Strength mechanical properties and microscopic mechanism of unburned artificial aggregate based on solid wastes

As the demand for natural aggregates in the construction industry increases, resource shortages and environmental concerns have become more prominent, making the development of artificial aggregates highly significant. This study investigates solid waste-based artificial aggregates prepared from fine sand, clay, cement, and other raw materials, focusing on their mechanical properties and underlying microscopic mechanisms. The unconfined compressive strength tests revealed that when the sample preparation pressure ranged from 5~10 MPa, strength increased significantly, with a slight increase observed between 10~15 MPa. Above 15 MPa, no further increase in strength was observed. Furthermore, the strength of unburned artificial aggregates was notably improved at a 50% agent-to-mud ratio. The addition of clay to fine sand enhanced soil properties, with strength peaking when 40% clay was added; however, excessive clay content reduced strength. Microstructural analysis using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) indicated that the sample with a 50% cement ratio exhibited the highest and most evenly distributed hydration products. In contrast, the 75% cement ratio sample formed a lamellar structure that hindered cement hydration, leading to reduced strength. Pore diameters were mainly in the 5~20 nm range under a 15 MPa preparation pressure. This study establishes the optimal parameters for producing solid waste-based artificial aggregates, offering a theoretical and technical foundation for addressing natural aggregate shortages and promoting sustainable resource utilization.