Toughening of concrete with ductile cementitious matrix: Proof of concept

Abstract

Fiber-reinforced concrete (FRC) is typically formulated by adding fibers to an existing concrete mixture. This limits the toughening potential, as fibers located away from the main crack tend to be underutilized. Here, we report a new composite system featuring non-close-packed coarse aggregates randomly embedded in a ductile fiber-reinforced cementitious mortar. The scientific objective is to validate the hypothesis that by prioritizing the ductility design of the mortar matrix, we can improve the fracture resistance of FRC while maintaining a constant fiber volume. For this purpose, both notched and unnotched beams were tested, and the damage patterns were evaluated by ultrasonics and surface crack observations. Our results reveal a simultaneous improvement of flexural strength and toughness, arising from an extended strain-hardening stage passing the first peak load. This contributes to an enhanced fracture resistance at small strains and limits the main crack propagation. Through crack and ultrasonic measurements, we confirm the existence of multiple crack branching, which raises the off-crack-plane energy in the ductile matrix. These preliminary findings could pave the way for a new toughening strategy in the design of FRC, focusing on enhancing the efficiency of fiber utilization through the ductility design of the mortar matrix.