Experimental and numerical investigation of minimum required fiber content in bending characteristics of 100 MPa UHPC-formulated concrete

Abstract

The present study investigates the lowest possible amount of steel and polypropylene fibers in improving the compressive and flexural strength, stiffness, and energy capacity of high strength 100 MPa concrete with a mix design similar to that of Ultra-High Performance Concrete (UHPC). Twenty-eight 100 × 200 mm cylindrical specimens with 0%, 0.2%, 0.4%, and 0.6% volumetric percentage of short steel fibers and polypropylene fibers were fabricated, which were at the lowest predicted percentages with respect to fiber content recommended in the literature. To assess the flexural performance of fiber-reinforced concrete panels, specimens with dimensions of 200 × 600 × 20 mm were made with the same steel and polypropylene fiber contents as cylindrical specimens. For each fiber percentage in flexural panels, two steel fiber and two polypropylene fiber specimens were tested under a three-point bending procedure. Results demonstrated the lowest fiber amount for compressive specimens and flexural panels. Fiber content as low as 0.2% for steel and 0.4% for PP can enhance both the strength and energy absorption capacity of the flexural panels. In addition, a formulation was proposed for estimating the concrete modulus of rupture based on experimental data. In the end, panels were modeled using ABAQUS software, and results were compared with test results. In the end, panels were modeled using ABAQUS software and results were compared with test results. The numerical predictions were in compliance with experimental observations and showed the stress distribution variations with respect to change in fiber type and percentage.