Reaction mechanism of magnesium potassium phosphate cement with high magnesium-to-phosphate ratio. (June 2018)

• Record Type: Journal Article
• Authors: Xu, Biwan; Lothenbach, Barbara; Leemann, Andreas; Winnefeld, Frank
• Is Part Of: Cement and concrete research. Volume 108(2018)
• Page Start: 140
• Page End: 151
• Publication Date: 2018-06
• Subjects: Magnesium potassium phosphate (MKP) cement -- Reaction mechanism -- Magnesium-to-phosphate (Mg/PO4) molar ratio -- Water-to-solid ratio (w/s); Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2018.03.013
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: 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/PO4 ) 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/PO4 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, Mg2 KH(PO4 )2 ·15H2 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.