Modelling compactibility of RCC specimens using the asphalt gyratory compactor

Abstract

The density of fresh Roller Compacted Concrete (RCC) pavement dictates its durability and mechanical characteristics. Achieving the required density depends on many factors but mainly on the thickness of the lift and the RCC mix constituents. To evaluate the compactibility of fresh RCC mixes prior to placement, current practices recommend using no-slump consistency tests such as the Vebe test. However, these tests lack sensitivity to the dryness of RCC mixes as well as to the placement thickness. This paper proposes an approach to evaluate the compacatibility of RCC specimens by estimating the energy required to achieve the specified density over the thickness of different mixes. In order to study the energy, the Superpave Gyratory Compactor (SGC) was incorporated as a consistent and accurate compaction tool. The SGC provides displacement records with gyration numbers that facilitate i) density calculations through volume change and, ii) model, the compactibility of RCC, mixes using vibrational mechanics. A damping coefficient and a time-dependent restoring force were estimated and used to calculate the mechanical energy at each gyration and the cumulative energy after 25 gyrations. The damping coefficient, which is a material property, was further used to determine the cumulative energy of different RCC thicknesses. This approach investigated the effect of the specified lower and upper aggregate gradation and the use of additives on compactibility and density of RCC mixes.