Optimization of Rutting Parameter for Crumb Rubber Modified Binder Using Response Surface Methodology (RSM)

Modification of binder with various additives is a very common method for improving its behavior. Crumb rubber is one of the additives which increase 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 optimization of this parameter by modeling its behavior at 64°C using crumb rubber. For this purpose, optimum Design of Experiments (DOE) method, 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 unaged samples. Results show that developed models have good prediction accuracy and the content of crumb rubber is more effective rather than other factors and the interaction of them. For optimization of rutting parameter, 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 in a certain content percentage of crumb rubber.