Scientists create stronger concrete that absorbs CO2 from the air

Researchers at Mepco Schlenk Engineering College in India have developed a new concrete formula that not only enhances strength but also absorbs carbon dioxide (CO2) from the atmosphere. This innovative concrete incorporates porous zeolite and bamboo biochar, materials known for their carbon-capturing properties. The study, published in Carbon Research, highlights the potential of this concrete to serve dual functions: structural support and carbon management.

Traditional cement production is a significant source of CO2 emissions due to the energy-intensive process and chemical reactions involved. While the new concrete does not eliminate these emissions, it offers a way to redesign concrete to absorb CO2 while reducing reliance on conventional cement and aggregate. The research team, led by Srinivasan Revathi, tested M35 grade concrete, commonly used in moderate traffic infrastructure, by replacing 25% to 50% of the fine aggregate with zeolite and substituting 0.5% to 1.5% of the cement with bamboo biochar.

Zeolite's microporous structure and bamboo biochar's carbon-rich composition make them ideal for increasing CO2 uptake. The researchers ensured that these additions did not compromise the concrete's strength. The optimal mix, containing 50% zeolite and 1% bamboo biochar (ZB5), demonstrated a compressive strength of 38.49 MPa, surpassing conventional concrete by 7.48%. Its split tensile strength improved by 15%, reaching 4.39 MPa.

ZB5 also showed superior carbon absorption capabilities. In a controlled environment, it absorbed 1.2 grams of CO2 per day, with carbonation penetrating 15 mm into the material after seven days. These results suggest that the concrete could play an active role in carbon management, although long-term outdoor performance remains to be seen.

The research underscores the potential for concrete to be more than a passive structural element. As Srinivasan Revathi stated, the integration of zeolite and bamboo biochar transforms concrete into an active tool for environmental remediation. The material could be used in various infrastructure applications, such as pavements and highway walls, particularly in high-emission areas.

While the current findings are promising, they represent a proof of concept. Further studies are needed to assess the durability and carbon absorption of the concrete under real-world conditions. Future research will explore different biochar types, concrete grades, and pre-soaked biochar to refine the formula for commercial use.

Reference: “Effect of zeolite and bamboo biochar as CO2 absorbant in concrete” by Srinivasan Revathi, Dobson Alice Elizabeth Tania, Sutharson Ancy Shadin and Jegatheesan Keerthana, 30 April 2024, Carbon Research. DOI: 10.1007/s44246-024-00116-1