Development of modified balanced mix design method for cold recycled asphalt mixture

Emulsified asphalt cold recycled mixture (EACRM) has gained significant attention for its low-carbon and eco-friendly attributes. However, its further application still restricts by the relatively low service performance. One critical reason is that the optimal emulsified asphalt content (OEC) cannot be precisely determined based on the service environment under the current design method. In this study, a modified design method to determine OEC of EACRM based on the balanced mix design (BMD) was proposed, which could comprehensively consider the effects of temperature variation and moisture invasion. Specifically, the temperature was classified into high, medium and low temperature, and the moisture invasion mainly referred to the freeze-thaw resistance. The related test methods and evaluation indicators were firstly put forward. Then, a case study was conducted with two kinds of emulsified asphalt (conventional emulsified asphalt and high viscosity modified emulsified asphalt) and a gradation of 100% reclaimed asphalt pavement (RAP) to verify the validity of the proposed method. Results show that the EACRM has the potential to own better concerned service performance with the proposed design method and evaluation system. Compared with the existing specification design (ESD) method, the proposed design method qualifies EACRM a significantly enhanced fatigue resistance, low temperature performance and moisture susceptibility. For the high viscosity EACRM, the fatigue cracking resistance, low temperature cracking resistance and water stability increased to 45.22%, 11.5% and 2.5%, while for the conventional EACRM, those indicators increased to 52.24%,15.98% and 2.6%. This is of great significance since it provides a new approach to improve the crucial performance of EACRM and also brings support to broaden its application scope.