Mechanical characteristics of the asphalt binders and mixtures were enhanced by utilising modifiers. The crumb rubber modifier has been introduced to the asphalt modification as an environmentally friendly procedure of scrap tires, to improve the mechanical characteristics of the asphalt. This study aims to modify the dry method for mixing crumb rubber modifier with asphalt and aggregate based on the binder mix design. To achieve this goal crumb rubber modified asphalt mixtures were prepared and tested by applying various tests such as Marshall Stability test, indirect tensile strength test, and wheel tracking test. Three mixing methods of CRM were studied regarding evaluating the stability, rutting, and moisture susceptibility. The crumb rubber modifier dry mixing method was modified and named the complex process. Better results were achieved for enhancing mechanical properties.

Introduction

To reduce the environmental effects of roads building and maintenance, necessary to find solutions capable of increasing the performance of the pavement while decreasing the negative impacts. In this context, the utilisation of recycled materials appropriate for other re-uses must be progressed and enhanced [1,2]. The fields of application of CRM in road constructions are miscellaneous. The previous researchers validate them are as numerous as the number of positive results achieved in recycling this material [1]. The usage of the recycled rubber from the End of Life Tires into the bitumen concretes was began in the 1960s. The technology that has spread more is the so-called Asphalt Rubber (AR) one. AR binders produced with the manufacturing process innovated by Charles McDonald, and that is at the foundation of the wet process. This method began with the mix of the end of life tire ground rubber with the asphalt binders utilising mechanical stirring systems, operating at temperatures ranging between 190 and 218 C, for a time interval of 45–۶۰ min [3–۶].