Grey target optimization and the mechanism of cold recycled asphalt mixture with comprehensive performance

To enhance the selection of material content for a cold recycled mixture of emulsified asphalt in hot and rainy areas, the effect of emulsified asphalt content, cement content and Reclaimed Asphalt Pavement (RAP) content on high temperature properties, moisture stability and the fatigue properties of cold recycled mixture were investigated. Based on multi-index weighted grey target theory, the performance of cold recycled mixture were analyzed and the material content were optimized. Then, the crack resistance mechanism of the cement-emulsified asphalt mortar was revealed via a scanning electron microscopy test. The results showed that emulsified asphalt content and cement content mainly affected the high temperature properties, while the effect of the RAP content on water stability was the most significant, and the fatigue performance was significantly affected by various factors under different the stress ratio. The proportions of 3.8% emulsified asphalt, 2% cement and 80% RAP were recommended by grey target optimization. Plentiful hydration products were found positioned in the interfacial crack between the asphalt and aggregate, enhancing the interfacial strength and improving the micro-interface deformation of the cold recycled mixture.