0000000001294192
AUTHOR
Hugo Lahalle
Investigation of magnesium phosphate cement hydration in diluted suspension and its retardation by boric acid
Abstract Magnesium phosphate cements (MPCs) are used for rapid repair works, but they may also offer prospects for the stabilization/solidification of deleterious waste. MPCs contain calcined magnesium oxide and a water-soluble acid phosphate, such as potassium dihydrogen phosphate (KH 2 PO 4 ). The main precipitated hydrate is then K-struvite (MgKPO 4 ·6H 2 O). This work aims at giving new insight into the processes involved in its formation. Since cement hydration is very rapid, the second objective is to understand how boric acid, a common admixture for field application, retards cement hydration. A multi-stage process is evidenced in diluted suspension: MgHPO 4 ·7H 2 O likely precipitat…
Conditioning metallic aluminum in magnesium phosphate cements
This work deals with the stabilization / solidification of radioactive waste using cement.More particularly, it aims at assessing the chemical compatibility between metallic aluminum and mortars based on magnesium phosphate cement. The physical and chemical processes leading to setting and hardening of the cement are first investigated. X-ray diffraction (XRD), thermogravimetry (TGA) and nuclear magnetic resonance spectroscopy (31P and11B MAS-NMR) arefirst used to characterize the solid phases formed during hydration, while inductively coupled plasma atomic emission spectroscopy analysis (ICP-AES), electrical conductimetry and pH measurementsprovide information on the pore solution composit…