Sea urchin spines inspire crack resistant cement

Despite being made mostly from calcite, which is usually very brittle and fragile, sea urchin spines are actually very strong thanks to a nanoscale “bricks and mortar” arrangement whereby layers of brittle crystalline blocks of calcite are interspersed with softer disordered layers. When force is applied to the brittle calcite, its crystalline block does crack, but the energy is then transferred to the soft disordered layer. Since this material has no cleavage planes to tear, it prevents further cracking.

By applying the same principle to the synthesis of cement, a team from the university’s Physical Chemistry department claim to have demonstrated cement with unprecedented fracture resistance.

Project leader Professor Helmut Cölfen describes the process as "encoding fracture-resistance at the nano-level". In this case, it meant identifying a material that bonds only with cement nanoparticles and nothing else in the cement. About ten negatively charged peptide combinations were identified that both adhere to and bond materials well.