Microstructural and mechanical evolutions of sustainable cement blends containing fly ash and calcium carbonate whiskers induced by high temperature

Calcium carbonate (CaCO3) whisker, as a new type of microfibrous material, has been extensively used in the reinforcement of cementitious materials. However, the combined effect of CaCO3 whisker and fly ash on mechanical properties of cementitious materials under high temperatures was still unknown. In this study, the coupling effect of CaCO3 whisker, and fly ash on mechanical properties of the cement was investigated. Two sets of cement mortars were fabricated, including CaCO3 whisker-based mortar which contained 0 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% CaCO3 whisker as cement substitution and CaCO3 whisker-based fly ash mortar which contained 30 wt.% fly ash in addition to 0 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% CaCO3 whisker as cement substitution. Mass loss, compressive strength, and flexural strength of these two sets of specimens before and after being subjected to high temperatures of 200°C, 400°C, 600°C, 800°C, and 1000°C were measured. Based on the results of the aforementioned tests, load-deflection test was performed on the specimen which exhibited the superior performance to further study its mechanical behavior after exposure to high temperatures. Moreover, microstructural analysis, such as mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM), was conducted to reveal the damage mechanism of high temperature and to illustrate the combined effect of CaCO3 whisker and fly ash on high-temperature resistance of the cement. Results showed that fly ash could improve the high-temperature performance of CaCO3 whisker-based mortar before 600°C and limit the loss of strength after 600°C.

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In-situ reaction between arsenic/selenium and minerals in fly ash at high temperature during blended coal combustion

Journal of Fuel Chemistry and Technology ◽

10.1016/s1872-5813(20)30089-x ◽

2020 ◽

Vol 48 (11) ◽

pp. 1356-1364

Author(s):

Jun HAN ◽

Yang-shuo LIANG ◽

Bo ZHAO ◽

Zi-jiang XIONG ◽

Lin-bo QIN ◽

...

Keyword(s):

High Temperature ◽

Fly Ash ◽

Coal Combustion ◽

In Situ Reaction ◽

Blended Coal

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Fly Ash Utilisation in Mullite Fabrication: Development of Novel Percolated Mullite

Minerals ◽

10.3390/min11010084 ◽

2021 ◽

Vol 11 (1) ◽

pp. 84

Author(s):

Pramod Koshy ◽

Naomi Ho ◽

Vicki Zhong ◽

Luisa Schreck ◽

Sandor Alex Koszo ◽

...

Keyword(s):

High Temperature ◽

Fly Ash ◽

Mineral Resources ◽

Nucleating Agent ◽

High Temperature Deformation ◽

Temperature Deformation ◽

Stable Phase ◽

Power Stations ◽

Firing Shrinkage

Fly ash is an aluminosilicate and the major by-product from coal combustion in power stations; its increasing volumes are major economic and environmental concerns, particularly since it is one of the largest mineral resources based on current estimates. Mullite (3Al2O3·2SiO2) is the only stable phase in the Al2O3-SiO2 system and is used in numerous applications owing to its high-temperature chemical and mechanical stabilities. Hence, fly ash offers a potential economical resource for mullite fabrication, which is confirmed by a review of the current literature. This review details the methodologies to utilise fly ash with different additives to fabricate what are described as porous interconnected mullite skeletons or dense mullite bodies of approximately stoichiometric compositions. However, studies of pure fly ash examined only high-Al2O3 forms and none of these works reported long-term, high-temperature, firing shrinkage data for these mullite bodies. In the present work, high-SiO2 fly ashes were used to fabricate percolated mullite, which is demonstrated by the absence of firing shrinkage upon long-term high-temperature soaking. The major glass component of the fly ash provides viscosities suitably high for shape retention but low enough for ionic diffusion and the minor mullite component provides the nucleating agent to grow mullite needles into a direct-bonded, single-crystal, continuous, needle network that prevents high-temperature deformation and isolates the residual glass in the triple points. These attributes confer outstanding long-term dimensional stability at temperatures exceeding 1500 °C, which is unprecedented for mullite-based compositions.

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An Experimental Study on the Melting Solidification of Municipal Solid Waste Incineration Fly Ash

Sustainability ◽

10.3390/su13020535 ◽

2021 ◽

Vol 13 (2) ◽

pp. 535

Author(s):

Jing Gao ◽

Tao Wang ◽

Jie Zhao ◽

Xiaoying Hu ◽

Changqing Dong

Keyword(s):

Heavy Metals ◽

High Temperature ◽

Fly Ash ◽

Municipal Solid Waste ◽

Solid Waste ◽

Liquid Slag ◽

Melting Process ◽

Waste Incineration ◽

Municipal Solid Waste Incineration ◽

Mswi Fly Ash

Melting solidification experiments of municipal solid waste incineration (MSWI) fly ash were carried out in a high-temperature tube furnace device. An ash fusion temperature (AFT) test, atomic absorption spectroscopy (AAS), scanning electron microscope (SEM), and X-ray diffraction (XRD) were applied in order to gain insight into the ash fusibility, the transformation during the melting process, and the leaching behavior of heavy metals in slag. The results showed that oxide minerals transformed into gehlenite as temperature increased. When the temperature increased to 1300 °C, 89 °C higher than the flow temperature (FT), all of the crystals transformed into molten slag. When the heating temperatures were higher than the FT, the volatilization of the Pb, Cd, Zn, and Cu decreased, which may have been influenced by the formation of liquid slag. In addition, the formation of liquid slag at a high temperature also improved the stability of heavy metals in heated slag.

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Microstructural and non-destructive investigation of the effect of high temperature exposure on ground ferronickel slag blended fly ash geopolymer mortars

Journal of Building Engineering ◽

10.1016/j.jobe.2021.103099 ◽

2021 ◽

pp. 103099

Author(s):

Jhutan Chandra Kuri ◽

Subhra Majhi ◽

Prabir Kumar Sarker ◽

Abhijit Mukherjee

Keyword(s):

High Temperature ◽

Fly Ash ◽

High Temperature Exposure ◽

Ferronickel Slag ◽

Temperature Exposure ◽

Non Destructive

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The Pre-Controlling Technology of Spontaneous Combustion in Gutter-Up Gob for Fully Mechanized Top-Coal Caving Face

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.634-638.3688 ◽

2013 ◽

Vol 634-638 ◽

pp. 3688-3695 ◽

Cited By ~ 1

Author(s):

Yang Xiao ◽

Shu Gang Li ◽

Jun Deng ◽

Xu Wang

Keyword(s):

Carbon Dioxide ◽

High Temperature ◽

Fly Ash ◽

Coal Mining ◽

Spontaneous Combustion ◽

Good Effect ◽

Air Leakage ◽

Coal Spontaneous Combustion ◽

Liquid Carbon ◽

Fire Extinguishing

In China, as popularizing the technology of fully mechanized top-coal mining and increasing the strength and depth of mining, the gutter-up gob can be formed. But the work of fire preventing and extinguishing for its coal spontaneous combustion is more complexity and difficulty. In this paper, based on geology parameters and mining practice for 93up12 fully mechanized top-coal caving face in Nantun coalmine, the form and character of gutter-up gob are analyzed. According to the hidden danger of high temperature for spontaneous combustion in the gob, we adopt the comprehension technologies of fire extinguishing and preventing which include sealing air-leakage, grouting, and injecting compound gel with fly-ash, foam of retarding oxidation, liquid carbon dioxide, and gas of nitrogen. By putting in practice the pre-controlling technology in gutter-up gob and monitoring data of target gases, it obtains a good effect and ensures the safety in production of the fully-mechanized top-coal caving face.

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