Performance Assessment of Bioasphalt Mixtures Containing Guayule Resin as an Innovative Biobased Asphalt Alternative

Guayule resin was investigated through mixture to assess its role in the field performance. For performance comparisons, conventional asphalt, neat guayule, asphalt–rubber–guayule, and guayule–rubber binders were implied. Field-simulated lab mixtures were made to investigate the major distresses. Modified Lottman, rut, semicircular bending, and disk-shaped compact tension tests were used to assess stripping, rutting, fatigue, and thermal cracking resistances. Stripping and rutting susceptibilities were also assessed by Hamburg wheel-tracking test. The outcomes disclosed that when the modified Lottman test was used, guayule containing a 7% air content was more susceptible to stripping than that containing a 3.5% air content, resulting in tensile strength ratios of 40% and 71%, respectively. All investigated mixtures did not reach out the stripping inflection point under the Hamburg wheel-tracking criteria. Asphalt offered the worst Hamburg rut depth, which was 3.2 mm after 20,000 passes. Guayule-based mixtures perfectly resisted rutting as proven by the rut test. Guayule offered the worst rut depth of 6.3 mm, indicating a great rutting resistance. The guayule-based mixture had a high fracture toughness at intermediate temperatures. Guayule and guayule–rubber mixtures offered a critical strain energy release rate of $0.65–0.69\mathrm{kJ}/{\mathrm{m}}^2$ compared to $0.46\mathrm{kJ}/{\mathrm{m}}^2$ for asphalt. They, however, tended to possess low thermal fracture resistance (less than the threshold fracture energy, $400\mathrm{J}/{\mathrm{m}}^2$). Conversely, a blend of 62.5% asphalt, 12.5% rubber, and 25% guayule offered $591\mathrm{J}/{\mathrm{m}}^2$ at its performance grade low temperature ($-16°\mathrm{C}$) and $409\mathrm{J}/{\mathrm{m}}^2$ at $-22°\mathrm{C}$ compared to $429\mathrm{J}/{\mathrm{m}}^2$ for asphalt at the later temperature, which represented the performance-grade low temperature of asphalt.