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. 2024 Mar 1;17(5):1151.
doi: 10.3390/ma17051151.

Effect of K+ Diffusion on Hydration of Magnesium Potassium Phosphate Cement with Different Mg/P Ratios: Experiments and Molecular Dynamics Simulation Calculations

Difei Leng  1 , Qiuyan Fu  1 , Yunlu Ge  1 , Chenhao He  1 , Yang Lv  1 , Xiangguo Li  1
Affiliations

Effect of K+ Diffusion on Hydration of Magnesium Potassium Phosphate Cement with Different Mg/P Ratios: Experiments and Molecular Dynamics Simulation Calculations

Difei Leng et al. Materials (Basel). .

Abstract

Magnesium potassium phosphate cement (MKPC) is formed on the basis of acid-base reaction between dead burnt MgO and KH2PO4 in aqueous solution with K-struvite as the main cementitious phase. Due to the unique characteristics of these cements, they are suitable for special applications, especially the immobilization of radioactive metal cations and road repair projects at low temperature. However, there are few articles about the hydration mechanism of MKPC. In this study, the types, proportions and formation mechanism of MKPC crystalline phases under different magnesium to phosphorus (Mg/P) ratios were studied by means of AAS, ICP-OES, SEM, EDS and XRD refinement methods. Corresponding MD simulation works were used to explain the hydration mechanism. This study highlights the fact that crystalline phases distribution of MKPC could be adjusted and controlled by different Mg/P ratios for the design of the MKPC, and the key factor is the kinetic of K+.

Keywords: K-struvite; diffusion kinetics of K+; magnesium potassium phosphate cement; newberyite.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
PSD, BET surface area and Langmuir Surface Area of dead burnt MgO.
Figure 2
Figure 2
Initial distribution of ions in MD models.
Figure 3
Figure 3
pH of solution of MKPC systems.
Figure 4
Figure 4
Possible effect of pH on K-struvite formation in MKPC systems.
Figure 5
Figure 5
The effect of K+ diffusion on the hydration of MKPC. On the left side, the K+ diffuses weakly; thus, it is more likely to form newberyite. On the right side, the K+ has a high degree of diffusion and could spread smoothly on the MgO surface, so it is easier to form K-struvite.
Figure 6
Figure 6
X-ray diffraction patterns for (a) MP1, (b) MP3, (c) MP5, (d) MP7.
Figure 7
Figure 7
Rietveld XRD refinement: mineral phase population (%) of hydration products of MKPC.
Figure 8
Figure 8
SEM and EDS analyses of MKPC hydration products for (a) MP1, (b) MP3, (c) MP5, (d) MP7.
Figure 8
Figure 8
SEM and EDS analyses of MKPC hydration products for (a) MP1, (b) MP3, (c) MP5, (d) MP7.
Figure 9
Figure 9
Flash pictures of MD simulation process. Please refer to the movie attachment for detailed video animation.
Figure 10
Figure 10
The number density distribution charts with Mg/P of 1, 3, 5.
Figure 11
Figure 11
Four parts model: Mg/P, principal crystalline phases and decisive factors.
Figure 12
Figure 12
The function between Mg/P and population of minerals (%).
See this image and copyright information in PMC

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