Enhancing Cement with Biochar: A Green Innovation

Incorporating biochar into cement paste enhances self-healing and hydration properties. It delays early hydration but improves it later, reduces autogenous shrinkage, and increases calcium carbonate content. Despite slightly lower compressive strength and higher electrical resistivity, biochar significantly improves crack filling and mechanical strength recovery.

June 3, 2024

1–2 minutes

Vafaei & Ghahremaninezhad (2024) Effects of BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More as a Green Additive on the Self-Healing and Properties of Sustainable Cementitious Materials. *ACS Sustainable Chemistry and Engineering.* https://doi.org/10.1021/acssuschemeng.4c02045

The integration of biochar as a green additive in cement paste introduces promising enhancements in both self-healing and hydration properties. This research delved into these benefits, examining early and later-age hydration, mechanical strength, and self-healing characteristics.

Early and Later-Age Hydration
Biochar’s impact on cement paste begins with an increased setting time and delayed early-age hydration. This is due to biochar’s ability to absorb alkalis, reducing their concentration in the pore solution. However, as the paste ages, hydration improves, a benefit attributed to biochar’s internal curing properties.

Mechanical and Transport Properties
While biochar slightly reduces the compressive strength and increases electrical resistivity, these effects are offset by the formation of macrovoids and higher water content. Despite these drawbacks, the overall mechanical properties and durability remain satisfactory for many applications.

Chemical Characterization
Advanced analytical techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis reveal that the healing products in biochar-modified cement paste predominantly consist of calcium–silicate–hydrate, calcium carbonate, calcium hydroxide, and ettringite. Notably, biochar increases the calcium carbonate content, enhancing the self-healing process.

Self-Healing Properties
Biochar’s most significant benefit lies in its self-healing capabilities. The three-point bend test and optical microscopy confirm improved mechanical strength recovery and crack filling in biochar-modified paste compared to control samples. This indicates that biochar not only aids in preventing crack formation but also enhances the healing of existing cracks.

Incorporating biochar into cement paste provides a sustainable way to enhance its properties, offering improved hydration, reduced shrinkage, and superior self-healing abilities. This green additive holds great promise for future construction materials, aligning with environmental and structural performance goals.