Jinwen Chen

The efficient treatment and resource utilization of shield tunnel spoil (STS) are important for sustainable underground construction in China. To improve the early mechanical performance and microstructural compactness of stabilized STS, this study investigated the solidification effect of a novel early-strength cementitious agent (ESCA) and compared it with ordinary Portland cement (P.O 42.5). Macroscopic mechanical tests, including unconfined compressive strength (UCS), stress–strain behavior, mass, and P-wave velocity measurements, were combined with scanning electron microscopy (SEM) and computed tomography (CT) analyses to reveal the mechanical response and microstructural mechanisms of stabilized STS. The results indicate that, compared with P.O 42.5, ESCA exhibits superior fluidity at lower water-to-solid (w/s) ratios, significantly shorter setting times, and higher compressive strength at all curing ages. The solidification efficiency of ESCA for STS is notably superior to that of P.O 42.5, with the peak strength, elastic modulus, mass, and P-wave velocity of ESCA-solidified specimens being higher than those of P.O 42.5-solidified specimens across the five dosages. Furthermore, ESCA material bonds more tightly with STS particles, resulting in lower porosity and a denser microstructure under the same stabilizer dosage. Overall, the combination of macroscopic mechanical properties and microstructural characterization demonstrates that ESCA material exhibits significant advantages in the efficient solidification and resource utilization of shield tunnel spoil.

Polyetheretherketone (PEEK) is widely employed in orthopedic applications due to its bone-mimetic mechanical properties and excellent biocompatibility, establishing it as a promising candidate for bone repair and regeneration. However, the investigation of structural integrity and microstructural features of PEEK implants has remained limited owing to its low atomic number (Z < 8) and hierarchical microstructure. This study presents a comparative characterization of PEEK implants by integrating laboratory X-ray computed tomography (CT) and synchrotron X-ray phase-contrast tomography (SXCT). Laboratory X-ray CT, operating on absorption contrast mechanisms, demonstrates adequate capacity for visualizing macroscopic defects and pore architectures, but exhibits limitations in resolving subtle density variations. In contrast, SXCT, employing phase-contrast imaging, significantly enhances discrimination of ultra-low-contrast features, including interconnected pore networks and localized density gradients. This work elucidates the complementary advantages and inherent limitations of both the imaging modalities for characterizing PEEK-based biomaterials. Furthermore, it demonstrates the potential extensibility of this comparative approach to other polymer composites, offering a methodology to investigate material–tissue interactions in orthopedic research and advancing the development of next-generation implantable devices.