Performance enhancement of green high-ductility engineered cementitious composites by nano-silica incorporation

•Excellent mechanical performance of ECC incorporating 100% RFA could be achieved.•Nano-silica densifies ECC’s microstructure and improves its mechanical strength.•1% nano-silica dosage is found to be the optimal content. To promote the sustainable development of construction materials, the green high-ductility engineered cementitious composites (GHD-ECC) incorporating 100% recycled fine aggregate (RFA) was developed. The effect of nano-silica (NS) at different dosages (0, 1%, 2%, and 3%) on the microstructural features and the macroscopic strength of GHD-ECC was investigated. The results of a comprehensive experimental study indicate that: (1) the four types of cementitious composites all exhibit multiple cracking characteristics, and the mechanical resistance of GHD-ECC is significantly improved owing to the addition of NS; (2) NS with high pozzolanic reactivity promotes the hydration reaction process, and the additionally formed hydration products fill the micropores and densify the microstructure of GHD-ECC; (3) the increase of both the matrix strength and matrix toughness leads to the enhancement of frictional bonding between fiber and matrix, which induces the transition of the failure mode from fiber pulled-out to fiber rupture and thus causes, to a certain extent, the degradation of the fiber bridging capacity. Based on the comprehensive investigation, the 1% NS dosage is found to be the optimal content, which not only meets the workability requirement but also contributes to the achievement of saturated cracking state and high mechanical resistance.