Fly Ash In Concrete Production Properties And Uses PdfBy Florrocvianess1960 In and pdf 12.05.2021 at 09:03 3 min read
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- Fly Ash in Concrete: Properties and Performance
- ACI PRC-232.2-18: Report on the Use of Fly Ash in Concrete
- US4256504A - Fly ash-based cement - Google Patents
- Properties of Low Strength Concrete made with Recycled Concrete Aggregate and Fly Ash
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Fly ash is a fine powder that is a byproduct of burning pulverized coal in electric generation power plants. Fly ash is a pozzolan, a substance containing aluminous and siliceous material that forms cement in the presence of water. When mixed with lime and water, fly ash forms a compound similar to Portland cement.
Fly Ash in Concrete: Properties and Performance
These quantities are about 0. Nowadays, this ash disposal process with its safe management becomes environmental important issues and major challenges to the industry, environmentalists, scientists and so on. As a consequence, this study principally deals with the assessment of different properties and uses of coal ash for safe environment around the plant area. Thus, the prime objectives of this research are to evaluate the physical, chemical and engineering properties of coal ash for its classification, suitable options of utilizations and safe environment under direct field investigation and laboratory analysis.
The analyzed major and minor chemical properties of coal ash indicate good quality ash. In addition, the major compositions suggest the similar quality while the concentration of SiO 2 In the case of engineering properties, grain size, hydraulic conductivity, consistency, compaction, compressive strength and shear strength aspects are presented.
The results replicate that effect of addition of coal ash with sand and cement can improve the quality of mixtures specifically increasing the consistency, compressive strength, shear strength and bearing capacity, whereas reducing the hydraulic conductivity of concrete or soil. At the end, a concise discussion has been drawn on the prospective utilizations and management of this ash for present and future environmental sustainability around the area.
According to the Bangladesh topographic sheet no. From the annual report of BPDB , every year 0. These ashes are dumped with water in two ash ponds near the BTPP, where this dumped water is being discharged by an artificial channel to the river Tilai. However, in the present day the amount of coal ash produced from this power plant cannot be ignored because of its direct or indirect impact on environment. Many researchers reported that the coal ash can contaminate the soil, water, air and other components of environment through the mobilization of toxic elements EPRI ; Silva et al.
The leaching of heavy or toxic elements from coal ash can cause acute or chronic toxicity in the soil and water environs Finkelman et al. The presence of calcium in the ash can limit the release of dissolved arsenic by formation of calcium arsenic precipitates EPRI Moreover, there are some researches conducted by Howladar , , Howladar and Hasan , Howladar and Karim , Howladar et al.
Thus, the prime objectives of this study are to ascertain the physical, chemical and engineering properties of the coal ash to develop the possible plan on the utilization of disposed coal ash which must be helpful to reduce the disposal problem around the area. Finally, this study describes and recommends the possible sectors of reuse and management of ash for safe and sound environment. During this process, the coal is crushed into powder-like fine materials which are pumped with compressed air into the boiler.
Coal powder is fired to generate heat, which plays the vital role to produce steam to run through the turbine. These collected particles are conventionally known as fly ash. At this plant, the fly ash does not exposed but automatically collected and transported by pneumatic supply line to make slurry and dump them into a large pond called ash pond where it is reserved under the water. Though there are many uses of ash, it is essential to understand the environmental impacts before its utilization.
Actually, the health and environmental hazards mainly come from the toxic and radioactive elements of the ash residues. Contaminated leaches from acidic fly ash can pose the highest toxicity problem for aquatic environments Roy et al. Coal ash composed of heavy metals like lead Pb is of large public concern due to toxicity to animals as well as human beings, especially young children Manz Fly ash also consists of considerable amount of organic and inorganic chemical components such as arsenic, cadmium, chromium, lead, mercury, selenium and copper which have adverse effects on living beings and can contaminate the environment as a whole.
Coal fly ash is a very fine material produced by the burning of pulverized coal in a thermal power plant carried by the flue gas and collected by the electrostatic precipitator. The research material of this analysis is disposed coal ash which collected from BTTP. Actually, the present research mainly deals with the assessment of physical, chemical and engineering properties by laboratory tests. In the case of understanding the common physical characteristics, the coal ash simply examined by naked eye with hand, whereas the chemical analysis of collected ash samples had been performed in laboratory.
Different types of methods were used to determine different parameters of the samples. To analyze the chemical properties of fly ash, primarily the necessary quantity of ash samples was digested with aqua regia.
Then the digested samples were analyzed by graphite atomization method and flame atomization method in atomic absorption spectroscopy AAS, Agilent, Australia.
Arsenic, chromium, cobalt, copper, cadmium and lead were measured by graphite atomization method. Zinc and manganese were measured by flame atomization method. Atomic absorption spectroscopy AAS is a spectroanalytical procedure for the quantitative determination of chemical elements employing the absorption of optical radiation light by free atoms in the gaseous state.
Graphite furnace atomic absorption spectrometry GFAAS [also known as electrothermal atomic absorption spectrometry ETAAS ] is a type of spectrometry that uses a graphite-coated furnace to vaporize the sample.
The evaluation of engineering properties of the samples such as particle sized, compressive strength, direct shear, permeability and consistency has been determined and estimated with the standard testing method in laboratory.
Particularly, the particle size has been determined with the ASTM sieves no. In this analysis the total of 48 cubic specimens of 0. Finally, the consistency of the coal ash has been specified by the IS The physical and chemical properties are the most important parameters for understanding the quality of the coal ash.
Physically, the fly ash of BTPP is a fine powdery material, with most of its grains that are recognizable by naked eye. The color of fly ash particles is either actually colorless or dark to very dark Diamond The color is one of the vital physical properties of fly ash in terms of estimating the lighter or darker substances qualitatively.
Usually, it is suggested that the lighter color indicates the presence of high calcium oxide, whereas darker colors suggest high organic materials. Studied ash is mostly light gray but ranges from gray to dark gray color where most of the particles sizes are silt to clay which replicates the calcium oxide-dominated coal ash produced from BTPP. It is well known that generally there are two types of fly ash such as class C and class F, where class C fly ash is normally generated from burning of sub-bituminous or lignite coals, and on the other side, burning bituminous or anthracite coals produce class F fly ash.
If we compare this ash with other countries, consequently the category of Bangladesh fly ash will be more understandable. From these scenarios, it is obvious that fly ash of the current analysis is more siliceous as compared to American, German and British coal fly ash. The major chemical compositions of coal ash Wardell In this research, the particle size gradation, unconfined compressive strength, compaction, hydraulic conductivity, direct shear strength and consistency level have been estimated to understand the engineering properties of coal ash.
According to Karim , fly ash is a fine, powder-like material in which grain sizes range from 0. However, Fig. The compaction is the process of densification of a material by appealing loads for increasing the dry density of material. In the case of compaction characteristics Fig. The mixture ratios are , The shear strength is the basic characteristic that determines the ability of soils to resist loading without failing Rodriguez et al. During the shear test, this study determined two shear strength components as cohesion and friction angle.
The results show that the cohesion increases 48— The hydraulic conductivity of a soil is dependent on the nature of the void system. Coal ash itself is a fine powdery material which has high porosity but negligible permeability. The permeability analysis of this study shows that average permeability is 1. The consistency of coal fly ash is another important engineering property which is measured by the Vicat apparatus using a mm-diameter plunger.
Shear stress vs. The physical and chemical properties of coal ash are generally responsible for the potential environmental hazards. In reality, fly ash has a noticeable negative impact on soil, water, air and so on of environment for its compositional variation. In addition, the pozzolanic nature of fly ash may help to harden the soil which directly hampers to grow the plant Haas and Macak The ash also affects the permeability of soil which helps to slow down water movement within the soil pores.
After Howladar et al. In the case of water bodies around the plant area, the contamination of both groundwater and nearby streams may be for now and long periods of time.
The water quality analysis by Howladar and Howladar et al. It is well known that long-term intake of As in drinking water is much risky for health, while it can cause the internal cancers and other dieses. In the field, it has been seen that the ash pond is getting dried day by day because of discharging the large amount of fly ash.
As a result, the fly ash layer is getting thicker, mixing with air and pollutes the air environment. Normally, during combustion, the finer components of coal ash react with air and consequently generate different toxic substances such as CO 2 , SO 2 and NO 2 which is readily taken up by living beings so poses a possibility of rising environmental contamination with health risk around this power plant for present and future. Polluted blackish water in Tilai river at the connecting point of the discharge channel of power plant.
The major utilization of fly ash is as an ingredient in concrete production. In fact, EPRI and Openshaw illustrated in detail regarding the various options of the utilization of coal fly ash with its associated environmental impacts. Usmen et al. Torrey , Chu et al. In reality, fly ash can be used in different sectors based on its physical, chemical and engineering properties.
In the case of cementing materials, coal ash can bind solid particles, e. Portland cements are frequently characterized by their physical properties. In the present study, Fig. The effective grain size of fly ash, D 10 , 0. The compressive strength for only fly ash is about zero which is thoroughly unable to bind cube or cylindrical mold, whereas if the fly ash mixed with cement in different ratios, the compressive strength increases with increasing cement content with curing duration.
These results indicate that the mixing of coal fly ash with cement can increase the strength of concrete with time. Thus, it is important to mention here that use of coal fly ash with cement in the case of concrete industry can achieve long-term strength and stable the structures. In other cases, coal ash can be used as an alternative of sand and soil improvement. The comparative grain size analysis of fly ash and sand is shown in Fig. From these figures, it is cleared that coal fly ash consists of about In fact, the role of fly ash to change some soil properties such as the reduction of bulk density, moduli of rupture, increased water holding capacities, and lower the hydraulic conductivity consequently improves the soil quality as a whole El-Mogazi et al.
Hence, considering the grain size of ash with its role, this study implies that it can be utilized as the alternative of sand as well as the improvement of soil properties for engineering purposes.
The other important use of coal ash is as materials for structural fills and embankments Ahmed ; Ferguson and Levorson From the present analysis, it has been observed that the compressive strength, direct shear strength, cohesion and angle of internal friction of fly ash show higher values than sand and soil which imply that the use of ash can enhance the stability as well as the longevity of fill materials for all kinds of structures.
Moreover, the utilization of ash in different sectors such as cementing materials, soil improvement and fill materials must be helpful for managing the coal waste of the industry as well the surrounding environment.
ACI PRC-232.2-18: Report on the Use of Fly Ash in Concrete
Study on properties of rice husk ash and its use as cement replacement material. This paper investigates the properties of rice husk ash RHA produced by using a ferro-cement furnace. The effect of grinding on the particle size and the surface area was first investigated, then the XRD analysis was conducted to verify the presence of amorphous silica in the ash. Furthermore, the effect of RHA average particle size and percentage on concrete workability, fresh density, superplasticizer SP content and the compressive strength were also investigated. Although grinding RHA would reduce its average particle size APS , it was not the main factor controlling the surface area and it is thus resulted from RHA's multilayered, angular and microporous surface.
US4256504A - Fly ash-based cement - Google Patents
The use of fly ash in portland cement concrete PCC has many benefits and improves concrete performance in both the fresh and hardened state. Fly ash use in concrete improves the workability of plastic concrete, and the strength and durability of hardened concrete. Fly ash use is also cost effective. When fly ash is added to concrete, the amount of portland cement may be reduced.
This paper presents a review on fly ash as prime materials used for geopolymer. Due to its advantages of abundant resources, less in cost, great workability and high physical properties, fly ash leads to achieving high mechanical properties. Fly ash is considered as one of the largest generated industrial solid wastes or so-called industrial by-products, around the world particularly in China, India, and USA.
These quantities are about 0. Nowadays, this ash disposal process with its safe management becomes environmental important issues and major challenges to the industry, environmentalists, scientists and so on.
Properties of Low Strength Concrete made with Recycled Concrete Aggregate and Fly Ash
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Я тоже хотел бы с ней покувыркаться. Заплачу кучу денег. Хотя спектакль и показался достаточно убедительным, но Беккер зашел слишком .
This is also true for conventional raw materials for production of Some of the other fly ash concrete properties depend on the use of.
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Не очень правдоподобное заявление. - Согласна, - сказала Сьюзан, удивившись, почему вдруг Хейл заговорил об. - Я в это не верю. Всем известно, что невзламываемый алгоритм - математическая бессмыслица. Хейл улыбнулся: - Ну конечно… Принцип Бергофского.