Development of LC3-ECC incorporating recycled fine aggregate: a novel sustainable and ductile material

Concrete structures exposed to the synergistic effects of aggressive environmental conditions and mechanical loading often exhibit inadequate toughness, brittleness, and susceptibility to cracking. Engineered Cementitious Composites (ECC), characterized by their ultra-high toughness and controlled crack propagation behavior, offer a viable solution to mitigate these issues. However, the production of ECC consumes a large amount of Portland cement and fine silica sand, which not only aggravates the shortage of natural construction resources but also causes a serious environmental burden. This study innovatively proposes to substitute Portland cement with limestone calcined clay cement (LC 3 ) and to replace silica sand with recycle fine aggregates (RFA) from waste concrete so as to develop the LC 3 -recycled ECC. This new kind of green material exhibits high toughness, high crack controlling ability, and high sustainability. In this work, four replacement ratios of silica sand by RFA, i.e., 0 %, 30 %, 60 %, and 100 %, are investigated. The tensile ductility is significantly improved with the usage of RFA, and the increasing ratio attains 80 % when 100 % RFA is used. Meanwhile, the compressive strength of LC 3 -ECC-RFA-100 % is not seriously compromised with only 20.5 % reduction being observed at 180 days. The tensile strength of ECC using RFA is retained, and an obvious increase is even observed for case of 30 % RFA incorporation. Since RFA exhibits self-cementing properties when contacting with the reactive components in LC 3 , the additional formed hydration products could enhance the fiber/matrix bonding strength, which contributes to the improvement of fiber bridging capacity and macroscopic tensile strength. Besides, the usage of RFA enhances the uniformity of fiber dispersion in cementitious matrix, which is highly beneficial to the achievement of high ductility. The findings in this work aim to provide theoretical support for the promotion and application of green and low-carbon LC 3 -recycled ECC in infrastructure construction.