Main challenge facing the cement industry is to reduce CO2 emissions while meeting global demand

Biochar concrete: challenges and opportunities for decarbonization
Somayeh Nassiri, Associate Professor, Civil and Environmental Engineering, UC Davis
Souvik Roy, PhD candidate, Civil and Environmental Engineering, UC Davis

The utilization of biochar in concrete has garnered attention recently due to its potential for carbon
sequestration. California has passed a bill that requires the cement sector to achieve carbon neutrality
by 2045. So, whether biochar can be used for carbon sequestration while maintaining the functionality
and durability requirements of infrastructure is of great interest.

This study explores the utilization potential of eleven distinct biochars derived from diverse feedstocks,
including wood, walnut shells, rice hull, and rice straw, in concrete paver applications. The investigated
wood species included forest management wood, including mixed conifer (Ponderosa pine, Douglas fir),
urban wood, sawmill waste, and slash from private forests. Biochar samples were sourced from various
bioenergy and biomaterial manufacturers who employed various thermal decomposition methods.
The collected biochars underwent rigorous characterization, including chemical composition, proximity
analysis, and water sorption. Before use in pavers, biochar samples were milled using a planetary ball
mill for 5 minutes, followed by sieving to ensure at least 66% achieved a particle size finer than 45µm.
Integration of these biochars into traditional masonry paver mixes, replacing portland cement at 2%,
5%, and 10% by weight, showed promising results in initial assessments of compressive strength.
This presentation emphasizes our current findings and outlines plans to explore durability and conduct
environmental life cycle analyses, providing a holistic understanding of the potential benefits and
challenges associated with this innovative biochar application in masonry paver mixes.

Carbon Reeducations by Avoidance  
• Calcareous or siliceous-aluminous materials in fine particles chemically react with calcium hydroxide in the concrete (water requried) …to form compounds with cementitious properties (ASTM C125)

Challenges Facing Cement and Concrete Sector   
• Implementation of new materials needed at much faster pace 
• To meet net zero 2045 (California): SB 596

Conclusions and Look Ahead 

• Carbon capture, use and storage needed to meet the 2045 neutrality goal in the cement sector 
• Biochar replacements up to certain amounts acceptable impact on strength 
• Durability and compatibility with chemical admixtures need to be assessed 
• Implementation easier for certain applications 
• Standardization required for concrete use lacking for structural concrete use • Demonstration projects needed 
• Cost competitiveness in the construction market

Contact us at: nassiri@ucdavis.edu