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Cement has a carbon problem. Here are some concrete solutions straight out of WSU

Washington State University researchers have made a groundbreaking discovery in the field of sustainable construction by developing an eco-friendly concrete formula that is carbon-negative. By infusing standard cement with biochar, a type of charcoal produced from organic waste, the researchers were able to create a concrete mixture that can absorb carbon dioxide from the atmosphere while maintaining its strength. This breakthrough could significantly reduce carbon emissions in the concrete industry, known for its high energy consumption and carbon footprint.

Eco-friendly cement/concrete production

Researchers at Washington State University have developed an eco-friendly, carbon-negative concrete formula that could significantly reduce carbon emissions from the concrete industry. By infusing standard cement with biochar, a type of charcoal made from organic waste, which has been fortified with concrete wastewater, the researchers were able to create a concrete mixture that absorbed up to 23% of its weight in carbon dioxide from the atmosphere, while maintaining comparable strength to regular cement.

Concrete production is known to be one of the most energy- and carbon-intensive manufacturing industries, responsible for approximately 8% of total carbon emissions from human activities worldwide. With over 4 billion tons of concrete produced globally each year, finding sustainable alternatives is crucial to mitigating the environmental impact of the industry.

Previous attempts to add biochar to cement as a substitute to reduce its carbon footprint had resulted in a significant reduction in concrete strength when biochar content exceeded 3%. However, the researchers at Washington State University were able to overcome this challenge by treating biochar in concrete washout wastewater, a waste material from concrete production that is highly alkaline and rich in calcium. The calcium in the wastewater induced the formation of calcite, which strengthened the biochar and eventually the concrete incorporating the biochar.

"We're committed to finding novel ways to divert waste streams to beneficial uses in concrete; once we identify those waste streams, the next step is to see how we can wave the magic wand of chemistry and turn them into a resource," said Xianming Shi, a professor in the Department of Civil and Environmental Engineering at WSU and the corresponding author of the research paper.

The researchers were able to add up to 30% biochar to their cement mixture, and the resulting paste had a compressive strength after 28 days that was comparable to ordinary cement, at around 4,000 pounds per square inch. This breakthrough could pave the way for the use of much higher dosages of biochar in cement, as the researchers were able to engineer the surface of the biochar to enhance its properties.

eco-friendly cement

The synergy between the highly alkaline concrete washout water and the porous biochar allowed for the precipitation of calcium carbonate onto or into the biochar, strengthening it and enabling the capture of carbon dioxide from the air. This means that a concrete made with this biochar-infused cement could continue to sequester carbon dioxide for the entire lifetime of the concrete, which is typically 30 years for pavement or 75 years for a bridge.

To commercialize this technology, the researchers have been working with the Office of Commercialization to protect their intellectual property and have filed a provisional patent application for their carbon-negative concrete formula. They have also received a seed grant from the Washington Research Foundation to gather more data for various use cases and are actively seeking industry partners from the building and construction sector to scale up production for field demonstrations and licensing of this technology.

The development of carbon-negative concrete has significant implications for sustainability in the construction industry. As the demand for eco-friendly building materials continues to grow, this breakthrough could potentially revolutionize the way concrete is produced, reducing its environmental impact and contributing to the goal of achieving zero-carbon built environments. By utilizing waste materials such as biochar and concrete washout water, this innovation not only reduces carbon emissions but also provides a valuable solution for waste diversion and resource utilization.

Graduate student Zhipeng Li and Professor Xianming Shi. Credit: Washington State University
Graduate student Zhipeng Li and Professor Xianming Shi. Credit: Washington State University

The researchers at Washington State University are at the forefront of this pioneering work, pushing the boundaries of what is possible in sustainable construction materials. With further research, development, and collaboration with industry partners, this carbon-negative concrete formula could soon become a viable and widely adopted solution for reducing the carbon footprint of the concrete industry, paving the way for a more sustainable future in construction and infrastructure development.



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