Evaluation of asphalt binder containing castor oil-based bioasphalt using conventional tests

Abstract The asphalt binder containing up to 30% castor oil-based bioasphalt was evaluated for suitability of paving applications using conventional tests at the laboratory. The test results and data analyses show that the addition of the bioasphalt into regular petroleum asphalt may result in varying effects on different properties of the asphalt binder. The penetration increases considerably with increasing bioasphalt content at a given temperature, indicating a softening effect of the bioasphalt. The standard penetration increases by about 2 (0.1 mm) per percent bioasphalt on average. The softening point decreases slightly with increasing bioasphalt content. However, the 15 °C ductility decreases significantly with increasing bioasphalt content from greater than 100 cm to about 44 cm when the content changes from 15% to 30%. The flash point and density are nothing unusual; while the solubility decreases notably with increasing bioasphalt content from 99.6% to 92.1% when the content changes from 0% to 30%. The mass change, the retained penetration, and the ductility after RTFO test vary moderately with increasing bioasphalt content, indicating acceptable aging resistance of the bioasphalt. The penetration index increases remarkably with increasing bioasphalt content, indicting a temperature susceptibility improving effect of the bioasphalt. Both the equivalent softening point and the equivalent breaking point decrease, while the plasticity temperature range increases slightly with increasing bioasphalt content. The losing in high temperature rutting resistance is surpassed by the gaining in low temperature cracking resistance due to the temperature susceptibility improving effect of the bioasphalt.