Translucent Concrete

We normally think of concrete as an unchanging, monolithic and, crucially, an opaque material. However, in the early 2000s, engineers and architects began experimenting with making translucent concretes like this light-transmitting block.

Concrete has been around since the Romans used this ‘liquid stone’ to create new forms at a much larger scale, allowing for architectural masterpieces like the Pantheon and the Colosseum. Traditionally, concrete has been primarily composed of cement, water and aggregates, but even ancient civil engineers knew that there were many ways to tweak the ratio of these ingredients and add new ones to achieve different effects. The Romans experimented with adding horsehair to strengthen concrete, animal blood to make it frost-resistant and even lard and milk to improve its plasticity.

Modern concretes have been reinforced with steel to increase their tensile strength allowing them to be turned into rowboats, reservoirs and skyscrapers. They have been made conductive with the addition of carbon fibre and carbon black, allowing for the manufacture of runways and roads that can clear themselves of snow when a current is passed through them. In a misguided use of a material now understood to be hazardous, asbestos was historically added to cement to create a fireproof roofing, wall-cladding and drainpipe material.

In this particular example of a reinvented ancient material, optical fibres have been added to the concrete mix, replacing traditional aggregates. Because of limitations in the way in which this material is produced, it is not currently being used on a large scale. The fibre optics have to be carefully arranged inside the concrete when it is poured so that light is transmitted horizontally across the material. As a result, it is much more expensive to make than traditional concrete and can only be manufactured as pre-cast or fabricated blocks, not poured on site. Other methods that have been explored for making translucent concrete include using transparent glass or plastic chips as aggregates or replacing binding materials with clear glues or resins.

Although this sample is described by manufacturers as transparent it is obviously not completely see-through. However when used on an architectural scale and back-lit, it transforms traditional concrete into a dynamic, twinkling canvas that shadows can play across, with dramatic effects.