Influence of the compaction process on the air void homogeneity of asphalt mixtures samples

The effectiveness of laboratory compaction methods, for reproducing asphalt mixtures specimens with the same characteristics as on the actual building site, remains relatively unknown. The present paper is aimed at investigating the variability in air void content, therefore in compaction level, of three asphalt mixture types: a continuously-graded mix, an open-graded sandy mix, and a gap-graded asphalt. Several types of compactors are tested and the influence of sample dimensions and compaction axis vs. the main sample axis regarding air void homogeneity are studied using gamma-ray measurement. This study shows that for the studied materials, the samples cored in the plate are the most homogeneous, the ones produced by gyratory compaction yield scattered results but rather homogeneous samples can be obtained by respecting geometry criteria for the samples to be produced, and by sawing the edges where the compaction is the least efficient.