Synergistic utilization of high-calcium fly ash and recycled brick powder in alkali-activated high-ductility composites: rheology, multiscale mechanical performance and microstructure

This study addresses the limitations in existing research on alkali-activated systems using high-calcium fly ash (HCFA), such as restricted strategies for performance control and insufficient fiber-matrix interface optimization. The synergistic effects of recycled brick powder (RBP) on the multi-scale performance of alkali-activated high-ductility composites (AA-HDC) were systematically investigated by RBP as a functional modifier. Results show that AA-HDC prepared using solely HCFA achieve a high compressive strength of 57.8 MPa, while the incorporation of RBP further enhances matrix and fiber-matrix interfacial performance through combined physical filling and chemical effects. This leads to pronounced multiple cracking behavior and a tensile deformation capacity exceeding 5%. Through microscopic interface characterization and pore structure analysis, the regulatory mechanism of RBP on the rheological and mechanical properties of AA-HDC was elucidated, offering a new pathway for developing high-performance, low-carbon ductile composites.