The influence of CO₂ accelerated carbonation on alkali‐activated fly ash cement under elevated temperature and pressure

Abstract

An alternative of wellbore cement system, formed through alkali-activation of fly ashes also knows as fly ash geopolymers, provides attractive properties due to its high compressive strength and durability against acidic conditions. However, changes in microstructure and mineralogical during accelerated carbonation affected by CO 2 alteration under elevated temperature and pressure have not been fully understood. This paper investigates and characterizes the alkali-activated binders fly ash based in the acidic environment under elevated temperature and pressure. The results found that scales such a layer was formed in the gel phase at the spherical surface of fly ash after carbonation process. The effect is that the surface of the gel phase became rough and porous. Carbonate and/or bicarbonate salts were identified as major phase in the sample after immersion test. In the activated fly ash cement, both calcium aluminate silicate hydrate (C-A-S-H) and sodium aluminosilicate hydrate (N-A-S-H) gels were formed; C-A-S-H gel was decalcified, forming calcium carbonate phase in the form of calcite, aragonite or vaterite. These findings were confirmed by the analysis and identification of Fourier-transformed infrared spectroscopy, X-ray diffraction and scanning electron microscopy tests on the changes in the cement system.

Effects of the addition of graphene on the compressive strength of geopolymeric mortar developed from k-feldspar mining waste

“…The agglomeration of these nanocrystallites by the remaining aluminosilicate material, in the form of a gel, forms a high-performance mineral binder, commonly referred to as geopolymer or alkali-activated material. The presence of the sodium aluminosilicate hydrate phase in these materials and the direct correlation with the occurrence of a successful alkali-activation reaction and increased mechanical strength was also observed by Rakngan et al (2018); Walkley et al (2018); Myers, Bernal and Provis (2017); Ridha et al (2018) andXiao et al (2020).…”

Evaluation of adsorbent materials for carbon dioxide capture

“…Various carbon dioxide adsorbents materials that have been proposed in recent years are classified into: (i) physical and (ii) chemical ones [1][2][3]. A significant factor in relation to the physical adsorbent is to balance a solid affinity to remove the undesired element from a gas stream along with the utilization of energy needed for their regeneration.…”