Studying the compressive, tensile and flexural properties of binary and ternary fiber-reinforced UHPC using experimental, numerical and multi-target digital image correlation methods

Compressive, tensile, and flexural properties of ultra-high-performance concrete (UHPFRC) specimens were studied in this research. Binary and ternary combinations of micro steel (MS), round crimped (RC), crimped (C), hooked-end (H), and polypropylene (PP) fibers were used in overall ratios of 2 % by volume of concrete. For this purpose, 100 × 200 mm cylindrical specimens, dog-bone specimens (length: 330 mm, width: 80 mm, thickness: 40 mm), and prismatic beams with a dimension of 100 × 100 × 500 mm (clear span: 450 mm) were cast and tested under compressive, tensile, and four-point bending tests (4PBT). A digital image correlation (DIC)-based method namely, multi-target digital image correlation (MT-DIC) was used to record the displacement and deflection values in tension and flexure tests. Furthermore, experimental findings were used in numerical simulations and additional analyses were carried out as complementary studies to provide a better understanding of the governing parameters; length, width, depth, and overall size of the beams. Results revealed that a hybrid combination of micro and macro steel fibers performs better than other specimens in all the investigated parameters and the MT-DIC method proved to be a very useful tool in capturing the displacement and deflection values. Furthermore, the inverse analysis approach for the numerical simulation of beams and nonlinear regression-based models captured the direct tension and flexural results with coefficient of determination (R2) values above 0.90.