Behavior Of Ash Research Articles

Engineering and Leaching Behavior of Lime-Treated Fly Ash Amended with Montmorillonite Nanoclay

Engineering and Leaching Behavior of Lime-Treated Fly Ash Amended with Montmorillonite Nanoclay

Effect of recycled polyester fiber reinforcement on the mechanical behavior and microstructure of red mud-improved volcanic ash

Effect of recycled polyester fiber reinforcement on the mechanical behavior and microstructure of red mud-improved volcanic ash

Mechanical, dry sliding wear and tensile fatigue behaviour of rice hush ash–derived silicon carbide dispersed LM25 metal matrix composites

Mechanical, dry sliding wear and tensile fatigue behaviour of rice hush ash–derived silicon carbide dispersed LM25 metal matrix composites

Behavior of Fly Ash at Different Mix Ratios with Plastic Recycled Polymers

Behavior of Fly Ash at Different Mix Ratios with Plastic Recycled Polymers

Numerical modelling of autogenous shrinkage of rice husk ash blended cement mortar

Addition of rice husk ash (RHA) is an effective internal curing method to mitigate self-desiccation and autogenous shrinkage of hydrating cementitious materials. Although a certain number of experimental researches on this topic have been carried out, a comprehensive study about numerical simulation of mitigating effect of RHA on autogenous shrinkage of cementitious materials is still scarce. In this study, a numerical model of autogenous shrinkage of rice husk ash blended cement mortar was proposed. The proposed numerical model was based on Pickett model and improved by taking visco-elastic behaviour of rice husk ash blended cementitious materials into account. Final setting time, chemically bound water, compressive strength, internal relative humidity (RH) and autogenous shrinkage of pure Portland cementitious materials and rice husk ash blended cementitious materials were experimentally studied. Liquid absorption capacity and water vapour desorption isotherm of rice husk ash were also measured. The comparison between the simulated and measured autogenous shrinkage showed that the autogenous shrinkage of rice husk ash blended cement mortar can be predicted accurately with the proposed numerical model.

The effect of elevated temperature on the performance of pozzolanic cement mortar

The current study focuses on the mechanical behavior of fly ash (FA) and wood ash (WA) as cement replacements at increased temperatures. Mortars containing 5, 10, 15, and 20% FA and WA as cement replacement were made and then exposed to temperatures of 200 ℃, 400 ℃, 600 ℃, and 800 ℃, with chosen samples being air-cooled or water-cooled. Curing times for the specimens were 28, 56, 150, and 365 days, respectively. For each age, compressive and tensile strength tests, weight loss at increased temperatures, and scanning electron microscopic examinations were performed. The control sample and FA at 10% replacement without temperature exposure showed a maximum compressive strength of 18 MPa and 1.4 MPa tensile strength at 28 days. Significant moisture was lost at high temperatures, decreasing strength performance. The control sample had a compressive strength of 23.3 MPa after 28 days of exposure to high temperatures under 600 ℃ air-cooled conditions. FA had the maximum value of 18.30 MPa at 15% replacement for 365 days air-cooled at 200 ℃, while WA had the highest strength of 16.40 MPa observed at 200 ℃ for 365 days. The cooling method had a considerable effect on the strength performance, with air-cooled being the better alternative. The study’s findings demonstrate the potential of FA and WA as environmentally friendly cement substitutes that can improve mortars’ durability and heat resistance at elevated temperature. This has significant implications for the building sector, particularly in regions prone to high thermal stress. It encourages the use of environmentally friendly materials without sacrificing structural integrity.

Fabrication, structural, morphological, and mechanical behaviour of fly ash doped clay ceramics based CO2 gas sensor

Various attempts have been made to fabricate fly ash-doped clay composites via solid state reaction method. Additionally, to investigate the structural, mechanical, surface morphology, and CO2 gas sensing behavior, the fabricated clay composites were sintered at three different temperatures 1000, 1100, and 1200 °C (COF1, COF2, COF3) for 4 h. The green and sintered densities of the fabricated composites were found to be in the range of 2.17–2.13 g cm−3 and 1.38 to 1.30 g cm−3. Further, various characterization techniques such as x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, universal testing machine (UTM) and scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDAX) were carried out. Moreover, to determine the compressive strength and Young’s modulus values, a universal testing machine (UTM) was used. The fracture toughness of the fabricated composites, COF2 and COF3 were found to be 7.84 MPa-m1/2 and 2.22 MPa-m1/2. The COF3 composite exhibited a sensing response, response time, recovery time of 3.39 at 1200 ppm CO2, 16.95 s and 18.05 s respectively. Consequently, this porous clay composite can be fabricated in a cost-effective and eco-friendly manner, hence beneficial for CO2 gas sensing applications.

Application of Bottom Ash with Hydrated Lime in Pavement SubgradeConstruction

Introduction: A structurally strong subgrade is always desirable in pavement construction so as to provide a resilient and durable foundation for the subsequent pavement layers for adequate performance under the given traffic load/volume and environmental conditions. Emphasizing the increased awareness for effective waste recycling and demand for a sustainable construction approach, re-utilizing industrial wastes in pavement subgrade construction can be a viable option. The potential re-utilization of bottom ash (BA), an incombustible by-product generated in huge quantities from coal combustion in thermal power plants, in replacing natural soil in the subgrade construction of pavements will not only limit the extent of disturbance to ecological balance through over-utilization of natural soil but also open an avenue for the reuse of bottom ash. Method: In this study, an effort was made to study the possible use of different percentage replacement of BA (0 to 60% with an increment of 15%) with natural soil with and without hydrated lime (5% by weight of soil-bottom ash mix) for applications in road subgrade. Laboratory investigations were conducted for basic soil characteristics, compaction properties, and strength evaluation through California bearing ratio (CBR) and unconfined compressive strength (UCS) tests. Result: The addition of 5% lime to the soil-bottom ash mixes decreased the plasticity index significantly. The highest MDD and the lowest OMC were found in soil with 45% bottom ash. The CBR results of control soil increased from 6.3% to 137.7% for soil-bottom ash mix containing 45% bottom ash and 5% hydrated lime, and the same combination showed a 104% increase in UCS. Conclusion: The observed results indicated that the coupled behavior of the bottom ash and hydrated lime treatment has effectively increased the soil's compaction and mechanical strength and its suitability for use in road subgrade construction.

Co-combustion of municipal sewage sludge and food wastes-derived anerobic digestates: Combustion characteristics, HCl/NO/SO2 emission and ash behaviors

Co-combustion of sewage sludge (SS) and food wastes-derived anerobic digestate (AD) is a promising way of waste-to-energy. Therefore, it is crucial to examine their combustion performance, ash behaviors, and gaseous pollutants emissions during the combustion of AD-SS blends using a thermogravimetric analyzer and a tube furnace combustion system. Results show that obvious interactions between AD and SS are observed in their co-combustion process. In terms of comprehensive combustion index, co-combustion can improve their combustion performance with the decrement of burnout temperature and enhanced combustion reactivity. Higher blending ratio of AD favors the increment of their ash fusion temperature, i.e., from 1109 to 1403 °C for deformation temperature due to the formation of high melting point minerals (i.e., Ca9Fe(PO4)7, 2CaO·Al2O3·SiO2). Significant in-situ reduction of NO and HCl as well as self-desulfurization is observed during the combustion of AD-SS blends. Compared to the theoretical values, the emission amount of HCl, NO, and SO2 is reduced by 0.13, 1.39, and 0.35 mg·g−1, respectively at 850 °C and blending ratio of AD to SS = 0.75:0.25. These phenomena are associated with the reducing environment and reducing substances by their high volatiles as well as the abundant minerals such as CaCO3 and Fe2O3 in AD and SS. However, high combustion temperature is unfavorable for chlorine fixation. This work provides a better understanding of their thermal behaviors, ash characteristics, and gaseous pollutants emission characteristics to realize their stable and clean incineration.

Thermal Studies of Fractionated Lignite and Brown Coal Fly Ashes.

Coal fly ash (CFA), a by-product of coal combustion, is a valuable raw material for various applications. However, the heterogeneous nature of the composition and properties of CFA provides challenges to its effective usage and utilisation. This study investigates the thermal behaviour of the fly ashes of lignite (FA1) and brown coal (FA2) and their fractions obtained by dry aerodynamic separation. Thermal analysis techniques, including thermogravimetry (TG), differential scanning calorimetry (DSC), and evolved gas analysis (EGA), were used to characterise the behaviour of the fly ash fractions while heating up to 1250 °C. The results reveal distinct differences in the thermal behaviour between ash types and among their different size fractions. For the FA1 ashes, the concentration of calcium-rich compounds and the level of recrystallisation at 950 °C increased with the decrease in particle size. The most abundant detected newly formed minerals were anhydrite, gehlenite, and anorthite, while coarser fractions were rich in quartz and mullite. For the FA2 ashes, the temperature of the onset of melting and agglomeration decreased with decreasing particle size and was already observed at 995 °C. Coarser fractions mostly remain unchanged, with a slight increase in quartz, mullite, and hematite content. Recrystallisation takes place in less extension compared to the FA1 ashes. The findings demonstrate that the aerodynamic separation of fly ashes into different size fractions can produce materials with varied thermal properties and reactivity, which can be used for specific applications. This study highlights the importance of thermal analysis in characterising fly ash properties and understanding their potential for utilisation in various applications involving thermal treatment or exposure to high-temperature conditions. Further research on advanced separation techniques and the in-depth characterisation of fly ash fractions is necessary to obtain materials with desired thermal properties and identify their most beneficial applications.

A thorough investigation into the adsorption behavior of sophorolipid-modified fly ash towards compound pollution of lead and tetracycline

Heavy metal ions and antibiotics were simultaneously detected in authentic water systems. This research, for the first time, employed synthesized sophorolipid-modified fly ash(SFA) to eliminate tetracycline(TC) and lead(Pb2+) from wastewater. Various characterization techniques, including SEM-EDS, FTIR, XPS, BET, and Zeta, were employed to investigate the properties of the SFA. The results showed that the sophorolipid modification significantly improved the fly ash's adsorption capacities for the target pollutants. The static adsorption experiments elucidated the adsorption behaviors of SFA towards TC and Pb2+ in single and binary systems, highlighting the effects of different Environmental factors on the adsorption behavior in both types of systems. In single systems, SFA exhibited a maximum adsorption capacity of 128.96 mg/g for Pb2+ and 55.57 mg/g for TC. The adsorption of Pb2+ and TC followed pseudo-second-order kinetics and Freundlich isotherm models. The adsorption reactions are endothermic and occur spontaneously. SFA demonstrates varying adsorption mechanisms for two different types of pollutants. In the case of Pb2+, the primary mechanisms include ion exchange, electrostatic interaction, cation-π interaction, and complexation, while TC primarily engages in hydrogen bonding, π-π interaction, and complexation. The interaction between Pb2+ and TC has been shown to improve adsorption efficiency at low concentrations. Additionally, adsorption-desorption experiments confirm the reliable cycling performance of modified fly ash, highlighting its potential as a cost-effective and efficient adsorbent for antibiotics and heavy metals.

Release dynamics, risk evolution and driving mechanisms of heavy metals in superalkaline fly ash co-disposed by MSW landfill

Fly ash from waste incineration is growing rapidly and has become a global problem. Landfill is the main treatment method, but the release behavior of ultra-alkaline fly ash needs further study. In this study, the release pattern of heavy metals from fly ash, the long-term risk after seepage, and the main control mechanisms were explored by indoor simulation experiments and process simulation modeling. The results show that carbonation is the main control mechanism for the release rate of heavy metals from super-alkaline fly ash, and the release rate is slow at the initial stage, but the release concentration of Zn and Pb may increase tens of times with the continuous reaction between the acidic substances in the leachate and the alkaline substances in the fly ash. The heavy metals released into the leachate can cause the concentration of Zn, Cd and Pb in the groundwater to exceed the standard by 39.50, 6.70 and 5.99 times due to seepage. Furnace type is the key controlling factor for background concentrations of heavy metals in ultra-alkaline fly ash, and the exposure concentrations of Cu, Cd, Zn, and Pb in ultra-alkaline fly ash from grate furnaces as well as the GT1 facility are 4.19, 4.19, 4.14, and 37.5 times greater than those of fluidized beds, respectively, with a higher risk of long-term landfill. Regionally, the regional occupancy rate of heavy metal concentrations indicated that the risk of adequate rainfall was high in the southeastern coastal region, which was five times higher than that in the inland northwest. Therefore, the long-term dynamics and risk evolution of Zn, Cd, and Pb in the groundwater around MSWLs in the coastal area should be paid attention to after the landfilling of ultra-alkaline fly ash in order to ensure the safety of the shallow groundwater environment after landfilling.

NaAlO2 activated slag and MSWI bottom ash: Phase assemblages and thermodynamic assessment of long-term leaching behavior

Long-term leaching (heavy metal ions) behavior of municipal solid waste incineration bottom ash (MSWI BA) is one of the issues limiting its application in alkali activated materials (AAMs). This study investigates NaAlO2 activated slag (partially replaced by MSWI BA) in terms of the reaction process and leaching behavior. A combined approach of experimental observation and thermodynamic modeling is utilized. The hardened pastes were evaluated by reaction kinetics, mineralogy, microstructure, strength, and leaching. The thermodynamic modeling included consideration of the raw materials chemistry and activator types. Results show that the modeled C(N)−A−S−H is in line with quantitative results. Specifically, modeled hydrotalcite content (3g/100g binder) is slightly higher than the experimental results (2g/100g binder) at 28 days. Furthermore, the uptake of Cu dramatically increases at 20 days by the generated C(N)−A−S−H gels, while the binding capacity of Sb, sulfates, and chlorides increases with the formation of hydrotalcite formation over time.

The impacts of furnace and fuel types on the hazardous heavy metal contents and leaching behavior of woody biomass fly ash

In efforts to reduce net CO2 emissions, the use of woody biomass as a fuel for power generation has grown rapidly. However, this practice is expected to generate large amounts of combustion ash. To support the subsequent use and disposal of combustion ash, it is important to understand its hazardous heavy metal (HHM) contents and leaching behavior. Therefore, we investigated the impacts of furnace type and fuel on HHM contents and leaching behavior based on 60 types of woody biomass fly ash (WBFA). A safety assessment of WBFA as fertilizer based on HHM contents revealed that 20% of the WBFA samples exceeded the prescribed standards. Therefore, WBFA would require preprocessing before reuse as fertilizer. The leaching test results showed that 95% of the WBFA samples could be landfilled as industrial waste without special treatment. However, prior to reuse in construction materials or soil amendments, it would be necessary to remove or fix HHMs to prevent leaching. Overall, WBFA generated from the combustion of waste wood as fuel tended to have higher HHM contents and leachate concentrations than WBFA from other woody biomass-based fuel types.

Evolution of physicochemical and leaching characteristics of municipal solid waste incineration fly ash in China under ultra-low emission standard

The physical and chemical characteristics of fly ash has changed significantly under ultra-low emission system and the current leaching system is no longer suitable for high alkalinity fly ash. This work investigated the pH values and evolution of physical and chemical characteristics of fly ash from 24 typical municipal solid waste incineration plants in China. The pH value of the leaching solution obtained by HJ/T 300–2007 presented two different acid and alkali characteristics, where high and low alkalinity fly ash accounted for 54.17% and 45.83%, respectively. The alkali content in fly ash increased significantly after ultra-low emission standard, increasing by 18.24% compared with before the implementation of GB 18485-2014. The leaching behavior of high alkalinity fly ash showed the illusion that they could enter the landfill only by the addition of a small amount of chelating agent or even without stabilization treatment, and its long-term landfill risk is significant. The phase change of high alkalinity fly ash and pH value change of the leaching solution after carbonation were the key factors for the leaching concentration change of heavy metals. Therefore, it is recommended to improve the existing leaching system or conduct accelerated carbonization experiments to scientifically evaluate the long-term leaching characteristics of high alkalinity fly ash, and to reduce the risk of heavy metal release from high alkalinity FA after entering the landfill site.

High temperature infiltration behavior and reaction characteristics of Colima volcanic ashes on gadolinium zirconate coatings deposited by atmospheric plasma spraying

Volcanic ashes are considered a serious threat to the aircraft industry. At high temperatures, they inflict severe thermochemical damage to the typical 7 wt.% yttria-stabilized zirconia thermal barrier coatings that protect the aircraft turbine. There is a need to evaluate alternative materials with excellent resistance to infiltration of molten siliceous particles, such as gadolinium zirconate. In this work, free-standing thermal barrier coatings of gadolinium zirconate were manufactured by atmospheric plasma spraying, varying deposit parameters to obtain different relative densities to evaluate the infiltration of molten Colima volcanic ashes for 1 h and 10 h at 1250 °C. The infiltration depth and the reaction products resulting from each interaction, were studied by different characterization techniques. In general, the coatings show high resistance to the infiltration of the volcanic ashes, reaching infiltration depths between 50 µm and 80 µm after 10 h of infiltration time. In this sense, gadolinium zirconate coatings are excellent candidates against the infiltration of Colima volcanic ashes compared to the typical yttria-stabilized zirconia-based thermal barrier coatings.

Pharmacognostical Studies on 'Jivanti' Part-III-Sarcostemma Brevistigma W. & A.

The present paper deals with the macro- and micro-Scopical studies of the vegetative parts of Sarcostemma brevistigma W.&A. The cell-contents, percentage extractives and ash values, fluorescence characters and behaviour of drug powder on treatment with different chemical reagents is also described.

Mechanical behavior and microstructure evolution of slag-fly ash based geopolymer stabilized sand

Geopolymers made from ground granulated blast-furnace slag and fly ash could effectively address the issues of high energy consumption and emissions associated with Portland cement, which is commonly used as a soil curing agent. In this study, the unconfined compressive strength and microstructure of geopolymer-solidified sand were presented and analyzed. The study focused on effect of the type and ratio of activator, the ratio of slag to fly ash, and the ratio of water to (activator and cementitious materials) (W/(A + C)) on the behavior of geopolymer stabilized sand. The results of computed tomography (CT), and scanning electron microscope (SEM) indicate that the variation in initial water content significantly affects the porosity of the specimen, which increased as initial water content increased. The cracks were mainly found at the joints between the individual aggregates and at the edges of the individual aggregates. The pore size distribution of the specimens was concentrated in the range 0.0761–5 μm, while the polymer particle distribution was concentrated in the range 0.0761–10 μm, with a concentration of over 90 %. A significant amount of cementing material was densely distributed around both the aggregates and the pores. CT and SEM testing techniques enable a thorough analysis and mutual verification of the self-compacting process, pore distribution, and size, as well as the distribution of cementing material within the specimens. The optimum ratio for B-S19 has been determined.

Melting and Flow Behavior of Coal Ash at High Temperatures Based on SiO2-Al2O3-CaO/Na2O Pseudoternary Phase Diagram.

The entrained-flow gasifier has a better adaptability to various coals. The composition of coal ash is an important factor affecting the high-temperature flow characteristics of molten slag. Based on the SiO2-Al2O3-CaO/Na2O ternary phase diagram, the high-temperature molten flow characteristics of slag located in the main phase regions of feldspar, melilite, diopside, and mullite were investigated by experiments and thermodynamic software calculations. The results indicate that the melting process of ash in the three phase zones is influenced by different factors. It was discovered by infrared spectroscopy analysis that the slag was dominated by Si2O52- ion clusters in the feldspar region. The slag in the diopside region had a slightly higher proportion of simple silicate ion clusters than the slag in the feldspar region, resulting in better fluidity. This is significant for revealing the mechanism of coal ash melting and flowing and guiding industrial coal blending.

The Ash-Forming Element Migration and Mineral Transformation during the Bamboo Combustion Process.

To investigate the effect of combustion temperatures on element transformation of ash, bamboo was fired using a muffle furnace at 550, 600, 700, 800, 900, and 1000 °C. Chemical compositions, micromorphology, and mineral and thermal behavior of ash were characterized. The main components included K2O, SiO2, P2O5, MgO, and CaO at a temperature of 550 °C. The high temperature decreased the content of K2O from 63.03 to 35.71% to improve the fusion characteristics of bamboo ash. 700 °C was a key temperature for designing a combustion system of bamboo, where bamboo ash had a maximum volatility. The mineral phases were chlorides, carbonates, and sulfates below a temperature of 700 °C, which transformed to complex silicates, aluminosilicates, and phosphates above a temperature of 700 °C. The temperature ranges of the three main stages were 550-980, 980-1190, and 1190-1500 °C, corresponding to mass losses of 11.52, 6.13, and 17.17%, respectively.