In situ synchrotron powder diffraction study of the setting reaction kinetics of magnesium-potassium phosphate cements. (January 2016)

• Record Type: Journal Article
• Authors: Viani, Alberto; Peréz-Estébanez, Marta; Pollastri, Simone; Gualtieri, Alessandro Francesco
• Is Part Of: Cement and concrete research. Volume 79(2016)
• Page Start: 344
• Page End: 352
• Publication Date: 2016-01
• Subjects: Kinetics (A). Reaction (A) -- X-Ray Diffraction (B) -- MgO (D) -- Chemically Bonded Ceramics (D); Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2015.10.007
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: This work reports a kinetic study of the formation of magnesium-potassium phosphate cements accomplished using in-situ synchrotron powder diffraction. The reaction: MgO + KH2 PO4 + 5H2 O → MgKPO4 · 6H2 O was followed in situ in the attempt of contributing to explain the overall mechanism and assess the influence of periclase (MgO) grain size and calcination temperature (1400-1600 °C) on the reaction kinetics. Numerical kinetic parameters for the setting reaction have been provided for the first time. The best fit to the kinetic data was obtained using a weighted nonlinear model fitting method with two kinetic equations, representing two consecutive, partially overlapping processes. MgO decomposition could be described by a first order (F1) model followed by a Jander diffusion (D3) controlled model. Crystallization of the product of reaction was modelled using an Avrami model (An ) followed by a first order (F1) chemical reaction. A reaction mechanism accounting for such results has been proposed.