Love it or hate it, concrete in the built environment is certainly here to stay and, if anything, its inclusion in projects is currently undergoing something of a renaissance.
Trellick Tower, London, 1966–1972, designed by Ernő Goldfinger. It is Grade II* listed.
For many, architectural concrete is summed up by the Brutalist architecture movement of the 60’s/70’s and, all too often, this modernist style epitomises all of its negative undertones: cold and grey, graffiti ridden, and all stark, angular forms. Combined with memories of times in the UK that were economically depressed, many feel absolutely no affinity with such buildings, even if they are now often lauded (not to mention Listed).
Add to this the degradation of many post-war structures (Spaghetti Junction among them) due to ‘concrete cancer’, and engineers as well as designers will soon declare their loathing!
RATP Bus Centre by ecdm architects: concrete elements into whose shuttering a 'pimply' template was placed. Photo © Benoit Fougeirol and Philippe Ruault
However, there is no escaping the fact that modern concrete is an effective form of ‘liquid stone’, and a highly sculptural, versatile and, dare I say it, desirable, material. Today, estimated use on a global scale is some 30 billion tonnes per annum, so there are plenty that appreciate its many advantages.
So what actually is concrete? These days, it generally a mix of cement, water and stone aggregate (small pieces of stone): the cement acts as a binding agent, producing a paste when mixed with water, that envelopes the aggregate and fills all voids between the stones and allows the resulting slurry to be formed, through a variety of means.
Concrete has a laudable and fascinating history, dating back to its use in Roman constructions dating back some two millennia. The Romans were master engineers and their unbelievably durable constructions are still evident today in many parts of the world. Roman concrete was also remarkably ‘green’, utilising natural resources such as lime and volcanic rock, which created a material very low in embodied CO2.
Numerous technical developments have moved the basic concrete mix on from what the Romans knew and loved. Rediscovered as a material in the 19th century, the first patent was submitted for ‘ferro-cement’ - a reinforced concrete with applications that included architecture - and until the 1960s, steel reinforced concrete was most commonly used.
At that point, alternative reinforcement technologies were developed eg the addition of metal, man-made or natural fibres, webbing, 3D steel reinforcement, micro-cements etc. These innovations have brought about an architectural revolution whereby hugely increased spans are now achievable, due to the high tensile strength and higher load bearing capacity of modern concrete. Reduced cross sections are also possible since there is no longer a need for cover over traditional reinforcement mesh or bars and self compacting concretes, with their higher plasticity, make it possible to produce the most extraordinary forms.
Deitingen service station on the A1 Zürich–Bern. Load-bearing shell by Heinz Isler, 1968
Innovation in concrete manufacturing methods continues, pooling knowledge from diverse disciplines such as chemistry, digital modelling and nanotechnologies. Reinforcement techniques advance annually, as does the subject of additives, for instance those that allow consecutive casting and hence vast, uninterrupted surfaces. Developments in high performance (or ultra high performance) concrete – UHPC - continue to push the technical boundaries of this highly versatile material yet further and today’s concrete is exceptionally durable and resistant to environmental forces, with very high compressive and flexural strength, and extensive anticipated lifetimes. These attributes make for a very low environmental impact, and minimal whole life cost.
fibreC fibreglass concrete, made by the Reider company, used here for the [C]SPACE Pavilion in London, designed by Alan Dempsey and Alvin Huang, 2008
fibreC fibreglass-concrete elements mit Bayferrox® pigments, used for Soccer City stadium, Johannesburg, designed by Boogertman Urban Edge + Partners
High quality concretes are now achieved through the specification of bespoke aggregates and pigments to ensure a consistent, and lasting, finish. As ever more diverse ingredients are incorporated, the options for finishing become more varied and exciting, with the exposed surface of concrete being finished in many different ways:
- One of the most well known ways of changing the visual appearance of concrete is to remove the top layer of cement that binds the aggregate. Depending on the extent of removal, this adds varying levels of texture to its surface. However, this textural change, brought about by exposure of the otherwise hidden aggregates, may not always be desirable. Very heavily etched, or brushed, surfaces, as seen commonly on 1960s and 70s prefab buildings and local authority planters, have unpleasant connotations and are best avoided these days!
- A simple light acid etch will lend an attractive texture to the surface, masking marks left by mould seams and exposing just some of the aggregate (ideally carefully selected to improve the overall appearance when visible).
- Where parts of the surface are protected with a mask, leaving others exposed to sandblasting, interesting patterns of contrasting texture can be produced.
- Polished concrete offers a highly attractive finish that, through careful selection of both binder and aggregate, can replicate granite; again, through masking, an attractive textural contrast with acid etched finishes can be achieved.
- Many materials might be embedded into the surface of concrete to provide textural interest and/or colour eg glass microspheres create an attractive light-reflective surface that is far from a standard concrete finish.
- Various methodologies exist for photo-engraving or photolithographic processes whereby an image is etched into the surface of a concrete panel, providing interest to what might otherwise be a dull façade.
Photo-concrete which uses a photo-engraving process: Zuber concrete works with shuttering technique by Reckli. Guteberg-Höfe, ap88 Architects
Herzog de Meuron set another trend in architecture: the photo-concrete façade of the Fachhochschule Eberswalde's library, 1998
Transparent concrete elements by Licatron - Light conductors are woven into the concrete
- Going far beyond simple finishing, the embedding of fibreoptic strands in concrete creates a translucent product, through which shadows can be seen.
Concrete seems to be finally shrugging off its negative undertones – Brutalist architecture, poor environmental credentials, pebble-dash finishes and all – and its potential in the built environment now appears limitless.
Witness the embracement of concrete throughout the Jubilee Line extension, and its ubiquitous presence throughout the project. Beautifully executed, and thoughtfully lit, here the architectural versatility of this remarkable material is fully exploited and exposed in all its glory.
No longer simply a material suited to monolithic substructures, development in the areas of pigments, additives and surface finishes have seen a major shift in thinking and concrete is becoming the material of choice for façades, floors, kitchen worktops and furniture. Many leading designers now fully appreciate the enormous versatility of concrete and are creating innovative designs that test the abilities of this mutlifaceted material to the full.
Foster and Partners Jubilee Line - Canary Wharf Station
So, could you come to love concrete?
Credits:http://www.architectsjournal.co.uk/what-is-it-about-concrete/8629916.article http://www.architonic.com/ntsht/concrete-in-architecture-1-a-material-both-stigmatised-and-celebrated/7000525 http://en.wikipedia.org/wiki/Concrete http://www.rsc.org/images/Construction_tcm18-114530.pdf http://www.wbcsdcement.org/pdf/CSI-RecyclingConcrete-Summary.pdf