Composition and structure of an 18-year-old 5M KOH-activated ground granulated blast-furnace slag paste

The main hydration products were C-A-S-H(I), present in both inner (Ip) and outer product (Op), and a Mg-Al layered double hydroxide (LDH), present only in the Ip. The composition of C-A-S-H(I) was the same in Op and Ip. Reduced scatter in the data with age suggests a tendency towards compositional homogeneity. The mean length of the aluminosilicate anions in the C-A-S-H(I) increased with age. The layer spacings of the C-A-S-H(I) and Mg-Al LDH had not changed significantly with age. The Mg/Al ratio of the LDH was about 2.6 and had not changed between 1 and 18 years.