Современная архитектура и строительство. Рябцева Е.В - 11 стр.

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ting concrete, but they also have a structural function in smaller building elements. In addition, they provide an
alternative to asbestos, which was widely used as a means of reinforcing cement-bonded elements in the past.
In view of its ductile properties, its high strength and durability, glass-fibre concrete has a wide range of appli-
cations, including semi-finished products and other elements. The use of steel-fibre-reinforced concrete is also
possible in the field of engineering construction; for example, in precast reinforced concrete floor elements or
for load-bearing walls without additional steel reinforcement. It is also used in industrial floor finishes or for
securing excavations in tunnel construction.
Textile-reinforced concrete is a logical development of fibre-reinforced concrete. Textile-like structures al-
low the alignment of the load-bearing reinforcement to be controlled and facilitate an economical exploitation
of the material. In conventional reinforced concrete construction, the concrete has the additional function of
protecting the reinforcement against corrosion. The use of technical textiles made of glass or carbon means that
the concrete cover can be reduced, thereby allowing the construction of thin-walled and three-dimensionally
shaped elements. The use of textile reinforced concrete is conceivable in many areas, even for complex load-
bearing shell structures. Used in precast elements as a kind of "integrated formwork" in combination with in-
situ concrete, it offers a number of advantages.
Various applications of textile-reinforced concrete are possible today, including the construction of facade
slabs with simple geometric forms, and the creation of shuttering components integrated in compound wall and
floor systems.
Production processes need to be developed that will allow the economical manufacture of various building
components with these materials. One possible application for textile-reinforced concrete lies in the creation of
finely dimensioned forms that would allow the actual load-bearing behavior to be visualized. As far as the sur-
face design is concerned, similar scope exists with this type of concrete as with self-compacting concrete.
Textile-reinforced concrete has a high load-bearing capacity, even with comparatively small cross-sectional
dimensions. It is, therefore, a sustainable form of construction, since the use of raw materials is relatively low,
thus helping to conserve resources. The high performance of textile-reinforced concrete is shown by the con-
struction of carving skis, which have been tested and function well.
The greatest step forward in concrete technology in recent years is certainly the development of self-
compacting types of concrete. Self-compacting concrete differs from vibrated concrete in that it contains a
greater proportion of fine-grain cement and aggregate. The concrete acquires its self-compacting properties in
conjunction with high-performance agents.
Roughly, 30 per cent of the volume of normal concrete consists of the cement-paste matrix. The maximum
size of the aggregate may be 8, 16 or 32 mm. The largest ingredient is the aggregate, which makes up more than
70 per cent of the volume. Depending on the water/ cement ratio, the volume of water will probably be slightly
less than 20 per cent. Self-compacting concrete differs from standard forms of concrete in that it generally con-
tains aggregate with a maximum size of 16 mm.
In high-performance concrete (i.e. high-strength and high-density concrete) there is a considerably greater
proportion of cement. The fine-grain material is generally formed by cement and micro silica. In most cases, the
coarse-grain aggregate will also have a maximum size of 16 mm (as in self-compacting concrete), but the water
content will be somewhat lower. In view of the much greater proportion of the bonding agent, the water/ ce-
ment ratio will also be somewhat lower.
Self-compacting concretes usually have a slump value of between 600 and 800 mm, which provides some
indication of the yield point of this type of concrete. The run-out time from the conical discharge funnel - which
as a rule lies between 10 and 20 seconds - is an indirect measure of the viscosity of the concrete. The combina-
tion of these two values determines the consistency of the self-compacting concrete.
Tests also have to be carried out to determine whether self-compacting concrete can flow between the rein-
forcement. So-called "block ring tests" have been developed for this purpose. The spacing of the bars should be
coordinated with the maximum size of the aggregate.
The choice of the appropriate mix proportions and the production of self-compacting concrete presuppose
specialist knowledge in this field. Although it is not necessary to use vibrators with self-compacting concrete, it
is possible to achieve sharply delineated forms and surface textures.
The Science Centre in Wolfsburg provides a further example of the architectural design scope offered by
self-compacting concrete today. This material is particularly relevant in the field of prefabrication, where there
is also a social dimension to this form of construction.
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