Concrete is the most abundant manufactured material in the world. It is primarily composed of water, cement, and aggregate (sand and gravel.) Cement manufacturing is responsible for about 8% of the world’s total CO2 emissions, primarily a result of the chemical reaction of heating limestone and the combustion of fossil fuels used to provide the heat.
A startup company spun off from the University of Wisconsin- Madison has developed a durable, inexpensive, and environmentally-friendly building material made from two harmful pollutants. The company, called Alithic, uses chemical reactions to pull carbon dioxide from the air and then mix it with industrial wastes like coal ash. A fan sucks air into a special cooling tower where it passes over an alkaline solution of sodium hydroxide, which reacts with carbon dioxide. The resultant solution is mixed with the coal ash forming a carbonate and releasing sodium hydroxide. The carbonate mineral product (known as supplementary cementitious material or SCM) can be substituted for traditional Portland cement for making concrete.
The process locks away carbon dioxide to produce a product that is cheaper and, in some cases, stronger than traditional cement. The coal ash Alithic uses comes from a local landfill. The company is also testing other waste streams from places like blast furnaces that contain useful materials like calcium and magnesium. So, the Alithic process removes carbon dioxide from the atmosphere, cleans up an environmental mess, and produces a viable substitute for traditional cement.
The Alithic material is being shipped to a number of ready-mix concrete plants, where potential customers are testing its binding properties.
