In many parts of the world, residential and commercial buildings are made of concrete and/or concrete blocks. Concrete is strong and durable. It resists damage from water and pests. But making the cement which is used in concrete is responsible for 8% of the global emissions each year.
That’s a big deal. It’s almost 4 times as much as the carbon emissions from transoceanic and coastal shipping. Let’s put it another way. Cement production creates a third as much carbon pollution as the world’s entire transportation sector. If we are serious about reducing carbon emissions, we need to find environmentally friendly, low carbon alternatives to cement.
Scientists at Martin Luther University Halle-Wittenberg say they have done precisely that. In research published recently in the journal Construction and Building Materials, they describe how industrial residues can be used to produce high-quality, climate-friendly materials.
The basic raw material for cement is limestone, which is converted to cement clinker in large furnaces. Not only do those furnaces consume an enormous amount of energy, the environmental impact of the process is disastrously large. “Around one ton of carbon dioxide is released during cement production for every ton of limestone. The majority of this is emitted by the limestone itself,” Professor Herbert Pöllmann, a geoscientist at MLU, tells Science Daily.
Replacing the limestone in cement production would result in greatly reduced carbon emissions, but to find acceptance in the commercial world the new material would need to have the same beneficial properties as traditional cement. The scientists experimented with two kinds of industrial waste — kaolin and aluminum. Kaolin, also called china clay, is a soft white clay used in the manufacture of china and porcelain. It is widely used in the making of paper, rubber, paint, and many other products, according to Encyclopedia Britannica.
“I don’t really like the term industrial waste. It is actually industrial residues that can still be used very effectively, for example to produce alternative forms of cement,” says Pöllmann. The researches investigated a number of different ratios of ingredients and analyzed the physical properties of the new cement products they formed. The biggest advantage is that both aluminum and kaolin contain no carbon dioxide that can be released during processing.
“You can use them to produce large quantities of cement that has great properties,” explains Pöllmann. He says producers could either switch completely to the more climate-friendly materials or produce cement mixtures that use a lower ratio of limestone and are therefore more climate friendly.
There are limits to the process, however. “There aren’t enough industrial residues to cover the global demand for cement,” Pöllmann says. So his team is also looking for suitable natural products such as volcanic ash or various mineral resources that have not yet been used industrially and that do not release carbon dioxide as well. As an example, there are other types of clay that could be substituted for kaolin.
Making cement with lower carbon emissions won’t save the planet all by itself, but it could make an important contribution to lowering atmospheric carbon dioxide. The Earth will need all the help it can get to avoid an existential event that could threaten millions of species, including humans.