Studies reveal ancient Roman ingredient made concrete stronger

Researchers have found a component was used in ancient Roman concrete to strengthen structures.

Today’s concrete flooring is a practical and cost-effective material suitable for many commercial applications, but in Italy there are Roman concrete seawater barriers that have lasted over 2,000 years without needing maintenance. This has led some scientists and constructors to look into how this has been achieved.

Studies of these Roman structures have found that the secret to this long-lasting concrete is that they contain volcanic ash. Although saltwater dissolves the ash, that process creates aluminous tobermorite crystals that make the concrete stronger than when it was originally manufactured.

People may assume that modern concrete is superior to that used in Ancient Rome, but research has shown that by using volcanic ash, their technology had an advantage to today’s. However, although aluminous tobermorite crystals can be added to concrete in a lab, this requires very high temperatures which weakens the concrete, making the technique impractical and not suited to the demands of modern construction.

Researchers found that concrete used in the Hamaoka Nuclear Power Plant in Japan, which was decommissioned in 2009, also contains aluminous tobermorite . They concluded that this happened naturally through seawater reacting with minerals in the concrete to produce silicon and aluminium ions, which over time formed the strengthening mineral. This made the concrete three times stronger than the average cement structure.

The researchers hope that their studies will lead to improved cement recipes for longer-lasting and stronger concrete flooring, as well as greater environmental credentials.