Dynamic mechanical behavior of magnesium oxysulfate-based titanogypsum foamed concrete: A macro- and meso-scale investigation

To address environmental pollution caused by the industrial byproduct titanogypsum (TG), a novel composite material of magnesium oxysulfate (MOS)-based titanogypsum (TG-MOS) foam concrete was fabricated using MOS foam cement as the matrix and TG as an additive. The dynamic mechanical properties of TG-MOS foam concrete with varying TG contents (0%, 2%, 4%, 6%, 8%, 10%) were investigated using an electromagnetic Split Hopkinson Pressure Bar (SHPB) system. From macro- and meso-scale perspectives, combined with high-speed photography of specimen failure processes, the structural characteristics, phase composition characteristics, fragment morphology, energy evolution, and constitutive models of TG-MOS foam concrete were analyzed. Results showed that the dynamic mechanical performance of TG-MOS foam concrete exhibited significant strain rate effects and TG content dependence. The dynamic mechanical properties were jointly determined by pore structure and matrix properties, with complex micro-meso features and strong discreteness. Post-impact specimens exhibited compressive failure modes, with fractal dimensions of fragment particles ranging from 1.01 to 1.92, indicating that overall damage was correlated with TG content and strain rate. Energy absorption capacity was positively related to strain rate, demonstrating enhanced energy dissipation mechanisms and plastic deformation ability. The dissipated energy ratio (ratio of dissipated energy to incident energy) reached 46.5% at 10% TG content. A dynamic damage constitutive equation is proposed for TG-MOS. These findings provide theoretical guidance for the engineering application of TG-MOS foam concrete.