Tensile Behaviour of Ultra-High-Performance Steel Fiber Reinforced Concrete

Reinforcing bars are provided in reinforced concrete structures on account of conventional concretes negligible resistance to tension. However, corrosion of steel reinforcement inevitably occurs due to carbonation and chloride ingress, which significantly reduces the service life of structures. An alternative to this predicament is now feasible with the advent in cementitious material technologies, such as ultra-high-performance, self-consolidating, steel fiber reinforced concrete (UHP-SFRC). The keystone of safe and economically feasible designs with UHP-SFRC is dependant on its characterization in tension. Thus, in the present work, a detailed research study including both experimental and analytical components was conducted to investigate the tensile behaviour of UHP-SFRC: tensile strength was quantified and correlated through direct tension test (DTT), four-point bending test (FPBT), splitting tensile test, nonlinear finite element analysis and a calibrated empirical expression in relation to cylinder compressive strength. In addition, effects of important parameters on flexural strength including casting methodology, volumetric ratio of steel fibers, aspect ratio of bending prism and prism size were assessed. Moreover, the bilinear stress-strain and stress-crack mouth opening relationships of UHP-SFRC were derived according to the inverse analysis procedures proposed by Annex 8.1 of CSA-S6 (2018) and Annex U of CSA-A23.1 (2019). Furthermore, a nonlinear finite element analysis software, VecTor2, was employed to develop numerical models with the ability to match the response curves obtained from FPBT. Analytical results indicated that cracking strength of UHP-SFRC derived from the inverse analysis method was generally greater than those obtained from direct tension test, splitting tensile test, nonlinear finite element models and the calibrated empirical expression. Additionally, inverse analysis and finite element analysis results indicated that the majority of prisms exhibited tension hardening behaviour with a hardening ratio greater than 1.1 and an ultimate tensile strain greater than 0.1%. In addition to tension tests, a host of non-destructive tests were conducted to assess the physical properties and durability performance of UHP-SFRC.