of the production process allow Insimbi Alloys to enable the contractor to provide a totally homogenous floor slab with panel sizes of up to 35m x 35m or 1200m˛ – without the need for saw cuts and reducing thickness.

In application, armoured joints will be required at the edge of each pour, given the practical limits on the area of floor that can be constructed at any one time, but high dosages of steel or polypropylene fibres mixed uniformly through the concrete redistributes the shrinking stresses through the drying phase, eliminating the need for saw-cut induced contraction joints. The only joints required are those at the perimeter of each pour.

This is a boon to both the contractor and the end-user, because joints are probably the biggest cause of floor problems, and the fewer joints that are provided mean less maintenance and higher efficiency.

This concept also reduces the on-site programming time, because it eliminates the need for steel reinforcement in advance of works; it also reduces the installation risk, because the reinforcement is always in the right place and the quality control process is simplified significantly.

It has also been established that using fibre reinforcement means that slab thickness can be reduced and cement replacement used. With thinner slabs and no requirement for remedial grinding, the on-site output is increased and considerable cost advantages achieved. In addition, trip hazards are eliminated because traditional reinforcement is not required in the concrete.

The below extract is presented via a major ready mix supplier who carried out extensive testing with fibres and this is the summary of his findings.

The properties of hardened concrete can be considerably improved through the addition of an adequate volume of suitable steel fibres. For the best results in hardened, fibre reinforced concrete, the fibres need to be aligned in the direction of the main tensile stress. Fibre reinforced concrete is also more effective if the distance between the fibres is as little as possible. Fibres in hardened concrete influence the tensile, compressive and shear strength, the cracking and deformation properties, and thus also the toughness of the concrete. 

In fibre reinforced concrete under flexural stress, the distribution of the strain is linear, assuming the sections remain even. Steel fibre reinforced concrete can transfer stress in the cross section, and is capable of bearing loads, even with a cracked tensile zone.

Frequently Asked Questions

Will steel fibres rust?

Outdoor Applications With Cracks-Laboratory and field-testing of cracked SFRC in environments containing chlorides has indicated that the cracks in concrete can lead to corrosion of the fibres passing across the crack. However, hairline cracks (crack widths <0.004-in.) do not allow corrosion of steel fibres passing across the crack. If cracks wider than 0.004-in. are limited in depth, the consequences of this localized corrosion are not structurally significant.

Examples of previous applications

Airport Runways and Aprons

Dam Walls

Pre Cast

Tunnelling

Heavy Duty Roads - UTCRCP

Warehouse Flooring

Division Contacts

Eddie Liechti

Director

Direct line: 011-865-8830
Email here

Gari Maidza-Shoko

Direct line: 082-781-8662
Email here