This week Vesta attended an inspiring lecture on architectural concrete. The lecture was held by Elaine Toogood from the Concrete Centre in England, who came over to highlight the fact that concrete can be beautiful, not just structural. It definitely worked. So much so that this week we thought we would share what is possible with you.
Architectural Precast concrete is a very different product from structural precast concrete. For a start, architectural precast uses white concrete. This can then be pigmented, and coloured aggregate chosen to create almost any colour. Nottingham Art’s Centre by Caruso St John is the perfect example of a yellow pigment. It also demonstrates how fabric can be used as a form liner to create an amazing pattern, in this case delicate lace.
Precasting concrete in complex patterns can be very expensive; one way around this is to use repetitive patterns. David Wlaker Architects and Swanke Hayden Connell have done just that with One Coleman Street.
They used only four different moulds to create this amazing undulating façade. The concrete is polished white concrete with white cement and sand. The particular combination was designed to be better wearing than Portland Stone.
Removing layers of the surface can change the colour of the cast pieces by increasing the amount of aggregate revealed.
This technique can be used to create different finished on the same precast panel. The different finishes are: As Struck, Retardant, Tooled, acid etched and Polished.
Acid etching is the most popular at the moment, and dependant on the depth of the etching you can create tonal variety, like suede or velvet.
This is another finish which is now possible. This requires covering an area in the pattern required, and then sand blasting the uncovered areas. This is best shown on Fiona Heron’s bollards at Bromley Station.
This effect is created through the use of a surface retardant. This retardant is placed in the pattern inside a framework, and once the concrete is poured, it acts to prevent the concrete from setting in the areas in contact with the retardant. The result is complex patterns that can be different for every panel. Such as Herzog and de Meuron’s Eberswalde Technical School Library.
Photo engraving Form Liners.
This method uses the light to create an image through the use of varied depth grooves, which are patterned. John Lyall Architects used this particularly effectively at the Pudding Mill Lane Pumping Station.
All precast concrete is poured into some form of framework. For structural purposes this is timber or steel moulds. For architectural purposes there are lots of alternatives. In this case a polyurethane mould. Like the form liners before, the mould acts to create a pattern in the concrete but being polyurethane, it can be reused over 100 times. There are bespoke and standard moulds. A release agent is critical in order to allow the mould to be removed from the concrete. RATP Bus Centre by ecdm architects is a great example of a repetitive textured mould.
Another way of creating texture and shape with fabric. This method doesn’t use a framework but pours the concrete in suspended fabric, allowing it to free form. Alan Chandler and Remo Pedreschi used this to great effect at the Chelsea Flower show to create organic forms.
Cast in Fabric.
Fabric can also be used in a formliner to create pattern and texture, or it can be set within the concrete for internal use. This creates a tactile finish, and uses either velvet, crystal, stitched linen or linen.
Graphic Relief Ltd has created moulds which can create very fine surface detail.
Pollution Eating Concrete.
Current technology has increased to such a degree that it is now possible to create “pollution eating concrete” which absorbs particles of pollution. Through treating a patterned area so that it does not have this pollution eating property and therefore becomes dirty, the design is revealed. Alessia Giardino has used these photo-reactive materials to create a lace-like pattern on concrete panels. This nanotechnology was created by Italcementi, which exposes a motif through the exposure to airborne pollution.
Self Cleaning Concrete.
There is now self cleaning concrete. This allows for amazing sculptural forms to be created and the forms will not be corrupted through getting dirty as the rain will wash it clean. Richard Meier’s Jubilee Church in Rome is a perfect example of how this can be used in an amazing way.
High Strength Concrete – Ductal.
Ductal concrete is an ultra high strength concrete used to create amazing fine architectural detail, and fine cladding. Zaha Hadid has championed this material in The Zaha Hadid Gallery in London.
Translucent Concrete, Light Emitting Concrete and Photo Luminescent aggregate are other new forms of concrete which are available now. We covered them previously in our EcoBuild 2013 blog http://www.vestaarchitecture.co.uk/ecobuild-future/
Thanks to Elaine Toogood, for bringing these amazing materials to our attention.
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