Quantitative analysis of C-(K)-A-S-H-amount and hydrotalcite phase content in finely ground highly alkali-activated slag/silica fume blended cementitious material

For the development of CO2-reduced binders for structural engineering and for predicting their performance, knowledge of the amount formed in weight fractions of the reaction products is essential. This paper presents a method to specify the hydration products of an alkali-activated slag/silica fume blended cementitious material by weight. The 29Si and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy to determine the C-A-S-H phases was coupled with energy dispersive analysis (EDX) technology to determine the bound K/Si ratio. Furthermore, the 27Al MAS NMR was used to define the amount of hydrotalcite. With the help of the developed model, the hydration phases of alkali-activated slag/silica fume blended cementitious material in dependency of the activator can be calculated. The results of the mass ratios deduced by NMR with coupled EDX was in agreement with the loss of ignition measured by thermogravimetric analysis (TGA). Consequently, the hydration products can be self-checked.