Reaction mechanism of magnesium potassium phosphate cement with high magnesium-to-phosphate ratio

Journal Article · Fri Jun 15 04:00:00 EDT 2018 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2018.03.013· OSTI ID:22806496

Xu, Biwan; Lothenbach, Barbara; Leemann, Andreas; Winnefeld, Frank ^[1]

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1. Laboratory for Concrete & Construction Chemistry, Swiss Federal Laboratories for Materials Science and Technology (Empa), 8600 Dübendorf (Switzerland)

Understanding reaction mechanisms of magnesium potassium phosphate (MKP) cement is of significant importance, as it is closely related to the optimum design of MKP cement-based materials. In this study, reaction mechanisms of MKP cements with a high magnesium-to-phosphate (Mg/PO{sub 4}) molar ratio of 8 were investigated at two different water-to-solid (w/s) ratios of 0.5 and 5. The experimental findings show that the use of this high Mg/PO{sub 4} molar ratio suppresses the formation of potassium-free magnesium phosphate hydrates. K-struvite is mainly formed with probably more phosphate than the theoretical value. Moreover, the w/s ratio plays a crucial role on governing the reaction path of MKP cements. The lower w/s ratio (w/s = 0.5) leads to higher potassium concentration and pH value, thus suppressing the formation of intermediate product, Mg{sub 2}KH(PO{sub 4}){sub 2}·15H{sub 2}O, which is formed at the higher w/s = 5. However, it causes the formation of minor amount of brucite at 28 d, which coexists with K-struvite in the paste.

• OSTI ID: 22806496
• Journal Information: Cement and Concrete Research, Journal Name: Cement and Concrete Research Vol. 108; ISSN 0008-8846; ISSN CCNRAI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CEMENTS
CONCENTRATION RATIO
HYDRATES
MAGNESIUM PHOSPHATES
PH VALUE
POTASSIUM PHOSPHATES
REACTION KINETICS
SOLIDS
WATER