Roman Concrete (Opus Caementicum)
The buildings and structures of ancient Rome have stood for a very long time, so the building materials they used must offer something to learn from.
Now, researchers from Berkeley Lab at the University of California have made a breakthrough in cracking the secret of their long life – the special formula the Romans used to make their concrete. Unlike modern concrete, in which Portland cement to bind the aggregate, Roman concrete uses a mortar mix of volcanic limestone, which reacts to form crystals that expand into the space within the concrete more effectively.
This performs the function of microfibers in Portland-based concrete, but better – more resistant to corrosion, and packing the space more tightly. This also cuts the risk of microcracking in the concrete over time, extending lifespan considerably – 2,000 years and counting, as a trip around Rome will prove.
Roman concrete is not just stronger than the modern version, it is also greener. The limestone and clay used in Portland cement needs to be heated to over 1,400 degrees Celsius in the manufacturing process, and this accounts for 7% of global carbon emissions. Roman concrete, on the other hand, needs nothing like this kind of heat, as the volcanic ash and lime they used reacts at a lower temperature. This means a potential new concrete formula that is stronger, greener, and longer lasting.