The development of the road network in urban areas has taken a new turn over the last few years. The emphasis is no longer on the development and construction of larger roads with a higher capacity.
The purpose is rather to try and improve safety and traffic conditions. Urban pavements are no longer exclusively reserved for motorists and free flow of traffic, but are more and more designed, devised and managed as a collective meeting place for multiple users, with a variety of functions.
On these pavements the purpose is to make motorists feel instinctively that they are no longer on a highway or a road but on a traffic area calling for more peaceful behaviour. This new orientation has necessitated a geometrical reorganisation of urban space with a range of requirements as regards safety, aesthetics, integration to the environment, placement, comfort and durability.
The cement concrete technique has closely accompanied this development. Long used as a structural component of urban pavements, buried under other surface materials, concrete now presents other possibilities of application as a finishing or surfacing material, characterised by a variety of colours, shapes and textures.
These urban concretes are currently undergoing significant development. The concrete market is estimated at approximately five million cubic meters per year.
Concretes that make a difference
The architectural value of concrete mainly depends on its possibilities as regards shape, colour and texture.
Shape does not concern the appearance of concrete as a material, but concerns the elements whose creation is only made possible by its plasticity . Since concrete is a castable material, in principle any shape is possible. Consequently concrete surfaces can be designed not only in two but also in three dimensions. They then become a spatial object with scarcements, ledges, hollows, reliefs, and curves. Imprinted concretes are a perfect illustration of this plasticity.
Colour is provided by the constituents of concrete. Grey or white cement, when mixed with the finest fractions of sand, provides the raw concrete with its background colour. This colour can be modified by addition of colouring, metallic oxides or even synthetic pigments. As for treated concretes, the colour of the largest elements, aggregates, will determine the tint of concrete to some extent. Depending on the intensity of treatment the aggregates will be more or less apparent.
Textured possibilities are also extremely varied. These go from close-textured surfaces (burlap treatment) to rough surfaces (washed, deactivated, shotblasted, bushhammered, imprinted, sandblasted, etc.). Depending on the treatment chosen, the relief of the concrete surface will be more or less marked, and the light play on its surface accordingly. The surface aspect will depend directly on the quality of the concrete’s stone skeleton, showing its intrinsic nature.
Combinations of shapes, colours and textures are innumerable. It is thus perfectly possible to imitate all kinds of natural stones and also have the technical advantage of making larger surfaces and very complex shapes.
This technique consists of removing the concrete’s surface mortar to expose the aggregates and give the surface specific design features as regards adhesion and/or surface aspect.
This technique consists in imprinting patterns or motifs on the surface of fresh concrete using dies or special moulds.
Hydroblasting or sandblasting
This technique consists in subjecting hardened concrete lining (24 to 48 hours after concreting) to a high-pressure sand and water jet.