Modified Brazilian Test for studying crack initiation and fracture behavior in SFRC using DIC & AE

This study presents a Modified Brazilian Test (MBT) designed to achieve stable and reliable indirect tensile characterization of Steel Fiber-Reinforced Concrete (SFRC) and Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC). The proposed configuration uses a T-shaped loading fixture with a hinge-based alignment mechanism to minimize eccentricity and promote uniform stress transfer, enabling central crack initiation without notches. Digital Image Correlation (DIC) and Acoustic Emission (AE) techniques were integrated to capture full-field strain localization and internal damage evolution. Experiments showed consistent crack initiation at a true strain of approximately 0.2% and at 52%–64% of peak load, evidencing the stabilizing role of steel fibers. The MBT demonstrated low scatter and high repeatability across specimens. A finite element model combining the Crack Band approach with Concrete Damaged Plasticity reproduced the load response, strain localization, and tensile damage patterns, supporting the interpretation of fracture mechanisms. The combined experimental–numerical framework provides a robust and practical methodology for assessing tensile behavior and fracture processes in fiber-reinforced concretes and for improving the reliability of indirect tensile testing configurations. • A Modified Brazilian Test (MBT) was developed for SFRC and UHPFRC. • The setup promotes stable central cracking without specimen notching. • DIC and AE enabled full-field and internal damage monitoring. • Crack initiation occurred at about 0.2% strain and 52-64% of peak load. • Numerical simulations reproduced load response and damage localization.