Effects of Interaction Conditions on Internal Network Structure of Crumb Rubber–Modified Asphalts

Investigation of the effect of interaction conditions on the development of the internal network structure of crumb rubber–modified asphalt (CRMA) was carried out. Enhancements in the CRMA physical properties, such as stiffness, expressed in the complex modulus (G^*), and elasticity, expressed in the phase angle (δ), as a result of the development of three-dimensional (3-D) entangled network structure were achieved. These results came from controlling the interaction conditions of CRMA synthesis to regulate the crumb rubber–modified (CRM) components that were responsible for the formation of the 3-D entangled network structure. Dissolution tests and thermogravimetric analysis (TGA) were performed on the extracted CRM particles after inter action with asphalt. A Fourier transform infrared (FTIR) spectroscopy investigation was performed on the liquid phase asphalt after separation of CRM. FTIR was used to investigate the state of the released CRM components, previously calculated by TGA, which were responsible for the formation of the 3-D network structure. Use of rheological, TGA, and FTIR tests confirmed that the enhancement of the CRMA's G^* and δ was dependent on the dissolution or release of CRM components under specific interaction conditions that led to the existence of a 3-D network structure within the liquid phase of the CRMA. The development of the 3-D entangled network structure in CRMA was found to be attributable to the release of most of the CRM natural and synthetic rubber components under specific interaction conditions. Enhancements in the CRMA G^* and δ provided improved rutting resistance and alleviated permanent deformation problems.