Grantee Research Project Results

Final Report: Reduction of Embodied Carbon in Concrete via Strength Enhancing Biochar-derived Graphene Products

EPA Contract Number: 68HERC25C0028
Title: Reduction of Embodied Carbon in Concrete via Strength Enhancing Biochar-derived Graphene Products
Investigators: Richard, Anthony R
Small Business: Acadian Research & Development LLC
EPA Contact: Richards, April
Phase: I
Project Period: December 16, 2024 through June 15, 2025
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2025) RFA Text |  Recipients Lists
Research Category: Small Business Innovation Research (SBIR)

Description:

The purpose of the research in this project is to demonstrate the use of wood-derived graphene oxide (GO) products as concrete additives to significantly improve strength, which translates to a reduction in materials needed for construction and therefore a reduction in embodied carbon. This project builds upon the previous SBIR Phase I where compressive strength improvements were achieved, but uses a new synthesis method designed to improve flexural strength as well. The GO material for this project is produced via a newly patented, low-cost method and is derived from wood instead of graphite, which has no domestic production, or coal, which has environmental implications associated with mining.

The project consists of three parts: materials synthesis, materials characterization, and testing in concrete. For materials synthesis the base feedstock material is wood which is pyrolyzed to produce biochar, and then converted to GO. GO is the oxidized version of graphene, and high temperature annealing of GO under inert atmosphere produces rGO through a thermal reduction process, which removes a portion of the oxygen. The biochar examined in this project was produced at two temperatures, 450 and 900°C.

Materials were characterized to determine if the GO synthesis process was successful, and to examine the effect of biochar synthesis temperature on concrete additive performance. These characterizations examine chemical and physical properties and include scanning electron microscopy (SEM), elemental analysis (CHNS/O), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and N₂ sorption analysis.

To examine the performance of the GO and rGO additives in concrete, mixes were produced with contents of 0%, 0.05%, and 0.5% of cement by weight. The concrete was examined for strength via compression, flexural, and tensile testing.

Summary/Accomplishments (Outputs/Outcomes):

The results show successful conversion of biochar to GO (increased oxygen groups and lattice defects, increased order in structure), and successful reduction of GO to rGO (loss of oxygen, further defects, layer contraction). A 5x increase in production scale was also performed in this project and was shown to be successful.

The addition of GO and rGO materials shows promise for increasing both long-term compressive strength and flexural strength, with materials showing a compressive strength increase of 10.7% at 28 days, and an increase of 34.9% in flexural strength.

This study has also shown that biochar, GO, and rGO materials can be successfully produced with greatly increased surface area. While the addition of an extra processing step would raise production costs, it is worth exploring the use of these altered products in concrete mixes as additive surface area is a property that has been identified as a potential factor in concrete strength.

Commercialization

There is excellent commercial potential for the GO additives produced in this project. The low-cost nature of the product means feasibility for large scale applications with concrete ($617 billion global market), and process improvements have lowered production costs even further.

Conclusions:

The greatest improvement in compressive strength was found with GO, while flexural strength had the greatest improvement by using a blend of GO and rGO. However, GO, rGO, and the blends all showed improvements in flexural strength. For tensile strength, rGO provided greater performance enhancement than GO. The material properties examined show that greater surface area is important, but the chemistry and morphology of the materials is also critical. These include the amount of residual volatiles, degree of graphitization, and lattice defects. Altogether, these results suggest that higher-temperature materials, particularly with respect to rGO, have a greater influence on the performance improvement of the concrete.