Researchers at Mepco Schlenk University of Engineering in India developed the mixture as a potential way to make construction materials more sustainable. Their approach addresses a major environmental challenge: rising atmospheric carbon dioxide levels, driven largely by fossil fuel use and cement production.

The team, led by Srinivasan Revathi, focused on two natural additives: zeolite, a porous mineral, and bamboo biochar, a carbon-rich material. Both have large pore volumes and high specific surface areas, properties that make them suitable for trapping gas molecules.

Testing stronger, carbon-capturing concrete mixtures

The researchers tested several versions of M35-grade concrete, which is commonly used in infrastructure designed for moderate traffic. They replaced fine aggregate with zeolite at concentrations of 25% and 50%. They also replaced cement with bamboo biochar at concentrations of 0.5%, 1% and 1.5%.

Each formulation was evaluated for compressive strength, split tensile strength, water absorption and impact resistance. The goal was to identify a mixture that could absorb more carbon dioxide without weakening the concrete.

One combination performed better than the others. The mixture containing 50% zeolite and 1% bamboo biochar, known as ZB5, achieved the strongest overall results.

The ZB5 mixture reached a compressive strength of 38.49 MPa, approximately 7.48% higher than conventional concrete. Its split tensile strength reached 4.39 MPa, representing a 15% improvement over the standard mixture.

The researchers attribute the increased strength to the interaction between zeolite’s aluminosilicate structure and the hardness of bamboo biochar. Together, these materials appear to create a denser and more durable cement-based matrix.

How the concrete captures CO₂

Strength was only part of the result. The ZB5 mixture also demonstrated the ability to absorb carbon dioxide.

When placed in a carbonation chamber, the concrete captured 1.2 grams of CO₂ per day. Over seven days, the gas penetrated 15 millimeters into the material.

The researchers linked this carbon uptake to zeolite’s micropore structure and bamboo biochar’s high carbon content. These properties may allow concrete to function not only as a structural material but also as a medium for capturing carbon dioxide from the atmosphere.

Corresponding author Srinivasan Revathi of the Department of Civil Engineering explained the significance of the findings:

“Our work demonstrates a dual-win approach. In addition to creating stronger concrete, we are turning a common building material into an effective tool for environmental remediation. By integrating zeolites and bamboo biochar, we can build structures that are not only durable but also actively cleanse the air of excess carbon dioxide, paving the way for truly sustainable infrastructure in high-emission areas such as city roads and industrial zones.”

Could carbon-capturing concrete support more sustainable construction?

The findings point to a potential new approach for developing lower-carbon building materials. Concrete made with the ZB5 formulation may be particularly useful in locations where carbon dioxide concentrations are relatively high.

Potential applications include concrete pavements, highway parapets and sewer pipelines. These structures could capture carbon dioxide from their surroundings while continuing to perform their usual engineering functions.

However, the researchers emphasize that the study remains a proof of concept. Additional testing is needed before the material can be widely adopted or considered suitable for large-scale construction.

Next steps for carbon-capturing concrete

Future research will examine how the concrete performs over time, including whether it can maintain its durability and carbon dioxide absorption capacity.

The researchers also plan to test other types of biochar, evaluate different concrete grades and mortar mixtures, and investigate whether pre-soaked biochar can further improve performance.

These studies will help determine whether the technology can be expanded to commercial and industrial applications. If the results continue to be positive, the approach could give the construction industry a way to develop stronger infrastructure while reducing some of the environmental impacts associated with the built environment.