Laboratory Investigation of Biochar-Modified Asphalt Mixture

The United States is promoting the establishment of a bio-based economy, generating energy and fuels from renewable organic matters rather than fossil fuels. Byproducts such as fractions of biochar not suitable for biofuel production are drawing extensive attention. ("Biochar" is defined by Oxford's online dictionary as "charcoal produced from plant matter and stored in the soil as a means of removing carbon dioxide from the atmosphere.") Recently, biochar produced with different production parameters was tried as an asphalt modifier owing to its carbon origin and proved to be positive in binder modification. This study evaluated the performance of hot-mix asphalt modified by one type of pyrolytic biochar with controlled production parameters. Typical carbon black powder pellets and microsized carbon fiber were selected as the reference additives. Multiple laboratory binder and performance tests were conducted to evaluate the rheological properties of the modified binder, rutting resistance, moisture susceptibility, and cracking resistance of asphalt mixtures. On the basis of test results, the biochar evaluated in this study proved to be an effective modifier in reducing the temperature susceptibility of the binder and thus increased the rutting, moisture, and cracking resistance of hot-mix asphalt. In addition, biochar proved to be a better asphalt modifier than did carbon black and carbon fiber.