Role of aggregate packing in enhancing concrete fracture response: insights from in-situ high-speed imaging

Much of the existing literature has focused on improving concrete's fracture response by focusing on binder composition.However, the critical role of aggregates and their packing efficiency on fracture response has not been studied in detail.Here, we investigate the impact of packing enhancement on fracture behavior by designing 4 unique concrete mixes with customized aggregate skeletons, utilizing a continuous packing model.Fracture assessment using the two-parameter fracture model (TPFM) and high-speed cross-sectional Digital Image Correlation (DIC) was employed to acutely capture strain distribution and crack propagation from 95% of the pre-peak to the peak load.We find that improving coarse aggregate packing efficiency from 88% to 93%, while maintaining constant binder content, increased fracture energy (Gf) by 35.29% and 39.48% for 3 and 7 days respectively.Likewise, for 3 and 7 days the critical stress intensity factor (K1C) increased by 46.08% and 51.66% respectively with the increase in packing efficiency.In summary, the results obtained quantify the impact of aggregate packing on concrete's fracture response.