Characterizing two types of zonation within slag rims of aged alkali-activated slag pastes through SEM and TEM
Y. Zhang (Southeast University, TU Delft - Materials and Environment)
Shizhe Zhang (Renewi Mineralz & Water, TU Delft - Materials and Environment)
Chen Liu (TU Delft - Materials and Environment)
Oguzhan Çopuroğlu (TU Delft - Materials and Environment)
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Abstract
In this paper, the authors characterized two types of zonation within slag rims in aged alkali-activated slag (AAS) systems through SEM and TEM technology. These two elemental zonation were closely related to the pore structure of AAS pastes, thus providing strong implication for the transport- and durability-related performance of AAS systems. The first type of zonation occurred in the rims of AAS specimens under sealed curing. It was found that lath-like hydrotalcite-like phase accumulated near the boundary while a generally homogeneous and foil-like C-(N-)A-S-H gel phases precipitated in the following sub-zone. When slag rims were thick enough, a new Mg-rich region occurred. The second type of zonation was noticed in the carbonated AAS pastes. For this kind of distribution pattern, C-(N-)A-S-H gel phases were observed near the boundary. Following, the accumulation of Mg and Ca occurred alternatively. Additionally, transformation mechanism between these two types of zonation was also proposed.
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