Effects of Na2O/SiO2 molar ratio on properties of aggregate-paste interphase in fly ash-based geopolymer mixtures through multiscale measurements

Effect of SiO2, Al2O3 and Na2O content and fly ash fineness on the structure and mechanical properties of fly ash based geopolymer

“…Geopolymer with higher Na2O/SiO2 ratio showed higher compressive strength and more compact structure. Khedmati et al (2018) received similar results. They found that the higher Na2O/SiO2 molar ratio showed more N-A-S-H (sodium aluminosilicate hydrate) gel formation, which increased the bonding strength between the geopolymer binder and the aggregate.…”

“…However, geopolymers with Si/Al ≥ 3 showed worse chemical stability than those with Si/Al ≤ 2.5, with the presence of efflorescence on the surface, which was attributed to their higher residual free K + . Several studies (Criado et al, 2007;Silva and Crenstil, 2008;Vargas et al, 2011;Tchakoute et al, 2013;Bignozzi et al, 2014;Gao et al, 2014;Khedmati et al, 2018) have reported that, in addition to SiO2/Al2O3 molar ratio, the Na2O/SiO2 and Al2O3/Na2O ratios also play an important role in the morphological, microstructural, and mechanical properties of fly ash based geopolymer. Vargas et al (2011) investigated the influence of different Na2O/SiO2 molar ratio, curing temperature and age on the mechanical and microstructural properties of fly ash based geopolymers.…”

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

“…The residual fly ash particles have the highest elastic modulus and hardness, followed by reaction products (N-A-S-H gels) and pores [29][30][31][32]. The elastic modulus of N-A-S-H gels in AAF is stable at around [16][17][18] GPa, independent of the curing procedure and the molar ratio of alkaline activator [29][30][31]. In regard to AAS, the unreacted slag exhibits the highest hardness and elastic modulus, attributing to the crystalline impurities [12,23].…”

Fly Ash Particle Size Effect on Pore Structure and Strength of Fly Ash Foamed Geopolymer

“…On the other hand, because of its advantages like good thermal insulation, light weight, and low cost [4,5], FLA has been widely used in some architectural elds like nonbearing wall construction, bathroom back lling and as functional materials such as thermal insulation material, sound-insulation material, and so on [6,7]. Apart from being used in the traditional building elds, FLA has been applied in di erent areas as a good raw material for the preparation of geopolymer [8][9][10][11][12]. For example, to prove the possibility of in-situ resource utilization of FLA, there are a good many scholars having done plenty of basic studies on this aspect [13][14][15], among which there is one proposing that y ash foamed geopolymer (FAFG) as back lling material can be an excellent combination of y ash consumption and coal mine re prevention [16,17].…”