How two eco-friendly French inventors want to replace concrete with clay


The construction industry is one of the main sources of greenhouse gases. Cement production alone is responsible for 5% of all the CO2 found in the atmosphere. But one French company has an alternative to concrete that is 20 times less pollutive.

Concrete is one of the most widely used construction materials in the world. In 2013, four billion tons of concrete were produced, according to a report published by the US Geological Survey in February 2014.

However, the environmental impact of this omnipresent material is rarely discussed. Yet, according to several studies, producing a ton of cement emits about 900kg of CO2.

Cement is a powder. When mixed with water, it sets after a few hours, then hardens into an extremely resistant material. To make the cement powder, you start by heating the raw materials (limestone and clay) at an extremely high temperature (1450°C) into a substance called clinker. This heating process explains why cement manufacturing uses so much energy.

Julien Blanchard and David Hoffman wanted to invent a new construction material, that would be just as solid as concrete but much more environmentally friendly to manufacture.

"Producing a tonne of clay cement is 20 times less pollutive than regular cement”

Julien Blanchard founded Argilus, a company based in the French town of Chaillé-sous-les-Ormeaux, in 2010. “Argile”, the root of the company’s name, means “clay” in French.

I wanted to get into eco-construction and so did my partner, David Hoffman, who is a chemical engineer. He’s the one who came up with a chemical process to turn clay into a material as durable as cement. We nicknamed the process “HP2A”, which stands for “High Performance Alkaline Activation” [Editor’s note: in French, "Haute Performance d’Activation Alcaline"].

Julien Blanchard holds blocks made of clay which he says are as solid as concrete. Photo : HP2A.

Chemist David Hoffman works in his laboratory. Photo : HP2A.

We make this material by creating a molecular reaction with alkaline metals. [Editor’s note: Alkaline metals are the chemical elements lithium, sodium, potassium, rubidium, cesium and francium.]

These reagents harden the clay powder into a “rock-like” consistency, all at room temperature. We don’t have to heat the substance at all, which immediately cuts down massively on the energy required to complete the process.

This photo shows the powdery clay hardening thanks to a chemical reaction. Photo: HP2A.

This photo shows the powdery clay hardening thanks to a chemical reaction. Photo: HP2A.


Our main ingredient is clay, which you can find on every continent [Editor’s note: Clay is formed when sedimentary rocks crumble]. That makes it inexpensive.

Also, using clay means that we aren’t using sand from beaches, which is often used in cement production. We are also fighting the depletion of beaches. [Editor’s note: Commercial exploitation of sand has already affected about 75% of beaches in the world, according to a documentary made by French TV channel Arte].

While manufacturing one tonne of cement emits 900kg of CO2, our studies show that making one tonne of clay cement only emits 50 to 100kg. That’s between 10 and 20 times less!

Most cement used in construction isn’t recycled. When you demolish a building that is made out of concrete, no one reuses the concrete to rebuild. [Editor’s note: In France alone, about 300 million tonnes of waste per year comes from the construction sites of public works projects. Concrete represents about 36% of that waste. It is estimated that only half of that concrete is recycled.]

Clay cement is recyclable and we can make it out of any kind of sand, including sand that comes from a demolition site. The last main advantage is that the cost of producing clay cement is the same, or cheaper, as the cement we use now.

This video presents their product.

We have patented our product and we want to start commercial production in 2017. We’ve already been contacted by big companies like Michelin, Total and Airbus, who are interested in our product. Currently, we employ fifteen people, but we want to double our staff.