The Inhibition of Aluminium Corrosion in OPC Based Composite Cements

The suitability of a supersulfated cement for nuclear waste immobilisation

“…The intensities of the reflections for ettringite were greater than those for bayerite. When these data are compared with similar results obtained from encapsulating aluminium metal in a 9:1 BFS:OPC [18,23], it is seen that the relative intensities of the bayerite/ettringite reflections in the SSC samples were significantly lower than those in the BFS:OPC samples. This suggests that the quantity of bayerite formed during corrosion of aluminium encapsulated in the SSC paste was less than in the BFS:OPC paste.…”

“…Other experiments performed by the authors investigating the generation of hydrogen in a 9:1 BFS:OPC system containing the same grade aluminium caused the lids of the polypots in which the samples were hydrating to burst open with the pressure of hydrogen generated within a few hours of hydration [18,23]. Photographs of the samples examined after hydrating for 28 days are shown in Fig.…”

“…Among these are sulfate activated slags, where, apart from CASAH, a significant amount of ettringite (a calcium aluminosulfate hydrate (Ca 6 Al 2 (OH) 12 (SO 4 ) 3 Á26H 2 O)) which contains a high quantity of water within its structure is formed and the pore solution pH is approximately 10.5-11 [21,22]. It has been reported that aluminium corrosion is limited in such a matrix, although further work is needed to confirm the reason for this [23]. A similar effect of limited aluminium corrosion has also been noted with calcium sulfoaluminate cement (CSA) [24] where ettringite is also the principal binder [25].…”

The potential for using slags activated with near neutral salts as immobilisation matrices for nuclear wastes containing reactive metals

“…The results indicated that the aluminium corrosion rate in SSC was much lower than that in PC and slightly lower than that in 9:1 BFS/PC when hydrated at either room temperature or 40°C. Work carried out by Collier et al [72], which investigated the effect on aluminium corrosion of using anhydrite and gypsum replacement levels of 10 and 20 wt.% in a 9:1 BFS/PC composite cement paste, also indicated that aluminium corrosion was reduced with the addition of anhydrite or gypsum. It should be noted that although anhydrite and gypsum were added as a replacement for the composite cement powders, the system formulated was similar to that of SSC.…”

“…SEM micrographs of the surface of the corroded aluminium strip encapsulated in 9:1 BFS/PC with no addition (upper) and 10 wt.% gypsum (lower) hydrated for 28 days[72].…”