Design and Development of Sustainable Geopolymers Based on Fly Ash, Slag, and Diatomaceous Earth: A Chemometric Approach

Coal is the main energy source for electricity generation in the world. In Morocco, 37% of electricity generation comes from combustion coal in thermal power plants. This combustion process generates large amounts of fly and bottom ashes. In recent years, these ashes became a great topic of interest because of their different uses and especially in construction materials. In this work, we assess radiation risks due to natural radioactivity in samples of fly and bottom ashes collected from JLEC (Jorf Lasfar Energy Company) thermal power plant, and different analyses are performed through two nuclear techniques such as gamma spectrometry and alpha dosimetry based on the use of LR115 films detectors. Our analysis shows that 226 Ra activities and 232 Th in both ash samples are well above the permissible activity. The values of the external risk index (Hex) and internal one (Hin) for these ashes are below unity, with the exception of 1.28 in fly ash for Hin. The obtained values for the equivalent radium Raeq and annual effective doses Ė in fly and bottom ashes are 324 Bq/kg and 210 Bq/kg, and 0.18 mSv/y and 0.11 mSv/y, respectively. The surface radon exhalation rates for the samples of fly and bottom ashes are 276 mBq • m −2 • h −1 and 381 mBq • m −2 • h −1 , respectively. Based on these results, we have shown that fly ash and bottom one from thermal power plant JLEC didn't have, in any case, a health risk to the public so it can be effectively used in various construction activities.

Coal is a well-known source of electric power generation all over the globe. Pulverized coal combustion and fluidized coal bed combustion are the two conventional methods involved in the combustion of coal in thermal power plants. Pulverized coal combustion is operated at >14000C while the fluid bed is operated at a temperature between 850-9000C. The first two reactions are the main reactions in the coal combustion process and they are exothermic reactions. CO2 and CO are the first two combustion products. The inorganic minerals in coal are released as waste products in the combustion plants in which fly ash made a large part of the waste materials. Fly ash is formed due to the incomplete combustion of coal. The fly ash from both methods contains SiO2, Al, etc, which are significant constituents. High-grade coal has a higher SiO2 than the low grade. An experiment was conducted by preparing four samples of fly ash heated at 5000C, 6000C, 7000C, and 8000C, and one unheated sample to investigate the chemical composition of the fly ash obtained from Xi’an Linyuan Silica Limited and to prove its suitability as raw material for the fabrication of refractory composites. SEM, EDS, XRD, and FTIR characterization were done on all five samples to determine the chemical parameters of the fly ash. According to the result and analysis of the four characterizations, it was discovered that the fly ash used in this research contains SiO2. SEM/EDS morphological analysis reveals the presence of spherical and a few geometrical crystalline-shaped structures known as cenospheres. Cenospheres are important components for the synthesis of refractory composites. The EDS micrographs show the percentages of silicon and oxygen in the fly ash. The FTIR results show Si-O-Si stretching in all the fly ash prepared samples. In the XRD, it was discovered that the fly ash was purely SiO2.

Uranium can be released into the environment from various activities such as the use of phosphate fertilizers, combustion of coal in thermal power plants, mining, and depleted uranium used in the wars. One of the talked about sources for such water contamination in Bathinda city is the fly ash from the coal-fired thermal power plants. To assess the role of fly ash and Chemical toxicity risk associated with uranium from the fly ash to the water, the coal, dry fly ash, ash slurry and water samples collected from the surrounding of Guru Nanak Dev Thermal Power Plant (GNDTPP) in the Bathinda city of Punjab state, India. The samples were analyzed using the X-ray fluorescence set up. In the present work, we found that uranium concentrations in the dry fly ash and coal samples were higher than permissible limit i.e. < 2 ppm but the concentrations in the ash slurry and water samples was below the safe limit of 30 μg l−1 as recommended by World Health Organization (WHO, 2011). The 38Sr concentrations are also found to be 0.103-1.210 ppm and with average value 0.576 ppm in the various types of water in surrounding of the thermal power plant. The concentrations of 42Mo are found to be 0.002-0.050 ppm and the average value 0.022 ppm below the safe limit of 0.07 mg/l as recommended by World Health Organization (WHO, 2011) and Bureau of Indian Standards (BIS, 2012). Chemical toxicity risk calculated in the form of lifetime average daily dose (LAAD) and hazard quotient. The lifetime average daily dose (LAAD) values of ash slurry and water samples were found to be lower than WHO (2011) recommended level of 1 μg kg−1 d−1, and the values of hazard quotient of the study samples were found to be lower than unity expect dry fly ash and coal samples were higher than permissible limit. The present study is concluded that uranium contamination in water of Bathinda city is not due to the Thermal Power Plant, and there is indicating no chemical toxicity risk due to uranium from the fly ash to the water.

Fly ash (FA) is a by-product created from the burning of coal in thermal power plants. FA mainly consists of mineral compounds that make them naturally caustic. Despite this, research has shown that FA may be utilized as an alternative material in civil engineering, hydrotechnics and agronomy. Leaching tests may provide theoretical validation that FA may be used as an alternative sorbent or additive in construction material. In this paper, the results of up-flow percolation tests performed on raw FA as well as lime and cement modified samples (MFA) are presented. This method was chosen as it yields the most reliable assessment of releasing heavy metals under long-term exploitation. The research has focused on the leaching behaviour of Sb, As and Se in raw, lime and cement MFA samples. Raw FA was found to leach Se, As and Sb metal ions, cement modification did not prevent Sb and Se leachates, while lime-modified MFA was found to be the most stable material.

Combustion of coal in thermal power plants generates ash as a residue, which depends on the quality of coal, specific to its ash content and calorific value. In a typical Indian scenario, a standard 210 MW thermal plant produces ∼57 T/hr total ash, which has 80:20 fly and bottom ash share, considering coal with 40% ash content. This study aims to harness the waste heat of fly ash collected at the bottom of the electrostatic precipitator (ESP) by coupling organic Rankine cycle (ORC) with 210 MW subcritical coal-fired thermal power plant works on R134a. Thermodynamic properties of R134a are taken from the PYroMAT library (python 3.6) to develop a computer-based program that estimates the variability of key parameters with respect to log mean temperature difference (LMTD). The main plant's efficiency was 28.714%, with main steam pressure, reheat pressure, and temperature being about 134.35 bar, 24.02 bar, and 540 °C, respectively, and combustion of coal is about 141.5 T/hr. The study shows additional generation from fly ash waste heat is about 30.5 kW with an increase in net power output (0.0145%) and net energy efficiency (0.0146%). The optimum value of LMTD for the evaporator, condenser, and recuperator is 40, 7, and 16 K, which yields the optimum energy efficiency and developed cost-effective design. The proposed system is economically analyzed, considering 25 years of equipment life and 14% of loan interest. The study shows that the payback period and the generation cost of electricity of ORC is about 6.22 years and INR 3.14 per kWh, respectively.

Effect of Reinforcement on Multi-tiered Fly Ash Wall

Fly ash, an environmentally hazardous solid waste is produced mostly from the burning of coal in thermal power plants. Due to continuous and high volume of material it requires, the road construction industry is often looked upon as a potential consumer of fly ash. The strength of fly ash has to be improved before it can be used as embankment material. The present paper investigates the possible utilization of randomly reinforced fly ash in embankment construction. This paper presents the results of laboratory investigation carried on randomly reinforced fly ash. Polypropylene fibers with different fiber length (6mm, 12mm and 24 mm) are used as reinforcement. Fly ash is compacted at maximum dry density with low percentage of reinforcement (0 to 1.50 % of weight of dry fly ash).Unconfined Compression Strength (UCS) tests and California Bearing Ratio (CBR) tests were conducted on unreinforced as well as reinforced fly ash samples to investigate behavior of fiber reinforced fly ash. The test results reveal that the inclusion of fibers in fly ash increases the UCS and CBR values. It is noticed that the optimum fiber content for achieving maximum strength is 1.00 % by dry weight of fly ash with a fibers having length 12 mm.

Fly ash (FA) is one of the particulate wastes generated during combustion of coal in thermal power plants. Around 110 million tons of FA is generated in the USA every year, and 60% of it is deposited in landfills. Utilization of FA can create value for this waste material and also help the environment. FA is essentially a mixture of metal oxides that can be used as a filler reinforcement in metal and polymer composites. FA as a filler material reduces the amount of metals and polymer, reducing embodied energy. Hollow FA particles, called cenospheres, can provide the advantage of low density in composites as well as higher hardness and strength. FA also reduces the coefficient of thermal expansion. This article provides a brief review to capture the state of the art on the mechanical and tribological behavior of composites reinforced with FA to identify the possible benefits of using this waste material. The corrosion performance of metal matrix FA composites is also explored. Future perspectives in this field are discussed based on the potential applications of FA-filled composites.

The recycling of fly ash obtained from the combustion of coal in thermal power plant has been studied. Coal fly ash was vitrified by melting at 1773 K for 5 hours without any additives. The properties of glasses produced from coal fly ash were investigated by means of Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. DTA study indicated that there was only one endothermic peak at 1003 K corresponding to the glass transition temperature. XRD analysis showed the amorphous state of the glass sample produced from coal fly ash. SEM investigations revealed that the coal fly ash based glass sample had smooth surface. The mechanical, physical and chemical properties of the glass sample were also determined. Recycling of coal fly ash by using vitrification technique resulted to a glass material that had good mechanical, physical and chemical properties. Toxicity characteristic leaching procedure (TCLP) results showed that the heavy metals of Pb, Cr, Zn and Mn were successfully immobilized into the glass. It can be said that glass sample obtained by the recycling of coal fly ash can be taken as a non-hazardous material. Overall, results indicated that the vitrification technique is an effective way for the stabilization and recycling of coal fly ash.

Aluminum metal matrix composites are attractive and effective materials because of their unique properties. These properties include high specific strength, light weight, high specific stiffness, excellent wear resistance, good corrosion resistance, and greater elastic modulus compared with the base alloy. They are used in aerospace, automotive, marine, mining, and mechanical structures. Fly ash, an inexpensive waste by-product obtained after the combustion of coal in thermal power plants, is considered as a reinforcement particle in the present study. The aim is to investigate the effect of fly ash in Al-10 weight percentage (wt%) aluminum oxide (Al2O3) metal matrix composites using statistical optimization techniques. One factor and Taguchi approaches are used in planning and designing the experiments. Al/10 wt% Al2O3 with 0, 5, 10, and 15 wt% fly ash composites are prepared with the powder metallurgy technique at 300, 400, and 500 MPa compaction pressure with 90, 120, and 150-μm fly ash particle sizes. The wt% of fly ash, compaction pressure, and particle size are the process parameters. Performance parameters such as ejection force and green density, hardness, and compressive strength are considered. The ejection force and green density decreased with the increase in the weight percent of fly ash. Hardness increased with the increase in fly ash content. Compressive strength increased with the increase in fly ash up to 5 wt% and subsequently decreased.

Coal fly ash is a waste, obtained from the combustion of coal in thermal power plants. Fly ash is harmful and its disposal is the major issue from an environmental point of view. As fly ash contains silica and alumina, it is thought of interest to use it for the synthesis of porous material like zeolite. In this work, the focus is on the utilization of fly ash for the synthesis of Mordenite type zeolite and its application in the toxic metals removal from aqueous solution. Coal fly ash based Mordenite type zeolite (FZS H ) was synthesized by seed assisted hydrothermal synthetic method using fly ash as a source of silica and alumina instead of using pure silica and alumina. The resultant material was characterized by various techniques, such as SEM‐EDX, XRD, TGA, FT‐IR, solid state NMR, BET surface area, etc. The XRD patterns confirm the presence of Mordenite phase in the FZS H zeolite. The sorption behavior of Pb 2+ and Cd 2+ towards commercial Mordenite and FZS H Mordenite type zeolite is investigated and compared. Percentage uptake obtained using FZS H and commercial Mordenite zeolite sorbent was found quite similar. The kinetic and thermodynamic studies reveal the favourable and spontaneous nature of the sorption.

Metal matrix composites are used mostly in space ships, aerospace, automotive, nuclear bio technology, electronic and sporting goods industries, but due to their high cost, experiments are usually done to reduce the cost of composites and inexpensive materials are utilized for metal matrix composites. Fly Ash is one of the most inexpensive and low density reinforcement available in large quantities as solid waste by product during combustion of coal in thermal power plants. So, composites with Fly Ash can be used to reduce the cost of the metal matrix for applications in automotive and small engine applications. It is therefore expected that the incorporation of Fly Ash particles in Aluminium alloy will promote yet another use of this low cost waste by product and at the same time has the potential for conserving energy intensive Aluminium and thereby, reducing the cost of Aluminium products. In this investigation, 10% SiC particles reinforced Al-MMC was prepared using stir casting method. The ratio of Hardness with respect to the weight fraction on the specimen was prepared. The various mechanical test via hardness & tensile test are taken to analyze the properties .The microstructure of Al-MMC’s were studied in SEM microstructure.

Electric power in India mainly depends on coal-fired power plants. Commonly, Indian coal comprises ash in the range of 30–45%. In order to sustain India’s economic growth, the country total coal demand is forecasted to more than double by 2030. Increasingly huge quantities of fly and bottom ash are produced in the country, thus leading to the necessity to duly plan safe and clean ways to handle, use, and dispose of the combustion by-products. Thermal power plant design nowadays must duly consider apprehensions related to water shortage, environmental guidelines, sustainable management and disposal of ash, along with growing consciousness pertaining to overall cost and power plant efficiency. The current paper discusses the problems associated with fly ash and its handling and mitigation measures. Fly ash generated while burning of coal in thermal power plants can be utilised for several favourable uses like manufacturing of cement, road construction, road embankment and development of ceramics or fertiliser.

The present study intends to improve the properties of local soil by mixing it with waste material coal ash. This coal ash is a byproduct generated from combustion of coal in thermal power plants. Finding worthwhile applications in the fields of construction makes effective use of this pollutant - coal ash. The present investigation describes the behavioral aspect of silty sand mixed with coal ash thereby improves the load bearing capacity of the soil. Investigation of results revealed that as the percentage of coal ash was increased from 10 % to 50 % there was improvement in UCS and CBR strength of subgrade soil thus improving it for bearing more load in foundation structures of pavements.

Fine-grained soils may have undesired characteristics such as high swelling potential and low strength, thus requiring improvements. One of the stabilization methods involves the use of fly ash. Fly ash is a waste material obtained from burning coal in thermal power plants. The use of fly ash is encouraged as an alternative material for soil stabilization, due to its features such as pozzolanic properties and economic availability. This paper describes the results of an experimental study on stabilization of a clayey soil with fly ash. Unconfined compressive strength (UCS), triaxial and consolidation tests were carried out on samples of kaolinite mixed with class C fly ash at different percentages and cured for 1, 7, and 28 days, in order to study the effects of class C fly ash on the mechanical behaviour of the stabilized soil. The results showed that the inclusion of fly ash significantly improves the strength characteristics of the soil. Curing time was also found to have a significant effect on improving the properties of the soil.