Toughness indices of fiber reinforced concrete subjected to mode II loading

This paper reports on some studies on development of test geometry and testing procedure to determine the toughness indices of fiber reinforced concrete in Mode II loading. The proposed test geometry consists of a beam, 150mmx150mmx600mm, with two-2mm wide and 15mm deep all-round notches. Tests were conducted to achieve Mode II fracture in plain and fiber reinforced concrete (FRC) beams. Steel fibers (length = 25mm and aspect ratio = 44.6) were randomly distributed in concrete at varying fiber volume frac- tions of 0, 0.5, 1.0 and 1.5%. The failure was observed to be essentially in pure shear along the predefined fracture plane. Plain concrete was observed to fail at an equivalent shear strain of 0.5%, while the shear strain was 8.0% in fiber reinforced concrete. The strength and toughness of concrete in Mode II loading have been improved by the addition of steel fibers to concrete. The shear strength of FRC increases as the volume frac- tion of fibers increases. Similar trend has been observed with the toughness of concrete. 1 INSTRUCTION In quasi brittle materials like concrete, a large fracture process zone (FPZ) is formed in front of a Concrete is used extensively in civil engineering crack like defect that consumes huge amount of the construction practice owing to its low production total energy. FPZ is also a source of size dependency cost, formability, and much desirable response. De- of many fracture parameters of concrete (Bazant and spite its several merits, it is weak in tension with less Kazemi 1990). Additional toughening mechanisms cracking resistance. The deficiency of concrete in arise due to the addition of fibers including fiber tension could be improved to a large extent if it is re- bending and internal work of fiber debonding and inforced with fibers (Wu et al. 2000). The fibers fracture (Beaudoin 1990).