Fracture process zone characterizations of multi-scale fiber reinforced cementitious composites

This research investigates the toughening effect of a multi-scale steel fiber reinforcement, consisting of a micro-macro fiber combination, within the fracture process zone (FPZ) of a cementitious composite. The reinforcement schemes investigated include: no fiber, micro-fiber only, macro-fiber only, and multi-scale fiber reinforcement. Fracture energy (G_f) experiments were performed to characterize the energy dissipation in the FPZ. Three different FPZ length (l_FPZ) measurement methods were employed using digital image correlation (DIC) post-processing - one established and two novel - to further understand the effects of multi-scale fiber reinforcement on the FPZ. The steel wool micro-fiber increased the G_f of a micro-fiber-only cementitious composite over a non-reinforced composite by approximately 200%. The steel wool also increased the G_f of a multi-scale fiber cementitious composite over a macro-fiber only version by 19–23%. These gains were achieved through a toughening of the FPZ, as indicated by corresponding increases in l_FPZ.