Modeling Rutting Behavior of Crumb Rubber Modified Binders Using Design of Experiments

In recent decades, modifying the binder with various additives for improving its behavior has been very noticeable by researchers. Crumb rubber is one of the additives which increases the rutting resistance of binder. The main objective of this study is to identify the factors affecting the resistance characteristics of binder regarding rutting and modeling its behavior at 64 °C using crumb rubber. For this purpose, one of the Design of Experiments (DoE) methods, i.e. Response Surface Methodology (RSM) was utilized taking into account four factors, including mixing temperature, mixing time, mixing speed and content percentage (by weight) of crumb rubber, as well as one response, rutting parameter. As a result, 30 modified binder samples were produced and Dynamic Shear Rheometer (DSR) test was conducted on the samples. Modeling was done and performance of the model was evaluated. Results show that developed model has a good prediction accuracy and the content of crumb rubber is more effective factor rather than other factors and the interaction of them. In addition, in a certain content percentage of crumb rubber, considering the mixing temperature and mixing speed at a low level and mixing time at a high level, the maximum rutting parameter could be achieved.