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
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.