Asphalt Multi-Integrated Rollers and Steel Drum Compactors: Evaluating Effect of Compaction on Permeability of Asphalt Pavements

Theoretical analysis supported by laboratory investigations and verified by field studies and observations has shown that defects caused by rolling compaction are the main contributors to early deterioration of asphalt surfaces. The conventional and widely used steel drum roller induces hairline cracks, which permit moisture to infiltrate pavement structure, causing the phenomenon known as stripping. In addition to inducing cracks, steel drums do not provide the desired uniformity in terms of density across the compacted width of the asphalt mat. Drummed rollers also produce poor compaction at unsupported edges of paved lanes. The asphalt multi-integrated roller (AMIR), an innovative compaction technology, offers a more effective alternative for overcoming problems of steel drum rollers by reducing permeability and, in turn, improving long-term performance of flexible pavements. A multistaged laboratory and field-testing program that measures permeability in terms of hydraulic conductivity was performed on pavement sections constructed using an AMIR side by side with a conventional steel roller. Asphalt concrete layers compacted by steel drum rollers were found, on average, to be up to 20 times more permeable than those compacted by the AMIR immediately after construction and as much as 10 times more permeable after 1 year. The major steps leading to the understanding of how rolling affects the permeability of asphalt layers and, consequently, the long-term performance of newly compacted pavements are discussed and presented.