news8

The house that foamed concrete built

As part of the regeneration of Sri Lanka’s south coast, Propump has helped develop low cost housing using foamed concrete. Built by locals in less than two weeks, the site’s foamed concrete ‘show home’ signalled the start of the area’s redevelopment following the devastation caused by the Indian Ocean Tsunami in 2004.

Completed on behalf of the Sri Lankan Government, the construction of the two-storey, five roomed foamed concrete house began with the erection of a solid steel framed structure. To ensure stability, the steel frame was built on a strip foundation – a trench filled with concrete – which was then further strengthened with a 200mm wide kicker to ensure structural integrity. A high strength 10 Newton/mm2 foamed concrete was then poured around the frame’s base.

As soon as the kickers had cured, each of the ground floor walls was clad with a shuttering ply. Applied to only the lower half of each wall, this allowed a staggered concrete application that could be easily completed with the minimal technology and limited manpower available.

The shutters were infilled manually with foamed concrete poured directly from steel buckets. The following day, once the concrete had set, the shuttering ply was vertically lifted and clamped higher up onto the now set concrete where the infilling process was repeated with an identical concrete mix. This process was repeated until all the walls had been formed. Once complete, the walls offered a plastic density of 1,200kg/m3 and an extremely high air content to provide good levels of thermal insulation.

With a continued policy of research and development, Propump Engineering, working in conjunction with The Affordable Housing Group, was involved in the early trials for low cost houses built using foamed concrete. The material was required to deliver an easily erectable structure, made with readily available materials and utilising the local population.

The foamed concrete was manufactured on-site in Sri Lanka using a standard concrete mixer (as the site had no access to fresh water or electricity), with local labourers manually weighing the sand, cement and water for the base mix. To add the foam, a custom-built, air powered foam generating system designed by Propump was used.

Developed for ease of transportation, the custom made portable foam generator was designed so it could be assembled and disassembled with its size and low weight enabling it to be small enough to be carried in a ruck sack for easy transportation

Upon completion of the shell of the Sri Lankan ‘show home’, a much higher level of resistant foamed concrete was supplied to form the ground floor slab. For this, concrete with a plastic density of 1,700kg/m3 was pour applied using the same method. To finish the project, a roof was constructed from coconut matting to provide waterproofing with a similar aesthetic to thatching.

Completed within an extremely short timeframe, the building was subsequently used as a security and storage centre for the low cost housing development. The project now stands as a fine example of the high quality and innovative foamed concrete solutions that can still be achieved without the need for computer-aided batching, weighing and mixing.

«