Effects of particle size regulation of coal gasification fine ash on the hydration behavior and the electromagnetic wave shielding performance of cement-based materials

• Enhancing the EM shielding properties of cement-based materials through the development of CGFA • Reveals the effects of CGFA particle size variation on the hydration behavior and shielding mechanisms of cement-based materials • Investigated the effects of CGFA particle size variation on the structure of cement-based materials • Utilizing industrial waste to produce cement-based electromagnetic shielding materials helps reduce fabrication costs and facilitates large-scale application Coal gasification fine ash (CGFA) possesses both hydration reaction activity and notable electromagnetic properties. Its application in cement-based materials not only enables the high-value utilization of industrial waste but also helps to addresses the prohibitive cost that has hindered the widespread adoption of traditional cement‑based electromagnetic shielding materials. However, research in this area remains relatively scarce. In this study, CGFA was prepared by ball milling into three particle-size distributions: untreated ash (D 0.9 = 249.1 μm), medium particle size (D 0.9 = 51.7 μm), and small particle size (D 0.9 = 10 μm). The effects of CGFA particle size on the structure, hydration behavior, and electromagnetic shielding performance of cement-based materials were investigated systematically. The results indicate that, although reducing CGFA particle size partially damages the porous structure of the carbon component, it markedly improves the dispersibility of CGFA within the cement matrix, thereby enhancing mortar compactness. After grinding, the reactive components in CGFA are further activated, promoting cement hydration and improving mechanical properties. When small-particle CGFA replaces 40% of the cement, the composite mortar still attains a compressive strength of 21.1 MPa, meeting the M20 load-bearing requirement of the standard. In addition, incorporation of CGFA significantly enhances the electrical conductivity and electromagnetic shielding performance of cement mortar. Small-particle CGFA more readily forms a well-developed conductive network in the mortar and lowers the percolation threshold, resulting in superior SE compared with untreated CGFA in the 1.13-3.95 GHz frequency band; conversely, in the 3.95-8.2 GHz band, the untreated CGFA exhibits better shielding performance. This work provides comprehensive and systematic data support for related research, while establishing reference ranges for particle size and content parameters in engineering applications.