Effects of compaction delay on the performance of porous asphalt mixture compacted at different thicknesses

Abstract

This study was conducted to ascertain the effects of specimen thickness and compaction delay on the properties of porous asphalt (PA) mixtures. The PA14 specimens were prepared at 4.5 % binder content. Crushed granite aggregate and conventional asphalt binder penetration grade 60/70 were used as the main ingredients for the preparation of the samples. The PA mixture was prepared using a bucket mixer and compacted using a Marshall hammer. Porous asphalt specimens were tested to evaluate the effects of compaction delay on mixtures at two different thicknesses, 40 mm and 60 mm. Four compaction process delay times were selected, namely 2 minutes, 5 minutes, 15 minutes and 30 minutes. The PA specimens were evaluated based on the temperature drop, permeability, resilient modulus and indirect tensile strength (ITS) tests. The temperature of each specimen was evaluated at every minute prior to the compaction of the PA mixture. From the test results, the temperature of the 40 mm thick specimens were lower compared to specimens compacted to 60 mm thickness. Additionally, the ITS of a PA mixture reduced as the compaction delay time increased. It was also found that the 40 mm thick specimen exhibited higher ITS compared to the ITS of 60 mm thick specimens. On the other hand, the mixture compacted with a 30 minute delay time exhibited the highest coefficient of permeability and air voids, which resulted in lower resilient modulus.