Zeolite and Bamboo Biochar Improve Concrete Strength and CO₂ Uptake

Researchers at Mepco Schlenk Engineering College in India have developed a concrete mixture that combines improved mechanical strength with the ability to absorb carbon dioxide under laboratory conditions. By incorporating zeolite and bamboo biochar, the team explored how mineral and biobased additives could give construction materials an additional environmental function.

Led by Srinivasan Revathi, the research addresses the challenge of reducing the environmental impact of concrete. Cement production contributes to CO₂ emissions, while construction requires materials that maintain reliable strength and durability.

Combining Mineral and Biobased Additives

The study examined two porous materials with large surface areas. Zeolite is an aluminosilicate mineral with a structure that can trap gas molecules. Bamboo biochar is a carbon-rich material produced by heating bamboo with little or no oxygen.

The researchers tested several formulations of M35-grade concrete. They replaced fine aggregate with zeolite at levels of 25% and 50%, and substituted bamboo biochar for cement at concentrations of 0.5%, 1% and 1.5%.

Tests assessed compressive strength, splitting tensile strength, water absorption and impact resistance, alongside CO₂ uptake. The aim was to identify a mixture that could capture carbon dioxide while maintaining or improving its engineering performance.

Higher Strength and Laboratory Carbon Uptake

The best-performing formulation, designated ZB5, combined 50% zeolite replacement of fine aggregate with 1% bamboo biochar replacement of cement. Its compressive strength reached 38.49 MPa, an increase of 7.48% compared with the conventional concrete mixture. Its splitting tensile strength reached 4.39 MPa, representing a 15% improvement.

The researchers associate these gains with the interaction between zeolite’s aluminosilicate structure and the bamboo biochar, which helps develop a denser cement-based matrix.

In a carbonation chamber, the optimal concrete specimen absorbed approximately 1.2 grams of CO₂ per day. After seven days, carbonation extended 15 mm into the material. These measurements describe laboratory performance; they do not establish the rate of carbon capture in outdoor conditions or demonstrate that the concrete is carbon-neutral over its life cycle.

Potential Applications and Further Development

For architects and designers working on infrastructure and public spaces, the research suggests a possible route towards concrete with both structural and carbon-capturing functions. Proposed applications include pavements, highway parapet walls and sewer pipelines, particularly in environments with elevated CO₂ concentrations.

The material remains a proof of concept. Further research will examine long-term durability and sustained CO₂ uptake. The team also plans to investigate other biochar sources, different grades of concrete and mortar, and whether pre-soaking biochar improves performance. These steps will help assess its suitability for wider commercial use.

Source: ScienceDaily
Photo: Vikesh zen