Testing concrete-encased steel from the 1950s for direct reuse

Steel is one of the most useful construction materials. It is strong, durable and efficient, it has been instrumental in our built environment since the mid-1800s. It is also easy to recycle -- in fact, most of the scrap steel in waste streams is already captured and properly recycled into new steel.

But this is only one half of the story. Making new steel requires finite materials including coal. Making new and recycled steel requires furnace temperatures above 1500 degrees C, which means intense energy use. Even if the energy could be sourced from renewables, the chemical process itself releases carbon dioxide, a greenhouse gas. Current methods of steel manufacture are impossible to decarbonise.

This means we will not be able to manufacture steel using current methods in a net zero economy.

Steel is commonly found in existing buildings. When those buildings are demolished, the steel scrapped, melted and recycled into new steelwork. While it sounds positive, it is very energy-intensive process. Some manufacturing methods cannot accommodate high volumes of scrap steel. In the UK, we generate more scrap than we can deal with, and 75% of it ends up being exported.

We need to close the materials loop and avoid remanufacturing when existing steel can be in perfect shape to be simply reused. Reused steel has a carbon footprint eight times smaller than traditional steel.

Steel made after 1970 was subject to standard manufacturing processes and sizes, so it is easy to validate for reuse. The Steel Construction Institute has a standard method to follow for those sections to be checked for reuse. But modern steelmaking started in 1855, so this leaves out a significant proportion of existing steel.

This project aims to validate a large stock of 1950s steel from four deconstructed buildings in London, by undertaking rigorous materials testing and quality analysis, and coming up with a reuse potential to keep the steel at its highest value.

The project is innovative because it extends the scope of knowledge and understanding to a stock of materials that is not covered by current protocols and might facilitate the road to reuse for a larger proportion of existing steelwork, helping to further close the materials loop.