Ferrocement is a construction material consisting of a thin layer of Portland cement mortar, reinforced with closely-spaced small diameter steel wire meshes or synthetic meshes that are distributed uniformly throughout the cross-section. Ferrocement is made from a rich cement mortar mix, thus yielding a better performance than reinforced concrete. Additionally, the shape of the pieces adds to its strength and resistance.
Ferrocement propertiesFerrocement’s extraordinary strength is the result of two factors. First, the armature consists of many overlapping layers of thin steel wire meshes, closely spaced among each other; and second, concrete has a remarkable capacity to resist deformation in the vicinity of the reinforcement – a characteristic that is taken into account for the arrangement of the armatures described above. Ferrocement’s mechanical performance, which is closely related to the armature’s specific surface, is very good. Ferrocement has a higher tensile strength than reinforced concrete, and maintains flexural behavior until the cracking point has been reached. Compressive strength is not modified or determined by the layers of metal mesh but by the compressive strength of the mortar matrix. The mesh we use has a minimum weight of 1.60 kg/m² and a yield strength of 2400 kg/cm². The steel content ranges from 180 to 250 kg/m³. The compressive strength of the mortar we use amounts to 400 kg/cm² approximately.
The history of ferrocement
Although ferrocement was intermittently used at first, this material is almost contemporary with reinforced concrete.According to Shah, who has written and published several articles about this subject, Joseph Louis Lambot was the first to build a row boat out of ferrocement in 1849. One hundred years later, in 1949, the boat still stayed afloat, and it is currently on display in the Brignoles museum in France. In the 20th century, the architect Pier Luigi Nervi carried out a series of experiments on ferrocement. He found out that this material was extraordinarily flexible and capable of resisting high impact, so he decided to use it as a boatbuilding material. Thus, Nervi built “Irene”, a 165 ton motor yacht with a 35 mm thick hull, that weighed 5% less and cost 40% cheaper than a similar wooden hull boat at that time. In 1949, Nervi also used ferrocement to build the Exhibition Hall at the World Expo in Turin. The central hall was built out of prefabricated units not exceeding 40 mm thick and with 98 meters span, without any intermediate support.