Methodology for Assessing the Enhanced Flexural Fatigue Life of Ultra High-Performance Concrete Due to Self-healing

This paper provides an overview of techniques for evaluating flexural fatigue life, delving into their applicability to ultra high-performance concrete (UHPC). The consensus on the impact of fibre inclusion on fatigue life of fibrereinforced concrete (FRC) remains elusive. The intricate interplay of varied fibre parameters, loading frequency, and matrix composition complicates the understanding of FRC behaviour under cyclical loads. The absence of standardized test procedures hampers the correlation and extension of published results. Despite these challenges, a positive impact on fatigue performance under flexural loading is revealed, suggesting that fibres, under tensile forces, bridge cracks and extend fatigue life. This paper proposes a methodology to assess self-healing induced enhancement of the flexural fatigue life of UHPC in high-cycle fatigue loading, focusing on stiffness and the rate of crack opening displacement. Initially, specimens underwent 700,000 cycles as a fatigue pre-healing condition. Following the healing process, the specimens were subsequently subjected to up to 2 million cycles at a frequency of 5.5 Hz. UHPC specimens demonstrated up to 10% improvement in stiffness and a reduction of up to one order of magnitude in the rate of crack opening displacement with three months of healing in submerged condition.