SEM- and DGFM-based evaluation of fracture parameters in self-compacting concrete incorporating silica fume and nano-silica

• Adding 10% SF or 1% NS had almost similar effects on the fracture properties of SCC. • Adding NS beyond 3% of cement weight negatively affects the fracture properties of SCC. • The most significant increase in the G f value occurred when 10% SF and 3% NS were added to the control sample. • The values of G f , K Ic , and CTOD c obtained from both the SEM and DGFM methods were nearly identical. This study is an experimental investigation that compares the fracture parameters of self-compacting concrete (SCC) containing silica fume (SF) and nano-silica (NS), utilizing the size effect model (SEM) and the double-G fracture model (DGFM). In total, eight mix designs were evaluated, each with different percentages of SF and NS, while maintaining a water-to-cement ratio (W/C) of 0.35. Three-point bending tests were conducted on a total of 120 notched beams. The results indicated that the most significant increase in the G f value occurred when 10% SF and 3% NS were added to the control sample. This addition resulted in a 22.96% increase in the G f value using the SEM method and a 21.40% increase with the DGFM method, compared to the control sample. Furthermore, the findings of this study showed that the values of G f , K Ic , and the critical crack tip opening displacement (CTOD c ) obtained using both the SEM and DGFM methods varied by 7.12%, 3.63%, and 8.14%, respectively.