Roman concrete has stood for 2,000 years while modern concrete crumbles in decades, and in 2023 MIT scientists finally worked out the strange self-healing secret hiding inside it

Modern concrete starts cracking within decades, yet Roman harbours and domes have survived two thousand years of waves and weather. For centuries the recipe looked lost. In 2023 a team at MIT found the answer hiding in tiny white flecks that everyone had dismissed as sloppy work, the lime clasts behind Roman concrete self-healing.