Influence of mechanical activation of fly ash on the properties of geopolymers investigated by <scp>XPS</scp> method

Kaňuchová, Mária; Drabova, M.; Sisol, Martin; Mosej, Juraj; Kozáková, Ľubica; Škvarla, Jiřı́

doi:10.1002/ep.12353

Cited by 16 publications

(5 citation statements)

References 19 publications

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“…In addition to Si-O and Si-O 2 , there remains a peak at a high binding energy for FA-1 and FA-2. According to the standard binding energy spectrum, it was found that this peak can be assigned to SiO 2 gel, which was also reported by Kanuchova [8,33].…”

Section: Xpssupporting

confidence: 78%

“…Fly ash can be considered as the world's fifth largest raw material resource [7]. Currently, one possible utilization of fly ash is in the synthesis of alkali-activated materials named geopolymers [8,9]. PC fly ash can successfully be used for the manufacturing of cement, building materials concrete, and concrete-admixed products [10], as it is categorized as a pozzolan, while CFB fly ash with a higher carbon content is broadly used as an insulator and adsorbent [6,11].…”

Section: Introductionmentioning

confidence: 99%

“…Gao et al [32] applied 29 Si and 27 Al magic angle spinning nuclear magnetic resonance (MAS-NMR) to determine the extent of the reaction within alkali-activated slag-fly ash and found that the increase in the activator modulus could lead to a reduction in the slag reactivity, together with significantly increased Q 3 (1Al) and reduced Q 2 (1Al) groups. Kanuchova et al [8,33] used X-ray photoelectron spectroscopy (XPS) to monitor the changes in chemical bonds (such as for the Si-O-Al-O bond) in the creation of geopolymers and also investigated the mechanical activation of fly ash. Hu [23] used 29 Si MAS-NMR and energy calculations to predict that Li occurrence within the Q 3 (0Al) and Q 3 (1Al) structures through the reaction with Q 4 (0Al) and Q 4 (1Al).…”

Section: Introductionmentioning

confidence: 99%

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Structural Characterizations of Aluminosilicates in Two Types of Fly Ash Samples from Shanxi Province, North China

et al. 2019

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In order to determine the structural characterization of aluminosilicates in two types of fly ashes, two samples from Shanxi Province, China were selected for study. One was from a pulverized coal boiler (FA-1), and the other from a circulating fluidized bed boiler (FA-2). FA-1 had a much higher content of silicon dioxide (SiO2) (70.30%) than FA-2(42.19%), but aluminum oxide (Al2O3) was higher in FA-2 (25.41%) than in FA-1 (17.04%). The characterizations were investigated using various methods including X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), magic angle spinning nuclear magnetic resonance (MAS–NMR) spectrometry, and X-ray photoelectron spectroscopy (XPS). The XRD analysis showed that FA-1 contained aluminosilicate glass, quartz and mullite, while FA-2 contained significant amounts of amorphous aluminosilicate, quartz and gypsum. The FTIR results showed an increased substitution of Al3+ for Si4+ as the band of asymmetric stretching vibrations Si–O(Si) (1100 cm−1) moved to 1090 cm−1 for FA-2, much lower than for FA-1(1097 cm−1). Moreover, the sharpness of the bands in the 1250–1000 cm−1 region for FA-2 indicates that the silicate structure of FA-2 was more ordered than for FA-1. It can be understood from the 29Si MAS–NMR results that Q4(mAl) (Q4 are connected via 4 bridging O atoms to mAl) is the main structural type in FA-1 and FA-2, and that FA-2 contains more Al, which substitutes for Si in the Q4 structure. 27Al MAS–NMR demonstrated that a combination of tetrahedral, pentahedral, and octahedral Al existed in FA-1 and FA-2. The Si 2p XPS spectra suggested that there were three forms of Si, including bridging Si (Si–O2), non–bridging Si (Si–O), and SiO2 gel. The content of Si–O2 for FA-1 was 37.48% higher than Si–O (28.57%), while the content of Si–O2 was 30.21% lower than Si–O (40.15%) for FA-2. The Al 2p XPS spectra showed that octahedral Al was the dominant form for FA-1 with a content of 40.25%, while the main phase was tetrahedral Al for FA-2 with a proportion of 37.36%, which corresponds well with the 27Al MAS–NMR results.

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Section: Xpssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural Characterizations of Aluminosilicates in Two Types of Fly Ash Samples from Shanxi Province, North China

et al. 2019

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“…Therefore, strong vibration milling not only weakens microstructure of certain components and enhance their reactivity, but also may lead to the formation of new aluminosilicate bonds between aluminate and silicate constituents of the fly ash as it caused more microstructural changes. Kanuchova et al [26] have observed an increase in binding energy with the appearance of new specifications for Al and Si atoms by XPS method in mechanically activated fly ash. Such changes of the binding energy indicate the appearance of new Al-O-Si bonds.…”

Section: Geopolymers Prepared From Fly Ashes Activated With Various Mmentioning

confidence: 99%

Reactivity of fly ashes milled in different milling devices

Chu

Davaabal

Kim

et al. 2019

Reviews on Advanced Materials Science

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The effect of two different milling devices, namely attrition mill versus vibration mill, on the reactivity of fly ash was studied. High calcium fly ash from 4th Thermal power station of Ulaanbaatar (Mongolia) was used for the experiments. The raw and processed samples were characterized by XRD, SEM, Particle size distribution, BET, Blaine surface area and density measurements. The efficiency of 1 hour milling was evaluated with the Blaine surface area set to be more than 5000 cm2/g. The physical and chemical properties of the attrition milled fly ash changed not much compared to the vibration milled samples. For example the d50 particle size became reduced from 29 µm to 6 µm by attrition milling and in vibration milled fly ash it was reduced to 7 µm. The density increased from 2.44 g/cm3 of raw fly ash to 2.84 g/cm3 and 2.79 g/cm3 in attrition and vibration milled samples, respectively. Mechanical milling revealed not only a particle size reduction but also the formation of a denser microstructure. As a result the vibration milled fly ash showed a weaker interaction with the alkaline solution (8 M NaOH used here) compared to the attrition milled fly ash. Consequently, compressive strength of the binder prepared using the attrition milled fly ash was higher, 61 MPa, while for vibration milled fly ash it was 49 MPa. For comparison unmilled fly ash, it was 21 MPa.

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“…In Slovakia, almost all of the heating plant waste, especially fly ash, is not utilized. It can be concluded that little attention is paid to this issue in Slovakia, which is reflected in the lack of evidence-based practices [40]. In this paper, the utilization of fly ash from Slovakia, mainly deposited in a heap, which creates an environmental problem, was used as a potential aluminosilicate material for the geopolymerization process.…”

Section: Introductionmentioning

confidence: 99%

Study on Mechanical Properties of Heap Deposited Fly Ash Based Geopolymers with Different Alkaline Activator Properties

et al. 2022

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Geopolymers can improve environmental protection and are therefore considered a 21st-century material that requires special attention. The main objective of this study was to examine the utilization of fly ash deposited on a heap as a potential raw material for the geopolymerization process. In this work, flexural and compressive strengths, as well as water absorption of geopolymers, were evaluated based on alkaline activator properties. Na2O content, SiO2/Na2O molar ratio and fly ash-to-water ratio were key observed factors. Mechanical strengths tests were conducted after 7, 28, 90, 180, and 360 days. The research findings showed that geopolymer cured at appropriate conditions and with a suitable alkaline activator can reach a compressive strength of more than 55 MPa. The presented study highlighted the possibility of the efficient use of fly ash to produce useful materials, i.e., geopolymers, which contribute to environmentally friendly solutions. This approach is fully in line with the principles of sustainable development.

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Influence of mechanical activation of fly ash on the properties of geopolymers investigated by XPS method

Cited by 16 publications

References 19 publications

Structural Characterizations of Aluminosilicates in Two Types of Fly Ash Samples from Shanxi Province, North China

Structural Characterizations of Aluminosilicates in Two Types of Fly Ash Samples from Shanxi Province, North China

Reactivity of fly ashes milled in different milling devices

Study on Mechanical Properties of Heap Deposited Fly Ash Based Geopolymers with Different Alkaline Activator Properties

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