The classic Doric columns
of the Parthenon in Athens are a universally-known symbol of a great
early civilisation. What is not so widely known is that they are
in some danger of falling down. The reason for this is that, in
the last century, they were restored. Not, one might think, a bad
thing. There is a problem, however. The architects and engineers
involved in this particular conservation project used steel reinforcement
in the new crossbeams they installed. Steel corrodes, which means
that the renovated columns are in trouble. This fact is not lost
on today's builders. They realise that the acidic nature of stone
building materials, such as concrete, and the effects of atmospheric
pollution, such as acid rain, can render steel a less-than-perfect
reinforcing material for stone - and particularly concrete - structures.
Quite simply, the use of steel reinforcement could limit the life
of a building.
Recognising the problem and composing composites
In the early 1980s, German companies developed
new methods of using glass fibre reinforced plastics (FRP) in concrete
constructions. Japanese and American companies further developed
the technology using alternative, non-corroding reinforcing materials.
These materials - similar to glass FRPs - can be used to impart
the same mechanical properties to concrete that can be obtained
using steel, while remaining resistant to a hostile environment.
Europe, however, had a problem: it did not have access to this new
materials technology and needed to develop its own. A Brite-Euram
project set out to put this right.
Dr Matthias Scheibe, a representative of the German SME SUSPA Spannbeton,
knows of the problems involved: he co-ordinated the project. "There
are a number of possible candidates to replace steel in reinforced
or pre-stressed concrete," he explains, "but one of the
major problems we had to tackle was anchoring these materials within
the concrete, so that they could be relied upon to produce the required
strength." That is exactly what the partners - including Belgian,
Dutch and German companies - did.
"We put together a consortium with all the required expertise,"
Dr Scheibe explains. "SUSPA concentrated on the development
of fibre reinforced plastics for use in concrete elements; AKZO
Nobel's main role was to evaluate, select and produce the various
FRPs we were interested in. The Technical University of Braunschweig
looked at anchoring the reinforcing materials and long-term testing
of the resulting concrete blocks, while the University of Gent studied
the behaviour of reinforced and pre-stressed concrete produced with
the candidate materials. At the same time, DYWIDAG and NEDRI optimised
the anchoring systems."
"But it wasn't just glass FRPs that we investigated,"
says Scheibe. "We also considered the use of aramid materials,
or AFRP, as well as carbon (CFRP). As the project progressed, it
became apparent that the different types of reinforcing systems
all had their strong and weak points. This led us to carry out continuous
modifications to the basic materials and to refine the production
technologies needed to make them. The final results demonstrated
that the various reinforcing materials all had valuable characteristics,
which were predictable, consistent and suitable for different applications."
Taking technology to the market
Suitable indeed. The partners are now
implementing the results in various ways. DYWIDAG has developed
the patented DYWIDUR® glass FRP system and is now embarking
on a global marketing and distribution campaign. Likewise, NEDRI
is conducting an aggressive marketing campaign to commercialise
CFRP products. For its part, SUSPA is continuing its own research
and development programme, with the ultimate aim of increasing the
level of acceptance of AFRPs in the construction industry.
The academic results for the two universities are also noteworthy.
In addition to the acquisition of scientific experience and know
how, between them they have created a new set of test methods which
look as though they could well serve as the basis for an internationally
accepted set of standards and norms.
"We've levelled the playing field," claims Scheibe. "For
a long time, the Americans and Japanese held a considerable lead
in this area of expertise, but now, European civil engineers have
the tools at their disposal to compete in a global market. The results
have already been used in pilot construction projects, such as tunnels
and bracings, and the new technology performs well. Europe now has
a strong position in fibre composites for use in structural engineering."