Stepping up with polymers - staircase development

Materials World magazine
1 Jun 2010

A staircase construction technique that uses blocks made of polystyrene and a polyurethane coating filled with concrete could lead to a made-to-measure alternative to heavy concrete steps according to its inventors.

In this process, each tier represents a single element that can be aligned in a similar way to building blocks.

The polystyrene formwork, shaped via a computer milling machine, remains part of the finished stairs. As opposed to a mould that is later removed, allowing ‘easier formation’. The single parts are then bonded together to complete the staircase, and the coating is added before the concrete is poured.

According to Kurt Wohlgemuth, product designer of SCAWO designer and Managing Director of Metall Concept in Sarentino, Italy, the staircase’s ability to be installed individually assists its adaptability, for example, for use in old buildings, where new features may not be easily installed without major reconstruction.

He says, ‘The formwork had to be made of material that was resistant yet light. We had to consider that after having it placed into a building, the concrete would be poured into the formwork. Therefore the material had to be recyclable, economic and easy to process’.

Alexander Kaserer, Simulation and Materials Project Manager at innovation park TIS in Italy, who scouted and developed the material with Wohlgemuth explains, ‘We experimented with six different materials, including concrete, wood and even leca stones but polystyrene met the requirements.’
Although the aim is to eliminate both weight and heavy duty installation, a plastic formwork could raise durability issues. However, Kaserer says, ‘The polymer element has to last only until the concrete is poured into it as a shaper, after this the concrete and coating forms the resistant part of the stair, so
durability is no less than a traditional construction.’

A staircase uses approximately 30kg of coating material and polystyrene cuttings are recycled. From the main body of the framework, Wohlgemuth claims all residual plastic parts are collected and pressed as new polystyrene sheets or used in the construction sector as insulating material.

Philip Purnell, Director of the Institute for Resilient Infrastructure, UK, has concerns however, on the design’s environmental feasibility. He says, ‘The implications of using plastic is always a concern as it generally has around 100 times the embodied energy/ embodied CO2 of concrete. Fourty kilograms of plastic is equivalent to about four tonnes of concrete and the carbon footprint of the staircases could be highly increased.

‘On the plus side, anything which reduces the amount of transport, manual and crane handling is welcome on both cost, time and health and safety grounds.’

The product, which is at commercial stage, has now been patented and the company is establishing manufacturing facilities. However, Wohlgemuth says the stairs will not be planned for mass production to maintain innovation input and a more tailored service.

Further information: TIS and Metall Concept