Semicircular bending fracture test to evaluate fracture properties and ductility of cement mortar reinforced by scrap tire recycled steel fiber

Abstract

The existing test methods using single-edge notched-beam (SEN(B)) specimens to characterize the fracture properties of cementitious materials have some drawbacks. A novel approach using a single fracture test to assessing multiple cementitious materials properties with semi-circular bending (SCB) specimens is presented in this study. In comparison with the conventionally used SEN(B) specimens, the fabrication of the SCB geometry is less material- and labor- intensive. The geometry is also more suitable for field applications due to the ease of extracting cylindrical specimens. In this study, the utility of the SCB fracture method has been demonstrated by testing cement mortars reinforced by recycled steel fiber (RSF) from scrap tire. Based on the SCB fracture test, adding 2% RSF into the cement mortar increased the critical stress intensity factor (KIcs) and the critical crack tip opening displacement (CTODc) by up to 45% and 90%, respectively, and the fracture energy parameters (Gf and GF) by up to 128% and 475%. The ductility indexes were defined based on stress intensity factors rather than tensile strengths, and the results reveal the extremely high ductility of the RSF reinforced cement mortar. It is also found that early age cement mortar specimens are less brittle than mature specimens. Additionally, the theoretical tensile strength was determined. By comparing the theoretical tensile strength with the splitting tensile strength, the level of size effect was evaluated, which again verified that the cement mortar reinforced by 2% RSF is more ductile compared to the plain cement mortar.