Discovery in Pompeii changes our understanding of Roman concrete

Archaeologists have discovered a nearly complete ancient construction site beneath the ruins of Pompeii. This unique find has allowed scientists to observe for the first time how the Romans prepared materials for building walls.

Chemical and microscopic analysis revealed that Roman workers mixed slaked lime with volcanic ash before adding water—a process known as hot mixing. This step generated heat and created microscopic limestone nodules that contributed to the mortar’s self-healing properties. This not only made ancient concrete incredibly durable but also capable of “healing” microcracks over time, with examples still visible 2,000 years later!

Furthermore, tools and materials were found alongside the dry ingredients at the worksite.

The discovery challenges previous historical interpretations, which relied heavily on descriptions by authors such as Vitruvius (De Architectura), and opens a new perspective on ancient construction technologies.