Secret of future cement strength lies in sea urchins?

Research carried out by the University of Konstanz, Germany, has helped to develop a cement that is resistant to fractures.

The research highlighted that while the spines of sea urchins are made mainly of calcite, a very brittle and fragile material, the way nature optimises the “brick and mortar”-style architecture gives the spines additional strength.

The guiding principle is to alternate hard (ie the brick) and soft (ie the mortar) layers as used by the sea urchin, When strength is applied to the brittle calcite, its crystalline block cracks but the energy is transferred to a soft, disordered layer which does not have planes that can tear.

The research team, led by Prof Helmut Cölfen, successfully synthesised nanoscale cement in line with this principle. Macromolecules were identified that adopt the function of mortar, fixing the crystalline blocks to each other in the nanometric scale, with the blocks assembled in an orderly manner. This results in a cement that is more resistant to fractures and hopefully, more durable.

"Our cement, which is significantly more resistant to fractures than any other that has developed so far, gives us completely new construction possibilities," Prof Cölfen said.

A pillar made of this cement could be built with a height of 8000m, before the material in its base was destroyed by its weight, according to the study. By comparison, normal steel, which has a value of 250MPa has 3000m as its upper limit.