Effects of matrix rheological properties on the distribution of steel fibers in concrete

Abstract

Steel fiber-reinforced concrete (SFRC) has emerged as a prominent construction material owing to its superior resistance to cracking and impact. The spatial distribution of steel fibers, governed by the rheological properties of the mortar, exerts a critical influence on the toughening efficiency and crack resistance of SFRC. In this study, seven types of cement mortars with various rheological properties and corresponding SFRCs were prepared and investigated to the effect of mortar rheology on fiber dispersion and spatial distribution. Quantitative correlations were established between the rheological properties and two-dimensional (2D) fiber dispersion indicators, including the fiber distribution coefficient (α), orientation coefficient (φ), and effective utilization rate (η). Additionally, the effect of these indicators on the mechanical performance of SFRC was quantified. The spatial distribution characteristics were subsequently analyzed using X-ray computed tomography (CT) with three-dimensional (3D) reconstruction of steel fibers. The results indicated that both φ and η attained peak values when the mortar’s yield stress ranged between 40.00 and 60.00 MPa and its plastic viscosity was within 0.40 to 0.60 Pa·s. Optimal fiber orientation coefficient (α = 0.90–0.92) and effective utilization rate (φ = 0.70–0.75) can enhance the compressive strength of SFRC to 33.6 MPa. The probability distributions of fiber distance r and angle θ followed normal distributions, while the angle φ conformed to an exponential distribution. This study contributes to optimizing the SFRC mixture design and enhancing fiber utilization, while the proposed fiber spatial distribution models serve as input for mesomechanical modeling of SFRC, thereby enabling the simulation of its anisotropic behavior governed by rheological properties.