Lijun Ma

To address the susceptibility of traditional concrete to explosive spalling and the lack of in situ damage-monitoring methods at high temperatures, in this study, a novel self-sensing, high-temperature-resistant Engineered Cementitious Composite (ECC) was developed. The matrix contains eco-friendly glass sand reinforced with a hybrid system of polypropylene fibers (PPFs) and carbon fibers (CFs). The evolution of mechanical properties and the multimodal self-sensing characteristics of the ECC were systematically investigated following thermal treatment from 20 °C to 800 °C. The results indicate that the hybrid system exhibits a significant synergistic effect: through PFFs’ pore-forming mechanism, internal vapor pressure is effectively released to mitigate spalling, while CFs provide residual strength compensation. Mechanically, the compressive strength increased by 51.32% (0.9% CF + 1.0% PPF) at 400 °C compared to ambient temperature, attributed to high-temperature-activated secondary hydration. Regarding self-sensing, the composite containing 1.1% CF and 1.5% PPF displayed superior thermosensitivity during heating (resistivity reduction of 49.1%), indicating potential for early fire warnings. Notably, pressure sensitivity was enhanced after high-temperature exposure, with the 0.7% CF + 0.5% PPF group achieving a Fractional Change in Resistivity of 31.1% at 600 °C. Conversely, flexural sensitivity presented a “thermally induced attenuation effect” primarily attributed to high-temperature-induced interfacial weakening. This study confirms that the “pore-formation” mechanism, combined with the reconstruction of the conductive network, governs the material’s macroscopic properties, providing a theoretical basis for green, intelligent, and fire-safe infrastructure.

To address the mechanical deficiencies of traditional pervious concrete and promote its practical implementation, this study developed a high-performance pervious concrete model using conventional materials and methods, achieving a permeability coefficient of 4.5 mm/s with compressive and flexural strengths exceeding 45 MPa and 5 MPa, respectively. Central composite design (CCD) response surface methodology was employed to investigate the individual and synergistic effects of the water–cement ratio (W/C), nano-silica (NS), and carbon fibers (CF) on permeability, compressive strength, and flexural strength. Statistical models demonstrating prediction errors within 7% of experimental values were established, supplemented by a microstructural analysis of the concrete specimens. The results demonstrated that (1) the W/C ratio significantly influences overall performance; (2) NS enhances mechanical strength while reducing permeability, though excessive NS content induces weak interfacial zones that compromise strength; (3) CFs exhibit negligible impact on compressive strength but substantially improve flexural performance; and (4) significant synergistic interactions are present across W/C ratio, NS, and CFs concerning flexural strength parameters, while no significant interaction was observed for compressive strength.