Pressure-Induced Geopolymerization in Alkali-Activated Fly Ash

Abstract

The present study investigated geopolymerization in alkali-activated fly ash under elevated pressure conditions. The fly ash was activated using either sodium hydroxide or a combination of sodium silicate solution and sodium hydroxide, and was cured at 120 • C at a pressure of 0.22 MPa for the first 24 h. The pressure-induced evolution of the binder gel in the alkali-activated fly ash was investigated by employing synchrotron X-ray diffraction and solid-state 29 Si and 27 Al MAS NMR spectroscopy. The results showed that the reactivity of the raw fly ash and the growth of the zeolite crystals were significantly enhanced in the samples activated with sodium hydroxide. In contrast, the effects of the elevated pressure conditions were found to be less apparent in the samples activated with the sodium silicate solution. These results may have important implications for the binder design of geopolymers, since the crystallization of geopolymers relates highly to its long-term properties and functionality.

Multiscale micromechanical analysis of alkali-activated fly ash-slag paste

“…Both peaks at −93 and − 97 ppm are denoted as Q 4 (3Al) and assigned to the Al-rich N-A-S-H gels, which belong to the reactive and highly polymerised aluminate phases [62]. The Q 4 (2Al) and Q 4 (1Al) sites represent the more stable Si-rich N-A-S-H types gels, which are located at −103 and − 109 ppm, respectively [87]. Finally, The peak at −116 ppm is associated with the Q 4 (0Al) site that corresponds to the presence of crystalline phases including quartz, mullite and maghemite in the original fly ash [9,62,88].…”

The Effects of Calcium Aluminate Cement Substitution on Physicochemical Properties of Geopolymer–Zeolite Composites

“…Geopolymers, classified as low-Ca AAMs, mainly consist of highly cross-linked zeolite-like A c c e p t e d m a n u s c r i p t ACCEPTED MANUSCRIPT amorphous aluminosilicate gel (N-A-S-H type) [3,8]. This gel is the main strengthening constituent in geopolymers which has the tendency of converting to crystalline zeolites, specifically in high temperature conditions [9,10]. Zeolites have a large porous structure and are frequently used as adsorbents for various pollutants.…”

Mechanical Characteristics of Soda Residue Soil Incorporating Different Admixture: Reuse of Soda Residue

“…FA is a corrosive waste, and large amounts of fly ash pollute the local air and environment. The main chemical compositions of FA consist of silicon, aluminum, and iron oxides, and the lime content is less than 10% [25,28]. SR has positive effects on the early strength, good stability, and microstructure of the FA [29], and the mixture of SR and FA as the potential cement and engineering soil alternative for building material.…”