METHOD OF TREATING AN ALKALINE GRANULAR CARBONATABLE MATERIAL

摘要

The invention concerns a method of treating an alkaline granular carbonatable material which contains aluminium metal and which has in particular a pH of at least 10. The method comprises an oxidation step wherein at least a portion of said aluminium metal is oxidised by contact with moisture. The aluminium should be oxidised to avoid swelling problems when using the granular material as aggregate. In the method according to the invention this oxidation is accelerated by providing at least one oxidising agent in said moisture, which oxidising agent has a higher redox potential than the water contained in said moisture. The method further comprises a carbonation step wherein the granular carbonatable material is at least partially carbonated to lower the pH thereof. In this way the formation of etthngite, which may also release aluminium ions which causing further swelling problems, can be avoided in the granular material or any ettringite present therein can be destabilised.