Investigation on the spalling failure of concrete under high strain rate loading by simulation and experimental method

Abstract

This study investigates the dynamic tensile failure mechanisms, namely spalling, and strength evaluation of concrete under high-strain-rate loading. Spalling occurs during one-dimensional stress wave propagation when a reflected tensile pulse superposes with the incident compressive wave. Utilizing a modified split Hopkinson pressure bar (SHPB) combined with the digital image correlation (DIC) and finite element modeling (FEM), we analyze the spalling process. Results reveal three distinct failure phases: (1) compression-rebound, (2) tensile stress development, and (3) fracture. Spalling duration decreases inversely with impact velocity. Critical parameters—initial fracture velocity, maximum tensile strain, and strain rate—show minimal sensitivity to velocity variations within the tested ranges. Dynamic tensile strength, determined via free-surface velocity rebound and dynamic stress-strain relationships, yielded consistent results validated by FEM simulations. The dynamic increase factor (DIF) for tensile strength ranged from 3.20 to 3.39 at strain rates of 13.00 s⁻¹ to 14.41 s⁻¹. While the Karagozian and Case (K&C) constitutive model predicted first crack locations, its ability to simulate subsequent crack patterns was limited due to concrete's inherent mesoscopic and microscopic heterogeneity. The findings of this paper enhance the understanding of concrete's dynamic tensile response and provide a basis for designing protective structures against blast and impact loads.