Municipal Solid Waste Incineration Bottom Ash Research Articles

Feedstock recycling of polycarbonate waste via thermochemical conversion supported by municipal solid waste incinerator bottom ash.

The rising demand for plastics has driven up its production, causing severe environmental challenges like CO2 emissions and microplastic pollution. Furthermore, improper disposal of incinerator bottom ash (IBA), a byproduct of municipal solid waste (MSW) treatment, poses additional environmental risks. This study explores a method for recovering non-petroleum-based monomers from plastic products. A smartphone case waste (SCW) is used as feedstock in this study and it is made of polycarbonate (PC), confirmed by thermogravimetric analysis and Fourier transform infrared spectroscopy. The MSW incinerator bottom ash (MSW-IBA) is used as a catalyst for thermochemical conversion of SCW. To determine the optimal pyrolysis conditions for BPA recovery, experiments were conducted under different atmosphere (N₂ and CO₂) and catalyst configurations (in situ and ex situ). The MSW-IBA leads to 127% higher yield of bisphenol A (BPA), the monomer of PC, at 600 °C under a N2 atmosphere, compared to non-catalytic conversion. In situ configuration of the catalyst loading leads to up to 147% higher BPA yield than ex situ configuration. The increased BPA production from SCW is most likely because metal oxides (e.g., CaO) present on the MSW-IBA catalyst promotes the cleavage of and C-O bonds, dissociation of CO (or CO2) and hydrogen extraction from C1-C3 hydrocarbon and H2. For the catalytic conversion of SCW under a CO2 atmosphere, CO2 adsorbs onto CaO in the MSW-IBA, decreasing the number of active sites. It deactivates the catalyst, resulting in a lower BPA yield (22.96 wt%) than the BPA yield obtained under the N2 atmosphere (25.86 wt%).

Structural and Textural Characteristics of Municipal Solid Waste Incineration Bottom Ash Subjected to Periodic Seasoning

The objective of this study was to determine the structural and textural description of municipal solid waste incineration (MSWI) bottom ash that was subjected to a six-month seasoning process. Bottom ash samples, with a particle size fraction of 0.063–0.1 mm, were seasoned in a closed landfill and collected for laboratory analyses at monthly intervals. The research focused on determining the structural parameters, using methods such as nuclear magnetic resonance spectroscopy (1H NMR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), and the textural parameters, using low-pressure nitrogen adsorption (LPNA) at −196.15 °C. The analyses of the porous structure of the bottom ash samples revealed differences in texture of ASH 1 to ASH 6, specifically in the pore volume (micro- and mesopores), specific surface area, and pore size distribution. Changes in the structural and porous characteristics of the samples were attributed to the duration of the seasoning process. The results of the structural analysis of the bottom ash suggest its application in the concrete industry, potentially enhancing the long-term mechanical strength of concrete. The results of the textural analysis indicate the possible use of MSWI bottom ash in environmental applications, as the internal surface area could be further developed.

Effects of Size and Mechanical Pre-Treatment on Aluminium Recovery from Municipal Solid Waste Incineration Bottom Ash

Municipal solid waste (MSW) is incinerated to reduce the volume and recover energy and materials. The generation of MSW has been increasing over the past few decades due to the increase in population and changing consumption habits. Rising environmental and economic concerns have increased the importance of waste treatment and recovery. Currently, MSW may take three alternate or parallel routes: direct recycling, incineration, or landfill, depending on the country and location. MSW incineration has three products in addition to energy: bottom ash, fly ash, and off-gas. After incineration, bottom ash usually still contains many materials to be recovered, such as glass, ceramics, and metals with a degree of oxidation. This study focuses on aluminium recovery from MSW incineration bottom ash from two different countries. The 2–30 mm fraction of aluminium particles was characterized in terms of its size, shape, and oxide thickness, and its effects on aluminium recovery were investigated. In addition, the ability of mechanical pre-treatment to remove oxides prior to melting was studied. The results were compared with the analytical modeling developed in this study. An increasing particle size and surface area resulted in an increase in aluminium recovery. Mechanical pre-treatment increased the yield for smaller particles to a larger extent than larger particles due to the difference in the oxide/metal ratio.

Assessment of mechanical and heavy metal leaching behavior of engineered cementitious composites incorporating ultra-high-volume municipal waste incineration bottom ash

This study aimed to explore the feasibility of incorporating 100% municipal solid waste incineration bottom ash (MSWIBA) as a replacement for fine aggregates in engineered cementitious composites (ECCs). To improve mechanical properties, three types of polymer fibers (PVA, PP, and PE) were used at dosages of 0-2% by volume. The impact of fiber content on compressive strength, elastic modulus, and other key performance indicators such as peak strain, ultimate strain, damage modulus, and toughness index was systematically investigated. Results showed that while the elastic modulus and peak stress slightly decreased with increasing fiber content due to fiber agglomeration and increased macro-porosity, fibers significantly enhanced the deformation capacity and toughness. For instance, the MSWIBA-ECCs with 2% PP fibers exhibited the highest compressive damage energy of 205.47 J, a 79.48% increase over the control group, demonstrating superior toughness. Additionally, the study developed a new constitutive model that accurately predicted stress-strain behavior considering fiber characteristics. Environmental assessment revealed that MSWIBA-ECCs effectively immobilized hazardous heavy metals (Cu, Ni, Pb, Zn), with a solidification efficiency of 97%, ensuring compliance with Chinese environmental standards. These findings suggest that MSWIBA-ECCs, combined with optimized fiber content, offer a sustainable and high-performance alternative for construction applications.

Production of high-strength eco-conscious ceramics exclusively from municipal solid waste

This research investigated the application of municipal solid waste incineration fly ash (MSWIFA), municipal solid waste incineration bottom ash (MSWIBA), and construction waste residue (CWR) as raw materials for the comprehensive conversion into municipal solid waste ceramics employing the SiO2-Al2O3-CaO-MgO (8 wt%) phase diagram. This study aimed to evaluate the influence of the addition of MSWIFA and sintering temperature on important ceramics properties, including linear shrinkage, water absorption, sintering range, and flexural strength. Additionally, relationships were established among these physical parameters using Pearson's correlation coefficient. The thermal behavior of the mixture was analyzed through automatic slag melting point tester and TG-DSC techniques. Furthermore, characterization of the crystalline phase transition and microstructure of sintered samples was performed by XRD, Factsage, and SEM. The results showed that both the addition of MSWIFA and the sintering temperature significantly influenced the crystal phase composition of the sintered ceramics. Moreover, the addition of MSWIFA and the sintering temperature had a significant influence on the pore structure of the ceramics. These ceramics exhibited exceptional properties, such as the extremely low water absorption rate of 0.08 % and the remarkable flexural strength of 124.78 MPa. Ceramics performance indicators were far higher than the requirements of China's national standard GB/T4100-2015. The sintering range had the capability to attain 30 °C, guaranteeing the feasibility of practical manufacturing processes. Furthermore, leaching concentration tests conducted on additive-free ceramic samples reveal a low risk of heavy metal contamination, as the heavy metals were effectively solidified within the crystalline and amorphous phases of the ceramics. The comprehensive utilization of MSWIFA, MSWIBA, and CWR for the production of fully solid waste ceramics not only yields cost reduction benefits but also promotes efficient utilization, presenting a feasible and highly promising approach to sustainable waste management.

Study on the Preparation and Performance of Lightweight Wallboards from MSWIBA Foam Concrete.

To reduce land use and avoid further pollution, incineration for power generation has become the main method for municipal solid waste treatment. This research focused on the potential for transforming Municipal Solid Waste Incineration Bottom Ash (MSWIBA) into a finely ground powder. The impact of the powder's fineness and the amount of water used on its effectiveness was analyzed using a method called grey theory. MSWIBA was used as a partial substitute for cement in making MSWIBA foam concrete and lightweight wall panels. By modifying the fineness and water utilization of the recycled micro-powder, its maximum activity index can be increased to 90.1. This study determined the influence of factors including apparent dry density, water-cement ratio, foaming agent dilution ratio, and admixture dosage on the strength of the recycled foam concrete, and established the optimal mix ratio. This study employed a combination of physical experiments and numerical simulations to elucidate the impact of panel material, core layer thickness, and layer sequence on sound insulation performance. The simulation results were in close agreement with the experimental findings.

Mechanical and microstructural properties of municipal solid waste incinerator bottom ash (MSWIBA) concrete exposed to salt erosion and drying-wetting cycles

In cold and saline soil areas, concretes usually experience multi-factor erosions, such as freezing-thawing cycles (FTCs), drying-wetting cycles (D-Ws), and salt erosion. To promote green and sustainable development of the construction industry, municipal solid waste incinerator bottom ash (MSWIBA) was adopted as a partial replacement for conventional fine aggregates in concretes. In this study, the coupled effects of the D-Ws and salt erosion (i.e., 5 % NaCl solution and 5 % Na2SO4 solution) were experimentally conducted to investigate the mechanical and microstructural properties of ordinary and MSWIBA concretes. The results showed that D-Ws had a negative effect on the mechanical properties of concretes. The depth and width of cracks in concretes increased with the D-Ws raised. During the D-Ws, the influence of salt solution on concretes could be divided into two stages. Initially, the filling effect of salt crystals was beneficial to the development of concrete strength. Subsequently, salt crystals accumulated in concretes caused cracks, and accelerated the deterioration of concrete specimens. Meanwhile, sodium sulphate reacted with hydration products in concretes to produce some expansive substances, the evident diffraction peaks of expansive substances (e.g., gypsum and ettringite) had been clearly observed after D-Ws. Thus, the damage effect of 5 % Na2SO4 solution (SS) to concrete structure was more serious than that of water (WT) and 5 % NaCl solution (CS). Furthermore, the total porosity of the concrete specimens generally decreased with the MSWIBA substitution rate increased. There was an optimal MSWIBA content for concretes to obtain the excellent mechanical and microstructural properties. In detail, when the substitution rate of MSWIBA was between 0 % and 33.0 %, it had an excellent effect on improving the pore structure of concretes. Specifically, the compressive strength of concretes was larger than 35.0 MPa when the substitution rate of MSWIBA with natural river sand was between 24.8 % and 57.8 %, whereas the substitution rate of MSWIBA should not exceed 33.0 % exposed to D-Ws. This study could provide a significant reference for the sustainable development of concretes in cold and saline soil areas, as well optimization and innovation usage of MSWIBA.

Reuse potential of municipal solid waste incinerator bottom ash as secondary aggregate: Material characteristics, persistent organic pollutant content and effects of pH and selected environmental lixiviants on leaching behaviour

Increasing municipal solid waste (MSW) production poses challenges for sustainable urban development. Modern energy-from-waste (EfW) facilities incinerate MSW, reducing mass and recovering energy. In the UK, MSW incineration bottom ash (MSW IBA) is primarily reused in civil engineering applications. This study characterizes UK-produced MSW IBA, examining its pH-dependent leaching behaviour and response to environmental lixiviants. Results show predominant components include a melt phase, primary glass and fine ash aggregations, and a chemical composition dominated by SiO2 (30–50 %), CaO (∼15 %), Fe2O3 (∼10 %), and Al2O3 (∼8%). X-ray absorption near edge structure (XANES) analysis shows that Zn and Cu are most likely oxygen-bound (adsorbed to oxy-hydroxides and as oxides) with some sulphur bound. Polychlorinated biphenyls (PCBs) and polychlorinated dibenzodioxins/furans (PCDD/Fs) are well below regulatory limits, and polycyclic aromatic hydrocarbons (PAHs) were undetectable. Leaching tests indicate trace elements mobilize at pHs ≤ 6. With a natural pH of 11.3 and high buffering capacity, significant acid inputs to the MSW IBA are required to reach this pH, which are improbable in the environment. Wood chip additions increase leachate’s dissolved organic carbon (DOC) and reduce pH, but had minimal impact on metal-leaching behaviour. Synthetic plant exudate solutions minimally affect metal leaching at realistic concentrations, only enhancing leaching at ≥ 1500 mg l−1 DOC. This work supports MSW IBA’s low-risk in specified civil engineering applications.

Compressed stabilised earth block synergistically valorising municipal solid waste incinerator bottom ash and sisal fiber: Strength, durability and life cycle analysis

Compressed stabilized earth blocks (CSEB) represent an eco-friendly substitute for traditional building materials, predominantly utilizing earth. Municipal Solid Waste Incineration Bottom Ash (MSWIBA) is a by-product of municipal waste treatment that can be creatively repurposed in construction projects. This research explores integrating MSWIBA as a substitute for Earth in CSEB production to conserve natural resources and repurpose waste, potentially reducing its landfill disposal. The sisal fibers (SF), often regarded as by-products of agricultural processes, offer an intriguing research material. The SF was treated with a 5 % NaOH alkaline solution to improve the CSEB bonding, increasing the flexural strength. The study aims to determine the optimal mix of stabilizers, in addition to a 10 % cement content, using various percentages of MSWIBA (10–40 % by weight of dry sand) and SF content (0.25–1 % by weight of dry soil). These blocks undergo comprehensive tests to determine their strength and durability. Wet and dry compression, flexural tests and indirect tensile tests were used to assess strength qualities, while wetting-drying cycles and acid exposure were used to determine durability. MSWIBA replaces 20 % sand in CSEB satisfying the strength. However, exceeding this amount increases void content and lowers strength, emphasizing the importance of balanced proportions for best performance. The 20 % MSWIBA and 0.75 % SF combination enhanced the compressive strength by 6.45 MPa, flexural strength by 0.92 MPa and water absorption by less than 18 %. The durability test displayed increases in compressive strength of 14.7 % and flexural strength of 93.48 % and optimized water absorption rate. Furthermore, microstructural analysis has been performed on CSEBs and the results highlight the importance of balanced cement and SF proportions for structural integrity. Life Cycle Analysis (LCA) investigation shows that construction costs using CSEB are 12.24 % higher than those with FCBs. Additionally, the study suggests that CSEB with MSWIBA and SF will be an environmentally sustainable construction material, considering factors such as energy usage, Global Warming Potential, and other environmental considerations

Impacts of advanced metals recovery on municipal solid waste incineration bottom ash: aggregate characteristics and performance in portland limestone cement concrete

The optimization of alternative materials in concrete production continues to garner considerable attention in order to meet sustainability goals and supplement natural materials. Portland limestone cement (PLC) and municipal solid waste incineration (MSWI) bottom ash (BA) have been proposed separately as green cement and coarse aggregate supplement in low-strength concrete production, creating sustainable products and alternative disposal scenario for a waste material. This study discusses the impact of advanced ash processing techniques on aggregates and presents the performance of concrete incorporating both of these products with PLC for the first time. Two sources of MSWI BA were investigated, one as-produced (TMR) and one processed with novel advanced metals recovery (AMR). The AMR process reduced total Al content in ash compared to TMR (20,500 vs 17,000 mg/kg), though not aluminum oxide content, as the AMR process targets metallic aluminum. A composition study on both aggregates supports a reduction in ferrous and non-ferrous metals following the AMR process. All control and test mixes met 28-day compressive strength requirements (17 Mpa). Both AMR and TMR MSWI BA-amended concretes yielded compressive strengths below control specimens (no ash) ranging from 17 to 23 MPa, with little to no difference observed dependent on MSWI BA processing. The life-cycle discussion supports benefits deriving from supplementing naturally mined materials and recovering ferrous and nonferrous metals with the AMR process.

Converting municipal solid waste incineration bottom ash into the value-added artificial lightweight aggregates through cold-bonded granulation technology

To effective recycle the Municipal solid waste incineration bottom ash (MSWIBA), this study adopts cold consolidation granulation technology to develop eco-friendly artificial lightweight aggregates (ALCBAs), and the materials are over 50 % dosage of MSWIBA, less 50 % fly ash (FA) or ground granulated blast furnace slag (GGBFS), and 10 % ordinary Portland cement (OPC). This study investigated the effects of different binder types and dosages on the properties of ALCBAs, including compressive strength, water absorption rate, bulk density, microstructures, pore development, heavy metal leaching behavior, and sustainability. The feasibility of ALCBAs to design green concrete was also explored. The results show that with higher content of MSWIBA and binders of FA, GGBFS and OPC, the ALCBAs with compressive strength greater than 2.5 MPa, bulk density of about 1000 kg/m3 and water absorption rate greater than 12 % was successfully developed. Increasing the content of FA/GGBFS is beneficial to improve the compressive strength and reduce the water absorption rate and the total porosity and lower the air bubbles percentage of ALCBAs. More importantly, both FA and GGBFS are mixed into ALCBAs, the compressive strength is at 2.5 MPa-3.0 MPa, the water absorption rate is significantly reduced, and the energy consumption, carbon footprint and cost are also significantly reduced. As the content of ALCBAs increases, although the compressive strength and splitting tensile strength are not as good as concrete with natural aggregates, the density of low-carbon concrete with ALCBAs gradually decreases, and the interface transition zone is gradually improved. Overall, ALCBAs can be beneficial to the conservation of natural resources (natural aggregates) and effectively solve the shortage of natural aggregates, and can be used to deal with the accumulation of solid waste in a green way, and it also can open up new channel for solid waste recycling.

Preparation and Hydration Properties of Sodium Silicate-Activated Municipal Solid Waste Incineration Bottom Ash Composite Ground-Granulated Blast Furnace Slag Cementitious Materials.

The production of municipal solid waste incineration bottom ash (MSWIBA) is substantial and has the potential to replace cement, despite challenges such as complex composition, uneven particle size distribution, and low reactivity. This paper employs sodium silicate activation of MSWIBA composite Ground-granulated Blast Furnace slag (GGBS) to improve the reactivity in preparing composite cementitious materials. It explores the hydration performance of the composite cementitious materials using isothermal calorimetric analysis, Fourier-transform infrared (FTIR) spectroscopy, XRD physical diffraction analysis, and SEM tests. SEM tests were used to explore the hydration properties of the composite gelling. The results show that with an increase in MSWIBA doping, the porosity between the materials increased, the degree of hydration decreased, and the compressive strength decreased. When the sodium silicate concentration increased from 25% to 35%, excessive alkaline material occurred, impacting the alkaline effect. This inhibited particle hydration, leading to a decrease in the degree of hydration and, consequently, the compressive strength. The exothermic process of hydration can be divided into five main stages; quartz and calcite did not fully participate in the hydration reaction, while aluminum did. The vibrational peaks of Si-O-Ti (T = Si and Al) were present in the material. The vibrational peaks of XRD, FTIR, and SEM all indicate the presence of alumosilicate network structures in the hydration products, mainly N-A-S-H and C-A-S-H gels.

Treatment of waste marine clay by alkaline-activated ground granulated blast-furnace slag and municipal solid waste incineration bottom ash

The construction of coastal areas generates a substantial volume of waste marine clay (WMC), which poses environmental and safety challenges during the stockpiling process. The improved preparation of WMC as roadbed materials emerges as a crucial pathway for resource utilization. However, the engineering performance and durability of roadbed materials prepared from WMC have always been a concern for scholars and engineers. This study employs alkali-activated ground granulated blast-furnace slag (GGBFS) and municipal solid waste incineration bottom ash (MSWIBA) to solidify WMC for preparation of the roadbed materials. The results showed that the combined utilization of alkali-activated GGBFS and MSWIBA to improve WMC can meet the environmental and mechanical requirements of roadbed materials. The incorporation of 5-20% MSWIBA could improve the water stability coefficient and California bearing ratio to more than 85% and 80%, respectively. The durability of roadbed material was significantly improved by addition of MSWIBA. After 12 dry–wet cycles, the strength of the material without MSWIBA and with 5% MSWIBA was 0 and 2.87 MPa, respectively. Following analysis of engineering properties and durability, the optimal dosage of MSWIBA was determined to be 5%. The enhanced durability can be attributed to the optimization of material gradation and pore structure achieved through the incorporation of a small quantity of MSWIBA. The carbon emission and normalized global warming potentials of roadbed material treated by MSWIBA and GGBFS were much lower than that of cementitious binders such as ordinary Portland cement. These findings indicate that MSWIBA has the potential to substitute natural aggregates like sand and gravel, effectively improving the durability of roadbed materials and promoting the safe and efficient recycling of solid waste resources.

Optimizing MSW incineration bottom ash reuse: A study on treated wastewater washing and leaching control

The current study introduces an innovative methodology by utilizing treated wastewater (TWW) from an effluent treatment plant as a washing agent to enhance the characteristics of incineration bottom ash (IBA). This approach addresses sustainability concerns and promotes the circular economy by reusing wastewater generated in municipal solid waste incineration facilities. Previous research has underscored the challenges of open IBA reuse due to elevated leaching of chlorides, sulfates, and trace metal(loid)s. Thus, the experimental setup explores various combinations of washing, with or without screening, to optimize the properties of soil-like material (SLM < 4.75 mm) and overall material (OM < 31.5 mm) fractions of IBA for unrestricted applications. Batch leaching tests were conducted on treated samples, and leaching characteristics were evaluated in accordance with regulatory standards, primarily the Dutch standard for unrestricted IBA reuse. The findings reveal that washing in isolation proves insufficient to enhance IBA properties; however, washing followed by screening, specifically for removing fines (<0.15 mm), proves effective in reducing contamination. The study identifies that multiple steps of washing and screening (with recirculation) process render OM and SLM fractions suitable for unrestricted reuse with a cumulative liquid-to-solid ratio of 6 L/kg and a total washing time of 15 min. The multi-step treatment was found effective in reducing sulfate contamination by 65–74 % and chloride contamination by 83–89 % in IBA fractions. This approach offers a promising solution for overcoming the limitations associated with IBA leaching, thereby promoting sustainable waste reuse practices.

Utilizing municipal solid waste incineration bottom ash and volcanic tuff to produce geopolymer materials

Large volumes of municipal solid waste incineration bottom ash (MSWIBA) are produced annually in China; however, their improper disposal causes serious ecological and environmental problems. This study investigated the feasibility of using MSWIBA and volcanic tuff to produce geopolymers. The effects of the MSWIBA content, silicon–sodium molar ratio, and alkali equivalent on the uniaxial compressive strength (UCS) and bulk density of the geopolymer samples were examined using single-factor and optimization tests. The test results showed that the UCS and bulk density of the geopolymer decreased as the MSWIBA content increased, whereas they increased as the alkali equivalent increased. As the silicon–sodium molar ratio increased, the UCS first increased and then decreased, and the change in bulk density was limited. In the final geopolymer preparation, the MSWIBA content was 17.85%, the silicon–sodium molar ratio was 1.71, and the alkali equivalent was 9.49%. According to X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive spectrometry, and nuclear magnetic resonance analyses, the main phases of the geopolymer under the final preparation parameters were quartz, sanidine, calcite, orthoclase, gismondine, and illite. During the geological polymerization process, a large amount of CNASH gel was generated and attached to the surface of the particles or filled the pores between the particles, resulting in a pore size of 0.01–1 μm. The heavy metals in the geopolymers exhibited a good stabilization effect owing to the CNASH gel. Except for Cd, which posed a medium risk, the remaining heavy metals posed low or no risk.

Research on using municipal solid waste incineration bottom ash for cement-stabilized macadam

Municipal solid waste incineration bottom ash (MSWIBA) is the waste generated by incineration power plants. Because of its low activity, it is an effective way to apply it to cement-stabilized macadam (CSM) in road construction. CSM was prepared using varying proportions of bottom ash (0%, 15%, 20%, 25%, 30%, and 35%) and different proportions of cement (3.5%, 4%, 4.5%, 5%, and 5.5%), respectively, to explore the effects of MSWIBA as fine aggregates on the characteristics of cement-stabilized MSWIBA macadam (CSBAM). MSWIBA was examined in terms of its microstructure, chemical makeup, and physical characteristics. Heavy metal leaching, water stability, splitting strength, unconfined compressive strength, and dry shrinkage were all investigated for CSBAM. The findings demonstrated that there was some cementitious and volcanic ash activity and that the bottom ash had a rough, porous surface. The strength of CSBAM decreased with the increase of MSWIBA dosage and increased with the increase of cement reference. Replacing fine aggregate with MSWIBA reduced the water stability of CSBAM. The water stability was better when the bottom ash dosage was more than 20%. Bottom ash reduced the dry shrinkage strain of cement-stabilized macadam, and CSBAM had better anti-dry shrinkage performance. CSBAM had a curing effect on heavy metals, and the leaching concentration of heavy metals was in accordance with the standard, which had less impact on the environment.

Waste to Resource: Enviro-Mechanical Suitability of MSW Incineration Bottom Ash in Flexible Pavements and Embankments

Waste to Resource: Enviro-Mechanical Suitability of MSW Incineration Bottom Ash in Flexible Pavements and Embankments

Characterization, pre-treatment, and potential applications of fine MSWI bottom ash as a supplementary cementitious material

With the development of waste recovery techniques, previous research has revealed that coarse fractions of municipal solid waste incineration (MSWI) bottom ash (BA) after proper treatment could be applied in the construction sector, while the fines are seldom recovered in practice and normally landfilled. This study explores the potential application of fine MSWI BA (0–2 mm) as a supplementary cementitious material (SCM) in Portland cement (PC) mixtures. Mechanical and chemical pre-treatment approaches have been designed with various conditions to optimize the treating process. The chemical and mineralogical compositions, as well as the metallic Al content in BA were characterized before and after the pre-treatment. It was found that both methods are effective in removing the metallic Al content in BA, Moreover, BA derived from mechanical treatment exhibited more contribution to the hydration reaction in PC mixtures, as revealed by the amount of reaction products and mineral phases formed in hardened trial mixtures. BA obtained was further partially blended in PC mortars to evaluate the performance as compared to SCMs and inert fillers. It was found that treated BA resulted in a slight retarding effect on the reaction kinetics. Treated BA behaved better than the coal fly ash to contribute to the strength development, while the inclusion of BA did not lead to significant influences on the workability.

Analysis of pore structure characteristics of MSWI bottom ash micro powder concrete

Municipal solid waste incineration (MSWI) bottom ash is a type of bulk waste. Its potential activity can be better harnessed after it is ground into a fine powder, leading to reduced carbon emissions. This paper investigates the pore structure of MSWI bottom ash micro powder concrete and its impact on mechanical properties. Standard tests were conducted to evaluate the mechanical properties of MSWI bottom ash micro powder concrete with four blending ratios under three water-binder ratios. Subsequently, a mercury intrusion test was performed to determine its internal pore structure characteristic parameters. Remaining specimens from the macroscopic test were sampled, and concrete specimens were observed using a high-power electronic environmental scanning microscope to analyze morphological characteristics at various multiples and curing ages. The results indicate that the pore structure of MSWI bottom ash micro powder concrete is uniformly distributed, displaying good fractal characteristics conducive to subsequent secondary hydration reactions. The inclusion of MSWI bottom ash micro powder increases concrete porosity, leading to a decrease in compressive strength. However, as the curing age increases, the value tends to approach that of ordinary concrete, suggesting that MSWI bottom ash micro powder exhibits potential hydraulicity, albeit with a slow hydration reaction. The observed pattern of MSWI bottom ash micro powder concrete aligns with that of ordinary concrete, wherein higher porosity corresponds to lower compressive strength. The addition of MSWI bottom ash micro powder increases concrete porosity, resulting in reduced compressive strength.

Recycling of municipal solid waste incineration bottom ash (MSWIBA) particles into natural fine sands for sustainable engineering cementitious composites

The manufacture of engineered cementitious composites (ECCs) consumes large amounts of natural fine aggregate. In this study, replacement of the natural fine aggregates in ECCs with municipal solid waste incineration bottom ash (MSWIBA) was found to reduce the consumption of natural river sand and the negative environmental impact of MSWIBA disposal. Previously, scholars have shown the potential of using MSWIBA particles as fine aggregates in concrete, but few scholars have evaluated ECCs with high percentages of MSWIBA powder in place of the natural fine aggregates. This study was conducted to design green ECCs by incorporating MSWIBA (BA–ECCs) to completely replace the natural silica sand with various fibers (PVA, PP and PE) and different fiber volume blends (0%, 0.5%, 1%, 1.5% and 2%) and to evaluate the BA–ECCs based on the fluidities, mechanical properties, microscopic morphologies, pore size distributions and heavy metal leaching capacities. The results showed that the addition of MSWIBA increased the porosities of the BA–ECCs. Compared with those of the control group, the maximum flexural strength of the BA–ECCs with 1.5% fiber doping were approximately 27.75% higher. There were relationships between the compressive strength and flexural strength and between the fiber volume content and strength. Moreover, microstructural observations revealed that the MSWIBA powder interacted strongly with both the matrix and the fibers, and the performance of the MSWIBA powder in the matrix was similar to that of a lightweight aggregate during internal curing. Additionally, fiber agglomeration (winding) at a 2% fiber content reduced the compressive and flexural strengths. The BA-ECCs showed lower heavy metal leaching contents than the MSWIBA, and the concentrations of various heavy metals were below the Chinese standards. Overall, this study could support research on the use of MSWIBA particles to prepare sustainable ECCs and recycle MSWIBA particles.