The studies were initiated when Textile Concrete Consultants MD Donald Hourahane, approached the C&CI with the concept. C&CI MD Dr Graham Grieve says that although studies on the use of synthetic fibres in concrete had been done in other countries, the studies that Hourahane is doing are unique in the South African context.
He adds that studies that Hourahane is currently carrying out are focused on woven synthetic fibres in concrete.
Grieve explains that, while concrete is a good material for compression, it does not react well in high-tension situations owing to its brittle qualities. The way to overcome this, however, is through the use of steel reinforcement (rebar) in the concrete, which reinforces the concrete element. The rebar is susceptible to rust when in contact with water, and, in particular, seawater. In an effort to prevent rust, a protective layer of ‘cover’ concrete is provided between the rebar and the outside of the concrete.
However, this does not prevent rust from occurring. Over time, owing to wear and tear, the protection provided by the cover concrete diminishes, allowing oxidation of the rebar. Once corrosion begins, the application requires maintenance.
“If one was to put a layer of plastic in between the rebar and the concrete it would be possible to completely prevent the oxidation process. This could have far-reaching effects on the construction industry, particularly when constructing bridges over water or buildings in coastal towns, such as Cape Town, Port Elizabeth, or Durban,” says Grieve. He adds that the use of the synthetic fibres will give the concrete application greater flexibility and will help the concrete element to resist the tendency to crack.
Grieve reports that the principle of using synthetic fibres in concrete applications has a long history. In the 1900s, horsehair was used to prevent cracking in the wall plaster in houses.
The use of synthetic fibres in concrete in South Africa began when a product manufacturer had to find an alternative to fibreglass when fabricating bargeboards for roofs. Currently, many bargeboards are fabricated from a concrete-synthetic fibre mix.
“This has sparked a revival in the local synthetic- fibre industry, where we see a number of companies focusing attention on niche market applications such as garden decorations,” says Grieve.
He adds that the use of synthetic fibres is common in applications such as decorative garden ornaments and barge-boards but that it is rare to find synthetic fibres used in structural applications such as buildings.
Grieve reports that the use of such fibres in concrete has diversified the concrete industry, enabling companies working with concrete to use the material for other applications. He says that, in the past, it was inconceivable to make a door out of concrete, but through the use of synthetic fibres, this is now possible.
The C&CI is a marketing organisation, which aims to grow the market share for concrete by providing information, technical and consulting services, research and development education, and training in marketing services and regulations.