Determination of Construction Temperatures of Crumb Rubber Modified Bitumen Mixture Based on CRMB Mastic

Crumb rubber modified bitumen (CRMB) has been widely used in pavement construction and provides an effective way to recycle waste tires and helps alleviate the "black pollution" problem. There are no current specifications regarding the appropriate mixing and compaction temperatures of the CRMB mixture. There is a direct relationship between the mixing and the compaction temperatures of the CRMB mixture and the viscosity of the CRMB mastic. In this study, we first prepared CRMB using crumb rubber powder and penetration grade 70 neat bitumen, then prepared the CRMB mastic using CRMB and fillers (limestone mineral powder and cement). Finally, we used the CRMB mastic and aggregate to make mixture specimens. The best air void of the specimens was subsequently used to demarcate the viscosity of the CRMB mastic, and the construction temperatures (including the mixing temperature and the compaction temperature) were calculated based on the viscosity of the CRMB mastic from the viscosity-temperature curves. Test results indicated that the best viscosity of the CRMB mastic was 2.7 ± 0.2 Pa·s and 3.9 ± 0.3 Pa·s that corresponded to the mixing and compaction temperatures, respectively.