ERI: Mechanism for Improved Strength in Fast Pyrolysis Biochar Concrete

Colorado School Of Mines, Golden CO

Investigators

Abstract

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). This Engineering Research Initiation (ERI) project will focus on elucidating the mechanisms that lead to improved strength in fast pyrolysis biochar concrete. Biochar is a carbon-rich material made from the pyrolysis of biomass. Biochar is produced via the thermal decomposition of biomass in a zero or limited oxygen environment. Since biochar is highly stable, the embedded carbon is resistant to decomposition, slowly releasing CO2 over hundreds or thousands of years. This results in long-term removal of carbon from the atmosphere, making biochar a powerful material for carbon sequestration. Fast pyrolysis of biomass generates also a bio-oil and synthetic natural gas, which can generate energy and decrease the use of fossil fuels. Recently, biochar has gained momentum as a carbon sequestering agent for use in concrete. However, this application has only utilized slow pyrolysis biochar, which has much different properties than the fast pyrolysis biochar adopted in this project. By using fast pyrolysis biochar, a preliminary study shows that when 15 percent of cement weight is replaced with biochar, the strength of concrete increases by nearly 40 percent. At 15 percent biochar to cement substitution, the biochar can offset the greenhouse gas emissions associated with concrete by at least 48 percent; at 32 percent biochar to cement substitution, the biochar would make concrete a carbon negative building material. To accomplish this goal, three primary objectives are identified: 1) to characterize the microstructural and physiochemical properties of three distinct fast pyrolysis biochar products; 2) to characterize the microstructure and chemical composition of cementitious materials made with these three biochar products; and 3) to analyze the strength behavior of the resulting concretes and the strength-microstructure relationship. Furthermore, this award contributes to the education of a female graduate student, and will provide research opportunities for middle school girls with events designed to address the reported gap between STEM interest/aptitude in adolescent girls and girls’ chosen career paths at later ages. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.