# Fracture Behavior of Steel-Fiber-Reinforced High-Strength Self-Compacting Concrete: A Digital Image Correlation Analysis

## TL;DR

This study uses steel fibers to improve the fracture resistance of high-strength self-compacting concrete and analyzes the results using digital image correlation.

## Contribution

The study introduces a detailed analysis of steel fibers' impact on HSSCC's fracture behavior using digital image correlation.

## Key findings

- Steel fibers increased peak load, fracture toughness, and fracture energy significantly in HSSCC.
- A fracture process zone formed in steel-fiber-reinforced HSSCC, unlike in HSSCC without fibers.
- Optimal mechanical properties were achieved at 1.2 vol% steel fibers.

## Abstract

In this study, steel fibers were used to improve the mechanical properties of high-strength self-compacting concrete (HSSCC), and its effect on the fracture mechanical properties was investigated by a three-point bending test with notched beams. Coupled with the digital image correlation (DIC) technique, the fracture process of steel-fiber-reinforced HSSCC was analyzed to elucidate the reinforcing and fracture-resisting mechanisms of steel fibers. The results indicate that the compressive strength and flexural strength of HSSCC cured for 28 days exhibited an initial decrease and then an enhancement as the volume fraction (Vf) of steel fibers increased, whereas the flexural-to-compressive ratio linearly increased. All of them reached their maximum of 110.5 MPa, 11.8 MPa, and 1/9 at 1.2 vol% steel fibers, respectively. Steel fibers significantly improved the peak load (FP), peak opening displacement (CMODP), fracture toughness (KIC), and fracture energy (GF) of HSSCC. Compared with HSSCC without steel fibers (HSSCC-0), the FP, KIC, CMODP, and GF of HSSCC with 1.2 vol% (HSSCC-1.2) increased by 23.5%, 45.4%, 11.1 times, and 20.1 times, respectively. The horizontal displacement and horizontal strain of steel-fiber-reinforced HSSCC both increased significantly with an increasing Vf. HSSCC-0 experienced unstable fracture without the occurrence of a fracture process zone during the whole fracture damage, whereas the fracture process zone formed at the notched beam tip of HSSCC-1.2 at its initial loading stage and further extended upward in the beams of high-strength self-compacting concrete with a 0.6% volume fraction of steel fibers and HSSCC-1.2 as the load approaches and reaches the peak.