Use of micro-Raman spectroscopy to study reaction kinetics in blended white cement pastes containing metakaolin

Curing temperature is known to play an important role in the formation, development, and stability of the hydrated phases appearing during pozzolanic reactions (chemical reaction between puzzolanic addition, metakaolin (MK), and calcium hydroxide from cement hydration). A typical example of this important reaction is to be found in meta kaolin-bearing cement pastes, characterized by hexagonal phases whose thermodynamic stability declines with rising temperature. These phases cannot be exhaustively researched with traditional techniques (such as X-ray diffraction) due to their poor crystallinity. Consequently, micro-Raman spectroscopy was used in the present study to explore the behavior of white cement paste blends containing 0, 10, and 25% MK at two curing temperatures (20 and 60 degrees C). This led to the identification, for the first time using Raman spectroscopy, of phases C(2)ASH(8)(1) (stratlingite) and C(3)ASH(6), which appear in the MK-white cement reaction. The C-S-H gel formed was characterized by Q(1) dimers and a C/S ratio of 1.3-1.5. Raising the curing temperature favored the formation of C(4)AH(13).Copyright (C) 2009 John Wiley & Sons, Ltd.