Abstract
Electrochemical impedance spectroscopy has been employed to monitor hydration of strontium monoaluminate (SrAl2O4) cement. Other supported techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, thermal analysis (DSC–TG–EGA) and microcalorimetry were also used. In the impedance spectrum at 102 day on a 0.5 water/cement ratio paste, a large double depressed low-frequency arc, a single depressed arc at middle-frequency region and a small part of a large depressed arc at high-frequency region were discriminated. It was due to the specific phase composition and crystal phase content in the fully hardened cement paste. Hence, the new electrochemical equivalent model R1(C1(R2W1))(C2(R3W2))(C3(R4W3))(C4(R5W4)) was implemented and fitted to the experimental results of the fully hydrated and hardened SrAH cement paste. Various hydration products including crystalline Sr3AH6, and amorphous phases SrAH7 and AH3-gel were formed at an early age of hydration. At final hydration process, the main reaction products detected are the ones most thermodynamically stable, i.e. crystalline Sr3AH6 and Al(OH)3. The heat evolution of SrAl2O4 cement under different temperatures (20 °C and 40 °C) was examined by isothermal calorimetry. The curing temperature was found to have a visible effect on cement hydration kinetics.
Highlights
With the recent dynamic quest for developing sustainable ceramics, refractory materials and building materials, it has been found that there is a need for more advanced material characterization techniques that can provide valuable insight into the nature and fundamental behaviour of the new classes of cementitious materials as fast as they are becoming available
Mickiewicza 30, 30-059 Krakow, Poland. Examples of these novel techniques that have been recently used for cementitious material characterization include X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectroscopy (NMR), X-ray microtomography and atomic force and lateral force microscopy (AFM and LFM) [1,2,3] apart from the most commonly used in cement chemistry, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS)
The processes by which SrAH cement paste transforms from a viscous suspension through a rigid gel/solid into a fully hydrated solid must be understood if the performance of this cement-based materials is to be reliably predicted from electrochemical impedance spectroscopy (EIS) measurement
Summary
With the recent dynamic quest for developing sustainable ceramics, refractory materials and building materials, it has been found that there is a need for more advanced material characterization techniques that can provide valuable insight into the nature and fundamental behaviour of the new classes of cementitious materials as fast as they are becoming available. These methods can be implemented for understanding and predicting, for example, cement hydration kinetics, microstructure development and longterm performance of various cementitious systems. The unique EIS response of hydrating cement paste should be expected at each stage of reaction
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