Investigation of aluminum nitrate as a set retarder of magnesium potassium phosphate cement: Mechanisms involved in diluted suspension. (December 2021)

• Record Type: Journal Article
• Authors: Cau Dit Coumes, Céline; Rousselet, Angélique; Xu, Biwan; Mercier, Cyrille Albert; Gauffinet, Sandrine
• Is Part Of: Cement and concrete research. Volume 150(2021)
• Publication Date: 2021-12
• Subjects: Magnesium potassium phosphate cement -- Aluminum nitrate -- Hydration -- Thermodynamic modelling; Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2021.106608
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: In this study, the influence of aluminum nitrate on the hydration process of magnesium potassium phosphate (MKP) cement was investigated experimentally and through thermodynamic modelling using diluted systems with Mg/PO4 molar ratio and water-to-cement ratio of 1 and 100 respectively. Three processes contributed to retard cement hydration: the acidic nature of aluminum nitrate which reduced the initial pH of the solution by two units, the early precipitation of a taranakite-like amorphous potassium aluminophosphate, which reduced the aqueous phosphate and potassium concentrations, and a salt effect due to the presence of soluble nitrate. Precipitation of potassium-containing magnesium phosphate hydrates, like Mg2 KH(PO4 )2 ⋅15H2 O and K-struvite, was prohibited, whereas precipitation of newberyite and cattiite was delayed. Furthermore, the modelled phase development with ongoing cement hydration agreed rather well with the experimental findings.