Corrosion of aluminium and magnesium in BFS composite cements

Abstract

Legacy radioactive wastes arising from reprocessing of nuclear fuels in the UK are classified as intermediate level waste (ILW), which contain things such as aluminium and magnesium. Blast furnace slag (BFS) composite cements are used to encapsulate ILW. These cements have a high pH which is advantageous to limit the mobility of some of the radioactive species but can cause corrosion of metals. The present paper describes some fundamental aspects of corrosion of aluminium and magnesium in BFS composite cements.

The corrosion of aluminium produced an interface between aluminium and cement which was porous with a series of zones containing bayerite (Al(OH)₃) and strätlingite (2CaO.Al₂O₃.SiO₂.8H₂O). With magnesium, the main corrosion product was found to be brucite (Mg(OH)₂) and the porous zone was less pronounced. The hydration of the bulk cement did not appear to be affected by the corrosion of these metals.

Keywords:

• BAYERITE
• STRATLINGITE
• CORROSION
• CEMENT
• BRUCITE