Cold-Bonded Lightweight Aggregates and their Application in Road Subgrade Soil Treatment

To promote the application of cold-bonded granulation technology in road engineering, this study used silty soil as the raw material and cement as the cold binder to convert silty soil with poor engineering performance into cold-bonded lightweight aggregates (CBLA) with tailored performance characteristics. The effects of different cement contents on the physical and mechanical properties of CBLA were systematically investigated. The evaluation indicators included granulation ratio, particle morphology, bulk density, water absorption, individual crushing strength (ICS), and cylinder compressive strength (CCS). The results indicated that the granulation ratio of CBLA reached a maximum value of approximately 89% at a cement content of 10%, after which it gradually decreased with further increases in cement content. With increasing cement content and curing age, the bulk density exhibited a clear upward trend. When the cement content was lower than 15%, water absorption decreased significantly. ICS ranged from 0.51 to 3.20 MPa. When the cement content reached 12%, both ICS and CCS achieved their optimal values, whereas further increases in cement content resulted in only marginal improvements in mechanical performance. By incorporating 0%–70% CBLA into silty soil for physical improvement, lightweight aggregate-improved soil (LA-Soil) was produced. Both laboratory and field tests demonstrated that the California bearing ratio (CBR) and resilient modulus of LA-Soil satisfied the requirements of high-grade highway subgrades. Therefore, it is recommended that the CBLA content in the improved soil should be controlled within the range of 50%–70%.