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Metakaolin-driven optimization of magnesium phosphate cement: Mechanical properties, durability, and microstructural evolution under aggressive environments

par Zhu, Jingtao;Snoeck, Didier ;Gu, Linlin;Zheng, Hao;Jiang, Song;Chen, Bing;Li, Desheng
Référence Construction & building materials, 497, page (143893)
Publication Publié, 2025-10-31

Article révisé par les pairs

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Résumé :

Magnesium phosphate cement (MPC) exhibits rapid setting and high early strength but suffers from limited durability under extreme environments. This study investigates the effect of metakaolin (MK) incorporation on the mechanical performance and microstructural evolution of MPC under low-temperature, salt freeze-thaw, and solution immersion conditions. Mechanical tests, including flexural, compressive, bond strength, and Vickers microhardness evaluations, were conducted, complemented by durability assessments after salt freeze-thaw cycling and immersion in deionized water, NaCl, and MgSO4 solutions. Microstructural characterization was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS). Results demonstrate that moderate MK incorporation significantly (p < 0.05) enhances mechanical properties and durability, with 10 % MK providing optimal strength and structural stability. MK addition refines hydration product distribution, promotes the formation of continuous silicoaluminophosphate gel networks, and densifies the interfacial transition zone (ITZ). The M5 and M10 groups exhibited superior strength retention under deionized water and NaCl immersion, while excessive MK (15 %) led to performance deterioration, particularly under sulfate attack. These findings highlight the potential of MK to improve the long-term durability and microstructural integrity of MPC systems in harsh environments.