LUO J J，ZHANG C，LIU S H, et al． Effect of NaH2PO4 on the carbonation and hardening properties of magnesium slag [J]. Journal of Henan Polytechnic University( Natural Science) ，

doi: 10.16186/j.cnki.1673-9787. 2024110024

Received： 2023-12-22

Revised： 2024-01-20

Online： 2026-07-20

Effect of NaH₂PO₄ on the carbonation and hardening properties of magnesium slag (Online)

Luo Jingjing1,2，Zhang Cheng1,2，Liu Songhui3，Zhang Yuyang1,2，Tang Xiaosong1,2，Shi Xingxiang1,2，Song Qiulei1,2

1. Suzhou Concrete and Cement Products Research Institude Co., Ltd., Suzhou 215004, China; 2.jiangsu High DurabilityConcrete Engineering Technology Research Center, Suzhou 215004, China; 3. School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Abstract: Objectives The physical and chemical properties, activation methods, and application pathways of magnesium slag were extensively studied. Among these, the carbon reduction and volume stability issues were solved by carbonation curing while expanding the application. This study aimed to enhance the carbonation reactivity of magnesium slag and elucidate the mechanisms behind this enhancement. Methods The effect of different NaH2PO4 concentrations on magnesium slag carbonation activity and mechanical properties was investigated. The phase composition, microstructure, and pore structure of carbonation products were analyzed using X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM-EDS), and low-field nuclear magnetic resonance (LF-NMR) testing. Results The results showed that the introduction of NaH2PO4 improved the carbonation reactivity and mechanical properties of magnesium slag. After 24 hours of carbonation, the compressive strengths of the five mixtures were 70 MPa, 74.6 MPa, 81.9 MPa, 92.2 MPa, and 81.8 MPa, respectively. Compared to the control group, the optimal 1.5 mol/L NaH₂PO₄ concentration increased the compressive strength and CO₂ uptake by 30.9% and 24.1%, respectively. Calcite and aragonite, along with highly polymerized silica gel, were primarily formed after carbonation. The crystal morphology of calcium carbonate changed from rod-shaped and cubic to spherical particles with NaH2PO4 addition. The microstructure and pore structure analysis showed that spherical calcium carbonate and highly polymerized silica gel densified the microstructure, reducing the porosity. This densification was the primary reason for the improved mechanical properties with the addition of NaH2PO4. Conclusions This study provided a new method to enhance the carbonation reactivity of magnesium slag. The preparation of carbon-sequestering building materials using magnesium slag demonstrated cost-effectiveness and excellent performance, laying the foundation for large-scale utilization of magnesium slag.

Key words: magnesium slag; carbonation curing; NaH₂PO₄; mechanical property