Determining the Void Ratio in Hot-Mix Asphalt Pavements Using Different Methods According to EN 12697

Abstract

Inaccurate air void ratio based on erroneous bulk density can seriously affect the performance of the roadway and its quality. Therefore, several methods were improved to measure bulk density by using different techniques in the developed countries, while the Saturated Surface Dry (SSD) traditional method has been used in Gaza strip till present days. This study aims at providing a better understanding of the effect of the selected bulk density measurement method on the percentage of voids using four methods namely; Dimensional Method, Dry Method, Surface-Saturated Dry Method, and Paraffin Sealing Method. At Laboratory, sixty-nine specimens were prepared, thirty-three of them were prepared in the Marshal Design System in order to determine the optimum bitumen content of the three different mix types, and thirty-six of the specimens were taken from mixtures design in order to determine bulk density. Laboratory results showed that the SSD method is the best choice for measuring bulk density in dense and mastic mixtures. In addition, there are no differences between SSD and dry methods in mastic mix. The experimental study shows that the dimensional method is the only method suitable for the determination of bulk density (Gmb) in porous mix despite it always gives underestimated results for Gmb in all asphalt mixes. As a result, the dimensional method can be used as an indicator for the upper limit of voids, while the dry method can be used as an indicator to the lowest limit, regardless the type of mix. The study recommended to use new techniques to determine Gmb in open graded mixtures with more accurate methods rather than traditional ones.