In the heart of China, researchers are tackling a critical challenge for the energy sector: enhancing the fire resistance of tunnel linings. Jing Wang, from the School of Transportation Science and Engineering at Jilin Jianzhu University, has led a groundbreaking study published in *Materials Research Express* (translated as “Materials Research Express”), focusing on high-performance shotcrete, a vital material for tunnel construction.
The study, titled “Investigation of the high-temperature resistance of glass aggregate enhanced sprayed high-performance concrete,” addresses the pressing issue of spalling in tunnel linings under elevated temperatures. “Our goal was to develop a heat-resistant and self-sensing shotcrete that could withstand the complex conditions often encountered in tunnels,” Wang explains.
The team created a innovative shotcrete by incorporating 0.9% carbon fibers, adjusting the content of polypropylene fibers, and replacing 75% of manufactured sand with recycled glass sand. The specimens were then exposed to temperatures ranging from 20 °C to 800 °C for two hours. The results were promising, with polypropylene fibers enhancing thermal resistance. “We found that 0.4% polypropylene fibers were the optimal dosage for improving thermal resistance,” Wang notes.
The study revealed that the strength of the shotcrete increased moderately up to 600 °C due to continued hydration, reaching maximum compressive, splitting tensile, and flexural strengths of 124.54 MPa, 8.44 MPa, and 11.69 MPa, respectively. However, beyond this threshold, the strength declined sharply. The self-sensing capability of the shotcrete also diminished with temperature and disappeared entirely at 800 °C.
Scanning electron microscopy confirmed the correlation between fiber melting, hydration changes, and mechanical degradation. Numerical simulations using ANSYS APDL indicated that fire exposure beyond one hour may cause compressive stress at the tunnel crown to exceed the concrete’s design strength, posing a risk of failure. “Limiting fire suppression time within one hour and prioritizing post-fire crown inspection are recommended,” Wang advises.
This research has significant implications for the energy sector, particularly in the construction and maintenance of tunnels. The development of heat-resistant and self-sensing shotcrete could enhance the safety and durability of tunnel linings, reducing the risk of failures and improving overall performance. As the demand for high-performance materials continues to grow, this study provides valuable insights into fire-resistant design and repair strategies for tunnel linings.
The findings published in *Materials Research Express* (translated as “Materials Research Express”) offer a glimpse into the future of tunnel construction, where advanced materials and technologies will play a crucial role in ensuring safety and efficiency. “Our research opens new avenues for the development of high-performance shotcrete that can withstand extreme conditions,” Wang concludes. This work not only advances scientific knowledge but also paves the way for practical applications that can benefit the energy sector and beyond.