Local solutions to reduce the carbon footprint of concrete

Excitement abounds at the Nemaska ​​Lithium construction site in Beaconcore in Centre-du-Quebec. The processing plant is starting to take shape. Ultimately, it should produce 34,000 tons of lithium hydroxide per year.

But a small amount of the ore is used to make batteries for electric vehicles. So mountains remain, and the company hopes to recycle a good portion of it.

A pilot project aimed at marketing concrete made with aluminosilicate residues produced at the site is being implemented. It is a powder with binding properties, which is why it can be used to replace cement.Dan Fournier, president of byproduct evaluation, explains.

With the help of a local company, Nemaska ​​Lithium produced an experimental concrete, the main components of which are aluminosilicates and slaked lime (clinker). This recipe contains 25% aluminosilicates, which significantly reduces the proportion of clinker, which is typically nearly 80% in standard cement (portland cement) in North America.

Nemaska ​​Lithium's goal is to create a circular economy.

Clinker production causes significant GHG emissions. For every tonne of finished product, approximately one tonne of carbon dioxide is released into the atmosphere.

By using these mining residues, the carbon bill will be reduced. The plant has an annual capacity of 220,000 tonnes of aluminosilicates, which are used to make cement.

According to Nemaska ​​Lithium, using this resource could reduce CO emissions by around 200,000 tonnes.₂ Compared to Portland cement recipe.

Now it has to prove that this new product competes in terms of quality with its competitors already in the market.

For this, two witness boards were shed last November; One is traditional concrete and the other is experimental concrete. They reveal the coming and going of construction trucks and the spreading of abrasive materials.

Interesting blocks

Nemaska ​​Lithium has teamed up with the Concrete Infrastructure Research Center at the University of Sherbrooke in this adventure to assess the durability of this new composite.

Experiments have already been carried out by our colleagues at the National Research Council. We are currently testing it on a large scale and it is working well.Director of the laboratory Prof. Areski reassures Tagnit-Hamo.

With solid expertise in the field, he works with industry, the Quebec government and other researchers to explore low-carbon cement options.

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The prospect of mine tailings looks promising, especially as projects for the exploitation of critical materials tend to proliferate. Eventually, he hopes Interesting blocksIt remains conditional No To accept new products.

To complete the offer, he checks another avenue at Val-des-Sources in Estrie. The tailings from the Geoffrey asbestos mine contain silica with pozzolanic properties.

There are about 800 million tonnes of the material, some of which is used to make cement. However, treatment must be carried out, especially to remove traces of asbestos. A big project, the outlines of which still need to be clarified.

Calcareous clay

Professor Tagnit-Hamou identified another avenue, which replaces the calcareous limestone.

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Limestone must be heated to over 1400 degrees Celsius, while clay must be heated to close to 750 degrees, which allows for the conservation of fossil fuels, such as oil or coal.

But above all, clay does not emit C0₂ When heated to high temp. One ton of limestone requires about 800 kilograms of carbon dioxide emissions.

Mr. Tagnit-Hamou advises Clayson Écominéral, which plans to open a clay quarry in the Gaspésie in the Matane department.

Its founding president, Joel Fournier, promises that calcined clay can be used up to 40% of the cement mix. In this case, he says it can be reduced Almost half Broadcasts GHG Compared to Portland cement.

Mr. According to Fournier's estimates, the deposit has the potential to deliver A million tons of calcareous clay per year for over 100 years.

So significant that the Cement Association of Canada estimates that total clinker production in the country in 2020 will be 11.4 million tonnes.

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Joel Fournier believes that manufacturing costs remain competitive during marketing. As evidence, he cites the fact that this resource is already being used in many countries in Europe, China, India and Cuba.

He is currently in discussion with several industry players. He has two options. The clay is sold directly to the cement factories and converted. Or build a factory on the site, which is estimated at $150 million and may raise questions of social acceptability.

If all goes well, he estimates production will begin within a year.

Oversight of innovations

Whatever happens, most innovations must be reviewed by government agencies. Conformity of the products should be ensured by testing the resistance and durability of the products. It is also necessary to quantify potential risks to health and the environment.

According to Professor Aresky Tagnit-Hamo, the stages tend to extend over time, fired by his previous experiences. For example, he tested a method of incorporating glass powder obtained from recycled bottles into cement. More than a decade passed between the first tests in 2004 and the adoption of the standards.

That's where the problem lies, he says. It is indeed a very long road. We must work to accelerate the adoption of standards.

Industry representatives, sometimes wary, encourage openness to new practices, as well as ministries and municipalities to support businesses by purchasing low-carbon concrete.

At the current rate, Professor Tagnit-Hamov believes that changes in practices are not fast enough to meet targets for reducing greenhouse gas emissions.

On the other hand, as we saw in the Northwold case, urgency is not always welcome.