Developments in decorative paving

Decorative Concrete is the wide heading which covers the many new developments in coloured concrete technology. Concrete which is both coloured and textured has been in use for over 30 years in its present form, mainly across the USA and Australia. In the UK it has been disregarded by many architects

and concrete professionals, even though it has been used here for over a decade. However, the acceptance of this new technology across mainland Europe and the middle-east has been extraordinary. During May and June I spent time in the Russian Federation and Bulgaria, and the response was remarkable. In post-communist Bulgaria, architects and developers are interested in these techniques and are prepared to apply them.

'Sofialand', a theme park in the centre of Bulgaria's capital city, will contain more than 25,000m^sup 2^ of stamped, stained and sand-blasted decorative concrete. For example, all walkways around the park will be coloured and stamped using seamless texture skins. These tools can be up to 2m in diameter and imprint the textured surface without bond lines or individual stones. They are ideal for the many curves and corners in this type of pathway. This finished surface can also be given extra design features, including the use of leaves, flowers, shells or even coins on the surface prior to imprinting. When the entire surface is finished and sealed, these 'fossilised' images are captured on the surface. The images can also be lightly acid-stained in a variety of colours to highlight them.

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Acid stains are a ferrous oxide solution suspended in a dilute hydrochloric acid and react with the cement on the surface of freshly poured or old concrete. It colours the surface with an attractive, durable finish, and is simply applied using a brush or sponge. The chemical reaction is characterised by fizzing as the solution is applied. Usually the chemical reaction stops after a few minutes as it is a very weak solution and water will neutralise it. Complex designs can be created by drawing shapes or images onto the concrete surface with a string-line or wax pencil, then incising them with a small angle grinder and diamond blade. These cuts are both functional and aesthetic and will prevent the different colour stains mixing or spreading across the design.

The recently developed sand-- blasting technique can be used to produce more complex surface designs. If stains are then applied, even more colourful detail can be accentuated, giving the effect of marble or terrazzo. Visitors to Las Vegas hotels will have witnessed the effects that are achievable using this combination of techniques. Sand-blast stencils are usually cut into an adhesive-backed rubber which is then fixed to the concrete surface. The pre-cut design is picked out and sand-blasted. The depth of cut can be regulated using aluminium oxide, silicon carbide or garnet in different grit sizes. Even large designs are possible using a method called tiling.

All these techniques are readily available, so the onus is on UK designers to become aware of what is available and to use these new innovations in decorative concrete paving to their full potential.

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AUTHOR_AFFILIATION

Glyn Thomas, Creative Impressions