Global warming due to increased carbon emissions is having devastating effects on the environment, leading to a surge in research on not only limiting carbon output but also designing carbon-negative materials that take in CO₂ from the atmosphere. One area of research with considerable potential in limiting these effects is CO₂-absorbing concrete, as it is one of the most used materials in the world and produces major amounts of carbon emissions. By designing concrete to absorb more CO₂ than is produced in its fabrication, carbon-negative structures like buildings and bridges become a possibility. Along with CO₂ absorption, the concrete must have robust mechanical properties for longevity as a structural material. Fiber-reinforcement is useful for improving mechanical toughness, although it can have adverse effects on other mechanical strengths like compressive and tensile strength; reinforcement using natural fibers, such as hemp, provides these improved properties while remaining sustainable. In this project, hemp-reinforced concrete samples were fabricated and cured in CO₂ atmospheres for 1, 7, 14, and 28 days for carbon absorption. Once removed, mechanical testing was performed to determine the compressive, tensile, and flexural strength as well as the toughness of the hemp and control samples. Thermogravimetric analysis (TGA) was used to determine the absorption of CO₂ as well. Mechanical testing showed a 300% increase in compressive strength with 28 days of CO₂ absorption; additionally, the hemp-reinforced concrete remained superior in toughness even as its strength increased. TGA determined the CO₂ absorption of the hemp-reinforced concrete cured for 28 days to be 10 g of CO₂/100 g of concrete. The improvement of the concrete’s mechanical properties and absorption of CO₂ demonstrates potential for the use of mechanically robust concrete in carbon-negative structures, opening pathways for more sustainable building materials.

Serafina France Tribe

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