An Experimental Study on the Flexural Fatigue Behaviour of Pre-cracked Steel Fibre Reinforced Concrete

Fatigue behaviour of concrete has become an increasingly popular topic in the last century, especially with the development of railway bridges. Fatigue loading may appear in various forms, from physically applied loads, to indirect loads, including corrosion and thermal fatigue among others. These fatigue loadings may occur independently or in conjunction with the applied fatigue loadings, which could exacerbate the fatigue process and likely decrease the lifespan of the structure. The mechanisms of fatigue failure in concrete may be divided into three phases: (1) crack initiation, (2) progressive growth of micro-cracks, and (3) convergence of micro-cracks to form macro-cracks. In fibre reinforced concrete (FRC), energy is dissipated in the wake of the crack tip, which increases the load carrying capacity, thereby providing post-cracking ductility. Unlike ferrous materials, concrete was found to exhibit no fatigue limit after 2 million load cycles. However, its performance may be influenced by stress levels, load frequency, boundary conditions, matrix composition, and number of applied cycles. In this paper, the flexural fatigue behaviour of pre-cracked steel fibre reinforced concrete was investigated. Various pre-cracks and load levels were considered. X-ray Computed Tomography (CT) scans were implemented to determine the extent of damage to the fibres within the concrete matrix after fatigue loading.