The use of asphalt-rubber gap-graded (AR-Gap) mix as a pavement material has gained importance due to its environmental benefits and enhanced performance. This paper reviews the current state-of-the-art pertinent to AR-Gap mix design research and practice. The various mix design practices of AR-Gap mixes adopted by various agencies were summarised. Furthermore, the performance characteristics of AR-Gap mixes such as drain-down, moisture susceptibility, permanent deformation, and fatigue cracking were also documented. The field performances of AR-Gap pavements were also reviewed. Due to an increased use of AR-Gap as a pavement material owing to its several benefits, there exists an extensive scope for further research to understand the material better, which will make it a promising sustainable pavement material in future. Furthermore, considering that AR-Gap mix design and construction technologies are yet to be fully implemented worldwide, the present work aims to be an up-to-date reference to provide benefits and issues associated with the AR-Gap mixes. However, based on the various research questions emanating out of the review process, it was adjudged that there is still further scope for advancing the current state-of-the-art pertaining to the AR-Gap mix design, and the contribution of rubber inclusions in assisting the mix’s augmented performance.

Pervious concrete (PC) is a class of porous materials that has found application in building materials, specifically in pavements, for its stormwater mitigation abilities. X-ray microcomputed tomography was used to understand and quantify the three-dimensional (3D) pore morphology, shape factors, and size descriptors in PC mixtures prepared with varying porosity. The Zingg pore shape classification indicated higher percent of rod-shaped pores and the frequency of spheroid-form pores was higher in single-sized mixtures, whereas dense mixtures had higher occurrence of blade-form pores. The average pore sphericity was in the range of 0.40–0.60, indicating semispherical pores. Few large-sized pores in PC had a significant influence on the relation between 3D pore-structural-permeability properties. The visualization of 3D pore structure indicated the importance of isolated pores in PC for periodic maintenance. The new findings on the pore structure will assist in mix design optimization, selection of mixtures, and modeling of PC.