Clay-based and Cement-free Concrete

The ETH spin-off Oxara, is developing a cement-free concrete made from clay-based excavation material to build affordable, sustainable houses. Source: ETH Zurich

“I have been enormously lucky in life, and I wish to give some of that luck back,” the 29-year-old Gnanli Landrou from Togo explains. His firm determination leaves no room for doubt: this young man will follow through with his plans. “My Vision is to enable access to dignified, healthy, affordable housing in Africa and other regions.”

During his studies, Landrou researched the challenges facing the global construction industry: the energy- and CO2-intensive production of cement, the dwindling supplies of construction grade sand and gravel, and the high cost of concrete, which is simply unaffordable in many countries. His experience had already taught him that traditional clay brick construction is a laborious, time-consuming process, and he knew that adequate housing was still lacking in his home country.

Landrou points out an important oversight, “When people build a house in this country, they first dig a hole and dispose of the excavated soil. Afterwards, they bring in tonnes of sand, gravel and cement to pour in the foundation and walls.” However, clay is an ideal construction material in and of itself, and it tends to be readily available right where it is needed. Why not combine the technologies of both cultures? That idea brought Landrou to ETH Zurich in early 2014, where he completed his doctorate at the Chair of Sustainable Construction.

“Once again, I was very lucky,” comments Landrou on his time as a doctoral student at ETH, where he found a supportive environment and an inspiring mentor in Professor Guillaume Habert. Together, they developed a process to turn clay-based excavation material into an alternative concrete without the addition of cement.

Landrou’s soil-based concrete can be poured while fresh; it hardens rapidly and is suitable for building floors and non-load-bearing walls. Its processing resembles that of conventional concrete and it uses a similar infrastructure. “Our technology gives clay construction nearly all the processing benefits of cement, while being about 2.5 times cheaper and 20 times more environmentally friendly,” explains Landrou. The market potential for non-structural building elements is considerable.

To enter this market, Landrou patented his technology after completing his doctorate. Since autumn 2018, he has been working on his spin-off Oxara. “We still haven’t decided whether we will licence the process to construction recycling companies that want to transform their excavation material into a valuable resource, or whether we will simply sell the mineral additives required for the soil-based concrete,” says the young entrepreneur.

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