A comparative study on geopolymers synthesized by different classes of fly ash after exposure to elevated temperatures

Jiang, Xi; Zhang, Yiyuan; Xiao, Rui; Polaczyk, Pawel; Zhang, Miaomiao; Hu, Wei; Bai, Yun; Huang, Baoshan

doi:10.1016/j.jclepro.2020.122500

Cited by 148 publications

(46 citation statements)

References 60 publications

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“…The samples were also investigated with a scanning electron microscope (Tescan VEGA 3) (Tescan Orsay Holding, Brno-Kohoutovice, Czech Republic) provided with energy-dispersive X-ray spectroscopy (EDS) (Oxford Instruments, Oxford, UK). As seen in the SEM micrographs ( Figure 6 ), the two geopolymer binders are composed mainly of amorphous phases, indicating a high degree of geopolymerization [ 20 , 21 ]. Close inspection of the SEM images revealed the presence of the unreacted precursor particles in the fly ash-basedgeopolymer ( Figure 6 b) [ 21 , 22 ].…”

Section: Resultsmentioning

confidence: 99%

“…As seen in the SEM micrographs ( Figure 6 ), the two geopolymer binders are composed mainly of amorphous phases, indicating a high degree of geopolymerization [ 20 , 21 ]. Close inspection of the SEM images revealed the presence of the unreacted precursor particles in the fly ash-basedgeopolymer ( Figure 6 b) [ 21 , 22 ].…”

Section: Resultsmentioning

confidence: 99%

“…A second mass loss of about 4% is observed in the temperature range of 450–650 °C, accompanied by exothermic effects in the DTA curve. This weight loss could be assigned to the decomposition of calcium hydroxide (Ca(OH) 2 ) [ 21 , 25 ].…”

Section: Resultsmentioning

confidence: 99%

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Preparation of Cement Clinker from Geopolymer-Based Wastes

et al. 2021

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In order to avoid potential environmental pollution from geopolymer-based material wastes, this work investigated the feasibility of using these materials as alternative raw materials in the preparation of cement clinker. The geopolymer binders and mortars were used as substitutes for natural mineral clays since they are rich in silica and alumina. Simulated geopolymer wastes were prepared by the activation of metakaolin or fly ash by an alkaline silicate solution. The cement-clinkers fired at 1450 °C for 1h were characterized by XRD, XRF, SEM-EDS, and a free lime (CaOf) content test. The anhydrous clinker mineral phases C3S (Ca3SiO5), C2S (Ca2SiO4), C3A (Ca3Al2O6), and C4AF (Ca4Al2Fe2O10) were well-crystallized in all investigated formulations. The free lime was lower than 1.3 wt% in all elaborated clinkers, which indicates a high degree of clinkerization. The results demonstrate that geopolymer binder and mortar materials are suitable substitutes for natural mineral clay incement clinker preparation.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Preparation of Cement Clinker from Geopolymer-Based Wastes

et al. 2021

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“…Recently, many projects have been undertaken to develop geopolymer-type binders using geopolymerization technology which consume less energy and are more environmentally friendly [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Influence of the Nature and Rate of Alkaline Activator on the Physicochemical Properties of Fly Ash‐Based Geopolymers

Alouani

Alehyen

Achouri

et al. 2020

Advances in Civil Engineering

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The influence of alkali cations on mix design of geopolymers is essential for their mechanical, thermal, and electrical performance. This research investigated the influence of alkali cation type on microscale characteristics and mechanical, dielectric, and thermal properties of fly ash-based geopolymer matrices. The geopolymers were elaborated via class F fly ash from the thermal plant Jorf Lasfar, El Jadida (Morocco), and several alkaline solutions. Morphological, structural, mechanical, dielectric, and thermal characteristics of materials synthesized via fly ash with different proportions of KOH and NaOH aged 28 days were evaluated. The physicochemical properties of class F fly ash-based geopolymers were assessed using X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX) analyses. Based on readings of the results obtained, XRD and FTIR analysis detected the creation of semicrystalline potassium/sodium aluminate-silicate hydrate (KASH/NASH) gel in the elaborated matrices after the geopolymerization reaction. The SEM analysis proved the formation of alkali alumina-silicate hydrate gel in the raw material particles after the polycondensation stage. Experimental compressive strength data indicated that the highest compressive strength (39 MPa) was produced by the alkaline activator (75% KOH/25% NaOH). The dielectric parameters values of the elaborated materials changed depending of the mass ratios KOH/NaOH. Dielectric findings demonstrated that geopolymers containing 100% NaOH have better dielectric performances. The fire resistance study revealed that the geopolymer binders induced by KOH are stable up to 600°C. Based on these results, it can be deduced that the formulated geopolymer concrete possesses good mechanical, dielectric, and fire resistance properties.

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“…Sulfates, chlorides, and other corrosive sources are widely observed in soils, ground water, river water, and seawater in salty saline and offshore areas [ 1 , 2 , 3 , 4 , 5 ]. Among the mostly observed ions in the environment, sulfates have been claimed to be one of the most aggressive ions to bring great damage to concrete structures [ 6 , 7 , 8 , 9 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

Degradation Mechanism of Concrete Subjected to External Sulfate Attack: Comparison of Different Curing Conditions

et al. 2020

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Sulfate induced degradation of concrete brings great damage to concrete structures in saline or offshore areas. The degradation mechanism of cast-in-situ concrete still remains unclear. This paper investigates the degradation process and corresponding mechanism of cast-in-situ concrete when immersed in sulfate-rich corrosive environments. Concrete samples with different curing conditions were prepared and immersed in sulfate solutions for 12 months to simulate the corrosion of precast and cast-in-situ concrete structures, respectively. Tests regarding the changes of physical, chemical, and mechanical properties of concrete samples were conducted and recorded continuously during the immersion. Micro-structural and mineral methods were performed to analyze the changes of concrete samples after immersion. Results indicate that the corrosion process of cast-in-situ concrete is much faster than the degradation of precast concrete. Chemical attack is the main cause of degradation for both precast and cast-in-situ concrete. Concrete in the environment with higher sulfate concentration suffers more severe degradation. The water/cement ratio has a significant influence on the durability of concrete. A lower water/cement ratio results in obviously better resistance against sulfate attack for both precast and cast-in-situ concrete.

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A comparative study on geopolymers synthesized by different classes of fly ash after exposure to elevated temperatures

Cited by 148 publications

References 60 publications

Preparation of Cement Clinker from Geopolymer-Based Wastes

Preparation of Cement Clinker from Geopolymer-Based Wastes

Influence of the Nature and Rate of Alkaline Activator on the Physicochemical Properties of Fly Ash‐Based Geopolymers

Degradation Mechanism of Concrete Subjected to External Sulfate Attack: Comparison of Different Curing Conditions

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