Operating tunnels are often located in complex geological conditions and are prone to various types of damage. Even after structural repair, the repaired material may be vulnerable to secondary damage. It is difficult to effectively repair operating tunnel damage. Hence, developing high-performance repair materials for tunnel structures is critical. This study aimed to develop repair materials by studying the synergistic effects of fiber and polymers. The effect of polyvinyl alcohol (PVA) fiber and PTB (COMPAKTUNA.PRO) emulsion on the compressive strength (40 × 40 × 40 mm, GB/T 17671-2020), flexural strength (40 × 40 × 160 mm, GB/T 17671-2020), uniaxial tensile properties (330 × 60 × 13 mm, JC/T 2461-2018), bond strength (40 × 40 × 160 mm, JC/T 2537-2019), rapid chloride migration coefficient (φ100 × 50 mm, GB/T 50082-2009), porosity (40 × 40 × 40 mm, SY/T 6490-2014), and scanning electron microscopy (less than 1 cm³, GB/T 27788-2020) was analysed. The test was completed in the laboratory of our school, and the average value of three specimens per mix ratio was taken. The results indicate that both PVA fiber and PTB emulsion addition reduce the compressive strength but significantly increase the flexural strength, tensile strength, and ultimate tensile strain of cementitious composite. The compressive-to-flexural strength ratio decreases, and the uniaxial compression toughness index increases. The cementitious composites exhibit good integrity after damage. The influence of the PVA fiber is more potent than that of the PTB emulsion. The PTB emulsion increases the impermeability and bonding strength of the cementitious composite and can improve the disadvantages caused by adding the PVA fibers. The bridging effect of the PVA fiber and the membrane-forming effect of the PTB emulsion together influence the performance and cause a synergistic effect to achieve superposition and complementation of advantages. The optimal content of the PVA fiber and PTB emulsion under the synergistic effect can be obtained. The findings can provide a theoretical basis for the optimal design and practical application of restoration materials.

The disposal of industrial solid waste poses significant challenges in the context of sustainable global development. This issue is particularly critical for low-calcium solid waste, which is generated in large quantities and accumulates in extensive stockpiles. Owing to its low reactivity, the high-value utilisation of such waste remains challenging. In this study, three representative and readily available industrial solid wastes—coal gangue (CG), fly ash, and blast furnace slag—were selected for investigation. CG was activated using a combination of chemical, thermal, and mechanical treatments. Experiments were conducted to improve the working performance of CG-based alkali-activated cementitious materials. The microstructural characteristics of the materials were characterised using isothermal calorimetry, nuclear magnetic resonance spectroscopy, and X-ray diffraction. The results indicated that the biomass ash-composite-modified sodium silicate solution provided the best working performance among the activators evaluated, outperforming conventional NaOH and sodium silicate solutions. The thermal activation parameters had a greater influence on the cementitious system than the grinding time. Under the investigated conditions, CG exhibited the highest cementitious reactivity after 2 h of grinding followed by calcination at 800 °C for 4 h. These findings provide a reference for the efficient activation of large quantities of low-reactivity solid waste and support its large-scale, high-value utilisation.