Concrete is still one of the most used materials in construction and for good reason: it's cheap, versatile, and relatively durable. Its negative environmental impact, though, is its biggest weakness. For this reason, research into possible avenues to reduce its carbon content as much as possible is blooming and a few avenues have been opened thanks to an unexpected ingredient: sugar.
Sugar, and especially products normally treated as sugar waste are what is propelling the research forward. Precipitated calcium carbonate (PCC) and sugarcane bagasse ash, for example, have been successfully used to reduce the environmental footprint of concrete production.
A study by Idaho State University has demonstrated that substituting a portion of the cement in concrete with PCC, a byproduct of sugar beet processing, can maintain the concrete's strength at levels comparable to traditional concrete. This approach addresses two major environmental concerns: reducing cement consumption, which is responsible for about 8% of global CO2 emissions, and repurposing industrial waste products.
In their experiments, the researchers replaced up to 30% of cement with PCC and found that the modified concrete still met the American Society for Testing and Materials standards. Additionally, the team explored using upcycled concrete aggregate instead of traditional sand or crushed stones, discovering that up to 100% of the aggregates could be replaced without sacrificing strength.
“From the various concrete mix designs, 25 to 30% of cement can be replaced with PCC and 0% to 100% of aggregates can be replaced with UCA, which can achieve a compressive strength of 28 MPa (4000 psi). This type of concrete helps to sequester carbon, reduce carbon emissions, and minimize waste disposal in landfills to obtain environmentally friendly concrete (PCC-UCA concrete).” (Phuyal K, Sharma U, Mahar J, Mondal K, Mashal M.)
Sugarcane bagasse ash is a byproduct of the sugar industry but is at the basis of one of the most interesting alternatives to bricks and concrete. This is made possible thanks to the pozzolanic properties of bagasse ash, which enhances the mechanical properties of concrete. Researchers have found that replacing a portion of cement with sugarcane bagasse ash can increase the compressive strength of concrete, with an optimal replacement percentage of around 5%. This substitution not only reduces the environmental impact of cement production but also provides a practical use for agricultural waste.
Sugarcrete, a biomaterial construction block developed by Grimshaw and the University of East London, uses sugarcane bagasse to offer a low-cost, low-carbon, and reusable material alternative to traditional brick and concrete. This material is significantly lighter than conventional bricks and has a considerably lower carbon footprint.
The development of these alternative concrete materials addresses significant environmental and economic challenges. The production of traditional cement is a major source of CO2 emissions, contributing significantly to global climate change. Furthermore, using waste products from the sugar industry, could translate to a more synergic approach between the two giant industries of construction and agriculture. As highlighted by Armor Gutierrez Rivas in this interview, "The largest crop by production volume can marry the largest requirement of another industry — such as bricks and fabrication of walls." This approach would not only mitigate the environmental impact of concrete, but also offer an economic benefit to the recycling of industrial and agricultural waste.
While the initial results are promising, these alternative concrete materials still require further research to reach drastic levels of carbon reduction. Moreover, as with many innovative solutions, regulations are a hard obstacle to overcome. Strict regulations and tests are obviously great to ensure the safety of the end-consumers, but can also hinder many low-carbon solutions in their strive to be competitive in the market.
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