Density profile of hot mix asphalt layer during compaction with various types of rollers and lift thickness

Abstract

The effects of different compactors and lift thickness on hot mix asphalt (HMA) have been persistently discussed among asphalt experts. In many cases, pavements paved with the high-in-place air voids permit water to penetrate the permeable pavement causing an increased tendency for pavement deformation. The thin lifts have had problems achieving high density, which leads to high-in-place air voids. The present paper is aimed at evaluating the effects of different compactors, an 11-ton steel drum compactor and a 15-ton pneumatic tyre roller, on the HMA mat with different ratios of thickness to nominal maximum aggregate size (t/NMAS). In order to achieve this aim, seven field sections with a total 36 locations with distinct HMA mixes, thicknesses and rolling patterns were built. Each of the sections was approximately 40 m long and 3.5 m wide. The section was constructed with t/NMAS ratio varying from 2.0 at the beginning to 5.0 at the end of the section. The air temperature during construction varied from 26 °C to 35 °C. More so, for comparison purposes, the simulated HMA mat temperatures using MultiCool 3.0 software and their respective measured temperature were also taken. The results indicate that the optimum number of passes to achieve maximum density is four passes. This could be achieved by merely using the steel roller with vibratory mode. However, the introduction of rubber tyre roller during the intermediate rolling initially reduced the density by one to two percent but started to increase after several passes.