Although it sounds like an oxymoron, floating concrete structures have been around for at least the last seventy years. Of course I’m thinking of the Mulberry Harbours used on the Normandy beaches during the Second World War. There are probably numerous other historical examples from before this time (the harbours were essentially giant caissons) but the shear scale of these structures (some up to five stories high!) mark them out as a significant achievement. Essentially the Mulberry Harbours were hollow concrete rafts which were towed into position and sunk where needed, allowing roadways to be constructed for the military machinery and supplies to get easily from ship to shore. Below is a photograph of a Mulberry Harbour in action which I found on a very informative page, here.
The use of polystyrene filled chambers to create the buoyancy of floating concrete structures has been in use since at least the early 1970’s and can be seen at many a marina or other waterside development. Usually they are rectangular blocks which are anchored but allowed to rise and fall with the tide, while connecting walkways and mooring bays.
I could talk about the much maligned material that is concrete, and how it’s reputation was scarred by third rate architects producing prefabricated tower blocks in the 60’s and 70’s – but that is another story. There have always been designers who saw the potential in the material and have created objects of great elegance and beauty – I only need to mention the stunning TWA Terminal (New York) design by Eero Saarinen in 1962 as an example.
I know, I’m getting off the point a little. But Saarinen’s designs prove that concrete is not just a leaden weight, a grey lump resulting in poorly designed and decaying flats – when used imaginatively it can float, even when it’s on land.
One use of floating concrete I came across recently was Floaty by AB Concrete Designs in Germany. I am assuming they use the polystyrene filled chamber technique and they use it to create a range of curvaceous pebble-like floating islands. These can be moored just about anywhere and provide stylish rest points for swimmers.
This is just one of many examples of an attractive, small scale and practical use for concrete.