The Effects of Various Concentrations of NaOH on the Inter-Particle Gelation of a Fly Ash Geopolymer Aggregate

Abstract

Aggregates can be categorized into natural and artificial aggregates. Preserving natural resources is crucial to ensuring the constant supply of natural aggregates. In order to preserve these natural resources, the production of artificial aggregates is beginning to gain the attention of researchers worldwide. One of the methods involves using geopolymer technology. On this basis, this current research focuses on the inter-particle effect on the properties of fly ash geopolymer aggregates with different molarities of sodium hydroxide (NaOH). The effects of synthesis parameters (6, 8, 10, 12, and 14 M) on the mechanical and microstructural properties of the fly ash geopolymer aggregate were studied. The fly ash geopolymer aggregate was palletized manually by using a hand to form a sphere-shaped aggregate where the ratio of NaOH/Na2SiO3 used was constant at 2.5. The results indicated that the NaOH molarity has a significant effect on the impact strength of a fly ash geopolymer aggregate. The highest aggregate impact value (AIV) was obtained for samples with 6 M NaOH molarity (26.95%), indicating the lowest strength among other molarities studied and the lowest density of 2150 kg/m3. The low concentration of sodium hydroxide in the alkali activator solution resulted in the dissolution of fly ash being limited; thus, the inter-particle volume cannot be fully filled by the precipitated gels.

Influence of Sintering Temperature of Kaolin, Slag, and Fly Ash Geopolymers on the Microstructure, Phase Analysis, and Electrical Conductivity

“…The unreacted spherical particles clearly could be visualised in Figure 2 . This was also in accordance with the results published by Alida et al [ 21 ].…”

“…The unreacted spherical particles clearly could be visualised in Figure 2. This was also in accordance with the results published by Alida et al [21]. As can be observed in Figure 7, the microstructure displayed the crystalline grains structure after the geopolymer sintered at 900 °C.…”

“…Each raw aluminosilicate (kaolin, fly ash, and slag) powder, encompassing NaOH molarity, alkaline activator, solid-to-liquid ratio, and curing temperature were based on previous works and are tabulated in Table 2 . The designated mixing design was based on the optimum mechanical performance [ 19 , 20 , 21 ]. The precursor material was mixed with the alkaline activator solution for 5 min.…”

Experimental Study of the Mechanical and Microstructure Characteristics of Coal Gangue Road Stabilization Materials Based on Alkali Slag Cementation

“…At present, the most widely used aluminosilicate materials in alkali-activated gel materials are fly ash and metakaolin. Studies have shown that alkali-reactive material concrete has excellent strength, corrosion resistance, fire resistance, and durability, and it can replace Portland cement as a concrete adhesive [24][25][26]. Therefore, alkali excitation technology is expected to become an important part of sustainable by-products.…”

Preparation and Characterization of the Functional Properties of Synthetic Aggregates from Silico-Manganese Slag

“…At the same time, it will have a serious impact on the ecological environment [ 4 ]. At present, it has been reported that industrial solid wastes such as fly ash (FA) [ 5 ], ground granulated blast furnace slag (GGBFS) [ 6 ], and steel slag [ 7 ] are used to prepare aggregates to replace some natural aggregates in concrete. It can not only slow down the mining of natural aggregates but also reduce environmental pollution.…”