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<p>Near all semicircular bending (SCB) samples compacted in the laboratory come from mixtures obtained from volumetric mix design where the optimal asphalt binder content is determined for a fixed air void content at a set compaction effort. However, with the progressive implementation of balanced or performance-based mix design, the optimal binder content is not always selected at a fixed air void content. The objective of this study was to investigate the use of the SCB test in asphalt mixtures designed according to performance-based requirements with no fixed air void content. It was found that laboratory-aged mixtures or mixtures with high reclaimed asphalt pavement (RAP) content tended to exhibit uncontrolled crack propagation when using the standard displacement rate of 50 mm/min at 25 °C, regardless of compaction effort, which hinders any comparison across mixtures. To allow for the comparison of cracking potential across mixtures, it was proposed to reduce the loading rate to 5 mm/min. When using these testing conditions on twelve different asphalt mixtures, no uncontrolled crack propagation was observed. The relative cracking potential assessed by three different indices (flexibility index, cracking resistance index, and balanced cracking index) followed the same trend. It was also found that three out of the six rejuvenating agents evaluated had a clear positive effect on cracking resistance. In conclusion, this study supports that the SCB test—with a modified displacement rate in this case—is a powerful tool to investigate the effect of rejuvenating agents on the cracking potential of high RAP mixtures also when using performance-based mix design methods with no fixed air void content requirement.</p>

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Use of the Semicircular Bending Test to Evaluate the Intermediate Temperature Cracking Potential of Asphalt Mixtures with High RAP Content and Rejuvenating Agents Designed without Following Volumetric Method

  • 期刊论文

  • 发表日期：

    2025年9月9日

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  • Geert Jacobs,
  • Jonatan De Bruyn,
  • Beza Taye,
  • Wim Van den bergh,
  • David Hernando

摘要

Near all semicircular bending (SCB) samples compacted in the laboratory come from mixtures obtained from volumetric mix design where the optimal asphalt binder content is determined for a fixed air void content at a set compaction effort. However, with the progressive implementation of balanced or performance-based mix design, the optimal binder content is not always selected at a fixed air void content. The objective of this study was to investigate the use of the SCB test in asphalt mixtures designed according to performance-based requirements with no fixed air void content. It was found that laboratory-aged mixtures or mixtures with high reclaimed asphalt pavement (RAP) content tended to exhibit uncontrolled crack propagation when using the standard displacement rate of 50 mm/min at 25 °C, regardless of compaction effort, which hinders any comparison across mixtures. To allow for the comparison of cracking potential across mixtures, it was proposed to reduce the loading rate to 5 mm/min. When using these testing conditions on twelve different asphalt mixtures, no uncontrolled crack propagation was observed. The relative cracking potential assessed by three different indices (flexibility index, cracking resistance index, and balanced cracking index) followed the same trend. It was also found that three out of the six rejuvenating agents evaluated had a clear positive effect on cracking resistance. In conclusion, this study supports that the SCB test—with a modified displacement rate in this case—is a powerful tool to investigate the effect of rejuvenating agents on the cracking potential of high RAP mixtures also when using performance-based mix design methods with no fixed air void content requirement.