• Mechanical optimization of wollastonite content is systematically clarified. • Three-stage dynamic behavior of alkali-activation modulus is revealed. • Modular effects on fracture mechanisms are quantified. • Modulus optimization criteria are proposed for high-performance materials. For the ambiguity surrounding the dynamic mechanical properties and microstructural evolution mechanisms of Magnesium Oxychloride Cement-Wollastonite Powder (MOC-WSP) materials in engineering applications, which results in a scarcity of experimental support for their formulation and structural design, this study conducted a systematic evaluation of these properties and mechanisms. The approach involved integrating an electromagnetic-driven Split Hopkinson Pressure Bar (SHPB) apparatus with high-speed camera technology (DIC), complemented by XRD and SEM analyses. By testing parameters such as dynamic peak stress, strain, Dynamic Increase Factor (DIF), elastic modulus, and energy dissipation under varying wollastonite powder contents (10%-40%) and alkali activation moduli (0-1.4), and combining these with static flexural and compressive strength tests, the study analyzed the material's dynamic characteristics and fracture mechanisms. Results show that a 30% wollastonite powder content yielded the optimal mechanical properties, significantly enhancing both static and dynamic strengths. When the alkali activation modulus was set to 1.0, the material exhibited the highest peak stress, excellent stress absorption, and energy dissipation capabilities, along with a notable acceleration of cement hydration reactions, XRD and SEM further indicate that the dominant MOC phase 5·1·8 and the C-(A)-S-H gel cooperatively form a gel-crystal skeleton that bridges pores and locks particles, underpinning the strength gain. This research clarify the correlation between wollastonite powder content and alkali-activation modulus, dynamic mechanical indices and microstructural features of MOC-WSP materials and offers crucial references for the formulation and structural design of magnesium oxychloride cement-based composites.
Wang et al. (Wed,) studied this question.