Optimization of asphalt mixture design using response surface method for stone matrix warm mix asphalt incorporating crumb rubber modified binder

The use of crumb rubber as an asphalt bitumen performance improver has received special attention. The high viscosity of crumb rubber modified binder (CRMB) and the need for high production temperatures in mixtures containing this type of bitumen necessitate the use of warm mix asphalt (WMA) technology. One of the important applications of CRMB is in special-use mixtures such as stone matrix asphalt (SMA). This study aimed to determine the optimal design of stone matrix warm mix asphalt containing CRMB. Therefore, the response surface method (RSM) was used to develop the response prediction models. Production temperature and the content of polyethylene wax and CRMB were considered independent variables of the study. Moisture sensitivity, flow number, resilient modulus, and critical stress intensity factor were used as response (dependent) variables to determine the optimal design of the mixture. The results showed that the prediction models of response variables can predict the performance results with acceptable accuracy. Production temperature and polyethylene wax content are the most important factors in prediction models. To achieve the optimal design of the mixture, minimizing the production temperature and resilient modulus and maximizing the flow number, resistance to moisture susceptibility, and critical stress intensity factor led to the achievement of desirable solutions. The optimal design of stone matrix warm mix asphalt containing CRMB at 135 degrees C, 7.02 % CRMB, and 2.1 % poly-ethylene wax using predictive models with 0.765 desirability were obtained.