Deformability enhancement of fiber-reinforced cementitious composite by incorporating recycled powder

Recycled powder (RP) from construction and demolish waste was used to replace fly ash and silica sand to enhance the tensile behavior of engineered cementitious composite (ECC) in the research. The average diameter of RP is less than 45 mu m. Four mixtures of RP-ECCs were prepared, in which 50% and 100% of fly ash or silica sand were replaced by RP. The tensile strain-hardening and multiple cracking behaviors of RP-ECC specimens were extensively observed with the increasing tensile load. Results demonstrate that the replacement of fly ash and sand by RP promote the strain capacity of ECC specimens. Moreover, specimens with 50% RP showed superior tensile and compressive strength over those with 100% replacement ratio and the reference specimens. The analyses at micro-scale and meso-scale indicate that the replacement of fly ash by RP does not change the fracture toughness of the cementitious matrix, but significantly enhanced the fiber bridging capacity. While the replacement of sand by RP lowers the matrix fracture toughness and has a negligible effect on the fiber bridging capacity. Finally, the superior tensile strain capacity of RP-ECC is well-explained by the pseudo-strain hardening index.