Effects of MXene on the hydration process, pore structure and mechanical performance of 3D-printed cementitious materials

This study investigates the influence of MXene on the hydration process, pore structure evolution, mechanical properties and printability of 3D-printed cementitious materials. Isothermal calorimetry, thermogravimetric analysis and mercury intrusion porosimetry were employed, together with compressive and flexural strength tests under different loading orientations and anisotropy assessment, to elucidate the multiscale mechanisms of MXene in 3D-printed cementitious materials. The results indicate that MXene incorporation markedly accelerates early hydration. The maximum hydration rate increased from 2.14 to 3.04 mW/g, accompanied by an earlier heat evolution peak and a 10.6–36.7% increase in cumulative heat release at 72 hours. The contents of chemically bound water and CH rose by approximately 21–49% and 19.4–45.6%, respectively. Meanwhile, the total porosity at 72 hours decreased by 15.5–24.4%, with the pore size distribution shifting toward finer pores. Mechanical performance exhibited a typical increase–decrease trend with dosage, and 0.06 wt.% was identified as the optimal content. At this level, the 3-day compressive and flexural strengths increased by 18.7% and 23.6%, respectively, while maintaining stable extrudability and satisfactory buildability. Overall, MXene enhances performance through heterogeneous nucleation-induced hydration acceleration, nano-filling-driven pore refinement and crack/interface regulation, whereas excessive addition leads to agglomeration and diminished effectiveness.