Effect of Curing Temperature, Activator Solution Composition and Particle Size in Brazilian Fly-Ash Based Geopolymer Production

Abstract

The geopolymer binder is a relatively new class of inorganic binding material of elevated mechanical strength and good chemical properties. This can be produced using clay minerals or byproducts of the industrial processes, such as metakaolin, fly-ash and blast furnace slag. In this work, geopolymers were produced by alkaline activation of a Brazilian fly-ash with simple and compound solutions (NaOH and NaOH + Na 2 SiO 3). The hardened specimens presented values of the mechanical strength close to 48 MPa when the activator used presented SiO 2 /Na 2 O ration close to 1.0 after 24 h of curing at 65 °C. The increase of the temperature to 90 °C favored the reactions of the N-AS -H gel (geopolymer) formation and compression strength increased to values close to 90 MPa after 24 h. It has been found that physical properties, such as density and porosity, varied when different SiO 2 /Na 2 O rations was present in alkaline solutions. Time, temperature of curing and particle size of fly-ash modified the mechanical and physical proprieties of hardened inorganic binder. Was observed the diffraction phases related to zeolitic phases and carbonate new bands of absorption were related to reactions of Na2O in excess with atmospheric CO 2. The variation of SiO 2 /Na 2 O modified the microstructural of the hardened specimens.

Non-conventional mineral binder-bonded lignocellulosic composite materials: A review

“…The cast pastes in the mold are then covered or sealed with a plastic film/sheet and cured at ambient temperatures, or a specified temperature for a certain period. At ambient temperatures, however, the reaction of the geopolymer precursors such as fly ash is very slow and the resulting geopolymers correspondingly show a slower setting and strength development (Patil et al 2014;Azevedo et al 2019). Previous studies (Tables 4, 5, 6, and 7) have shown, that higher temperatures increase the reactivity of alumino-silicate phases in the geopolymer precursors.…”

Evaluation of different fly ash samples on the production of alkali-activated materials

“…The absorption bands of the fly ash and AAM at 3667 and 1641 cm -1 are due to the stretching and deformation of H-O-H and O-H groups, respectively. These bands are related to weakly bound water molecules, adsorbed on the surface or trapped in the cavities of the inorganic binder [26]. Bands at 1090 and 458 cm -1 are associated with the stretching and bending of Si-O or Al-O bands, respectively [27].…”

Aspectos Higiênico-Santinários De Carnes Bovinas Comercializadas Na Cidade De Barreiras-Ba

“…According to the compressive strength results, it is likely that between 28 and 90 days, the remaining portlandite was consumed to form more C-S-H and C-S-(A)-H from MK. Another assumption is that, because it contains silica, the activator Na 2 SiO 3 functioned as pozzolan, promoting the formation of more C-S-H and C-S-(A)-H phases and contributing to the maintenance of better mechanical stability [23] . For a definitive conclusion, it is necessary to analyze the evolution of the microstructure as a function of time until more advanced ages.…”