Ash Disposal Research Articles

Investigation of engineering properties of sun-dried bottom ash based eco clay blocks

Eco blocks can be produced by using engineering and agricultural wastes to protect ecology. Thermal power plant wastes namely fly ash and bottom ash will be a major predicament for the environment Arenas et al. (2013) [1], Aggarwal et al. (2007) [2], Datta et al. (2019) [8]. So globally, research work is being focused to find various options for using these waste materials, and making use of them in the construction industry is one of the effective methods of exploitation. In India, presently about 710 million tonnes of fly ash and bottom ash are generated every year. India's coal consumption gives two-thirds of electricity generation with 35% fly ash in India. Cement's fly ash requirement is about 151 MT will be required in 2030, but 128MT of fly ash will be remaining as unutilized. This needs an additional 2300 ha of land and 1.30 billion cubic meters of water for ash ponds exacerbates the problems of disposal of fly ash only. Bottom ash about 60MT disposal will make us miserable Asokan et al. (2005) [3]. Making use of bottom ash in equal proportion to fly ash is done in this research. A small proportion of the Natural clay has been used as a significant proportion. Coconut shells collected locally were used as reinforcing materials. The preliminary experimental investigation was done to observe the effect of fly ash, bottom ash and clay as partial replacement of cement to act as supplementary cementitious material. The compressive strength at 28 days of testing revealed that a replacement of 15% of clay, bottom ash and fly ash with equal proportions has achieved the optimum strength.

Sulphate resistance of lightweight aggregate concrete comprising sieved palm oil fuel ash as fine aggregate replacement

Oil palm shell (OPS) and palm oil fuel ash (POFA) disposal from palm oil industry causes environmental pollution. The present research investigates the compressive strength and sulphate resistance of oil palm shell lightweight aggregate concrete containing palm oil fuel ash as partial fine aggregate replacement. Sieved POFA was used as partial fine aggregate replacement from 0% up to 20% by weight of sand. Water cured specimens were tested to determine compressive strength and durability towards sulphate attack. Use of 10% POFA slightly enhances concrete strength and durability against sulphate attack via pozzolanic reaction from the fraction of fine ash present.

An experimental study on controlled low strength material (CLSM) for utilization as sustainable backfill

Disposal of ash produced by coal-based power plants is a global problem because of its fineness and lack of space for its pondage. In recent years, efforts have been made to reutilize ash for different applications, viz., manufacturing of cement, bricks, tiles, in concrete, for soil stabilization, construction material for roads and bridge abutments, etc. However, there is a need to find more applications for the complete utilization of ash. In this direction, the present work explores potential of fly ash and pond ash for development of controlled low strength material (CLSM), an alternative material for backfilling applications. The performance of different compositions of CLSM have been studied, by partially replacing sand and cement, with pond ash and fly ash, respectively. Experimental studies have been performed to obtain flowability, hardening time and compressive strength (soaked and unsoaked conditions) for different CLSM combinations. In the present study, 20% binder content and 80% filler content has been considered, with a water/binder (w/b) ratio of 1.7 based on initial trials. Further, variation in percentage of fly ash and pond ash as partial replacement of cement and sand, respectively, have been evaluated. From the test results, it can be concluded that upto 75% replacement of sand by pond ash (60% of overall mix) is possible for development of CLSM with desired properties. Furthermore, the 28-days average compressive strength observed for CLSM varies from 0.4 MPa to 1.8 MPa for the studied combinations. This range of strength is favourable for backfilling applications, wherein, excavation in future may be necessary. Though the study results are quite encouraging towards development of CLSM using pond ash and fly ash, further studies on durability properties and minimizing the variation in properties would help towards developing sustainable CLSM for environmentally friendly infrastructure development.

Optimizing the design of sintered fly ash light weight concrete by Taguchi and ANOVA analysis

The unutilized fly ash disposal to landfills is a severe threat to the environment. It deteriorates surface and groundwater quality which seriously affects the health of surrounding people. The present study develops lightweight concrete (LWC) with sintered fly ash aggregates (SFA) and does experimental and statistical analysis. For this purpose, LWC with different proportions of coarser and finer aggregates (80:20, 50:50, and 20:80), a saturation of SFA done with presoaking for 30 minutes in 11%,14%, 16% water and time of vibration 15 s, 30 s, and 45 s were taken into consideration while making LWC. The compressive strength, density, and segregation index were calculated for the specimen. Taguchi orthogonal array L9 was used to find the optimum value of each parameter. The statistical analysis by the Taguchi method indicates presoaked with 14% of water, 80:20 proportion of coarser and finer SFA and 30 s compaction is giving optimum results. The presoaked parameter is found to be the most influential among all on the basis of ANOVA analysis.

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.

An Assessment of the Phytoremediation Potential of Planted and Spontaneously Colonized Woody Plant Species on Chronosequence Fly Ash Disposal Sites in Serbia-Case Study.

In this study, the potential of planted (Tamarix tetrandra Pall. ex M.Bieb. and Robinia pseudoacacia L.) and spontaneously colonized (Amorpha fruticosa L. and Populus alba L.) woody species for the phytoremediation of potentially toxic trace elements (TEs) such as As, B, Cr, Cu, Mn, Ni, Se, and Zn, from the chronosequence fly ash (FA) deposit lagoons (L1 and L2) at the ‘Nikola Tesla A’ Thermal Power Plant (TENT-A) in Serbia were analyzed. The differences in the pseodototal and bioavailable (DTPA-extractable) concentrations and mobility (AR index) of TEs in FA at the examined lagoons are a result of the time-conditioned influence of weathering (3 and 11 years respectively) and vegetation development on changing the basic physical and chemical properties of FA (texture, pH, EC, CEC, C, N, and bioavailable P and K) and its toxicity. This resulted in differences in the concentration of TEs in the roots and leaves of the examined plants at L1 and L2. All examined species accumulated Cr the most in the root (BAF > 1 and TF < 1), which suggests that they are good stabilizers of this element. Biological indices for As (BAF > 1 and TF < 1) identified T. tetrandra and A. fruticose as good stabilizers of As. P. alba stood out as accumulating the highest levels of B, Ni, and Zn, T. tetrandra the highest levels of Cu, Mn, and Se, and R. pseudoacacia the highest levels of As and B in leaves (BAF > 1; TF > 1), which makes them good extractors of these elements from the FA at TENT-A. However, due to toxic concentrations of As, B, Se, and Zn in their leaves, they are not recommended for the phytoremediation of the investigated lagoons through the process of phytostabilization. Under conditions of elevated total Cu and Ni concentration in FA, the content of these elements in the leaves of A. fruticosa at both lagoons were within the normal range. This, in addition to a good supply of essential Zn, the stabilization of As and Cr in the roots, an increase in BAF, and a decrease in TF for B with a decrease in its mobility in ash over time, singles this invasive species out as the best candidate for the phytostabilization of TEs in FA at the TENT-A ash deposit site.

Leachability of Heavy Metals from Autoclaved Fly Ash-Lime Building Bricks

The fly ash as a byproduct of coal-fired power plants constitutes vital ecological problems. In Turkey, approximately 15 million tons ofashes are generated via the combustion of 40 million tons of lignite yearly. Worldwide, a number of investigation and applications wereundertaken to utilize fly ash in order to overcome the environmental problems. One of the application area of fly ashes is the production of building bricks. Characterization of fly ash samples from Seyitomer and Yatagan coal-firing power plants were conducted inthis study. TCLP 1311, ASTM3987-85 and EN 12457-2 leaching tests on the cylindrical fly ash/lime brick (FA/LB) samples which wereproduced from Seyitömer and Yatagan thermal power plant fly ash-lime mixtures were performed to determine the leachability ofsome chosen trace elements. The results show that the release of all trace elements was lower than the hazardous material limit valuesof waste acceptance. Thus, non- fired fly ash bricks are an advantageous way to solving environmental effect of disposal of fly ashes.

The mechanical properties improvement of environmentally friendly fly ash-based geopolymer mortar using bio-mineralization

The reasonable disposal and utilization of fly ash is an essential environmental issue for coal energy stage. As a novelty green cementation method, biomineralization has been innovatively applied to improving engineering performance of loose materials by generating cementing. This paper reported the feasibility of using microbially induced carbonate precipitation (MICP) partly instead of cement as a bonder to producing fly ash-based geopolymer mortar. The influence of mixture proportion, bio-chemical solution formula on engineering performance, water absorption, and dry density of composites were evaluated. The microstructure characteristics and mineral composition of mortar were also investigated. The results showed that MICP significantly improved the strength by 16%–45% of high-volume fly ash based geopolymer mortar with appropriate MICP formula. However, excessive chemical solution concentration significantly weakened the strength by even −14%. The water absorption was even reduced by 16.8% due to the production of CaCO3. The reduction of residual Ca2+ concentration, SEM, and EDS analysis of microstructure and composition confirmed the formation of CaCO3, which was fundamental to strength improvement and water adsorption reduction of mortar. XRD and FTIR analysis demonstrated the diversity of calcium carbonate crystal forms induced by different MICP formula, which affected the engineering performance of mortar. The BET results showed that appropriate MICP formula reduced the cumulative pore volume, leading to the more compact structure. Although the maximum pH of mortar reached 13, MICP still played a role in strength improvement. This study demonstrates that MICP can be selected as a binder, partially replacing cement, for making fly ash-based eco-friendly geopolymer mortar. However, it should be note that the strength of geopolymer mortar is still relatively low in the current formula. More research is needed to further improve the mechanical properties of the mortar. In addition, the relationship between bio-chemical concentration ratios on mechanical properties as well as the viability of bacteria in fly ash based geopolymer mortar also need to be further investigated.

Evaluation of rheological and durability characteristics of sugarcane bagasse ash and rice husk ash based binary and ternary cementitious system

Implementation of biomass based power plants is substantially increased worldwide, and hence large quantity of agro-waste ashes is disposed as waste. The reuse of agro-waste ashes as supplementary cementitious materials helps to solve problems associated with intensive carbon emission from cement plants and the disposal of agro-waste ashes. Although earlier studies are reported on the use of sugarcane bagasse ash and rice husk ash as a pozzolan in concrete, studies on their combined use in the production of ternary cement are highly limited. Hence, the present study focuses on the performance evaluation of the sugarcane bagasse ash and rice husk ash based ternary blended cementitious system. The performance of the ternary blended concrete is also compared with sugarcane bagasse ash based binary blended concrete. Rheological characteristics, compressive strength, rapid chloride penetration test, water sorptivity index, and porosity of the blended concrete is investigated. The yield stress, plastic viscosity and consistency index are increased with the increase in the addition of sugarcane bagasse ash and rice husk ash. The highest compressive strength is observed for ternary blended concrete with 10% bagasse ash and 5% rice husk ash, followed by blended binary concrete with 20% bagasse ash. The decrease in portlandite was evidently observed for binary and ternary blended samples with the addition of bagasse ash and rice husk ash using X-ray diffractogram and thermal analysis. Reduction in chloride permeability, water sorptivity index and porosity was observed for agro-waste ashes blended concrete than control concrete.

Ash formation and the inherent heavy metal partitioning behavior in a 100 t/d hazardous waste incineration plant

Hazardous waste incineration (HWI) ash is also defined as hazardous waste and its disposal performance depends largely on the ash compositions as well as the potential environmental risk of heavy metals. In this work, HWI ashes of four sampling sites were collected in a 100 t/d hazardous waste incineration plant with rotary kiln over three consecutive days. The formation characteristics of ash samples including heavy metal partitioning were given, with further discussions on the melting disposal of HWI ash mixtures. Results showed significant differences in the ash compositions among the sampling sites. Caused by NaHCO3 injection as de-acidizing adsorbent, the sum of Na, S and Cl content in bag filter ash even exceeded 70%. Cu/Mn/Cr tended to transfer into the bottom ash due to low volatilities, while Zn/Pb/Cd/Se/As were more likely to be enriched in the ash particles. In particular, chemical adsorption at medium- to high- temperature range was dominant for As enrichment in the waste heat boiler ash. Despite the complexity and diversity of raw hazardous wastes, little difference was found in the melting temperature of bottom ash during the sampling period. However, it could vary by more than 200 °C for fly ash due to the fluctuation of alkali components in raw wastes. Moreover, slagging medium was encouraged in order to achieve rapid and complete melting of ash mixtures. The objective of this study is to gain knowledge on the HWI ash formation and inherent heavy metal partitioning behavior, expecting to provide guidelines on the deep harmless disposal of HWI ash in future.

Strength and durability properties of geopolymer paver blocks made with fly ash and brick kiln rice husk ash

In India the generation of agro waste rice husk ash is abundant. The utilization of rice husk ash in development of geopolymer binders can be suitable to alleviate the environmental problems associated with disposal of rice husk ash. Further, the utilization of rice husk ash generated from the stacks of brick kilns has not been addressed in past, particularly in development of geopolymer binders. This study proposes development of geopolymer paver (GEOPAV) blocks utilizing brick kiln rice husk ash (BKRHA). It presents fresh, mechanical and durability properties of GEOPAV blocks blended with fly ash, BKRHA, natural aggregates, NaOH and Na2SiO3 solution, and cured in both sundry and room temperature conditions. Microstructural analysis using scanning electron microscope (SEM) and X-ray diffraction (XRD) was adopted to study the influence of BKRHA on hardened properties of GEOPAV blocks. The results show that addition of BKRHA reduce the workability of GEOPAV mixes due to micro porous surface with honeycombed structure of BKRHA particles. The addition of BKRHA showed negligible improvement in compressive strength of GEOPAV blocks. However, the major advantage was observed with improved split tensile strength and flexural strength for GEOPAV blocks with BKRHA. Further, the durability properties in terms of resistance to acid and frost attack was significantly improved with the addition of BKRHA in GEOPAV blocks. Such improvements can be attributed to high amounts of amorphous silica in BKRHA which contribute towards dissolution and formation of polymeric gel, and thereby serve as a binder to enhance the geopolymer matrix making it dense. Finally, all the developed GEOPAV blocks satisfy the IS 15658–2021 specification requirements and perform much better when compared to commercially available paver blocks.

Technogenic Influence of the Composition of Ash Waste of the Zmiiv Power Plant on the Pedosphere

Purpose. The aim of the study is to analyze the geochemical composition of ash and slag waste at the Zmiiv Thermal Power Plant (TPP) and to identify the features of migration of heavy metals (HM) from the place of storage of ash and slag waste into the ecosystem. To achieve this goal, the following tasks were solved: geochemical analysis of ash and slag waste at Zmiiv TPP; study of the reliability of HM migration into the soil in the places of ash and slag waste storage. Methods. The content of heavy metals in ash, slag and soil were investigated using atomic absorption analysis (AAA) on a spectrophotometer S-115. X-ray diffraction analysis was used to determine the solid inorganic part of ash and slag. Results. Ash and slag of Zmiiv TPP contain Cu, Cr, As, Cd, Ni, Pb in quantities that are several times higher than the maximum permissible concentration (MPC). For ash and slag waste, the total pollution index is Zc = 43, which corresponds to a high level. That is, this artificially created horizon is dangerous. HM migrate into groundwater and into the soil near the ash dump due to the infiltration of atmospheric precipitation, emissions from water pipelines, filtration of water through the base of the ash dump of the Zmiiv TPP. To determine soil contamination near the ash dump, soil analyzes were performed at a distance of 0 ... 100 meters. At a distance of up to 100 meters from the dump, there is an excess of MPC in the soil for the content of Ni, Cu, As, Cr. At a distance of up to 100 meters from the dump, an excess of the MPC in the content of Ni, Cu, As, Cr is observed. Concentration factor exceeds unity for Cr, As, Cu, Cd, Ni. The content of Pb and Zn reaches background values only at a distance of more than 100 meters. The calculation of the total soil pollution indicator allows us to classify these soils as moderately hazardous and permissible. However, there are several significant disadvantages of the Zc indicator. First of all, it does not take into account the differences in the potential hazard of chemical elements, and, most importantly, the synergistic effects of polymetallic pollution. The coefficient of the synergistic effect of heavy metals is 26.64 (in the soil of the ash dump), then it decreases, but even at a distance of 100 meters it is 11.23, that is, at a distance of 0 ... 100 m from the ash dumps, the condition of the coefficient of synergistic effect is less than one. It has been established that Cu, Ni, Zn and Cr are characterized by low mobility in the soil near the ash dump, therefore they accumulate in the ecosystem near the ash dump, which is explained by the neutral and slightly alkaline soil pH values (pH = 8.0 ... 8.5). The ratio of mineral phases to glass is unstable; however, it should be noted that aluminosilicates, calcium silicates and glass predominate in ash and slag. Сompounds with HM are confined mainly to amorphous clay aggregates and sooty-carbon formations of ash, to a lesser extent to slag glass and even less to grains of quartz sand. Conclusions. Since the ash contains such fractions that can be easily carried by wind, it should be assumed that the HM entry into the ecosystem is also by air, which also contributes to air pollution. The solution to the problem of ash and slag waste disposal should be found in the production of building materials, in road construction, but it is necessary to study the composition of ash and slag and the probability of HM migration depending on the conditions of use.

Silica derived from variety of sources and its functionalized forms as an antiblock additive in polypropylene

Silica derived from a variety of sources and its functionalized form has been studied as an antiblock additive in polypropylene (PP). Commonly, inorganic antiblock additives are added to PP films to reduce the blocking and facilitate the separation of polymeric films. However, such types of additives can cause a reduction of clarity in transparent films. In the present work, a comparative analysis of silica obtained from various sources specifically from rice husk ash and its further functionalization/modifications using n-octyltriethoxysilane has been performed. Since silica synthesized via rice husk ash was obtained from waste (rice husk ash), this further solves the problem of ash disposal. The functionalized forms of various silica have been characterized using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The morphological analysis was performed using scanning electron microscopy (SEM). The melt flow index (MFI), yellowness index, and other mechanical characterizations including tensile and impact strength were performed for 30–40 μm thick tubular quenched polypropylene (TQPP) films. These films were evaluated to have high transmittance (above 93%), high clarity (above 98%), and very low haze (less than 2%) indicating high transparency and improved optical properties. The blocking force and optical properties are quite similar for TQPP film containing silica synthesized from rice husk ash and commercially grade silica and hence proving silica synthesized from rice husk ash to be an effective substitute for commercial silica in TQPP films.

Risk assessment of lead and cadmium leaching from solidified/stabilized MSWI fly ash under long-term landfill simulation test

The long-term effectiveness concern of municipal solid waste incineration (MSWI) fly ash (FA) disposal has been placed more emphatic recently, however, few studies worked on the control of leaching risk of heavy metals under the long-term stability. In this study, the leaching properties and risk assessment of two representative solidified/stabilized (S/S) FA wastes, i.e., sodium dithiocarbamate (DTC) chelator treated and Portland cement + chelator combining treated, were evaluated by a long-term cycles assessment method which coupled multifaceted environmental stresses (e.g., freezing-thawing, drying-wetting, accelerated carbonation). The results showed that the cement/chelator had a better long-term stability and exhibited ~55% lower cumulative overall pollution toxicity index (OPTI) than chelator treatment after the test, which was always rated as “low risk” during the cycles. In addition, the cement/chelator exhibited ~23.3% smaller cumulative mass release rate than the chelator treatment after 6 cycles and restrained the transformation of Pb and Cd from stable states to removable fractions, which attributes to its great erosion resistance and compact pore structure. Under the cumulative external factors and carbon dioxide attacks, the decalcification of hydrate products (e.g., C-S-H, hydrocalumite), as well as deterioration of pore structure are the critical factors increasing the local erosion, cracking and heavy metals release. Thus, the optimization of S/S waste microstructure (e.g., enhancing binder system) and landfill site conditions (e.g., reducing rainfall impact) could be propitious to the S/S waste risk control and management.

Aromatic and aliphatic production of catalytic pyrolysis of lignin using ZSM-5/Al-SBA-15 catalyst derived from high-calcium fly ash

In this work, lignin was utilized as biomass feedstocks to study the feasibility of fuels and chemical production, while fly ash was used for synthesizing ZSM-5 (FA-ZSM-5) and SBA-15 (FA-SBA-15) catalysts for upgrading pyrolysis products. The use of fly ash offers several benefits such as reducing the fly ash disposal cost, solving environmental problems, and significantly increasing high valued products. Catalytic fast pyrolysis of kraft lignin using ZSM-5/ SBA-15 catalyst prepared from fly ash was studied using a pyrolysis-GC/MS system. The influence of temperature (400–600°C) during thermal pyrolysis, the FA-ZSM-5 and FA-SBA-15 ratios (1:0 ,2:1, 1:1, 1:2, 0:1), and lignin-to-catalyst ratios (1:5 and 1:10) on the hydrocarbon selectivity was investigated. Non-catalytic pyrolysis volatiles consisted of a high proportion of guaiacol compounds (G-type, 66.7%) and p-hydroxyl phenols (H-type, 18.0%). The presence of zeolite catalysts contributed to enhance both aliphatic and aromatic production, while a proportion of guaiacyl decreased significantly. The highest selectivity of aliphatic and aromatic HCs was achieved at feed to catalyst ratios of 1:10. Coupling HZSM-5 and Al-SBA-15 catalysts were more reactive in converting the alkoxy-phenol (G-type) and p-hydroxyphenyl compounds (P-type) toward both aliphatic HCs and monocyclic-aromatic HCs (MAHs), particularly benzene, toluene and xylene (BTX). Among all catalysts, FA-ZSM-5/ FA-SBA-15 ratio of 1:2 showed the optimum dual catalyst ratio to enhance the highest yield of aliphatic and aromatic hydrocarbons of 15.1 and 21.4 % with the acceptable yield of phenolic compounds (34%). ZSM-5/ SBA-15 catalyst prepared from fly ash showed high efficiency to convert solid lignin to MAHs (BTX). The decrease in the PAHs selectivity seemed to be good performing of this dual catalyst because it expected to decrease the coke formation on the catalyst surface.

Experimental Investigation on Waste Utilization of Steel Fiber and Fly Ash in Concrete with Partially Replacement of Cement

Abstract: In India, major part of electricity is produced from thermal power plants. These thermal power plants use different types of fuels for combustion. During combustion of coal as a fuel in these thermal power plants, a byproduct namely fly ash is produced. Indian coal has highest ash content as compared to coal found in other countries. There are nearly 85 thermal power plants in India which uses coal as source for power generation and thus produces a large amount of fly ash. This fly ash is disposed in soil, which in turn causes a lot of environmental problems. To overcome this disposal of fly ash into the soil, it can be used in concrete by partially replacing with cement. This study deals with investigation for M25 Grade of newlineconcrete to study the mechanical properties of Steel fiber reinforced concrete newline(SFRC) containing fiber of an interval of 0.5% from 0.0% to 2.0% by new line weight of cement. In this study are steel fibres are used and compare properties with conventional concrete. In this study we are casting 6 cubes and 6 cylinders out of which 2 each for 7, 14, 28 days. Keywords: Steel fibres, Cement and Compressive Strength, GGBS, Fly Ash, SFRC, Cement, Compressive Strength, Split Tensile Strength

Preparation of high-quality glass-ceramics entirely derived from fly ash of municipal solid waste incineration and coal enhanced with pressure pretreatment

The disposal and high-volume reutilization of municipal solid waste incineration fly ash into environmentally friendly construction materials have been gaining significant interest over the years. This study proposed a new method to produce glass-ceramics with enhanced mechanical properties and chemical leaching characteristics from fly ash and coal fly ash with mechanical pressure pretreatment. A series of co-sintering experiments were conducted by varying proportions of fly ash and coal fly ash, the pretreatment mechanical pressures and sintering temperatures, and the effectiveness was measured by analyzing the thermal behavior, compressive strength, leaching behavior of heavy metals, mineralogical and microstructural characteristics of sintered samples. The results showed that the obtained glass-ceramics exhibited distinguished physicochemical properties, a maximum compressive strength of 51.00 ± 0.86 MPa was obtained. The leaching concentrations of five heavy metals in sintered samples were much lower than the standard limitation. The morphology results showed the coal fly ash addition positively enhanced the stabilization of heavy metals and the formation of new mineral phases. And the compressive strength was evidently improved with the increase of pretreatment pressure, which was attributed to the microstructure transition and increased crystalline degree. These findings suggested that the production of glass-ceramics entirely from fly ash and coal fly ash with pressure pretreatment is a promising method by minimizing the energy consumption together with the co-disposal of two solid waste streams.

Valorization of incinerator bottom ash for the production of resource-efficient eco-friendly concrete: Performance and toxicological characterization

In recent times, the quantity of wastes generated from industries, hospitals, construction sites etc. is perpetually increasing from year to year. Producing concrete utilizing waste or discarded materials as a partial replacement to fine or coarse aggregates is one among the effective ways of waste utilization. The disposal of incinerator bottom ash usually produced by the incineration of inorganic constituents of the municipal solid wastes (MSW) in an eco-friendly way is one of the issues of concern, globally. By the way, the present study is related to the utilization of MSW incinerator bottom ash and recycled demolition waste aggregate as partial replacement materials for fine and coarse aggregate, respectively to produce eco-friendly concrete. This study adopted an innovative pretreatment technique for stabilizing the MSW incinerator bottom ash. Five distinct M20 grade concrete mixes were produced with different proportions of fine aggregate, MSW incinerator bottom ash, coarse aggregate, and recycled demolition waste aggregate along with cement and water. The incinerator bottom ash was replaced at 5% and 10% quantities with fine aggregate and the recycled demolition waste aggregate was replaced at 40% and 60% of the weight of the coarse aggregate. The strength and durability properties of the M20 grade concrete were analyzed. It was noticed that the strength and durability properties of the eco-friendly concrete specimens produced by incorporating 5% - incinerator bottom ash and 40% - recycled demolition waste aggregate were superior to that of the control mix concrete. Laboratory tank leaching tests showed that the eco-friendly concrete do not pose any significant environmental hazard. Furthermore, the microstructural analysis through scanning electron microscope (SEM) images, revealed dense aggregate paste matrix interfaces with less micro-pores and insignificant micro-cracks due to the incorporation of incinerator bottom ash as a partial replacement to the fine aggregate.

Sustainable Transportation, Leaching, Stabilization, and Disposal of Fly Ash Using a Mixture of Natural Surfactant and Sodium Silicate.

The present study evaluates the transportation, leaching, and stabilization ability of novel saponin extracted from the fruits of Acacia auriculiformis. To enhance the dispersing behavior of the fly ash slurry (FAS) at a lower dosage of sodium silicate, A. auriculiformis was incorporated in FAS. In addition to the rheological study, an attempt has been made to remove heavy metals through leaching for the safe disposal of FAS. Critical factors such as the fly ash (FA) concentration, saponin dosage, surface tension, ζ potential, temperature, and combination of saponin and sodium silicate, affecting the rheology of FAS, were extensively studied. The addition of a nonionic natural surfactant saponin has been proved to enhance the wettability of FA particles by decreasing the surface tension of FAS. The obtained rheology results were compared with the stabilization yield of the previously reported commercial surfactant cetyltrimethylammonium bromide. The incorporation of sodium silicate in the FAS system was found to be phenomenal in the settling and stabilization of FAS, thereby developing reaction products like sodium aluminum silicate (N-A-S). This facilitates the sustainable disposal of FA preventing air pollution after dewatering. The formation of N-A-S was further supported by scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies.

A comparative study on solidification/stabilization characteristics of coal fly ash-based geopolymer and Portland cement on heavy metals in MSWI fly ash

Cement-based solidification/stabilization (S/S) is a widely approach applied for municipal solid waste incineration (MSWI) fly ash. Although Portland cement on MSWI fly ash S/S has been widely developed, the economical and environment-friendly binders should be explored to reduce the energy and improve MSWI fly ash S/S performances. A comparative study about MSWI fly ash S/S treatment with coal fly ash-based geopolymer and Portland cement was carried out in this work. Specifically, physical and chemical characteristics of MSWI fly ash, compressive strength, leachability and chemical speciation transformation of heavy metals, microstructures and morphology of S/S samples were investigated. Results showed that leaching concentration of Pb, Cd and Zn in MSWI fly ash was 5.36 mg/L, 40.3 mg/L and 129.0 mg/L respectively. It was 34.7, 160.2 and 0.29 times higher than Standard GB16889, far exceeding the requirements for municipal solid waste landfill. Leaching tests indicated that immobilization rates of Pb, Zn and Cd with geopolymer S/S treatment were exceeding 99%. Compressive strength of geopolymer and Portland cement S/S samples curing for 28 days varied from 14.3 to 22.4 MPa and 2.5–10.8 MPa, respectively. In summary, geopolymer exhibited better immobilization performances on MSWI fly ash than Portland cement. In geopolymer S/S samples, active aluminosilicate in MSWI fly ash participated the geopolymerization reaction and generated new phases such as Friedel’ salts (3CaO•Al2O3•CaCl2•10H2O) and hydrocalumite (Ca2Al(OH)6Cl2H2O). It not only promoted the bulk resource utilization and disposal of fly ash, but also realized the effective encapsulation of heavy metals and chloride ions. Therefore, geopolymer is a more promising candidate for MSWI fly ash S/S treatment.