Preparation and properties of artificial cold-bonded lightweight aggregate high-strength concrete

In this study, an artificial aggregate (AA) with excellent performance was prepared from concrete waste slurry (CSW) as raw material using cold-bonding granulation technology combined with a carbonation reinforcement process, and lightweight aggregate high-strength concrete (LAHC) was developed, focusing on the physical properties, mechanical properties, and microstructure of the aggregate, as well as the workability, mechanical properties, and shrinkage properties of the LAHC. The study results demonstrate that using cold bonding technology combined with a carbonation enhancement process to produce AA from CSW as a raw material is feasible. The particle size distribution of the spherical artificial aggregate mainly ranges between 4.75 mm and 14 mm. The aggregates have loose bulk densities of 950-1100 kg/m³, water absorption rates of 9.96%-12.89% at 1 hour, individual pellet strengths of 13.68-15.64 MPa, and cylinder compressive strengths of 8.18-9.17 MPa; pressurized carbonization 3 d for AA individual pellet strength and cylinder compressive strength increase by approximately 14% and 12%, wet carbonization 10 min increases by approximately 9% and 8%, the water absorption rate decreases by approximately 23% and 14%, respectively, wet carbonization shows higher efficiency advantages; prepared artificial LAHC 28 d compressive strength up to 45.2 MPa, flexural strength 4.7 MPa, and the 28 d compressive strength of the prepared artificial LAHC can reach 45.2 MPa, flexural strength 4.7 MPa, density 1807.6 kg/m³, which meets the requirements of LAHC; the spherical AA itself has a certain water-reducing function, and pre-wetting treatment can help to alleviate the problem of shrinkage of the LAHC, and the pre-wetted AA in 24 h can reduce the shrinkage rate of the concrete in 90 d by 10.0%. The research results provide a reference for the new generation of sustainable concrete materials.