Effect of Mixture Compaction on Indirect Tensile Stiffness and Fatigue

Abstract

When constructing laboratory samples of bituminous mixture that are intended to have the same characteristics as the in situ pavement layer, the most important factor to consider is compaction. It is widely accepted that different laboratory compaction methods produce samples with different orientations and distributions of aggregates, and different distributions and shapes of voids. The effect of different laboratory compaction procedures (namely, roller, Marshall, vibrating hammer, and gyratory techniques) on the indirect tensile stiffness and fatigue properties of two standard Irish bituminous mixtures (namely, hot-rolled asphalt and dense base coarse macadam) was investigated. The roller compaction method produced specimens of lower stiffness, similar to site compacted samples. The influence of the compaction method on the fatigue strength of asphalt mixes would appear to be mixture dependent; mixes with grading profiles that are designed for aggregate interlock were found to have higher fatigue strengths, provided the material was compacted using a method that would facilitate reorientation of the aggregates.