Role of Fe-Bearing Component in Perlite-Based Geopolymer When Structural and Phase Transformations

Abstract

Normally, the component composition of building materials makes a significant contribution when formation of final performance properties of them. Moreover, new types of binding systems, in spite of their poor knowledge, this effect on the structural characteristics of final composites also takes place. In this work, perlite-based geopolymer binder as an example, was studied.
 In framework of the study, it was found that the application of grinding mill with a metal lining leads to the formation of Fe- milling yield, which is included into crushed raw materials (perlite) com-position.
 It was established that the particles of the resulting Fe- component are nanoscaled.
 The X-ray phase and chemical analyzes were used to determine the mechanism of the effect of the Fe- component on the properties of perlite-based geopolymer. 
 Microstructure of the hardened geopolymer paste were studied using SEM microscopy. Phase and mineral composition of geopolymer paste obtained by XRD-analysis showed, when the hardening process, nanosized iron hydroxide or bernalite Fe(OH)3(H2O)0.25 is formed in the geopolymer system, that is 5 times more than metallic iron. This is initiates the structure destruction and confirmed by the low values compressive strength of the geopolymer stone.
 Keywords: Fe-bearing component, metallic milling yield, geopolymer binder, friable structure, the Scherrer formula

The Correlation of Temperature-Mineral Phase Transformation as a Controlling Factor of Thermal and Mechanical Performance of Fly Ash-Based Alkali-Activated Binders

“…The results of XRF analysis demonstrated an elevated concentration of carbon, wherein the case of FA1 and FA2 ash products, those concentrations exceeded the limits regulated by ASTM C618. In previous research studies, the authors of [ 36 , 37 ] reported on the negative impact of unburned carbon as an inert component in a fly ash system, which resulted in poor alkali-activated binder structure formation, and therefore a reduction in strength performance.…”

“…Earlier studies [ 36 , 37 ] have shown that the use of milling equipment with metallic lining for dispersion fly ash powders resulted in milling yield in the form of Fe component. When Fe reacts with water during the alkali activation process, it turns into iron hydroxide Fe(OH) 2 with the volume 3–4.5 times larger than that of Fe.…”

Effect of Mixing Procedure and Chemical Composition on Physical and Mechanical Performance of Geopolymers

“…The presence of alkaline cations in aluminosilicate component allows avoiding the introduction of an additional amount alkaline activator or its reducing, saving relatively high compressive strength values (up to 37 MPa). In addition, the presence of Na + and K + cations in the structure of perlite explains the equally effective use of alkali NaOH and KOH as perlite based geopolymer activators [26].…”