Composition Of Fly Ash Research Articles

Technological and Environmental Behavior of Coal Fly Ash in Lime-Based Materials

Coal fly ash is considered an industrial by-product derived from coal combustion in thermal power plant. It is one of the most complex anthropogenic materials. Its improper disposal has become an environmental concern and resulted in a waste of recoverable resources. The aim of this paper is to study the physico-chemical characteristics of binders based on coal fly ash and lime in order to develop an eco-cement. The various characterization tests carried out are X-ray fluorescence, X-ray diffraction, compressive strengths, thermophysical properties and setting time. X-ray fluorescence and X-ray diffraction were used to determine the chemical composition and phases of fly ash, lime and binders. This allowed us to see that the chemical composition of fly ash is similar to that of cement. Compressive strengths of mortars containing 20%, 40%, 60% and 80% of fly ash have shown that fly ash has a long-term positive effect which might be related to a pozzolanic activity. The L3 binder consisting of 60% of coal fly ash and 40% lime has a higher compressive strength than the others. The binder setting start time is greater than that of cement but shorter than that of lime. The study of the thermophysical properties of the L3 binder shows that it has a higher thermal resistance than cement mortar. Moreover, it heats up less quickly because of its low effusivity compared to that of the latter. This analysis highlighted the principal characteristics that must be taken into account to use coal fly correctly in lime-based materials.

Investigation of fracture toughness in mixed mode for hybrid laminated polymer composites using an A4PB type specimen

In this paper, the fracture toughness of hybrid composites for with and without fly ash composites is evaluated for asymmetric four-point bend test specimens. The preparations of specimens are by simple hand layup technique. Specimens are tested under a universal testing machine for peak load. And concluded that the specimens with fly ash composition yield better fracture toughness compared to without flyash. The scanning electron microscope study shows that the crack starting and progression is mainly dependent on s/d ratios.

The effect of including biomass on the rheological and pozzolanic properties of Portland limestone cement- case study

Various investigations have been presented on the possibility of using agro-allied industry waste in concrete, with the goal of achieving a cleaner environment and environmentally friendly construction. Biomass fly ash (BFA) and limestone clinker are waste from steam/power plants and the cement industry, respectively, and are of high relevance to economic and environmental problems. The effect of including biomass on the rheological and pozzolanic properties of Portland limestone cement (PLC) pastes are presented. The BFA was used as partial replacement for PLC as supplementary cementitious materials (SCMs). The rheological properties (yield stress, viscosity and thixotropy) of the cement paste were determined using a parallel-plate rotational rheometer. The pozzolanic properties were determined using thermogravimetric analysis (TGA) by measuring the amount of calcium hydroxide (CH), and calcium silicate hydrate (CSH) of the hydrated paste, as well as the reaction kinetics. Different characterization techniques including X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and scanning electron microscopy (SEM) were used to study the microstructure and mineralogy of the BFA. It was observed that the mineral composition of the biomass fly ash is like class C fly ash. At 15% of cement replacement the paste exhibits better rheological properties: lower yield stress and lower viscosity up till 120 min after mixing, which is an important factor in ready-mix concrete plants. However, a better pozzolanic behavior was observed at 20% cement replacement. From the results obtained, the properties of the paste containing BFA is very sensitive to water/binder ratio (w/b). Above 20% cement replacement, it is suggested to use viscosity modifying agent (VMA) to get a better rheology and pozzolanic behavior.

Effect of calcium on enhanced carbon capture potential of coal fly ash zeolites. Part II: a study on the adsorption mechanisms.

Coal fly ash zeolites (CFAZs) of type X with low (Na-X) and medium (Na-Ca-X) content of calcium were synthesized by alkaline conversion of lignite coal fly ash generated by combustion of lignite with lower and higher limestone amounts, extracted from different coal deposits and burned in separate thermal power plants. The concentration and state of Ca in the zeolites were investigated by energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). CFAZs Na-Ca-X with a medium Ca-content were found to outperform their lower calcium counterparts Na-X in terms of carbon capture capacity. This provoked our research interest in elucidating the role of Ca in the CO2 retaining mechanism. CFAZs Na-X and Na-Ca-X were studied in consecutive dynamic adsorption cycles, after thermal regeneration at a temperature of 80 °C, at which only the physically adsorbed CO2 molecules can be released. Desorption was investigated by thermogravimetric TG-DTG analyses over a wide temperature range. In situ Fourier-transform infrared (FTIR) spectroscopy was performed to elucidate the structural features of Na-X and Na-Ca-X CFAZs and the types of their accessible adsorption sites. It was found that the role of Ca is to increase the number of accessible Na+ cations in SII and SIII positions in the zeolites where they can simultaneously adsorb two CO or CO2 molecules, which benefits their adsorption capacity. This study raises an issue on coal ash classification for the synthesis of zeolites with carbon capture applications.

Effect of Dolomite Addition on Fly Ash Based Ceramic Membrane to Reduce COD and BOD of Liquid Waste

Ceramic membrane technology plays an essential role in separation fields such as wastewater treatment. Fly ash as a membrane material has proven to be very effective for many separation processes, including water and air purification, as well as industrial and environmental resource recovery. This study aims to develop a microfiltration ceramic membrane based on fly ash with the addition of dolomite. The synthesized ceramic membranes were then characterized using XRD, SEM, and TGA. Ceramic membranes are used to reduce COD and BOD levels in tofu industrial wastewater. The results showed that the value of membrane porosity tends to increase with the addition of dolomite 0% (D0) to 30% (D30). The increase in the porosity value in the membrane was followed by a decrease in the average pore size, namely 1.6994 m at D0 and 1.1730 m at D30. The membrane with 30% dolomite composition has the best mechanical properties with a compressive strength of 35.29 MPa and superior thermal resistance. This is very beneficial for the use of membranes in the long term. Meanwhile, the membrane filtration ability and the ability of the membrane to reduce COD and BOD levels of waste increased with the addition of dolomite from 0% to 30%. However, the decrease in COD and BOD was smaller in the membrane with 45% dolomite. D30 membrane can reduce COD 80% and BOD up to 71.44%. D30 membrane is the most effective fly ash and dolomite composition in forming pores on the membrane with the best COD and BOD reduction performance.

Experimental study on the washing characteristics of fly ash from municipal solid waste incineration.

The disposal of fly ash with high salt content has become an important bottleneck for the further application of municipal solid waste incineration (MSWI). In this study, the soluble salt content and composition of fly ash from different MSWI were analysed. The composition of fly ash was affected by incinerator type and flue gas cleaning system, especially the type of deacidification solvent. The soluble salt content in fly ash from MSW grate incinerator can be over 35.16%. Most of the soluble salt was calcium salt and chloride salt. The effect of washing parameters including liquid/solid (L/S) ratio and washing time on salt removal from fly ash were studied. Raw fly ash contained high chlorine (Cl) with the maximum of 19.83% and it can be significantly reduced by washing. Double-washing and secondary-washing had better performance than single-washing on salt removal. The secondary-washing did not only save water, but also reduced the energy cost during evaporation for crystallising soluble salt. Based on the analysis of variance (ANOVA), L/S ratio was the most principal factor for salt and Cl removal of fly ash by washing.

Assessment of the structure, composition, and agrochemical properties of fly ash and ash-and-slug waste from coal-fired power plants for their possible use as soil ameliorants

Coal combustion byproducts—fly ash (FA), bottom ash (BA), and ash and slag waste (ASW)—are of considerable interest for the development of their application as soil ameliorants since these harmful wastes are produced in large quantities and need to be utilized or processed. Moreover, if FA is studied quite well in this respect, much less data exists on the BA and ASW, with fewer opportunities for their other economically justified use. Thus, this research focused on the possibility of FA and BA (ASW) application as soil ameliorants. Ash samples from power plants in European Russia were selected since they are not studied in detail before. To estimate the impact of ash application, changes in key indicators reflecting the soil quality, its suitability for growing safe products were assessed: particle size distribution, acidity, nutrient, and potentially toxic elements (PTEs; heavy metals and metalloids) concentration, and their potential availability for plants. The application of ash samples to soddy-podzolic soil contributed to pH normalization, confirming the possibility of using these wastes as a stabilizer of soil acidity at the optimum ratio of ash to the soil of 1:2 or 1:5. ASW samples can aggregate with soil particles, contributing to agrophysically valuable aggregates 250–2000 μm. Despite the contents of PTEs, ASW can be considered a safe material as the legislatively established standards are not exceeded.

Influence of Graphene Nanoplatelets on the Compressive and Split Tensile Strengths of Geopolymer Concrete

Geopolymer is now a more advanced alternative to cement and available substitute for OPC while graphene nanoplatelets (GnP) are new nanomaterials with extraordinary properties that can enhance and improve the strength of cementitious materials. Although graphene reinforced concrete has intriguing potential, its implementation in construction requires better knowledge of the impact of GnP on the properties of concrete related to durability. Studies on the compressive and tensile strength performance of geopolymer concrete (GPC) containing GnP are needed. The present study investigated the influence of reinforcing GPC with varying percentages of GnP on the compressive and split tensile strengths of GPC. The addition of GnP ranged from 0.0%, 0.25% and 0.5% by weight of total binder. It has been observed that the addition of GnP increased the compressive strength by 30% and the tensile strength by 22% in comparison to a reference sample with a specified composition of fly ash and sodium metasilicate. In addition, the effect of GnP on enhancing the compressive strength of the geopolymer was shown to diminish as the amount of sodium metasilicate increased.

Fouling Simulations of a Passive Part of the Testing Combustion Facility

Results from the previous work of Strouhal et al. (2020) suggest that the used CFD fouling model together with user-implemented subroutines is not sufficient for obtaining satisfactory agreement with deposits observed in a described experimental device. The objective of this work is to create a basis for qualitative improvements of the simulation results. This includes using more detailed geometry and testing an influence of variation of parameters of two implemented fouling models. An accurate estimation of these parameters requires either empirical evidence from device operation or detailed information about fly ash composition and properties, which is usually accessible only for individual fly ash constituents. The goal of the sensitivity analysis was to show influence of these parameters on deposition rates, identify insignificant parameters for the tested range of particle properties and diameters and the most significant parameters for each of the six tested fly ash size fractions. To the authors’ knowledge, such an analysis is not present in available literature. The first tested model shown that one parameter to be significantly higher compared to other, except for the smallest particles. For the second model, all parameters were found to be significant at least for one examined particle diameter. Elastic deformation, plastic deformation and adhesion are thus considered important across the tested range of particle properties and sizes, at least for the fouling model used.

Crack formation behavior of composite fly ash – bentonite (FAB) in landfill liner system

This study aims to investigate the influence of different mixtures on the phenomenon of desiccation cracking in bentonite-fly ash mixtures as a landfill liner system. Fly ash is quite potential to be used as a landfill liner mixture because it has a low hydraulic permeability or conductivity value. This study uses class F fly ash from the Paiton power plant production process, Indonesia, which has been distributed commercially. Desiccation test was conducted in this study. The composition of fly ash and bentonite which is used are pure fly ash (FAB0), fly ash and bentonite 15% (FAB15), fly ash and bentonite 20% (FAB20) and fly ash and bentonite 25% (FAB25). The smallest CIF value is found in the pure fly ash layer. However, the pure fly ash cannot be used as landfill liner because the high permeability value. Therefore, the addition of bentonite will increase the possibility of crack formation. This study reveals that the addition bentonite in the fly ash composite will increase the crack. However, determining appropriate mixture composition is critical when working on the landfill liner system.

Briquettes from Biomass Waste

This research made three kinds of briquettes from various biomass waste, including alaban wood charcoal and rubber seed shells mixed with coal bottom ash and coal fly ash. The purpose of the study was to obtain the characteristics and quality of briquette combustion. Making briquettes is by drying, grinding, and sifting raw materials then mixed with adhesive, printing and drying. Briquettes were made with variations in composition and pressure and the particle size of the material passing through the 50 and 250 mesh sieves. Briquettes produced from alaban wood charcoal and coal bottom ash, or fly ash, obtained more bottom ash or fly ash composition characteristics. The moisture content and calorific value would be lower while the ash content was higher. While the initial ignition time, the combustion duration is getting longer, but the burning rate would decrease. Briquettes made from rubber seed shells and coal bottom ash obtained variations in composition and pressure that affect the characteristics and quality of combustion. The higher the rubber seed shell composition and pressure, the lower the water and ash content, but the calorific value increased.

Pengaruh Penggunaan Ternary Blend Fly Ash Dengan Volume Tinggi dan Abu Sekam Padi Terhadap Kuat Tekan Beton Mutu Tinggi

This study aims to find the effect of ternary blended: cement, fly ash (FA), and rice husk ash (ASP) on the compressive strength of high-strength concrete. The composition of FA and ASP used for cement replacement were 0%, 10% ASP, 30% FA, 10% ASP+30% FA, 10% ASP+40% FA, and 10% ASP+50% FA. The water-cement factor (FAS) and binder used are 0.3 and 500 kg/m3 fresh concrete, respectively. The specimens used for compressive strength is cubes of 100×100×100 mm with tests at the age of 1, 3, 7, 28, and 56 days. The results showed that the use of 10% ASP increased the compressive strength of the concrete compared to the control concrete but required more superplasticizers. The use of 30% FA as a cement substitute showed a decrease in compressive strength compared to control concrete but reduced the use of superplasticizer. The use of a combination of FA and ASP as a substitute for cement showed a decrease in compressive strength under control concrete and concrete using 30% FA. The decrease in the compressive strength of concrete with the combination of ASP and FA is beyond the initial expectation. This may be due to the disproportionate use of FA compared to ASP so that the reaction that occurs is not optimal to form calcium silicate hydrate (CSH). However, the use of ternary blended cement, FA, and ASP still has added values which is better workability than without using FA.

Electrical conductivity and EMI shielding studies of iron-decorated polypyrrole-fly ash nanocomposites

Iron decorated Polypyrrole-Fly ash nanocomposites have been synthesized by varying compositions of fly ash with 5, 10, 15, 20 and 25 wt% using in situ polymerization. The morphology, structural characteristics were confirmed by various spectroscopic methods like X-ray Diffraction, Scanning Electronic Microscopy, FTIR, Tunnelling Electron Microscopy. The X-ray diffraction showed that the crystallinity of the samples increased with the increasing fly ash concentration. The electron microscopic techniques confirmed the uniform decoration of iron particles which are uniformly distributed in the polypyrrole – fly ash nanocomposites. DC conductivity measurements revealed that the samples exhibited semi conducting behaviour. The EMI shielding effectiveness of the as-prepared composites have been investigated in the frequency range 2 – 3 GHz (S-band) of the microwave region. The EMI shielding effectiveness results exhibited that the 25 wt% Fe-Ppy-FA composite absorbed more power among all other composites. These nanocomposites can be used for EMI shielding applications.

Statistical analysis of sustainable geopolymer concrete

Geopolymer concrete is an environment-friendly material and is presently accepted as an alternative to conventional concrete. It utilizes industrial by-products like fly ash and slag to reduce CO2 emissions associated with cement production. Due to the variability of fly ash composition and concrete casting conditions, significant variability is observed in the performance of the concrete produced with such materials. In this study, a non-linear regression technique is used to develop predictive models for the compressive strength of high and low calcium fly ash geopolymer concrete. The criteria such as root mean squared error (RMSE), the statistical significance of model coefficients, and the R-squared values were adopted. The developed models were validated using plots comparing the experimental and predicted response and plots showing residuals. The dependency of the compressive strength on the significant parameters were highlighted using contour and adjusted response plots. From the contour plots, it was observed that, for geopolymer concrete sourced from the high calcium fly ash, compressive strength increases with the molarity of sodium hydroxide, the activator-to-binder ratio, and the curing temperature; while it decreases with the increase in coarse aggregate content. Similar contour plots, for the case of geopolymer concrete sourced from low calcium fly ash, exhibited improvement in compressive strength increases with the molarity of sodium hydroxide, the activator-to-binder ratio, and the ratio of Na2SiO3 –NaOH solutions; at the same time, it decreases with the increase in water-to-geopolymer solids ratio. For low calcium fly ash geopolymer concrete, the proposed model predicts that compressive strength of 90 MPa could be obtained for fly ash with oxide composition comprising a silica-to-alumina ratio of 4. The regression models developed in the present study will be helpful to develop a design mix for geopolymer concrete comprising either high calcium fly ash or low calcium fly ash.

On the significance of interfacial chemistry on the strength of fly ash-cement composites

Despite the large number of studies on supplementary cementitious materials, the underlying physicochemical interfacial processes that govern their strength remain obscure. To address this knowledge gap, this paper strives to establish a relation between the chemical composition of fly ash (FA) at the molecular level and the macroscopic compressive strength in cement hydrates-FA composites. We develop a multiscale modeling framework that links the fundamental physicochemical attributes of calcium silicate hydrate (C-S-H)-FA interfaces across molecular (~1 nm), mesoscopic (~100 nm), and microscopic (~10 μm) length scales. We observe that FA's chemical composition affects the interfacial properties across all scales. FAs with higher network-modifier cation concentration show stronger molecular and mesoscale interfacial properties and statistically significant higher macroscopic compressive strength. This is particularly interesting for Class F FA, where early-age reactivity is negligible.

Assessment of the Macro- and Microelement Composition of Fly Ash from 50-Year-Old Ash Dumps in the Middle Urals (Russia)

The paper considers the macro- and micro- element composition of two ash dumps in the Middle Urals, where meadow and forest communities have been spontaneously forming for 50 years, as well as the effect of the plants on the changing composition of the ash. Higher contents of Cu, Co, Sn, Ga, and Yb were found in the deep ash layers of both dumps, while in the upper 20-cm layer, the trace element composition depended on the influence of different plant communities. Higher contents of Sr, Cr, Ni, Sn, and Co were revealed under meadows, and Ba, Zr, and La were found under the forest. The levels of element accumulation in the aboveground and underground parts of dominant plants were revealed. Increased content of Be, Ce, Ga, La, Sc, Y, and Yb was detected in areas where meadow plants were dominant and Zn and Ba in forest areas. The toxic elements Cd and Pb were highly accumulated in both communities, whereas Co was found only in meadows. The studied materials can serve as a base to assess the feasibility of processing and/or utilizing fly ash from ash dumps in the Middle Urals and similar ash dumps in other regions situated in the southern taiga.

Volumetric strain behaviour and self-healing of large scale engineered cementitious composite and normal concrete panels under natural conditions

The application of engineered cementitious composite (ECC) in liquid containing structures (LCS) may help to improve the cracking performance of these structures. This study investigates the hydration temperature, shrinkage, cracking and self-healing behaviors of 10 m length ECC and normal concrete (NC) panels under real field conditions of volumetric strains. The restrained panels of NC and ECCs, with different compositions of fly ash (ECC/FF) and slag (ECC/SL), were designed to represent a segment of LCS and were cast and monitored on site for seven months under natural temperature changes of wet/dry and freeze/thaw cycles. A detailed microstructural analysis was completed on full depth drilled cores to explore the self-healing efficiency of different crack layers. At 28 days, only ECC/SL exceeded the ACI 224R limit for crack width of concretes to be used safely in LCS. However, at longer ages, unlike ECC/FF and ECC/SL panels which showed significant healing of their volumetric strain cracks, the NC panel experienced a sharp increase in crack widths up to seven months of monitoring. Different concentrations of CaCO3 and C-S-H/CH products were characterized at the top, core and bottom layers of crack lines, confirming higher self-healing performance of the volumetric strain cracking in ECC/FF compared to ECC/SL and NC segments.

Effect of power plant operating conditions on fly ash and bottom ash composition: a case study from power plant in Lampung

Fly ash and Bottom ash (FA-BA) are solid waste produced from the coal-generated power plant. FA consists of fine powder particles with diameters varying from 0.5-100 µm, while BA consists of coarser particles with a diameter of 0.125-2 mm. FABA and feed coal samples were collected from the power plant in Lampung to distinguish the effect of power plant operating conditions on FABA composition. Feed coal characteristics were examined by proximate and petrography analysis. Organic and inorganic components of FABA were identified using petrography analysis, while the detailed mineralogical composition of FABA was determined using X-Ray diffraction analysis. Moreover, major oxides of the feed coal and FABA were determined using inductive ICP-AES. From the analysis, it was found that FA composition is mainly organic material in the form of unburned carbon (UC). The abundance of UC content (up to 74.68%) indicates the inefficiency of the coal combustion process. In terms of inorganic, quartz is the most abundant mineral found in the FABA sample, up to 50.15%, in contrast to the glass content that was only 17.41%. A minor amount of spinel (0.03-2.00%) was found associated with Fe-oxide mineral. Kaolinite was only found in the BA sample from a landfill source and interpreted as external input from the dumping ground. The high content of UC and quartz will decrease the compressive strength of the material construction product providing a negative impact on the utilization of FABA.

Influence of Using Various Percentages of Slag on Mechanical Properties of Fly Ash-based Geopolymer Concrete

In order to implement the concept of sustainability in the field of construction, it is necessary to find an alternative to the materials that cause pollution by manufacturing, the most important of which is cement. Because factory wastes provide siliceous and aluminous materials and contain calcium such as fly ash and slag that are used in the production of high-strength geopolymer concrete with specifications similar to ordinary concrete, it was necessary for developing this type of concrete that is helping to reduce CO2 (dioxide carbon) in the atmosphere. Therefore, the aim of this study was to study the influence of incorporating various percentages of slag as a replacement for fly ash and the effect of slag on mechanical properties. This paper showed the details of the experimental work that has been undertaken to search and make tests the strength of geopolymer mixtures made of fly ash and then replaced fly ash with slag in different percentages. The geopolymer mixes were prepared using a ground granulated blast-furnace slag (GGBFS) blend and low calcium fly ash class F activated by an alkaline solution. The mixture compositions of fly ash to slag were (0.75:0.25, 0.65:0.35, 0.55:0.45) by weight of cementitious materials respectively and compared with reference mix of conventional concrete with mix proportion 1:1.5:3 (cement: sand: coarse agg.), respectively. The copper fiber was used as recycled material from electricity devices wastes such as (machines, motors, wires, and electronic devices) to enhance the mechanical properties of geopolymer concrete. The heat curing system at 40 oC temperature was used. The results revealed that the mix proportion of 0.45 blast furnace slag and 0.55 fly ash produced the best strength results. It also showed that this mix ratio could provide a solution for the need for heat curing for fly ash-based geopolymer.

Environmentálně rizikové chemické prvky na odkališti Brno-Hády

The studied area is located in Brno-Vinohrady. This location was used for fly ash dumping. Fly ash as a product of coal combustion was deposited there in period from 1967 to 1997 from the in the Červený mlýn and Špitálka heating plants. This material has the ability to absorb pollutants, especially heavy metals in its structure. Elevated concentrations of these elements thus represent a potential environmental risk. The main impulse to have a closer look at this waste dump and the fly ash composition is the planned building of a leisure complex in this area in the near future.The fly ash morphology was investigated by a scanning electron microscope (SEM). The results proved the presence of microspheres. On their surface, heavy metals and other contaminants can be accumulated. The contents of heavy metals were determined in the studied material by atomic absorption spectroscopy (AAS) and X-ray fluorescence (XRF) analysis. Measured values were compared with the limit values of environmental pollution published by the Ministry of the Environment of the Czech Republic and with the results of previous studies from the same place. The limits were exceeded slightly by cobalt (Me = 41.62 ppm; Max = 58.30), and a lot of arsenic (Me = 380.62; Max = 593.35). Amount of arsenic was thus compared with the exposure models, which were created for this location earlier. Its concentration transgressed the line of potential risk for a human organism. The number of radionuclides in the analyzed material by laboratory gamma-ray spectrometry (Me: K = 1.75 %, eU = 6.50 ppm, eTh = 16.75 ppm) was converted to the specific activity of 226Ra (am; Me = 212.40 Bq kg-1) and compared with the limit which is 370 Bq kg-1. Thismethod proved that the deposited material does not contain potentially dangerous amounts of natural radionuclides.Based on the results of this study, especially on the amount of arsenic, the waste dump Brno-Hády represents a potentially dangerous location for the human organism and requires adjustments for possible future utilization as a leisure complex.