Reflective cracking is frequently reported as the most common distress affecting resurfaced pavements. An asphalt rubber membrane interlayer (ARMI) approach has been traditionally used in Florida to mitigate reflective cracking. However, recent field evidence has raised doubts about the effectiveness of the ARMI when placed near the surface, indicating questionable benefits to reflective cracking and increased instability rutting potential. The main purpose of this research was to develop guidelines for an effective alternative to the ARMI for mitigation of near-surface reflective cracking in overlays on asphalt pavement. Fourteen interlayer mixtures, covering three aggregate types widely used in Florida, and two nominal maximum aggregate sizes (NMAS) were designed according to key characteristics identified for mitigation of reflective cracking, that is, sufficient gradation coarseness and high asphalt content. The dominant aggregate size range—interstitial component (DASR-IC) model was used for the design of all mixture gradations. A composite specimen interface cracking (CSIC) test was employed to evaluate reflective cracking performance of interlayer systems. In addition, asphalt pavement analyzer (APA) tests were performed to determine whether the interlayer mixtures had sufficient rutting resistance. The results indicated that interlayer mixtures designed with lower compaction effort, reduced design air voids, and coarser gradation led to more cost-effective fracture-tolerant and shear-resistant (FTSR) interlayers. Therefore, preliminary design guidelines including minimum effective film thickness and maximum DASR porosity requirements were proposed for 9.5-mm NMAS (35 µm and 50%) and 4.75-mm NMAS FTSR mixtures (20 µm and 60%) to mitigate near-surface reflective cracking.
The major role of interlayer mixtures is to mitigate reflective cracking by absorbing or dissipating concentrated stress, and relatively low-stiffness materials are typically used. However, there is a concern that interlayer mixtures may increase rutting potential due to the low-stiffness materials used. The dominant aggregate size range (DASR) porosity has been successfully applied for structural mixtures to ensure enhanced rutting performance. This study mainly focused on developing the new DASR porosity requirement for interlayer mixtures that ensure acceptable rutting performance in the mix design phase. Ten interlayer mixtures with a broad range of DASR porosities were evaluated using the asphalt pavement analyzer test. Results indicated that the gradation characteristics of interlayer mixtures played an important role in rutting performance. Also, a relationship between DASR porosity and the rutting potential of interlayer mixtures was identified that resulted in the establishment of the preliminary DASR porosity requirements.
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