HYDROGARNET FORMATION DURING AUTOCLAVING AT 180-DEGREES-C IN UNSTIRRED METAKAOLIN-LIME-QUARTZ SLURRIES

Autoclaved metakaolin-lime-quartz slurries with Ca/(Si+Al) composition of 0.8 and Al(Si + Al) ratios between 0.03 and 0.38 were investigated . Hydrogarnet was always among the first phases formed and invariably appeared before 11 Angstrom tobermorite. With increasing reaction time for Al/(Si + Al) ratios less than or equal to 0.13, the amount of hyd rogarnet decreased and finally disappeared while 11 Angstrom tobermori te increased concurrently. For Al/(Si + Al) ratios > 0.13, hydrogarnet coexisted with 11 Angstrom tobermorite after 4 h and beyond. Thus, in the presence of aluminous additives, hydrogarnet formation appears to play a more significant role in relation to 11 Angstrom tobermorite f ormation than was thought previously. Increasing addition of metakaoli n retarded the lime-quartz reaction, while enhancing the initial C-S-H formation. (C) 1998 Elsevier Science Ltd