Mechanical and microscopic performance of engineered cementitious composites: effects of fly ash fineness and calcium content

Fly ash-engineered cementitious composites are high-ductility, fiber-reinforced materials designed to enhance structural performance while reducing cement consumption and environmental impact. However, variations in FA source and production lead to significant differences in particle fineness and calcium content, which affect the mechanical and microstructural behavior of ECC. To address this issue and promote broader engineering applications of ECC, this study investigates the effects of FA fineness and calcium content on the strength, ductility, and microstructure of ECC. Three FA types were incorporated, and the resulting composites were evaluated through mechanical testing, XRD, TGA, SEM, and nanoindentation. The results indicate that ECC incorporating FA with moderate fineness and CaO content achieved the highest tensile strength, flexural strength, and stress index. In contrast, ECC with ultrafine FA and high CaO content exhibited superior ductility and a significantly higher PSH index. This study offers novel insights into designing durable, high-performance, and low-carbon ECC materials.