Residual Strength and Toughness of Nano and Micro Scale Fiber Reinforced Cementitious Composites

This study reports a significant synergistic effect of using combined networks of nanoscale fibers (CNTs) and micro scale fibers (PPs) on the key mechanical properties of OPC mortars that define a uniquely tough and energy-absorbing material. The flexural strength at the first crack, δ, were firstly investigated by conducting three point close loop bending tests on prismatic specimens of mortars reinforced with 0.1 wt% CNTs and/or 0.73 wt% PPs. To further assess the mechanical performance of the proposed nanocomposites after the formation of the first-crack, the residual strength and the energy absorption capability of the nanocomposite mortars are also investigated at three post-crack stages, 3δ, 5.5δ and 10.5δ, according to the ASTM C1018. The experimental results showed that a combination of nano and micro scale fiber reinforcement yields a composite with a significantly enhanced load-carrying capacity at the elastic stage, as defined by the approximately 100% higher first crack strength. The multi scale fiber reinforcement has also an exceptional impact on improving the tensile strain-capacity of resultant composite after the formation of the first crack. The observed 90% increased residual strength and post-crack toughness of CNT-PP reinforced mortars indicate an improved ductility over the mortars reinforced with microscale PP fibers alone.