The Internal Structure of a Low-Calcium Fly Ash

1987 ◽  
Vol 113 ◽  
Author(s):  
Carol I. Kilgour ◽  
Sidney Diamond
Keyword(s):  
Fly Ash ◽  
Pore Solution ◽  
Glass Composition ◽  
Term Treatment ◽  
Bearing Material ◽  
X Ray ◽  
Glass Dissolution ◽  
Low Calcium ◽  
Internal Structures ◽  
Mullite Composition

ABSTRACTA low calcium fly ash, rich in iron oxide, was subjected to shaking in 1% HF for up to 20 hours, and measurements were made at intervals of the following parameters: total weight loss, composition of the dissolved material, x-ray peak intensities of crystalline components and residual glass, and internal structures present within the fly ash spheres as revealed by the progressive dissolution treatments. The same fly ash was subjected to similar but longer-term treatment with simulated cement pore solution (potassium and sodium hydroxide). The compositions of the magnetically separated fraction and the non-magnetic residue were also separately determined. As a result of these studies, it was suggested that: (a) the time at which all of the potassium is dissolved might be used as an indicator of the completion of glass dissolution; (b) the position of the x-ray band for residual (more resistant ) glass shifts to higher 2Θ angle before the glass is completely dissolved; (c) in this fly ash, as determined by chemical analysis, all of the iron is in the magnetically-separable fraction, a feature that permitted estimation of the overall glass composition; and (d) this fly ash contains certain poorly understood components including silica-rich spheres, small spheres yielding EDXA signals only for iron, and “patches” of silica and alumina bearing material not of mullite composition, but all of which are highly resistant to HF dissolution.

scholarly journals Alkali-Silica Reaction Resistance and Pore Solution Composition of Low-Calcium Fly Ash-Based Geopolymer Concrete

2020 ◽  
Vol 5 (11) ◽  
pp. 96
Author(s):  
Jiawei Lei ◽  
Jiajun Fu ◽  
En-Hua Yang
Keyword(s):  
Fly Ash ◽  
Pore Solution ◽  
Systematic Investigation ◽  
Alkali Silica Reaction ◽  
Geopolymer Concrete ◽  
Portland Cement Concrete ◽  
Solution Composition ◽  
Low Calcium ◽  
Underlying Mechanisms ◽  
One Year

Low-calcium fly ash-based geopolymer concrete is generally reported to be less vulnerable to alkali-silica reaction (ASR) than conventional ordinary Portland cement concrete. However, the lack of understanding of pore solution composition of the low-calcium fly ash-based geopolymer limits the investigation of the underlying mechanisms for the low ASR-induced expansion in the geopolymer concrete. This study presents a systematic investigation of the pore solution composition of a low-calcium fly ash-based geopolymer over a period of one year. The results show that the pore solution of the fly ash geopolymer is mainly composed of alkali ions, silicates, and aluminosilicates species. The lower expansion of the geopolymer concrete in the current study is most probably due to the insufficient alkalinity in the geopolymer pore solution as the hydroxide ions are largely consumed for the fly ash dissolution.

Determination of glass content and estimation of glass composition in fly ash using quantitative X-ray diffractometry

Fuel ◽  
2006 ◽  
Vol 85 (16) ◽  
pp. 2268-2277 ◽  
Author(s):  
C WARD ◽  
D FRENCH
Keyword(s):  
Fly Ash ◽  
Glass Composition ◽  
Glass Content ◽  
X Ray

scholarly journals Simultaneous removal of aqueous Zn2+, Cu2+, Cd2+, and Pb2+ by zeolites synthesized from low-calcium and high-calcium fly ash

2017 ◽  
Vol 76 (8) ◽  
pp. 2106-2119 ◽  
Author(s):  
X. D. Ji ◽  
Y. Y. Ma ◽  
S. H. Peng ◽  
Y. Y. Gong ◽  
F. Zhang
Keyword(s):  
Fly Ash ◽  
Contact Time ◽  
Ph Value ◽  
Heavy Metal Concentration ◽  
Sorption Kinetics ◽  
Order Kinetic ◽  
Adsorbent Dosage ◽  
X Ray ◽  
Low Calcium ◽  
High Calcium

In this study, zeolites were synthesized from low-calcium (LCZ) and high-calcium (HCZ) fly ash, respectively. Subsequently, the zeolites were tested for their removal effectiveness for four aqueous cations, namely, Zn2+, Cu2+, Cd2+, and Pb2+, as a function of contact time, pH value, adsorbent dosage, and initial concentration of heavy metals. Both zeolites were characterized by X-ray diffraction, X-ray fluorescence spectrometry, scanning electron microscopy, specific surface area, and cation exchange capacity. The results show that HCZ mainly consists of an unnamed zeolite (Na6[AlSiO4]6·4H2O), whereas LCZ mainly consists of faujasite-type zeolite. The optimum sorption conditions were pH = 6.0; adsorbent dosage = 1.0 g·L−1; temperature = 25 °C; contact time = 100 min; and initial heavy metal concentration = 100 mg·L−1. The sorption kinetics of the four aqueous cations on both LCZ and HCZ followed the pseudo-second-order kinetic model, and the sorption isotherm data fitted well with the Langmuir isotherm model. For LCZ, the maximum adsorption capacities of Zn2+, Cu2+, Cd2+, and Pb2+ were 155.76, 197.86, 123.76, and 186.22 mg·g−1, respectively. For HCZ, the values were 154.08, 183.15, 118.91, and 191.94 mg·g−1, respectively. The zeolites were regenerated by NaCl solution (1 mol·L−1) and showed high removal efficiency. In conclusion, zeolites produced by fly ash are promising materials for removing Zn2+, Cu2+, Cd2+, and Pb2+ from wastewater.

SCANNING ELECTRON MICROSCOPY AND ENERGY-DISPERSIVE X-RAY SPECTROSCOPY OF LOW-SULFUR COAL FLY ASH

2009 ◽  
Vol 10 (1-4) ◽  
pp. 147-166 ◽  
Author(s):  
Bruno Valentim ◽  
James C. Hower ◽  
Alexandra Guedes ◽  
Deolinda Flores
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fly Ash ◽  
Coal Fly Ash ◽  
Energy Dispersive ◽  
X Ray ◽  
Low Sulfur ◽  
Scanning Electron

scholarly journals Principles of Different X-ray Phase-Contrast Imaging: A Review

2021 ◽  
Vol 11 (7) ◽  
pp. 2971
Author(s):  
Siwei Tao ◽  
Congxiao He ◽  
Xiang Hao ◽  
Cuifang Kuang ◽  
Xu Liu
Keyword(s):  
Biological Samples ◽  
Phase Contrast ◽  
Recent Progress ◽  
Phase Contrast Imaging ◽  
Contrast Imaging ◽  
X Ray ◽  
X Ray Imaging ◽  
Internal Structures ◽  
X Ray Absorption ◽  
Made In

Numerous advances have been made in X-ray technology in recent years. X-ray imaging plays an important role in the nondestructive exploration of the internal structures of objects. However, the contrast of X-ray absorption images remains low, especially for materials with low atomic numbers, such as biological samples. X-ray phase-contrast images have an intrinsically higher contrast than absorption images. In this review, the principles, milestones, and recent progress of X-ray phase-contrast imaging methods are demonstrated. In addition, prospective applications are presented.

scholarly journals Practical Prediction Models of Tensile Strength and Reinforcement-Concrete Bond Strength of Low-Calcium Fly Ash Geopolymer Concrete

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 875
Author(s):  
Chenchen Luan ◽  
Qingyuan Wang ◽  
Fuhua Yang ◽  
Kuanyu Zhang ◽  
Nodir Utashev ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Bond Strength ◽  
Prediction Models ◽  
Splitting Tensile Strength ◽  
Geopolymer Concrete ◽  
Structural Factors ◽  
Test Results ◽  
Portland Cement Concrete ◽  
Low Calcium

There have been a few attempts to develop prediction models of splitting tensile strength and reinforcement-concrete bond strength of FAGC (low-calcium fly ash geopolymer concrete), however, no model can be used as a design equation. Therefore, this paper aimed to provide practical prediction models. Using 115 test results for splitting tensile strength and 147 test results for bond strength from experiments and previous literature, considering the effect of size and shape on strength and structural factors on bond strength, this paper developed and verified updated prediction models and the 90% prediction intervals by regression analysis. The models can be used as design equations and applied for estimating the cracking behaviors and calculating the design anchorage length of reinforced FAGC beams. The strength models of PCC (Portland cement concrete) overestimate the splitting tensile strength and reinforcement-concrete bond strength of FAGC, so PCC’s models are not recommended as the design equations.

scholarly journals Preparation of Synthetic Zeolites from Coal Fly Ash by Hydrothermal Synthesis

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1267
Author(s):  
David Längauer ◽  
Vladimír Čablík ◽  
Slavomír Hredzák ◽  
Anton Zubrik ◽  
Marek Matik ◽  
...  
Keyword(s):  
Fly Ash ◽  
Coal Combustion ◽  
Power Plants ◽  
Coal Fly Ash ◽  
Thermal Power ◽  
Product Analysis ◽  
Coal Combustion Products ◽  
X Ray ◽  
Wide Range ◽  
Silica Alumina

Large amounts of coal combustion products (as solid products of thermal power plants) with different chemical and physical properties cause serious environmental problems. Even though coal fly ash is a coal combustion product, it has a wide range of applications (e.g., in construction, metallurgy, chemical production, reclamation etc.). One of its potential uses is in zeolitization to obtain a higher added value of the product. The aim of this paper is to produce a material with sufficient textural properties used, for example, for environmental purposes (an adsorbent) and/or storage material. In practice, the coal fly ash (No. 1 and No. 2) from Czech power plants was firstly characterized in detail (X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), particle size measurement, and textural analysis), and then it was hydrothermally treated to synthetize zeolites. Different concentrations of NaOH, LiCl, Al2O3, and aqueous glass; different temperature effects (90–120 °C); and different process lengths (6–48 h) were studied. Furthermore, most of the experiments were supplemented with a crystallization phase that was run for 16 h at 50 °C. After qualitative product analysis (SEM-EDX, XRD, and textural analytics), quantitative XRD evaluation with an internal standard was used for zeolitization process evaluation. Sodalite (SOD), phillipsite (PHI), chabazite (CHA), faujasite-Na (FAU-Na), and faujasite-Ca (FAU-Ca) were obtained as the zeolite phases. The content of these zeolite phases ranged from 2.09 to 43.79%. The best conditions for the zeolite phase formation were as follows: 4 M NaOH, 4 mL 10% LiCl, liquid/solid ratio of 30:1, silica/alumina ratio change from 2:1 to 1:1, temperature of 120 °C, process time of 24 h, and a crystallization phase for 16 h at 50 °C.

scholarly journals Fly Ash Coated with Magnetic Materials: Improved Adsorbent for Cu (II) Removal from Wastewater

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 63
Author(s):  
Maria Harja ◽  
Gabriela Buema ◽  
Nicoleta Lupu ◽  
Horia Chiriac ◽  
Dumitru Daniel Herea ◽  
...  
Keyword(s):  
Fly Ash ◽  
Adsorption Capacity ◽  
Copper Ions ◽  
Synthetic Wastewater ◽  
Bet Surface Area ◽  
Isotherm Models ◽  
Batch Adsorption ◽  
Maximum Adsorption Capacity ◽  
Copper Adsorption ◽  
X Ray

Fly ash/magnetite material was used for the adsorption of copper ions from synthetic wastewater. The obtained material was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area, and vibrating sample magnetometer (VSM). Batch adsorption experiments were employed in order to investigate the effects of adsorbent dose, initial Cu (II) concentration and contact time over adsorption efficiency. The experimental isotherms were modeled using Langmuir (four types of its linearization), Freundlich, Temkin, and Harkins–Jura isotherm models. The fits of the results are estimated according to the Langmuir isotherm, with a maximum adsorption capacity of 17.39 mg/g. The pseudo-second-order model was able to describe kinetic results. The data obtained throughout the study prove that this novel material represents a potential low-cost adsorbent for copper adsorption with improved adsorption capacity and magnetic separation capability compared with raw fly ash.

Development of low-calcium fly ash-based geopolymer mortar using nanosilica and hybrid fibers

2021 ◽  
Author(s):  
Keyu Chen ◽  
Dazhi Wu ◽  
HaiXiang Chen ◽  
Guoqing Zhang ◽  
Ruolan Yao ◽  
...  
Keyword(s):  
Fly Ash ◽  
Hybrid Fibers ◽  
Low Calcium
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