Could Roman concrete have clues on how Pyramid of Giza was built – and saved?

The enduring mystery of how the ancient Egyptians built the Great Pyramid of Giza – with its 2.3 million multi-tonne stone blocks – has puzzled researchers for centuries.

Mainstream archaeology holds that the pyramids were constructed from natural limestone or granite blocks precisely cut and hauled into place.

An alternative scientific theory suggests the blocks might have been cast from an early form of concrete, but that idea has long faced a critical question: how could such an artificial material survive for more than 4,500 years, while some modern buildings could suffer wear and damage in merely a few decades?

Now, a new study on nearly 2,000-year-old Roman concrete may provide a materials-science clue that breathes new life into the concrete hypothesis.

Published in the peer-reviewed academic journal Science Advances in July, the research reveals that ancient Roman concrete not only resists decay but actually grows stronger over centuries through a self-healing process.

A team led by Zhu Xiaohong of Beijing University of Technology, with collaborators from the University of California, Berkeley, the University of Michigan, Lawrence Berkeley National Laboratory and the University of Illinois Urbana-Champaign, analysed concrete taken from a communal latrine at Hadrian’s Villa in Tivoli, Italy.

Using high-resolution imaging, they discovered the material’s remarkable durability stems from the gradual formation of calcite crystals that fill pores and microcracks.