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New wave Ferrocement has been used to create a spectacular wave-shaped roof in Saudi Arabia,

There are very few limits, any structural requirements can be met and lots of money can be saved. A statement like this would surely warm the heart of many structural engineers, but Alphacrete Construction Linings UK director Derek Russell is also convinced that the use of ferrocement could well be the key to cheaper and more environmentally friendly construction.

Russell has just finished building what he hopes is an excellent example of just what can be achieved with ferrocement. The offices of the Yanbu Cement Company in Saudi Arabia feature some unusual designs, including a spectacular wave-shaped roof.

Ferrocement - a combination of lightweight reinforcement and sprayed mortar, often with a polystyrene insulating layer - has been around since the end of the last century. But although it has been used extensively in marine engineering, including for boat hulls, it is relatively unknown in the UK construction industry.

The lightweight, high strength and highly durable system offers the benefits of conventional materials but requires no shuttering to put it up and can be used to build practically any design, however strange, says Russell.

The material can be preformed as panels and sent to site, or structures can be built in situ. In Yanbu, Alphacrete has been consulting and supervising on a contract to build the new office complex for Yanbu Cement Company, designed by Italian architect Franco Audritto of Studio 65.

Construction of the Yanbu works was straightforward and required only a small amount of plant on site. For the wave shaped roof, Taiwan-based contractor Ritser first built the longitudinal beams that follow the shape. These are made up of two 8mm steel reinforcing bars with 6mm bars zig- zagging between them. Once erected, transverse beams of the same construction are placed at 1m centres along the roof.

To the underside of this frame, reinforcing mesh and two layers of hexagonal wire (chicken wire) were attached, forming 'trays' of reinforcement. An insulating layer of 100mm thick blocks of polystyrene was then slotted into these and trimmed to leave a 10mm gap. Further layers of mesh were then placed on top.

Once the frame is complete, the cement rich (2:1 sand to cement mix) mortar was sprayed on to both sides of the frame using a concrete pump, creating a smooth finish. The mortar bonds with the steel and also with the outer surface of the polystyrene.

Design of the complicated shapes is simplified by using a repeated pattern of reinforcement based on that needed at the point of highest stress, which Russell says is still economical, as materials are light and cheap. 'For Yanbu, a section of the main arch which is twisted was used as the basis for the roof reinforcement design.'

Russell, who was originally a marine engineer and designed floating quays using ferrocement, is a staunch proponent of the material and sees it as one solution to the massive problem of providing low-cost housing in developing countries.

He says that houses built from moulded panels manufactured in the countries themselves could cost as little as £5,000. No foundations would be needed, he claims. 'The floor of the house can have beams moulded on to the underside to act as a raft foundation. All you need is a piece of level ground to put it up.' Erection is also rapid. Russell estimates it would take eight hours once the materials were on site. 'All the plumbing and electrical ducts can be moulded into the wall panels,' he adds.

Ferrocement buildings are also earthquake resistant, because of the ductile nature of the material, developed from the need to cope with a wide variety of stresses when used in boat hulls.

The main environmental benefit of the system is that it employs a much smaller amount of material than conventional methods, he adds.

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