Experimental Investigating the Effect of Glass Fibre on Mode I, Mode II, and Mixed Mode (I-II) Fracture Toughness and Crack Propagation in Fibre-Reinforced Concrete

Concrete is the most widely-used material in civil engineering and often contains the cheapest and most common matter. It can therefore cause irreparable damages due to cracks and fractures. The creation of fibre-reinforced concrete in recent years has largely rectified the aforementioned shortcomings. This study uses the direct crack Brazilian disk test to evaluate fracture toughness and crack propagation in fibre-free and glass fibre concrete samples in 0.2, 0.35 and 0.5 volume percentages. Moreover, fracture toughness and crack propagation from pre-existing cracks were calculated for samples in mode I, mode II, and mixed mode (I-II). The samples were subjected to the Brazilian disk test at 0, 15, 28.83, 45, 60, 75 and 90-degree angles relative to the pre-existing crack’s trajectory. Laboratory investigations showed that the wing crack at sub 75-degree (0<α <75) angles was initiated from the pre-existing fracture’s tip and approached loading trajectory as the load on the crack growth and propagation trajectory continued. At the same time, crack initiation at 75-degree angles and above begins at a distance of d from the tip, which is greater in fibre-free samples. The results also showed that using 0.2% glass fibre in mode I, II and mixed mode (I-II) resulted in a higher fracture toughness than fibre-free samples.