Performance evaluation of recycled cement-stabilized gravel strengthened with multi-source solid-waste-based composite slurry and its mixtures

To improve the mechanical performance of cold-recycled cement-stabilized gravel and address practical problems including poor mechanical properties and high dispersion of recycled cement-stabilized gravel (RCSG), a strengthening method for RCSG coated with multi-source solid-waste-based composite slurry was proposed. A multi-source solid waste-based composite slurry containing slag powder, steel slag powder and carbide slag was developed. The recommended paste-to-aggregate mass ratio and slurry concentration for RCSG strengthening were determined. The mixing proportion of slurry raw materials together with the strengthening procedure for RCSG were recommended. The effects of strengthening procedure and RCSG replacement content on the performance of cold-recycled cement-stabilized gravel mixtures were evaluated. The results show that the recommended mass ratio of ground granulated blast-furnace slag, steel slag powder, carbide slag, and sodium silicate was 60:40:4:1. A slurry concentration of 50%, a paste-to-aggregate mass ratio of 1:8, and mechanical mixing for 5 min were recommended as the strengthening parameters based on the experimental results. After treatment with this procedure, the 7 d and 28 d interfacial bonding strengths of fine RCSG reached 0.71 and 0.96 MPa, respectively, with the 7 d interfacial bonding strength increased by 77.5% compared with the untreated group. The crushing and abrasion values of coarse RCSG decreased to 19.09% and 8.98%. At a 30% replacement rate, the 7 d and 28 d unconfined compressive strengths of the strengthened cold-recycled cement-stabilized gravel mixtures increased by 104.4% and 103.8%, respectively. The proposed multi-source solid-waste-based composite slurry effectively improved the mechanical performance of RCSG and cold-recycled cement-stabilized gravel mixtures. This study provides experimental support for the strengthening and reuse of RCSG in pavement base applications.