Carbon Neutrality: Can Concrete get on the Road to Net Zero?

Why is eco-friendlier concrete the future?

Cement production is the single biggest industrial cause of carbon pollution in the world, responsible for 8% of global emissions. It equals the entire world’s automobile fleet. But within about ten years, we will have the technologies necessary to decarbonise cement production. With these innovations, Australia can lead the way in zero-carbon cement.

Types of green concrete

As cement is the most significant producer of CO2 emissions in concrete, many have concentrated on substitutes to lower the amount of cement required per batch, including industrial waste materials from foundries, quarries, power plants, feed mills, and other sources. However, there are various aggregate substitutes, such as recycled concrete, glass, and waste plastic. Companies can save water in the concrete pouring process by adding superplasticizers or other water-reducing admixtures to concrete, in addition to substituting cement, aggregate, or sand.

Several eco-friendly cement substitutes are available, but they can only replace a portion of the cement used in concrete. Popular alternatives include fly ash, furnace slag, rice husk ash, silica fume and post-consumer or waste glass. Furthermore, there are also alternatives such as wood ash, sawdust, foundry sand, sludge from pulp and paper mill clarifiers, and de-inking solids from paper recycling companies.

Aggregate replacements come in a variety of forms, including material from dredging ports and waterways, recycled carpet fibre, excavated rock from tunnels, scrap wood, rubber tyres, pulp and paper mill residuals, and recycled bricks from demolished structures. The most well-known aggregate alternatives are glass, recycled concrete, waste plastic, and foundry sand.

Carbon Negative Concrete

100% carbon-negative concrete is only now entering the market by using carbon dioxide in production. The carbon dioxide can be obtained from industrial plants which is absorbed and converted into citric acid. As well as drastically reducing the final amount of carbon created, the citric acid replaces some of the water necessary for the process resulting in additional environmental benefits for an eco-friendly project.

Geopolymer

Geopolymer concrete offers the same long-term performance as Portland cement but without the environmental footprint. Geopolymer is created using reactive aluminosilicate components and alkali-activation technologies. Unlike Portland cement, geopolymer does not rely on limestone and clay, nor does it require heating to roughly 1450 degrees Celsius for calcination, the process that eliminates carbon dioxide. Fly ash, the very fine particles produced by coal-fired power plants is one industrial waste that can be used in the manufacturing of geopolymers. Because Australia relies heavily on coal-fired power plants rather than nuclear energy, 14 million tonnes of fly ash are produced each year. Only a tiny portion of this waste is utilised; more than two-thirds is disposed of in landfills. The conversion of these industrial wastes to greener alternatives has the potential to reduce CO2 emissions by up to 80%.

Green concrete ingredients can range from cement to aggregate to sand substitutes, and newer varieties of carbon-negative concrete are on the market. Green concrete is the future, and Australia is well-positioned to lead the way in the concrete revolution, thanks to high-quality research, available technology and affordable industrial waste products.

written by Asle Kommedal