Leaching of magnesium potassium phosphate cement pastes under alkaline conditions - Archive ouverte HAL Access content directly
Journal Articles Applied Geochemistry Year : 2024

Leaching of magnesium potassium phosphate cement pastes under alkaline conditions

Lixiviation des pâtes de ciment à base de phosphate de magnésium et de potassium dans des conditions alcalines

Abstract

Some legacy radioactive waste containing aluminum (Al) metal need to be stabilized and solidified before their final disposal. Currently, Portland cement (PC) is extensively used for conditioning low- or intermediate-level radioactive waste. However, the high alkalinity of PC leads to strong corrosion of Al metal, which is associated with significant dihydrogen release. Therefore, it is important to investigate alternative binders that show better chemical compatibility with Al metal. Magnesium potassium phosphate cements (MKPCs), comprising equimolar amounts of MgO and KH$_2$PO$_4$, are interesting candidates since their pore solution pH may fall within the passivation domain of Al metal. The understanding of their long-term durability, especially under alkaline conditions, is however incomplete. Hence, MKPC paste samples (with fly ash as a filler) were submitted to semi-dynamic leaching tests using an alkaline solution under well-controlled conditions. The leachates were analyzed over time using ICP-AES, and the leached solids were characterized by XRD, SEM/EDS, and $^{31}$P MAS-NMR spectroscopy. Leaching induced a decrease in the content of crystalline K-struvite (MgKPO$_4$·6H$_2$O), the main hydrate of the paste samples, as well as the precipitation of calcium-deficient hydroxyapatite (CDHA), brucite (Mg(OH)$_2$) and possibly magnesium silicate hydrates, OH-LDH or PO4-LDH phases. The experimental data were then used as an input for numerical simulations using the reactive transport code HYTEC.
Fichier principal
Vignette du fichier
version alpha.pdf (2.59 Mo) Télécharger le fichier
Origin Files produced by the author(s)

Dates and versions

hal-04609800 , version 1 (12-06-2024)

Identifiers

Cite

Laura Diaz Caselles, Céline Cau Dit Coumes, Pascal Antonucci, Angélique Rousselet, Adel Mesbah, et al.. Leaching of magnesium potassium phosphate cement pastes under alkaline conditions. Applied Geochemistry, 2024, 170, pp.106067. ⟨10.1016/j.apgeochem.2024.106067⟩. ⟨hal-04609800⟩
20 View
2 Download

Altmetric

Share

Gmail Mastodon Facebook X LinkedIn More