Effects of coarse aggregate and wavy steel fiber volumes on the critical stress intensity factors of modes I and III cracks in self-compacting concrete using ENDB specimens

Abstract

This study investigated the effects of coarse aggregate and wavy steel fiber volumes on pure modes I and III fracture toughness (KIF & KIIIF) for which 72 Edge Notched Disc Bend (ENDB) specimens were made using four different coarse aggregate volumes (30, 40, 50 and 60%) and three different wavy steel fiber volumes (0.15, 0.3 and 0.45%). They were then examined with the three-point bending test. Results showed that increasing the coarse aggregate volume from 30% to 50% increased pure modes I and III fracture toughness, and increasing it from 50% to 60% reduced the fracture toughness because the fiber-coarse aggregate interaction caused fibers to negatively affect the resistance against fracture. The KIF-KIIIF comparison showed that the fiber effect was more evident and critical in the tearing mode (mode III). Since the fracture theory prediction criteria showed that the KIIIF/KIF ratio had a 0.7–0.9 variation range based on varying coarse aggregate and fiber volumes, it can be concluded that these criteria can well predict pure failure modes I and III of self-compacting concrete. Analysis of variance (ANOVA) was conducted on fiber-reinforced self-compacting concrete composites, and the post hoc Tukey test was used to study if the effects of the pairwise variables were significant on pure modes I and III fracture toughness.