Digital Evaluation of Voids in Mineral Aggregate (VMA) in Asphalt Mixtures Using Photogrammetric and Image Processing Techniques

Precise control of internal voids within Hot Mix Asphalt (HMA) mixtures is imperative to ensure long-term pavement durability, resistance to environmental aging, adequate workability during placement, and fatigue performance under repeated loading. These internal air spaces represent a pivotal consideration in the design of asphalt mixtures, as they exert a direct influence on the mechanical behavior and service life of the mixture. Among the most critical volumetric indicators used to evaluate these aspects is the Voids in Mineral Aggregate (VMA), a fundamental design parameter in HMA specifications. Conventional approaches to determining VMA, particularly those reliant upon Marshall mix design procedures, necessitate extensive laboratory testing, the expertise of trained personnel, and a considerable investment of time. In order to address these limitations, this study explores the application of an automated photogrammetric technique based on computer vision, using low-cost mobile phone imagery, to estimate VMA in HMA specimens. The specimens were prepared in accordance with the Marshall method, and VMA values were ascertained through the implementation of both standard laboratory protocols and the proposed image-based approach. The photogrammetric workflow entailed the capture and processing of high-resolution images to facilitate the reconstruction of accurate vertical and horizontal cross-sections. A comparative analysis revealed minimal discrepancy between the two methods, suggesting that the proposed approach provides a reliable, efficient, and cost-effective alternative for VMA estimation and asphalt mixture evaluation.