scholarly journals Action Time-Effect and Mechanism of Low-Calcium Fly Ash in Cement-Based Composites

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 681
Author(s):  
Na Yan ◽  
Qingqing Tang ◽  
Ying Zhang ◽  
Guowen Sun
Keyword(s):  
Fly Ash ◽  
Nitrogen Adsorption ◽  
Chemical Effect ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Degree Of Hydration ◽  
Surface Areas ◽  
Activity Effect ◽  
Low Calcium ◽  
Pore Size Distributions

This study was conducted in order to investigate when low-calcium fly ash plays a physical or chemical effect and what is the chemical effect proportion of low-calcium fly ash. Two types of low-calcium fly ash and quartz powder, with similar fineness as active and inert admixtures, were used as materials in this study. Under different water/binder ratios and hydration ages, the effects of the different types of admixtures and their dosages on the flexural and compressive strength of the composites were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption methods, in addition to an assessment of the degree of hydration of the fly ash, were employed to observe the hydration products at different ages, the microstructures of the hydration products, as well as their surface areas and pore size distributions. The results show that during the hydration period of 28 days, the low-calcium fly ash has a micro-aggregate filling physical effect. However, after 56 days, the hydration degree of fly ash begins to exceed 1%. This illustrates that the low-calcium fly ash has both the pozzolanic activity effect and micro-aggregate filling effect. In contrast, the low-calcium fly ash hydrated for 90 days is still dominated by the physical filling effect.

Structural and surface aspects of thermally treated copper aluminium mixed hydroxides

1991 ◽  
Vol 69 (10) ◽  
pp. 1511-1515 ◽  
Author(s):  
Awad I. Ahmed ◽  
S. E. Samra ◽  
S. A. El-Hakam
Keyword(s):  
Pore Structure ◽  
Copper Content ◽  
Textural Properties ◽  
Nitrogen Adsorption ◽  
Phase Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas ◽  
Structure Surface ◽  
Adsorption Desorption

CuO–Al2O3 catalysts containing various amounts of copper oxide have been prepared by precipitation. The phase changes were studied by X-ray diffraction. The results obtained revealed that the thermal treatment of solid CuO–Al2O3 at 700 °C produced only crystalline CuO. Heating to 900 °C led to the formation of copper alumina spinel together with unreacted CuO and γ-Al2O3. The spinel content was found to increase with increasing copper content. Nitrogen adsorption–desorption isotherms on the calcined samples have been measured. Surface areas have been calculated and the pore structure analysed. The textural properties of the system were found to depend on both the copper content and the calcination temperature. Key words: CuO, Al2O3 catalysts, structure, surface area, pore structure.

scholarly journals Preparation and Characterization of a Novel Amidoxime-Modified Polyacrylonitrile/Fly Ash Composite Adsorbent and Its Application to Metal Wastewater Treatment

2022 ◽  
Vol 19 (2) ◽  
pp. 856
Author(s):  
Yan Sun ◽  
Xiaojun Song ◽  
Jing Ma ◽  
Haochen Yu ◽  
Gangjun Liu ◽  
...  
Keyword(s):  
Fly Ash ◽  
Adsorption Process ◽  
Single Layer ◽  
Nitrogen Adsorption ◽  
Order Kinetic ◽  
X Ray Diffraction ◽  
Order Kinetic Model ◽  
Pseudo Second Order ◽  
High Degree

The polyacrylonitrile/fly ash composite was synthesized through solution polymerization and was modified with NH2OH·HCl. The amidoxime-modified polyacrylonitrile/fly ash composite demonstrated excellent adsorption capacity for Zn2+ in an aqueous medium. Fourier transform-Infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption, X-ray diffraction, and scanning electron microscopy were used to characterize the prepared materials. The results showed that the resulting amidoxime-modified polyacrylonitrile/fly ash composite was able to effectively remove Zn2+ at pH 4–6. Adsorption of Zn2+ was hindered by the coexisting cations. The adsorption kinetics of Zn2+ by Zn2+ followed the pseudo-second order kinetic model. The adsorption process also satisfactorily fit the Langmuir model, and the adsorption process was mainly single layer. The Gibbs free energy ΔG0, ΔH0, and ΔS0 were negative, indicating the adsorption was a spontaneous, exothermic, and high degree of order in solution system.

Study of the catalytic activity of Al-Fe pillared clays in the Baeyer–Villiger oxidation

Clay Minerals ◽  
2012 ◽  
Vol 47 (2) ◽  
pp. 275-284 ◽  
Author(s):  
L. S. Belaroui ◽  
A. Bengueddach
Keyword(s):  
Textural Properties ◽  
Nitrogen Adsorption ◽  
Pillared Clays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dissolved Iron ◽  
Surface Areas ◽  
Accessible Surface ◽  
Adsorption Desorption ◽  
Villiger Oxidation

AbstractThree types of AlFePILCs pillared clays have been prepared from Algerian clay precursors. They have been characterized and tested in the Baeyer–Villiger oxidation of cyclohexanone to caprolactone using benzaldehyde and oxygen as oxidant at room temperature. The structural and textural properties of the catalyst have been determined by X-ray diffraction, nitrogen adsorption-desorption isotherms and Mössbauer spectroscopy.The different activities of the clays have been related to their Fe contents and accessible surface areas. The induction period observed before the reaction started has been attributed to the dissolution of a portion of the Fe3+ cations, mediated by either the perbenzoic acid intermediate or the benzoic acid co-product. The reaction was indeed catalysed by a few ppm of dissolved iron cations and the catalysis of the Baeyer–Villiger oxidation reaction should mechanistically be considered as homogeneous.

Influence of Fly Ash Fineness on Autoclaved Energy Conservation Block's Performance and Hydration Products

2014 ◽  
Vol 599 ◽  
pp. 302-309 ◽  
Author(s):  
Bao Guo Ma ◽  
Li Xiong Cai ◽  
Shou Wei Jian ◽  
Lei Su
Keyword(s):  
Fly Ash ◽  
Microscopic Analysis ◽  
Production Performance ◽  
Strength Increase ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
Specific Strength ◽  
Autoclaved Aerated Concrete ◽  
Aerated Concrete

This article discussed the influence of FA fineness on the production performance and usability through the autoclaved aerated concrete slurry gas foaming curve and basic physical properties of blocks; meanwhile, studied the influence of different fineness FA on the composition and morphology of hydration products through X-ray diffraction analysis and scanning electron microscopic analysis, The results show that in the cement-fly ash-lime system autoclaved aerated concrete, the higher fineness of FA, the more water it need, and more sensitive the slurry presents; when the FA residue decrease from 17.8% to 8% through a 0.045mm square hole sieve screen, its specific surface area enlarge from 325m2/Kg to 388m2/Kg, the autoclaved aerated concrete specific strength increase by 53.24% and 40.96% in the case of the same ratio of water and resemble extended degree, respectively. Keep on increasing FA fineness does harm to its specific strength. The crystallinity of tobermorite, which is the main hydration products of autoclaved aerated concrete decreases with the increasing of FA fineness, however, crystallite size become larger.

Investigation on Jurassic Shale Gas Reservoir Characteristics from Northern Qaidam Basin

2017 ◽  
Vol 748 ◽  
pp. 441-445
Author(s):  
Gui Xi Xu ◽  
Shu Zhong Wang ◽  
Xiang Rong Luo ◽  
Ze Feng Jing
Keyword(s):  
Mineral Content ◽  
Qaidam Basin ◽  
Nitrogen Adsorption ◽  
Test Results ◽  
X Ray Diffraction ◽  
Gas Reservoir ◽  
Average Pore ◽  
X Ray ◽  
Shale Gas Reservoir ◽  
Surface Areas

The Jurassic continental shale from northern Qaidam basin was selected as the research object, through the analysis of X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and nitrogen adsorption experiment, the mineral composition and pore structure characteristics of Jurassic continental shale from the northern Qaidam basin have been investigated in detail. All shale samples studied are quite rich in clay minerals. The clay mineral content ranges from 59.8% to 83.3% with an average of 74.6%, and the brittle mineral content accounts for 16.5% to 39.3%. Nitrogen adsorption test results indicate that for mesopores and macropores of shale samples the average pore width is 2~200 nm, mainly centering on 10~50 nm, and the micropores of the shale samples have a centralized distribution of 0.5~1 nm. The shale samples show high specific surface areas of 4.6~15.2 m2/g. According to SEM results, interparticle mineral matrix pores are main pore type and slit-type pore are well developed.

scholarly journals Influence of Fly Ash on Mechanical Properties and Hydration of Calcium Sulfoaluminate-Activated Supersulfated Cement

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2514
Author(s):  
Zhengning Sun ◽  
Jian Zhou ◽  
Qiulin Qi ◽  
Hui Li ◽  
Na Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Flexural Strength ◽  
Heat Evolution ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Calcium Sulfoaluminate Cement ◽  
Calcium Sulfoaluminate ◽  
Granulated Blast Furnace Slag ◽  
Compressive And Flexural Strengths

This paper aimed to report the effects of fly ash (FA) on the mechanical properties and hydration of calcium sulfoaluminate-activated supersulfated cement (CSA-SSC). The CSA-SSC comprises of 80% granulated blast furnace slag (GBFS), 15% anhydrite, and 5% high-belite calcium sulfoaluminate cement (HB-CSA) clinker. The hydration products of CSA-SSC with or without FA were investigated by X-ray diffraction and thermogravimetric analysis. The experimental results indicated that the addition of FA by 10% to 30% resulted in a decrease in the rate of heat evolution and total heat evolution of CSA-SSC. As the content of FA was increased in the CSA-SSC system, the compressive and flexural strengths of the CSA-SSC with FA after 1 day of hydration were decreased. After 7 days of hydration, the compressive and flexural strength of CSA-SSC mixed with 10 wt.% and 20 wt.% of FA rapidly increased and exceeded that of ordinary Portland cement (OPC), especially the flexural strength. Moreover, the compressive strength of CSA-SSC mixed with 30 wt.% of FA after 90 days of hydration was close to that of OPC, and flexural strength of CSA-SSC mixed with 30 wt.% of FA after 7 days of hydration was close to that of OPC. The hydration products of the CSA-SSC and CSA-SSC mixed with FA were mainly ettringite and calcium silicate hydrate (C-S-H).

Comparison of FT-IR, Thermal Analysis and XRD for Determination of Products of Cement Hydration

2010 ◽  
Vol 168-170 ◽  
pp. 518-522 ◽  
Author(s):  
Zhi Hua Ou ◽  
Bao Guo Ma ◽  
Shou Wei Jian
Keyword(s):  
Thermal Analysis ◽  
Fourier Transform ◽  
Cement Hydration ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Cement Pastes ◽  
X Ray ◽  
Degree Of Hydration ◽  
Ft Ir

Fourier Transform Infrared Spectroscopy (FT-IR), thermal analysis and X-Ray Diffraction (XRD) are commonly performed to study the hydration products in cement pastes. The three methods were compared in this frame to detect products of cement hydration at different ages, especially at early ages (before 24h ages). The results indicate from the present experiment that CH (Calcium hydroxide) can be detected by three methods at all ages; C-S-H can be distinguished by FT-IR at all ages; ettringite may be detected by FT-IR before 24h ages and by XRD at all ages; and monosulphate can be detected by FT-IR before 24h ages. The process of cement hydration, characterized by formation and development of some hydration products, can be clearly observed by three methods. FT-IR is suggested for detecting the major hydration products before 24h ages, FT-IR and XRD are suggested for detecting the major hydration products after 24h ages, and thermal analysis is suggested for analyzing the degree of hydration quantitatively.

Utilization of CFB Fly Ash in Eco-Cement: Mechanical Properties and Microstructural Analysis

2010 ◽  
Vol 150-151 ◽  
pp. 885-889 ◽  
Author(s):  
Xiao Ming Liu ◽  
Yu Li ◽  
Ling Ling Zhang ◽  
Da Qing Cang
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Circulating Fluidized Bed ◽  
Microstructural Analysis ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Cement Pastes ◽  
X Ray ◽  
Xrd Techniques ◽  
Furnace Slag

The disposal of circulating fluidized bed (CFB) fly ash has been a serious environmental problem in the development of our society. In this work, the feasibility of recycling CFB fly ash as a blended material incorporating blast furnace slag (BFS), clinker and gypsum for the preparation of Eco-cement has been investigated. The mechanical properties of CFB fly ash based Eco-cements, including CFB fly ash–clinker system, CFB fly ash–ground BFS system, and CFB fly ash–ground BFS–clinker system, were evaluated in this paper. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to analyze the microstructural changes and the hydration products of the CFB fly ash based Eco-cement pastes. The results indicated that it is feasible to use CFB fly ash along with BFS and clinker to produce Eco-cement. The hydration products of CFB fly ash based Eco-cement are mostly ettringite and amorphous C-S-H gel, which are principally responsible for the strength and structure development of CFB fly ash based Eco-cement in the hydration process.

A COMPARISON OF THE X-RAY DIFFRACTION AND NITROGEN ADSORPTION SURFACE AREAS OF CARBON BLACKS AND CHARCOALS

1948 ◽  
Vol 26a (4) ◽  
pp. 236-242 ◽  
Author(s):  
J. C. Arnell ◽  
W. M. Barss
Keyword(s):  
Carbonaceous Material ◽  
Nitrogen Adsorption ◽  
Activation Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbon Blacks ◽  
Surface Areas ◽  
Crystallite Surface ◽  
Adsorption Surface ◽  
Order Of Magnitude

The surface areas, as determined from X-ray diffraction and low temperature nitrogen adsorption data, were compared for a number of carbon blacks and activated charcoals. Comparative data were also obtained on samples of charcoal at various stages of activation and after calcination. The X-ray diffraction data indicated that all the samples examined were composed of small graphitelike crystallites of the same order of magnitude, which had specific surfaces of about 2500 to 3000 sq. m. per cc. The nitrogen adsorption surface of a highly activated charcoal was found to be about equal to the X-ray surface. It is suggested that the crystallite surface represents the potential adsorption surface of a carbonaceous material and, providing that crystal growth does not occur during activation, the activation process makes these surfaces available to external adsorbate.

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