A recent research led by MIT has discovered that Roman concrete was made differently than previously believed.
The researchers studied samples of Roman concrete from an archaeological site in Italy and found small chunks of lime in the concrete. These lime clasts were not due to poor mixing or materials but were intentionally added by the Romans. The lime was mixed with the pozzolana and water at high temperatures, called “hot mixing.” This method produced concrete with unique properties and self-healing abilities.
When cracks formed in the concrete, water would react with the lime clasts to create a calcium-rich solution that hardened and glued the crack back together. This self-healing ability explains why Roman concrete has survived for thousands of years, even in seawalls exposed to the ocean’s constant pounding.
The researchers have successfully recreated this Roman concrete and are now working on making it commercially available as a more environmentally friendly option compared to modern concretes.