Comparative Evaluation of Methods for Determining Bulk Density and Air Voids in Compacted Asphalt Mixtures

Accurate determination of bulk density and air void content is fundamental to asphalt mix design, construction quality control, and pavement performance evaluation. This study evaluates and compares bulk density and voids obtained from Marshall-compacted specimens (unsealed), Marshall-compacted specimens with automatic vacuum sealing, and gyratory-compacted specimens, including sealed and unsealed variants. Data were obtained from multiple laboratories following a common testing protocol, with only results from laboratories achieving z-scores within ±2 considered for analysis. Results indicate systematic differences between methods, with vacuum sealing and gyratory compaction yielding higher bulk densities and lower air void contents compared to unsealed Marshall specimens. The findings highlight method-dependent biases and provide guidance on the appropriate application of each method for mix design, construction quality control, and pavement evaluation.