Ultra-high-performance concrete (UHPC) is a cementitious composite that offers exceptional strength and durability; however, its adoption in India remains limited due to reliance on imported proprietary mixes, highlighting the need to develop and evaluate non-proprietary UHPC using locally available materials. This study presents an experimental investigation into the flexural and fracture behaviour of six UHPC mixes with target compressive strengths ranging from 100 to 175 MPa, systematically comparing different supplementary cementitious materials (SCMs) at a constant fibre content of 1.5%. Flexural testing of thirty notched beams per mix enables the determination of mean and characteristic flexural strengths, fracture parameters, and post-peak behaviour, with explicit quantification of uncertainty and data variability. The results indicate that SCM selection plays a critical role in governing post-peak flexural response. Silica fume based mixes exhibit superior post-peak behaviour, whereas ground granulated blast furnace slag–alccofine based mixes achieve comparable strength and fracture performance, offering practically viable alternatives in regions where silica fume is scarce or expensive. Digital image correlation analysis reveals fracture process zones extending up to 80%–90% of the ligament depth at crack mouth opening displacements of 0.4–0.5 mm. Fatigue tests on a selected mix at three stress levels demonstrate a progressive reduction in fatigue life with increasing stress, while a stiffness-based damage index varies linearly with normalised fatigue cycles. An exploratory crack mouth opening displacement-based fatigue failure criterion is proposed as an early-warning indicator and a potential performance-based fatigue design parameter for UHPC. The integrated static, fracture, and fatigue characterisation provides valuable insights for the broader adoption of cost-effective UHPC in structural applications.
V. et al. (Fri,) studied this question.