Investigation of damage mechanism of sawdust-magnesium oxychloride cement composites under uniaxial compressive load using AE and DIC techniques

As a novel building material, sawdust-magnesium oxychloride cement composites (SMOCC) provide a sustainable solution for the construction industry with low-carbon and environmentally friendly benefits. To enhance its applicability in load-bearing structures for low-rise buildings, it is crucial to conduct comprehensive research on its damage evolution and crack development under uniaxial compression tests. This study examines various strain rates and sawdust content as experimental variables to cross-validate and analyze the damage mechanisms of SMOCC using energy evolution, acoustic emission (AE), and digital imaging techniques (DIC). Additionally, a Gaussian mixture model-support vector machine (GMM-SVM) method is utilized to achieve precise quantitative assessment of crack type ratios, and the mercury intrusion porosimetry (MIP) and the scanning electron microscopy (SEM) tests are employed to evaluate the impact of sawdust on SMOCC. The results indicate that an increased strain rate significantly enhances the peak stress of SMOCC, while the reduction in peak strain increases the likelihood of brittle failure. Conversely, increasing the sawdust content leads to the opposite effect. The early dissipation energy of SMOCC decreases with higher strain rates but rises with increased sawdust content. The GMM-SVM analysis effectively quantifies the proportion of crack types during loading and, alongside DIC strain cloud maps, elucidates the crack extension process. Furthermore, MIP and SEM analyses reveal that SMOCC with 75 % sawdust content exhibits a smaller peak pore size and stronger internal bonding, enhancing crack resistance and ductility at high strain rates (10⁻³s⁻¹). Finally, Pearson correlation analysis reveals negative correlations between strain rates and sawdust content with the percentage of tensile cracks. © 2025 Elsevier Ltd