How two engineers from Thuringia want to create affordable homes in developing countries and crisis-hit regions.

Sand is one of the most important raw materials on Earth. For example, it is a crucial ingredient in concrete and thus a bedrock of modern housebuilding practices. But not all sand is the same. The grains of sand that is used to make concrete need to be big enough to bind properly with the other ingredients. Desert sand is actually unsuitable because it is ground down by being in constant motion due to weather conditions. However, a piece of highly innovative engineering from Germany is turning this very material into an extremely versatile building material.

Modular kit system for housebuilding

Working in collaboration with the Chair of Building Chemistry and Polymer Materials at the Bauhaus-Universität Weimar, Thuringia-based Polycare Research Technology GmbH has developed a process that involves adding an unsaturated polyester resin and additional additives to desert sand to produce a viscous compound with a curing time of just 20 minutes. Fully cured after 24 hours, the compressive and flexural strength of the polymer concrete can be up to five times greater than that of cement concrete, depending on the composition of the filler material. However, the principal aim of engineers Gerhard Dust and Gunther Plötner was to “help people help themselves” in regions where safe accommodation is scarce.

It was therefore important that the building material can be used by untrained people with no access to construction machinery. Polycare meets this requirement with its Modular Assembly System (MAS). While it is still in a viscous state, the polymer concrete is poured into one of five basic moulds, where it cures to form blocks that, at first glance, look very similar to LEGO^® bricks, and indeed work in the same way, albeit on a larger scale. But besides its modular design, the concept also shares another similarity with our MB Building Kit System. Cavities inside the modules are used to bolt together individual layers for stability, which means they can subsequently be disassembled in a non-destructive way, so that the blocks can be reused elsewhere.

A sand house a day

Even the machine needed to cast the components was designed with mobility in mind, ensuring it can be transported easily and set up close to the building site. The plant has been successfully tested with sands of various grain sizes from Namibia to North Africa. Moreover, in crisis-hit areas, filler materials can be sourced from the demolition of destroyed buildings, for example. The necessary additives such as the special resin only make up 10 percent of the polymer concrete, which greatly simplifies logistics operations.

A single plant can produce approximately 16 metric tons of polymer concrete per eight-hour shift, which is enough to build a single-story house with a footprint of just under 50 m². Due to the construction-relevant physical properties of the material, a solid subsurface is the only requirement for a building project. Special foundation strips made from the same material form the foundations for the first bricks and also mark out the floor plan of the building. Further special components in the Modular Assembly System (MAS) make it easy to incorporate windows and doors.

Effective protection from the elements

The virtually seamless, interconnecting system offers very good protection from the elements on its own. However, in areas where the local climate requires, the cavities of the individual basic elements can be filled with additional insulating material. The polymer concrete is also frost-proof, as it does not absorb water. What’s more, it exhibits excellent resistance to abrasion and is not susceptible to major temperature fluctuations. It does not need to be plastered, painted or tiled, but can be, if required, and the completed houses also satisfy the quality requirements of European building standards.

Another important property of the corrosion-resistant polymer concrete is how resistant it is to external influences from aggressive waste water and mineral oils, which is particularly important in regions with poor infrastructure. The houses can also withstand the influence of acids, alkalis, fumes and gases without sustaining any damage. At the same time, the polymer concrete itself does not react with the environment. If buildings have only been required on a temporary basis and the blocks are no longer needed, they can be mechanically destroyed with ease and then recycled.

Pilot project in a future market

However, these are not the only properties that are important for the widespread success of the project. Given the often limited financial resources of governments and aid workers on the ground, and the large volume of housing that is required, it is important that buildings can be put up fast and at low cost. The benchmark in this respect is a sample house that has been built behind Polycare’s head office. It took two people less than 12 hours to construct the single-storey building, which boasts 37 m² of living space. Material costs came in at less than 3000 euros.

Polycare passed an initial endurance test during a presentation in Namibia. The southern African country has long-term plans to build 200,000 affordable homes to improve the quality of life for large sections of the population on a sustainable basis. A study is now being carried out to clarify how an initial model settlement based on the German technology could be financed.

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