Influence of warm mix additive on internal structure of dry process crumb rubber modified mixtures

Abstract

Performance of asphalt concrete depends highly on its internal structure, which is affected by production temperature, compaction effort and material properties. This study aims to evaluate the internal structure and performance of dry process crumb rubber modified mixtures with warm mix asphalt (WMA) additives. In order to evaluate the effect of WMA additive on these properties, dry process crumb rubber modified WMA mixtures were prepared under different production temperatures applying different compaction efforts. In addition, a radial inhomogeneity analysis tool is developed considering the size fraction and location of aggregate particles, while iPas software is utilized to quantify the contact zone properties. The performance of each test mixture is also evaluated through stability, rutting, and cracking tests. The study outcomes indicate that WMA additive reduces the segregation level of dry process crumb rubber mixtures. In spite of the favorable influence of the WMA additive, there seems a slight decrease in the total contact length and number of contact points of the samples. It is shown that both the control and the WMA mixtures can offer similar performances when compacted at lower temperatures or the same temperature under less compaction effort. The use of DryWMA allows for longer haul distance, less energy for production and limited exposure to fumes during construction.