Road builders tap into termite technology: the environmentally-friendly Ecobond process is being used to build rural roads at lo

FRUSTRATED BY ONE of the multiplying and seemingly indestructible termite mounds on his property, a South African engineer gave one a hard kick. The first unintended consequence; he broke his leg. The second; South Africa, Zambia and soon other Southern African countries will receive new environmentally-friendly roads, based on termite technology.

"The idea came from my best, best friend, a South African named Jan Lund, who in his garden tried to kick those hills away. On his third try he broke his leg. After that, he came to me and said, 'This is something! We need to replicate this technology for construction,'" said Kim Andersen, the Danish Managing Director of Lusaka-based Ramogatia Construction.

A 10-year pilot project in South Africa and 3000 laboratory tests later, the process, dubbed Ecobond, received European Union and Danish government funding to construct roads in Zambia.

"After Zambia, we are going to move out to different countries. Botswana and Malawi are interested, because they have big road problems," Andersen said, indicating the environmentally-friendly termite technology is cheaper than conventional asphalt roads and more durable, putting less strain on African infrastructure budgets for road maintenance.

Though termites are popularly known as wood-devouring pests, of the 3000 known species, three-quarters are classified as soil-feeding termites. Their diet consists of non-cellular organic material mixed with clay minerals.

Synthetic soil

Andersen explained, "We don't use diesel fuel to build, and that makes our roads more environmentally friendly than asphalt roads. We owe it to those small termite insects who make those big hills. We found an abandoned hill, and we took tests of the solution the termites use to harden the soil. Our synthetic version is mixed with water and applied to any soil or crushed stone to make the same hardness and water insolubility. It dramatically increases the bearing capacity of the soil."

Termite mounds are composed of clay content usually 20 per cent higher than in nearby soils, reflecting the insects' preference for smaller clay particles for construction. (However, Ecobond roads contain no more than 20 per cent clay content.) While being transported in the insects' mouths or five gut compartments, the particles are saturated by pH and other chemicals, which add nutrients and hardness. The nutrients account for greater soil fertility at the base of the mounds, which extend one metre into the earth but can rise over two metres in height, so plant life proliferates around them.

"Soil particles probably undergo modifications through the insect's gut because of the extremely alkaline pH, reaching values up to 12," noted a study published in the Brazilian periodical 'Scientia Agricola'.

Termites have inspired engineers in Africa before. Termite mound construction has been studied by UK researchers. Architectural firms seeking to give high-rise buildings the airflow and climate control achieved by the insects gave copied the mounds' internal engineering.

Having duplicated in Ecobond the chemical properties of the "cement" created by termites to harden their mounds, Andersen's team launched their first. This was a pilot project in South Africa's Mpumalanga Province that since 1996 has carried more than 15mn vehicles including 1,000 large trucks per day. The roadbed has shown only nominal wear.

The construction process is similar to building an asphalt or gravel road but for a chemically-treated 100mm thick Ecobond slab in the place of a layer of crushed stone. A 6.0mm bitumen seal is placed over the Ecobond Slab for heavy traffic, or dispensed with if the road is to bear only lighter traffic. Despite intense heavy traffic, a new bitumen seal was not needed on the pilot project until the road's tenth year.

The road's main component, soil, is found on site, and is mixed with 20 to 60 kg of Ecobond and 20 to 100 litres of water for every 2000kg of soil or crushed stone/soil mixture, with no more than 50 per cent of a mixture comprised of crushed stone.

Cheaper than milk

"You already have 97 per cent of the required building material--soil or stone--on site, at no cost. The other three per cent, the Ecobond, is cheaper than milk, and retains the beautiful natural soil appearance. It is also transportable by man or mule over otherwise inaccessible terrain," said Andersen.

With Danish funding, road construction has begun in rural areas in Zambia as yet unconnected by any road network. "We have expanded and improved the road infrastructure in Zambia, and created lots of jobs because the road work is labour-intensive. Our company does not bring our own workmen to a site. We hire from the villages. We bring the chemicals and some machines, train the local people for a week before construction; show them how it is done, and they do the rest," Andersen said.

The local workforces are motivated by the reward of having modern roads in their regions.

Funding from the European Union finances some of the road work. "We are also funded by different health organisations that need to have the roads done so they can come out to the villages, and open new clinics," he said.

Andersen plans to put termite technology to use on other construction schemes, hardening railway embankments, lining tunnels and basements, making aircraft landing strips and sports fields, constructing pylons, poles and pipes, and even applied artistically to create poolside artificial rocks, statues and decorative tiles.

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