| Abstract |
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The use of CR in the bitumen industry has significantly evolved in last few decades but has not quite been able to capture the market like other polymers. Despite a reasonable amount of work done in the field of bitumen modification, when CR is used as a bitumen modifier, there are still some areas that are mainly based on assumptions and not completely addressed and validated. One such is the phase separation of the primary components during extended storage of CRMB blends. Due to the different densities of the constituents, inadequate dispersion of CR particles into the bitumen and lack of chemical reaction a significant phase separation of the constituents has been reported in past. Is this study, CRMB blends produced with varied combinations of material constituents were investigated for storage stability. However, evaluation of storage stability and ultimate phase separation of the modified binder using softening point observation may be inadequate. Therefore, observations were mainly based on the differences in visual and analytical observations of top and bottom sections of the storage tubes using XRay computed tomography technique. The properties were the softening point results of the similar specimens. Based on the observations, the phase separation was found to be mainly dependant on the density and dispersion of the CR particles in the blend after different storage intervals. On the other hand, CR concentration in the blend has played a key role. Therefore, the variation in the storage stability was also attributed to increased inter-particle distance. The higher the CR concentration, the lower would be the difference in the storage properties of the top and bottom sections. The improved property was related to the reduced movement of the CR particles in CRMB blends with higher CR concentration such as 17.5%. This also resulted in the restriction to excessive settling or floating of CR particles, irrespective of the significant differences in the densities of the two phases. However, the idea of increased CR concentration in the CRMB blend to achieve high storage stability may not be useful due to a poor workability of the blend, while pumping and mixing with aggregates. Keywords - Bitumen, Crumb Rubber (CR), Crumb Rubber Modified Bitumen (CRMB), Density, X-Ray Computed Tomography (X-Ray CT) and softening point. |
