Prediction of Hydraulic Conductivity of Fly Ash Built-in Mineral Sealing Layers

2017 ◽  
Author(s):  
Mariola Wasil
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Laboratory Tests ◽  
Physical Parameters ◽  
Low Permeability ◽  
Empirical Formulas ◽  
Semi Empirical ◽  
Sealing Layer ◽  
Compaction Method

Mineral barrier protects the groundwater and soil from contamination by insulating the leakage of harmful substances from landfill. One of the most important parameters, which decides about usefulness of material to built-in sealing layers, is hydraulic conductivity. Researchers have conducted investigations with the possibility of utilising fly ash as a mineral sealing layer material, which is justified by its low permeability and other properties. It is known that laboratory tests of hydraulic conductivity are often long-term and require expensive equipment. Therefore, to avoid this, researchers trying to assess permeability of tested material with empirical or semi empirical formulas. The aim of the paper is to compare the results of hydraulic conductivity of fly ash obtained from the laboratory tests and from estimation using different empirical formulas. Fly ash was compacted by the Standard Proctor compaction method at the optimum moisture content. The results obtained from empirical equations were variable. It was observed that the Kozeny-Carman formula and other, based on a few physical parameters of the soil, gave better results in prediction of hydraulic conductivity of fly ash than equations based on only one parameter.

Hydraulic conductivity behavior of soilcrete specimens created from dredging sand, cement, and bentonite

2021 ◽  
Author(s):  
Hoang-Hung Tran-Nguyen ◽  
Bich Thi Luong ◽  
Phong Duy Nguyen ◽  
Khanh Duy Tuan Nguyen
Keyword(s):  
Hydraulic Conductivity ◽  
Mekong Delta ◽  
Research Data ◽  
Low Permeability ◽  
High Permeability ◽  
Seepage Flows ◽  
Southern Vietnam ◽  
Hydraulic Gradients ◽  
Conductivity Behavior

Abstract Dredging sand is an inexpensive material utilized to rise elevations of highway embankments and earth levee bodies in the Southern Vietnam. However, high permeability of the dredging sand can cause failures due to seepage flows during annual flood seasons. The dredging sand mixing cement with or without bentonite is expected to be suitable low permeability as an impermeable material. However, hydraulic conductivity of soilcrete and bentonite specimens created from dredging sand taken in the Mekong delta has limit research data. This study aims at better understanding the hydraulic conductivity of dredging sand samples taken in Dong Thap province mixed with cement and bentonite. The effects of the hydraulic conductivity of soilcrete and bentonite soilcrete specimens on time, cement contents, bentonite contents, cement types, and hydraulic gradients were investigated. The tests followed the ASTM D5084 standard using the both falling head-constant tailwater and falling head-rising tailwater methods. The results indicate that: (1) the hydraulic conductivity of the soilcrete and bentonite specimens decreased with increasing in testing duration and cement contents; (2) the hydraulic conductivity of the soilcrete specimens was lower 104 to 105 times than that of the compacted sand; (3) the hydraulic conductivity of the bentonite soilcrete specimens was lower 10 times than those of the soilcrete specimens; (5) the PCS cement can induce long-term reduction of soilcrete hydraulic; (6) effect of hydraulic gradients on soilcrete hydraulic conductivity was ignorable; (6) the soilcrete hydraulic conductivity varies from 10− 9 to 10− 10 m/s.

Influence of Fly Ash on Clay Liner

2012 ◽  
Vol 518-523 ◽  
pp. 2543-2546
Author(s):  
Xue Jing Sun ◽  
Yong Sheng Zhao ◽  
Zhi Wei Sang
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Moisture Content ◽  
Laboratory Tests ◽  
Optimum Moisture Content ◽  
Compacted Clay ◽  
Landfill Sites ◽  
Cracking Performance ◽  
Desiccation Cracking ◽  
Different Content

Compacted clay is commonly used as an essential material for reducing the permeability in landfill sites. However, compacted clay has defect with shrinkage and desiccation cracking during cyclic drying and wetting, which may increase hydraulic conductivity of compacted clay. It’s necessary to modify clay, and make it have anti-cracking performance. The main objective of the study is to determine the content of fly ash on clay. Laboratory tests were done to determine optimum moisture content, hydraulic conductivity, volume shrinkage on different content fly ash modified clay. It was determined that a certain proportion of fly ash can improve the permeability of clay, and reduce the cracking clay.

Hydraulic conductivity of saturated granular soils determined using a constriction-based technique

2012 ◽  
Vol 49 (5) ◽  
pp. 607-613 ◽  
Author(s):  
Buddhima Indraratna ◽  
Vo Trong Nguyen ◽  
Cholachat Rujikiatkamjorn
Keyword(s):  
Particle Size ◽  
Hydraulic Conductivity ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Granular Medium ◽  
Laboratory Tests ◽  
Filter Material ◽  
Granular Soils ◽  
Empirical Power ◽  
Semi Empirical

This study presents a new semi-empirical approach for predicting the saturated hydraulic conductivity of noncohesive (granular) soils through a constriction size–based technique. For the same particle-size distribution of a granular filter material, there can be many different void distributions depending on the as-compacted density. Therefore, particle-size distribution is not unique in determining the hydraulic conductivity as proposed in numerous earlier studies. In contrast, the constriction-size distribution is unique for a given as-placed density of the material, and therefore it is a better representation of hydraulic conductivity as proposed in this study. Accordingly, the hydraulic conductivity of a granular medium can be represented by an empirical power function that has been established on the basis of 60 laboratory tests.

A review of the mechanical and leaching performance of stabilized/solidified contaminated soils

2014 ◽  
Vol 22 (1) ◽  
pp. 66-86 ◽  
Author(s):  
Reginald B. Kogbara
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Contaminated Soils ◽  
Superior Performance ◽  
Complex Nature ◽  
Optimum Water Content ◽  
The Matrix ◽  
Long Term Performance ◽  
Term Performance

Stabilization/solidification (S/S) technology, which basically involves chemical fixation and immobilization of contaminants (primarily metals) in the matrix of cementitious binders, is widely used for treatment of contaminated soils. This paper presents a critical review of the performance of commonly used blended binder systems in S/S technology. The binders considered are Portland cement and blends of cement–fly ash, cement–slag, lime–slag, and lime–fly ash. This work compares and evaluates the performance of contaminated soils treated by the binders in terms of commonly used mechanical and leaching properties, including unconfined compressive strength (UCS), bulk density, hydraulic conductivity, and leachability. The long-term performance of S/S-treated soils is also reviewed. It was observed that the inclusion of slag in a binder blend gave superior performance compared to fly ash. Generally, the leachability of common contaminants in soil can be reduced to acceptable levels with approximately 20%–35% dosage of the different binders. The UCS was observed to be optimum around the optimum water content for compaction. The hydraulic conductivity was approximately 10−9 m/s over time. Long-term performance of treated soils showed consistent effectiveness over a period of 5–14 years with fluctuations in mechanical and leaching behaviour caused by the complex nature and variability of S/S-treated soils.

Agglomeration in an Industrial FBC Boiler

2003 ◽  
Author(s):  
L. Jia ◽  
E. J. Anthony
Keyword(s):  
Fly Ash ◽  
Bulk Density ◽  
Significant Contribution ◽  
Strength Development ◽  
Physical Parameters ◽  
Reaction Sintering ◽  
High Melting Point ◽  
Boiler Operation ◽  
Chemical Behaviour

An industrial FBC boiler operated by a paper products company encountered significant fouling problems that required boiler shutdown and maintenance to remove deposits. CETC investigated the fouling problems. Samples from the boiler were analyzed and the results indicated that fouling was associated with near-quantitative conversion of CaO in the deposits to CaSO4, with particle expansion and possible chemical reaction sintering. There was no evidence, with possibly the exception of deposits on the distributor tuyeres, of any significant contribution from the elements traditionally associated with ash softening, e.g., Na and K. Vanadium was not considered an issue, because earlier work showed that V quantitatively combines with CaO (or MgO if present), to form high melting point vanadates. Extended sulphation tests on both bed ash and limestone were conducted in the laboratory. The results confirmed that sulphation alone was sufficient to cause strength development in the bed solids. There was also a clear difference in the strength development between bed and fly ash. Fly ash agglomerates were much weaker than those of bed ash. The long-term sulphation tests also demonstrated that the presence of “inert” ash components helps to reduce the degree of conversion of CaO to CaSO4 and to reduce the strength of the deposits. Strength development tests showed that the current limestone used in this particular boiler formed exceptionally strong deposits after being exposed to sulphation conditions for extended periods of time at 850°C. Thus it appeared that if this limestone was replaced it might benefit boiler operation. Kaolin is used at the plant to reduce distributor tuyere fouling. Chemical analysis of the deposits suggested that kaolin may help to reduce fouling, but this may well be due to physical rather than chemical behaviour of the kaolin. This work suggests that the kaolin could be replaced by another refractory material, suitably low in Na and K, since the sulphation levels in the deposits were sufficient by themselves to lead to strength development, and so any benefit of the kaolin action as an alkali metal “getter” is probably offset by that fact. Attempts to find some significant physical parameters to differentiate the tendency of bed ashes to agglomerate were not successful in this work, although previous work has suggested that bulk density may be important, with materials having a higher bulk density showing a greater tendency to agglomerate.

Subcritical Crack Growth and Long-Term Strength in Rock and High-Strength and Ultra Low-Permeability Concrete

2009 ◽  
Vol 58 (6) ◽  
pp. 525-532 ◽  
Author(s):  
Yoshitaka NARA ◽  
Masafumi TAKADA ◽  
Daisuke MORI ◽  
Hitoshi OWADA ◽  
Tetsuro YONEDA ◽  
...  
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
High Strength ◽  
Low Permeability ◽  
Term Strength

scholarly journals Classifying the Biological Status of Honeybee Workers Using Gas Sensors

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 166
Author(s):  
Jakub T. Wilk ◽  
Beata Bąk ◽  
Piotr Artiemjew ◽  
Jerzy Wilde ◽  
Maciej Siuda
Keyword(s):  
Gas Sensors ◽  
Laboratory Tests ◽  
Test Chamber ◽  
Ambient Air ◽  
True Positive Rate ◽  
True Positive ◽  
Positive Rate ◽  
Parameters Of Accuracy ◽  
Selection Of

Honeybee workers have a specific smell depending on the age of workers and the biological status of the colony. Laboratory tests were carried out at the Department of Apiculture at UWM Olsztyn, using gas sensors installed in two twin prototype multi-sensor detectors. The study aimed to compare the responses of sensors to the odor of old worker bees (3–6 weeks old), young ones (0–1 days old), and those from long-term queenless colonies. From the experimental colonies, 10 samples of 100 workers were taken for each group and placed successively in the research chambers for the duration of the study. Old workers came from outer nest combs, young workers from hatching out brood in an incubator, and laying worker bees from long-term queenless colonies from brood combs (with laying worker bee’s eggs, humped brood, and drones). Each probe was measured for 10 min, and then immediately for another 10 min ambient air was given to regenerate sensors. The results were analyzed using 10 different classifiers. Research has shown that the devices can distinguish between the biological status of bees. The effectiveness of distinguishing between classes, determined by the parameters of accuracy balanced and true positive rate, of 0.763 and 0.742 in the case of the best euclidean.1nn classifier, may be satisfactory in the context of practical beekeeping. Depending on the environment accompanying the tested objects (a type of insert in the test chamber), the introduction of other classifiers as well as baseline correction methods may be considered, while the selection of the appropriate classifier for the task may be of great importance for the effectiveness of the classification.

scholarly journals Assessing Stream-Aquifer Connectivity in a Coastal California Watershed

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 416
Author(s):  
Bwalya Malama ◽  
Devin Pritchard-Peterson ◽  
John J. Jasbinsek ◽  
Christopher Surfleet
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Water Level ◽  
Time Series Data ◽  
Series Data ◽  
Low Permeability ◽  
Pumping Tests ◽  
Stream Flows ◽  
The Impact

We report the results of field and laboratory investigations of stream-aquifer interactions in a watershed along the California coast to assess the impact of groundwater pumping for irrigation on stream flows. The methods used include subsurface sediment sampling using direct-push drilling, laboratory permeability and particle size analyses of sediment, piezometer installation and instrumentation, stream discharge and stage monitoring, pumping tests for aquifer characterization, resistivity surveys, and long-term passive monitoring of stream stage and groundwater levels. Spectral analysis of long-term water level data was used to assess correlation between stream and groundwater level time series data. The investigations revealed the presence of a thin low permeability silt-clay aquitard unit between the main aquifer and the stream. This suggested a three layer conceptual model of the subsurface comprising unconfined and confined aquifers separated by an aquitard layer. This was broadly confirmed by resistivity surveys and pumping tests, the latter of which indicated the occurrence of leakage across the aquitard. The aquitard was determined to be 2–3 orders of magnitude less permeable than the aquifer, which is indicative of weak stream-aquifer connectivity and was confirmed by spectral analysis of stream-aquifer water level time series. The results illustrate the importance of site-specific investigations and suggest that even in systems where the stream is not in direct hydraulic contact with the producing aquifer, long-term stream depletion can occur due to leakage across low permeability units. This has implications for management of stream flows, groundwater abstraction, and water resources management during prolonged periods of drought.

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

Minerals ◽  
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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