scholarly journals Characteristics and impact of aged coal ash with slag emplaced in a karst cave: the case of Divaška jama, Slovenia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Andreea Oarga-Mulec ◽  
Sara Skok ◽  
Tatjana Simčič ◽  
Janez Mulec
Keyword(s):  
Harmful Effect ◽  
Bottom Ash ◽  
Coal Ash ◽  
Karst Cave ◽  
Mineral Phases ◽  
Cave Sediments ◽  
Microbial Metabolic Activity ◽  
Cave Sediment ◽  
Ecotoxicological Assays

AbstractA mixture of coal bottom ash and slag, with a fraction of fly ash (CAFAS) from steam locomotives, was placed in the cave Divaška jama to delimit and level tourist trails. Emplacement began in 1914 and carried on for several decades. The CAFAS mixed with other cave material gradually changed its structure and appearance. Currently the concentration of some elements in the CAFAS (As, Cu, Hg, Ni, Pb, Zn), and also to a lesser extent in cave sediments (Cr, Cu, Ni), indicates a possibly harmful effect on sediment-associated biota based on ecotoxicological assays. Compared to the cave sediment, the CAFAS contains distinctly different mineral phases and presents a different source of radioactivity. Microbial metabolic activity of CAFAS is low, 0.22 μl O2/gDW h, but higher than that of cave sediment. The present environmental hazards from CAFAS are estimated to be low. Whereas the emplacement of CAFAS was seen initially a long-term solution for waste disposal and management of the cave, it turned out that CAFAS enriches the underground environment with inorganic and organic compounds and disperses pollution into the cave ecosystem. After its removal from the cave, the CAFAS should be investigated thoroughly due to its susceptibility to alteration.

Coal ash as structural fill, with special reference to Ontario experience

1988 ◽  
Vol 25 (4) ◽  
pp. 694-704 ◽  
Author(s):  
P. S. Toth ◽  
H. T. Chan ◽  
C. B. Cragg
Keyword(s):  
Fly Ash ◽  
Groundwater Monitoring ◽  
Bottom Ash ◽  
Coal Ash ◽  
Engineering Properties ◽  
Physical Behavior ◽  
Corrosion Studies ◽  
Groundwater Regime ◽  
The Impact

Fly ash and bottom ash obtained from coal-fired electric power generating stations can be used as alternatives to natural materials for the construction of structural fills. The engineering properties of coal ash pertinent to its use in structural fills are discussed. Four case studies of coal ash structural fills are presented. The performance of these fills was monitored during and after construction. These cases demonstrate that the physical behavior of fly ash is similar to that of silt and that it can be handled with similar methods. Groundwater monitoring data from existing fly ash fills are presented to show the impact that ash leachate migrating into the groundwater regime has on water quality. Results of long-term corrosion studies are presented to show that metals buried in ash, used in such structures as culverts, cable ducts, guard rails and streetlights, are not adversely affected. Ash leachate was found not to be detrimental to good-quality concrete structures. Key words: fly ash, fill, compaction, leachate, corrosion, concrete.

Improvement Of The Method Of Winter Concreting With The Use Of Heating Wires

2019 ◽  
pp. 51-58
Keyword(s):  
Harmful Effect ◽  
Electric Heating ◽  
Strength Development ◽  
Construction Sites ◽  
Dominant Position ◽  
Heating Wire ◽  
Hands On ◽  
Basic Parameters ◽  
Monolithic Structures

Long-term experience of application of a method of electric heating by heating wires of the monolithic concrete and reinforced concrete structures erected in winter conditions is analyzed. This method, developed by the author of the article, took a dominant position on the construction sites due to the simplicity and efficiency in comparison with the mass applied in those years, the method of electric heating of concrete with steel round and strip electrodes. The data on labor intensity, material and energy costs in comparison with the method of rod electric heating are presented. Step-by-step technological operations on preparatory works and electric heating of monolithic structures with the use of extensive hands-on material, which formed the basis for the development of technological regulations, supplemented by a number of new proposals to improve the technology of works, are concretized. In order to work out the optimal mode of heat treatment, the studies of the concrete thermal conductivity factor in the process of its heating and strength development were carried out. The method for calculation of the basic parameters of concrete electric heating is presented. For simplification of calculations, for a wide contingent of masters, superintendents and technical personnel, the nomogram , making it possible with sufficient accuracy under the construction conditions to calculate the necessary heating parameters, was developed. The necessity of grounding the heating wire remaining in the concrete to reduce the harmful effect of magnetic radiation from various appliances and household appliances on the human body is noted.

scholarly journals Reactivity of Ground Coal Bottom Ash to Be Used in Portland Cement

J ◽  
2021 ◽  
Vol 4 (3) ◽  
pp. 223-232
Author(s):  
Esperanza Menéndez ◽  
Cristina Argiz ◽  
Miguel Ángel Sanjuán
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Bottom Ash ◽  
Blended Cement ◽  
Coal Ash ◽  
Pozzolanic Reaction ◽  
Natural Sand ◽  
Coal Bottom Ash ◽  
Novel Material ◽  
Pozzolanic Properties

Ground coal bottom ash is considered a novel material when used in common cement production as a blended cement. This new application must be evaluated by means of the study of its pozzolanic properties. Coal bottom ash, in some countries, is being used as a replacement for natural sand, but in some others, it is disposed of in a landfill, leading thus to environmental problems. The pozzolanic properties of ground coal bottom ash and coal fly ash cements were investigated in order to assess their pozzolanic performance. Proportions of coal fly ash and ground coal bottom ash in the mixes were 100:0, 90:10, 80:20, 50:50, 0:100. Next, multicomponent cements were formulated using 10%, 25% or 35% of ashes. In general, the pozzolanic performance of the ground coal bottom ash is quite similar to that of the coal fly ash. As expected, the pozzolanic reaction of both of them proceeds slowly at early ages, but the reaction rate increases over time. Ground coal bottom ash is a promising novel material with pozzolanic properties which are comparable to that of coal fly ashes. Then, coal bottom ash subjected to an adequate mechanical grinding is suitable to be used to produce common coal-ash cements.

Precipitation of heavy metals from coal ash leachate using biogenic hydrogen sulfide generated from FGD gypsum

2013 ◽  
Vol 67 (2) ◽  
pp. 311-318 ◽  
Author(s):  
Madawala Liyanage Duminda Jayaranjan ◽  
Ajit P. Annachhatre
Keyword(s):  
Heavy Metals ◽  
Hydrogen Sulfide ◽  
Sulfate Reduction ◽  
Bottom Ash ◽  
Coal Ash ◽  
Reduction Process ◽  
Fgd Gypsum ◽  
Sulfate Reducing ◽  
Sulfate Reduction Process ◽  
Biological Sulfate Reduction

Investigations were undertaken to utilize flue gas desulfurization (FGD) gypsum for the treatment of leachate from the coal ash (CA) dump sites. Bench-scale investigations consisted of three main steps namely hydrogen sulfide (H2S) production by sulfate reducing bacteria (SRB) using sulfate from solubilized FGD gypsum as the electron acceptor, followed by leaching of heavy metals (HMs) from coal bottom ash (CBA) and subsequent precipitation of HMs using biologically produced sulfide. Leaching tests of CBA carried out at acidic pH revealed the existence of several HMs such as Cd, Cr, Hg, Pb, Mn, Cu, Ni and Zn. Molasses was used as the electron donor for the biological sulfate reduction (BSR) process which produced sulfide rich effluent with concentration up to 150 mg/L. Sulfide rich effluent from the sulfate reduction process was used to precipitate HMs as metal sulfides from CBA leachate. HM removal in the range from 40 to 100% was obtained through sulfide precipitation.

Microstructure and Mechanical Properties of Ambiently-Cured Blended Coal Ash-Based Geopolymer Concrete

2016 ◽  
Vol 857 ◽  
pp. 400-404
Author(s):  
Tian Yu Xie ◽  
Togay Ozbakkaloglu
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Compressive Strength ◽  
Fly Ash ◽  
Bottom Ash ◽  
Coal Ash ◽  
Geopolymer Concrete ◽  
Mass Ratio ◽  
Blended Coal ◽  
Microstructure And Mechanical Properties

This paper presents the results of an experimental study on the behavior of fly ash-, bottom ash-, and blended fly and bottom ash-based geopolymer concrete (GPC) cured at ambient temperature. Four bathes of GPC were manufactured to investigate the influence of the fly ash-to-bottom ash mass ratio on the microstructure, compressive strength and elastic modulus of GPC. All the results indicate that the mass ratio of fly ash-to-bottom ash significantly affects the microstructure and mechanical properties of GPCs

Compressive Strength and Density of Cementless Unfired Lightweight Brick Utilizing Coal Ash from Coal-Fired Thermal Power Plant

2013 ◽  
Vol 594-595 ◽  
pp. 527-531
Author(s):  
Mohamad Ezad Hafez Mohd Pahroraji ◽  
Hamidah Mohd Saman ◽  
Mohamad Nidzam Rahmat ◽  
Kartini Kamaruddin ◽  
Ahmad Faiz Abdul Rashid
Keyword(s):  
Compressive Strength ◽  
Power Plant ◽  
Thermal Power Plant ◽  
Thermal Power ◽  
Bottom Ash ◽  
Coal Ash ◽  
Hydrated Lime ◽  
Raw Material ◽  
The World ◽  
Blastfurnace Slag

Millions tons of coal ash which constitute of fly ash and bottom ash were produced annually throughout the world. They were significant to be developed as masonry brick to substitute the existing widely used traditional material such as clay and sand brick which were produced from depleting and dwindling natural resources. In the present study, the coal ash from coal-fired thermal power plant was used as the main raw material for the fabrication of cementless unfired lightweight brick. The binder comprising of Hydrated Lime (HL)-activated Ground Granulated Blastfurnace Slag (GGBS) system at binding ratio 30:70, 50:50 and 70:30 were used to stabilize the coal ash in the fabrication process of the brick. Foam was used to lightweight the brick. The compressive strength and ambient density were evaluated on the brick. The results indicated that the brick incorporating HL-GGBS system achieved higher strength of 20.84N/mm2 at 28 days compare to the HL system with strength of 13.98N/mm2 at 28 days. However, as the quantity of foam increase at 0%, 25%, 50%, 75% and 100%, the strength and density for the brick decreased.

scholarly journals Long-term Properties of Coal Ash Embankments

2015 ◽  
Vol 1 (4) ◽  
pp. 1-6
Author(s):  
Atsuko Sato ◽  
Takahiro Yamanashi ◽  
Satoshi Nishimoto ◽  
Teruyuki Suzuki ◽  
Shinichiro Kawabata
Keyword(s):  
Coal Ash

scholarly journals Influence of the Size of Coal Ash FAU Zeolites Used as Dopants on the Sensing Properties of Nb2O5 Thin Films

2020 ◽  
Vol 2 (1) ◽  
pp. 3
Author(s):  
Katerina Lazarova ◽  
Silviya Boycheva ◽  
Marina Vasileva ◽  
Denitza Zgureva ◽  
Tsvetanka Babeva
Keyword(s):  
Thin Films ◽  
Power Plants ◽  
Thermal Power ◽  
Coal Ash ◽  
Reflectance Spectra ◽  
Sensing Properties ◽  
Volatile Organic ◽  
Coating Method ◽  
Reflectance Measurements

In this study, solid waste from coal combustion in thermal power plants (TPPs) was used for the synthesis of zeolite Na-X samples. They were prepared by the long-term alkaline atmospheric conversion of coal ash collected from the electrostatic precipitators in the TPP “AES Galabovo”. When used in the form of thin films/layers, the optical detection of volatile organic compounds (VOCs) is possible due to a change in their reflectance spectra and color. In order to improve the sensing properties of synthesized zeolites, they were wet milled for 60 s and both milled and unmilled zeolites were used as dopants for the niobium oxide matrix in the form of thin films deposited by the spin-coating method on a silicon substrate. The surface morphology and structure of both zeolite powders were studied by scanning electron microscopy, while their size was determined by dynamic light scattering (DLS) spectra. Optical constants (refractive index, n, and extinction coefficient, k) and the thickness of the films were calculated from reflectance measurements. The change in the reflection coefficient ∆R of the films was determined from measured reflectance spectra prior to and after exposure to probe acetone molecules. An increase in the reaction of the films with milled zeolites to acetone, compared to the samples with unmilled zeolites, is demonstrated.

scholarly journals Lime Treatment of Coal Bottom Ash for Use in Road Pavements: Application to El Jadida Zone in Morocco

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2674 ◽  
Author(s):  
Souad El Moudni El Alami ◽  
Raja Moussaoui ◽  
Mohamed Monkade ◽  
Khaled Lahlou ◽  
Navid Hasheminejad ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Low Cost ◽  
Thermal Power ◽  
Experimental Studies ◽  
Bottom Ash ◽  
Coal Ash ◽  
Road Construction ◽  
Dry Density ◽  
Second Phase ◽  
Lime Treatment

Industrial waste causes environmental, economic, and social problems. In Morocco, the Jorf Lasfar Thermal Power Station produces two types of coal ash with enormous quantities: fly ash (FA) and Bottom ash (BA). FA is recovered in cement while BA is stored in landfills. To reduce the effects of BA disposal in landfills, several experimental studies have tested the possibility of their recovery in the road construction, especially as a subbase. In the first phase of this study, the BA underwent a physicochemical and geotechnical characterization. The results obtained show that the BA should be treated to improve its mechanical properties. The most commonly used materials are lime and cement. In the selected low-cost treatment, which is the subject of the second phase of the study, lime is used to improve the low pozzolanicity of BA while calcarenite sand is used to increase the compactness. Several mixtures containing BA, lime, and calcarenite sand were prepared. Each of these mixtures was compacted in modified Proctor molds and then subjected to a series of tests to study the following characteristics: compressive strength, dry and wet California Bearing Ratio (CBR), dry density and swelling. The composition of each mixture was based on an experimental design approach. The results show that the values of the compressive strength, the dry density, and the CBR index have increased after treatment, potentially leading to a valorization of the treated BA for use in a subbase.

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