Concrete

Without steel, concrete is a material that works exclusively in compression. Its direct ancestor is the Roman opus caementicium, which made it possible to build monumental domes still intact today, such as that of the Pantheon.

The final strength of concrete depends closely on Abrams' Law, according to which compressive strength is inversely proportional to the water/cement ratio (w/c). Excess water, not taking part in the chemical hydration reaction of the clinker, evaporates leaving capillary voids that drastically reduce the mechanical performance and durability of the element.

The main limit of plain concrete is its poor tensile strength (about one tenth of its compressive strength) and its brittle behaviour. For this reason, today it is used in its pure state only where tensile stresses are zero or negligible: massive foundation works, gravity dams, screeds, sub-bases (blinding concrete) and precast blocks.