The effects of compaction temperature on CRM mixtures made with the SGC and the Marshall compactor

Abstract

The compaction temperature of crumb rubber modifier (CRM) asphalt mixes needs to be determined cautiously because the viscosity and the amount of the CRM binder affects the compactability of the mixtures. In this study, a laboratory investigation was carried out on the volumetric properties of CRM mixtures fabricated using the Superpave gyratory compactor (SGC) and the Marshall compactor as a function of compaction temperature. Two CRM binders were incorporated into HMA mixtures. Two other mixtures were produced with the control binder (PG 64-22) and SBS-modified binder (PG 76-22) and used for comparison purposes. The CRM binders were produced using one base binder (PG 64-22) with 10% or 15% ambient CRM (−40 mesh) by weight of the binder. For this research, the Superpave and the Marshall mix designs for four different asphalt binders were conducted to determine the optimum asphalt contents (OAC). A total of 128 specimens were manufactured using the SGC and the Marshall compactor at various compaction temperatures (116, 135, 154, and 173°C). The volumetric properties were obtained and analyzed using the statistical methods. The results from this study indicated that (1) the compaction temperatures used in this study significantly affected the volumetric properties of the CRM mixtures, regardless of the compaction methods (the SGC and the Marshall compactor); (2) the CRM mixtures in both the SGC and the Marshall compactor showed the higher VMA values than the control and SBS-modified mixtures; (3) a general trend of the volumetric properties as a function of compaction temperature and compaction method was found for the CRM mixtures used in this study.