Concrete Experimentation
Ferrocement
Ferrocement is a term for concrete which is thin in section, is heavily reinforced with several layers of wire mesh, and is mixed with a high ratio of cement to sand and minimal quantity of water, just enough to trigger hydration, the chemical reaction with cement that forms concrete.
On Kythnos, a hybrid structural system is in operation, with the ferrocement working in tandem with an underlying frame. In GBB I, the frame is made of the 4x4-cm wood posts of the original panels, while the other three structures employ dexion angles. Dexion is a system of perforated mild steel angles — a kind of grown-up version of the Erector Set or Meccano toys.
The sequence of construction was as follows:
Assemble a frame defining each polyhedral face (panel) using dexion angles (56mmx36mm) bolted together (the frame of the first structure was wood). Intermediate vertical angles every 60 cm reinforce the frame and hold the insulation panels in place.
Assemble the frames into the overall configuration of the building.
Tie onto the inside of the panels a layer of chicken wire (2.5 cm galvanized mesh) to support the interior plaster.
Insert rigid insulation into the panel frames.
Hang outside reinforcement (two layers of chicken wire separated by 5mm reinforcement rod.
Plaster the exterior using a sand:cement:water mixture of 2:1:0.6, applied about 2.5 cm thick to cover the reinforcement.
Plaster the interior with conventional plaster.
Paint
Ferrocement surfaces exhibit elastic deformation properties, more closely relating to the encased steel meshes, than does conventional concrete. A hard strike with a fist to the center of a panel prompts drum-like vibrations.
This elastic property, in conjunction with the system of assembly, where the dexion structural members are bolted together and all interior and exterior plaster is encased in wire mesh, points to good earthquake resistance.
Greece is earthquake country, and it is comforting to know that we sleep in light-weight buildings which, in a worst-case scenario, may bend and deform but would not send heavy concrete slabs crushing down on our beds.