Early Age Microstructural Transformations of an Inorganic Polymer Made of Fayalite Slag

Abstract

Three types of binders were investigated by combining a water granulated fayalite slag and three different activating solutions (NaOH, SH; Na-silicate, SS; and a 1:1 mixture of the two, SH + SS). A reactivity test proved that the slag dissolves in the alkaline environment, releasing both Si and Al. Through rheological measurements it was found that the most alkaline solution (SH) led to a very fast structure build-up, followed by the activating solution SS+SH; when SS was used, the storage modulus did not increase even after 2 h. A similar trend was observed by calorimetry, where the paste with SH resulted in heat release within minutes, followed by SH + SS. These transformations were also followed by in situ ATR-FTIR, indicating changes in the vibrational bands attributed to asymmetric stretching vibration of [SiO 4 ] with 3 or 4 NBO/Si. In the case of the sample activated with SH, a new band appeared after 96 h and continued to increase in intensity at later times. For SS + SH activating solution, a new band appeared after 96 h, increasing over time, whereas the originally present band at 940 cm -1 became more distinct. For the sample with only SS, no vibrational changes were detected after 24 h. In conclusion, the fayalite slag is a reactive material that can undergo microstructural changes toward new reaction products, with the choice of the activating solution being a crucial factor in the process.

Inorganic polymers made of fayalite slag: On the microstructure and behavior of Fe

“…The fayalite slag shows a similar chemical and mineralogical composition as in previous works, Tables and , respectively. A lower FeO and slightly higher SiO 2 , ZnO, and Al 2 O 3 contents are observed.…”

“…The microstructure of the slag was the same as presented in previous work . The exact composition of the amorphous fraction is important for the calculation of the composition of the resulting binder, as this is the most reactive phase .…”

“…The mineralogical composition of the slag and IP samples was determined by quantitative X‐ray powder diffraction (QXRPD) analysis using a Siemens D500 diffractometer. For the QXRPD preparation, 10 wt% of analytical grade crystalline Al 2 O 3 was added as internal standard and the procedure followed was identical to that previously published, using Rietveld refinement . The particle size distribution of the slag was determined by laser scattering on a Malvern Mastersizer Micro Plus analyzer, to control if the slag reached the desired fineness after milling.…”

A Proposal for a 100 % Use of Bauxite Residue Towards Inorganic Polymer Mortar

“…Other iron-rich precursor materials, for example copper [23], lead [24], or ferro-nickel slags [25,26], have shown already a potential for the synthesis of inorganic polymers and the reuse of industrial wastes. Characteristics include, among others, a partially vitrified structure and ferrous iron [27].…”

“…This takes place preferentially in the interface between BR and quartz grains [5] in view of the locally established eutectics. The chemistry of BR is in fact located in the FeO-Al 2 O 3 -CaO-SiO 2 domain and semivitreous precursors can be formed from such compositions that are prone to form inorganic polymers [23,27].…”