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Journal ArticleDOI

NaOH-activated ground fly ash geopolymer cured at ambient temperature

TL;DR: In this paper, ground fly ash (GFA), with a median particle size of 10.5μm, was used as source material for making geopolymers cured at room temperature, and compressive strength tests and microstructure observations using SEM, EDX, XRD and FTIR were performed.
About: This article is published in Fuel.The article was published on 2011-06-01. It has received 755 citations till now. The article focuses on the topics: Fly ash & Geopolymer.
Citations
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Journal ArticleDOI
TL;DR: An overview of advances in geopolymers formed by the alkaline activation of aluminosilicates is presented along with opportunities for their use in building construction as mentioned in this paper, with respect to fresh and hardened states, interfacial transition zone between aggregate and geopolymer, bond with steel reinforcing bars and resistance to elevated temperature.

899 citations

Journal ArticleDOI
TL;DR: In this paper, a fly ash-based geopolymer concrete for curing in ambient condition can be proportioned for desirable workability, setting time, and compressive strength using ground granulated blast-furnace slag (GGBFS) as a small part of the binder.

855 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarized and examined the scientific advances in the preparation, properties and applications of fly ash-based geopolymer and proposed a new green cement based on fly ash.

578 citations

Journal ArticleDOI
TL;DR: In this paper, a new type of geopolymer composite was synthesized from two industrial wastes, red mud (RM) and rice husk ash (RHA), at varying mixing ratios of raw materials and the resulting products characterized by mechanical compression testing, X-ray diffraction, and scanning electron microscopy to assess their mechanical properties, microstructure, and reaction reactions.
Abstract: A new type of geopolymer composite was synthesized from two industrial wastes, red mud (RM) and rice husk ash (RHA), at varying mixing ratios of raw materials and the resulting products characterized by mechanical compression testing, X-ray diffraction, and scanning electron microscopy to assess their mechanical properties, microstructure, and geopolymerization reactions. Prolonged curing significantly increases the compressive strength and Young’s modulus, but reduces the ductility. Higher RHA/RM ratios generally lead to higher strength, stiffness, and ductility, but excessive RHA may cause the opposite effect. The compressive strength ranges from 3.2 to 20.5 MPa for the synthesized geopolymers with nominal Si/Al ratios of 1.68–3.35. Microstructural and compositional analyses showed that the final products are mainly composed of amorphous geopolymer binder with both inherited and neoformed crystalline phases as fillers, rendering the composites very complex composition and highly variable mechanical properties. Uncertainties in the composition, microstructure, the extent of RHA dissolution, and side reactions may be potential barriers for the practical application of the RM–RHA based geopolymers as a construction material.

513 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of NaOH concentration on the physical properties of the final product was investigated by applying curing on geopolymer mortars in different NaOH concentrations at different temperatures and for different curing times.
Abstract: In this study, geopolymer mortar was produced using Class F fly ash from the thermal power plant in Kutahya Seyitomer (Turkey). The changes caused by the geopolymerization on the properties of the final product were investigated by applying curing on geopolymer mortars in different NaOH concentrations at different temperatures and for different curing times. The purpose of this process was to determine the relationship between alkali solution concentration, curing temperature and curing time. In order to determine the effect of NaOH concentration on geopolymer mortars, three different molarities of NaOH concentrations (3 M, 6 M and 9 M) were used together with sodium silicate (water glass) solution. The samples were cured at two different temperatures (65 and 85 °C). Physical properties such as porosity, bulk density, apparent density and water absorption, and mechanical properties such as flexural strength and compressive strength were determined from the 7-day geopolymer mortar samples after the curing process. As a result, this study determined that curing temperature and curing time had an effect on the physical properties of the geopolymer mortars. It was observed that NaOH concentration had a clear effect on the properties of the mortar cured at 85 °C. Compressive strength values of 21.3 MPa and 22 MPa were obtained from the mortar of 6 M concentration cured at 65 °C for 24 h and from a sample of the same mortar cured at 85 °C, respectively. Compressive strength values of the geopolymer mortars cured at 85 °C increased depending on the curing time and the increase in NaOH concentration. Given the strength values obtained, the optimal thermal curing temperature and the optimal NaOH concentration were 85 °C and 6 M, respectively.

396 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the mechanism of activation of fly ash with highly alkaline solutions is described, and the product of the reaction is an amorphous aluminosilicate gel having a structure similar to that of zeolitic precursors.

1,779 citations

Book
01 Jan 2008

1,224 citations

Journal ArticleDOI
TL;DR: In this article, the effect of storing at room temperature before the application of heat on phase composition and phase composition was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SEM.

790 citations


"NaOH-activated ground fly ash geopo..." refers background in this paper

  • ...Initial curing at elevated temperatures between 40 and 95 C improved geopolymerization, which led to a high compressive strength of the geopolymer [3,8,10,13]....

    [...]

  • ...The broad bands around 1650 cm 1 and 3480 cm 1 were assigned to the stretching vibration of –OH and bending vibration of O–H–O, respectively [13]....

    [...]

Journal ArticleDOI
TL;DR: The activation of fly ash/slag pastes with NaOH solutions has been studied in this paper, where the authors established the equations of the models describing the mechanical behaviour of these pastes as a function of the factors and levels considered.

745 citations

Journal ArticleDOI
TL;DR: In this article, the basic properties viz., workability and strength of geopolymer mortar made from coarse lignite high calcium fly ash were investigated, and the results revealed that the workable flow of the geopolymers was in the range of 110 −±5% −135 −± 5% and was dependent on the ratio by mass of sodium silicate to NaOH and the concentration of NaOH.
Abstract: In this paper, the basic properties viz., workability and strength of geopolymer mortar made from coarse lignite high calcium fly ash were investigated. The geopolymer was activated with sodium hydroxide (NaOH), sodium silicate and heat. The results revealed that the workable flow of geopolymer mortar was in the range of 110 ± 5%–135 ± 5% and was dependent on the ratio by mass of sodium silicate to NaOH and the concentration of NaOH. The obtained compressive strength was in the range of 10–65 MPa. The optimum sodium silicate to NaOH ratio to produce high strength geopolymer was 0.67–1.0. The concentration variation of NaOH between 10 M and 20 M was found to have a small effect on the strength. The geopolymer samples with high strength were obtained with the following practices: the delay time after moulding and before subjecting the sample to heat was 1 h and the optimum curing temperature in the oven was 75 °C with the curing duration of not less than two days.

706 citations


"NaOH-activated ground fly ash geopo..." refers background in this paper

  • ...0 MPa [3]....

    [...]

  • ...Initial curing at elevated temperatures between 40 and 95 C improved geopolymerization, which led to a high compressive strength of the geopolymer [3,8,10,13]....

    [...]