Effect of sample geometry on bulk relative density of hot-mix asphalt mixes

Abstract

This study emanated from the revision of South African mechanistic-empirical pavement design method. At the CSIR road pavement laboratory, the bulk relative density (BRD) of compacted hot-mix asphalt (HMA) mixes is determined on cores and beams with different number of cut/cored surfaces. Significant variations in voids were observed in the HMA core and beam samples from the same compacted slabs. The objective of this paper is to present the findings of the effect of specimen geometry and cut surfaces on BRD, and the calculated air voids of five South African HMA mixes using the conventional saturated surface dry and the vacuum sealing methods. The BRD results obtained from the two methods showed that the number of cut surfaces significantly affects the BRD of the compacted samples used for this study. However, the BRDs/air voids were comparable regardless of the sample geometry. It is suggested that compacted samples prepared for the determination of HMA properties such as permanent deformation and fatigue life should have the same number of cut surfaces regardless of the sample geometry.