Chemical Distributions of Different Sodium Hydroxide Molarities on Fly Ash/Dolomite-Based Geopolymer

Abstract

Geopolymers are an inorganic material in an alkaline environment that is synthesized with alumina–silica gel. The structure of geopolymers consists of an inorganic chain of material and a covalent-bound molecular system. Currently, Ordinary Portland Cement (OPC) has caused carbon dioxide (CO2) emissions which causes greenhouse effects. This analysis investigates the impact on fly ash/dolomite-based-geopolymer with various molarities of sodium hydroxide solutions which are 6 M, 8 M, 10 M, 12 M and 14 M. The samples of fly ash/dolomite-based-geopolymer were prepared with the usage of solid to liquid of 2.0, by mass and alkaline activator ratio of 2.5, by mass. After that, the geopolymer was cast in 50 × 50 × 50 mm molds before testing after 7 days of curing. The samples were tested on compressive strength, density, water absorption, morphology, elemental distributions and phase analysis. From the results, the usage of 8 M of NaOH gave the optimum properties for the fly ash/dolomite-based geopolymer. The elemental distribution analysis exposes the Al, Si, Ca, Fe and Mg chemical distribution of the samples from the selected area. The distribution of the elements is related to the compressive strength and compared with the chemical composition of the fly ash and dolomite.

Influence of Fe2O3, MgO and Molarity of NaOH Solution on the Mechanical Properties of Fly Ash-Based Geopolymers

“…The mechanical strengths of the samples obtained, comparable to Portland cement, justify the use of these geopolymer pastes in the production of geopolymer concretes and in the production of precast concrete. Results obtained in the current study are in accordance with results previously obtained in the literature, while completing the knowledge about the production of alkaline-activated geopolymer materials [ 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 ].…”

Synthesis of Metakaolin Based Alkali Activated Materials as an Adsorbent at Different Na2SiO3/NaOH Ratios and Exposing Temperatures for Cu2+ Removal

“…This rigid structure is the outcome of a process that involves the complete dissolution of the aluminosilicate phase in alkali solution, which generates two separate tetrahedral ends made of aluminosilicate, silicates (SiO 4 ), and aluminates (AlO 4 ) that are joined by oxygen atoms. Accordingly, two major phases, which are aluminosilicate dissolution and separation into alumina and silicate end, and the polycondensation/polymerization stage, are likely to be produced based on the ratio of SiO 2 to Al 2 O 3 in the raw material [ 20 , 40 ]. Therefore, the proportion of [SiO 4 ] 4− to [AlO 4 ] 5− is one of the relevant metrics for evaluating the alkali activation process and the structural properties of the resulting alkali activated materials.…”

“…Subsequently, the chemical and mineralogical composition of the raw materials, the kind of alkaline activators, their concentration, and the ratio of main chemical activators such as Na 2 O/SiO 2 , SiO 2 /Al 2 O 3 are all parameters that influence alkali activation [ 39 , 40 , 41 ]. In that sense, the main objective of this study is to study the porous distribution behaviour for heavy metal adsorption.…”

Fabrication and characterization of fly ash-based geopolymer and its performance for immobilization of heavy metal cations

“…The presence of a small peak at 2θ around 22° indicated the presence of traces of quartz. After reacting with the activating solution, the intensity at an angle of 22° decreased showing that the amount of crystalline quartz phase was reduced [7,19]. This phenomenon, coupled with the presence of hump shift, was a characteristic of the formation of geopolymers.…”

“…Since the main components of fly ash are alumina and silica, it is possible to use it as geopolymers' raw material [3,4]. Other materials such as kaolinite and metakaolin can be used as raw materials for geopolymers as well, but the manufacture of geopolymers from fly ash provides more advantages [5][6][7].…”