Search Results (36)

This work focuses on the use of municipal waste incineration bottom ash (MSWI) for the development and production of products suitable for use as construction products. The generation of these ashes is increasing every year due to the incineration of municipal waste. There are currently three incineration plants operating in major cities in Lithuania. The non-hazardous bottom ash remaining from the incineration process is stored in dedicated sorting and aging sites until it is used as an inert form of aggregate for the installation of road foundations. However, it has been observed that these ashes have a tendency to bind and cement when exposed to atmospheric precipitation at the storage site. Based on this characteristic, it was decided in this study to use alkaline activation of the ash to accelerate the bonding process and to create a dense, non-porous composite concrete structure. This activation method is known to create another problem during ash bonding, where the presence of metallic aluminum particles in the ash leads to the release of hydrogen gas and makes the structure of the cured samples porous. For the purposes of the study, it was decided to create a completely different mixture structure and not to use additional water in the mixtures tested. A very low water/solids ratio (W/S) of <0.08 was used for the alkaline activation of the mixtures. All the water required for ash activation was obtained from sodium silicate and sodium hydroxide solution. Metakaolin waste (MKW) was used to adjust the SiO₂/Na₂O/Al₂O₃ ratio of the mixtures. Vibro-pressing was used to form and increase the density of the samples. And for the formation of the concrete structure, 0/4 fraction sand was used as aggregate. The final alkali-activated sample obtained had properties similar to those of the very widely used vibro-pressed cementitious paving tiles and did not exhibit hydrogen evolution during alkali activation due to the very low W/S ratio. The best results were achieved by samples with a highest compressive strength of 40.0 MPa and a tensile strength of 5.60 MPa, as well as a density of 1950 kg/m³. It is believed that this alkaline activation and vibro-pressing method can expand the use of MSWI ash in the development of building products. Full article

As urbanization progresses rapidly, the pollution of heavy metal wastewater and the disposal of municipal solid waste incineration bottom ash (MSWI-BA) have emerged as significant challenges. MSWI-BA is a porous material recognized as an environmentally friendly adsorbent. To prevent escalating costs in future practical engineering applications, this study employed unmodified, natural MSWI-BA. This research assessed the adsorption capabilities of MSWI-BA for Pb(II) and Zn(II) through static adsorption experiments, which included adsorption kinetics and isotherm studies. The influence of various factors on the adsorption performance of MSWI-BA was investigated through adjusting the solution pH and the amount of ash, competitive adsorption conditions, and regeneration experiments. Advanced techniques, including ESEM-EDS, XRD, and FTIR, were utilized to analyze the adsorption mechanisms. The results indicated that under the conditions of pH values of 4 and 5, a temperature of 318 K, and an ash dosage of 0.1 g/20 mL, the maximum adsorption capacities of MSWI-BA for Pb(II) and Zn(II) were 89.09 mg/g and 33.77 mg/g, respectively. MSWI-BA demonstrates robust regeneration potential over multiple cycles, validating its practical feasibility. The principal mechanisms for removal include chemical precipitation, ion exchange, and surface complexation. By repurposing it as an efficient and low-cost adsorbent, this represents a sustainable strategy. Full article

Glass in mixed municipal solid waste (MSW) is often lost for recycling. Glass recovery from incineration bottom ash (IBA) after MSW incineration (MSWI) is technically feasible by sensor-based sorting, but rarely applied. Especially IBAs from fluidized bed combustion contain high recoverable glass amounts, but upgrading this glass is required for recycling in the packaging glass industry. This study examines different upgrading setups based on sensor-based sorting to improve the glass quality from two Austrian fluidized bed IBAs. Sensor-based sorting removed extraneous material like ceramic, stones, porcelain, metals, and lead glass. The fractions produced were characterized by manual sorting and X-ray fluorescence analysis. The glass fractions before upgrading contained 85–89% glass, of which 67% and 83% could be recovered after four sorting steps. Previous sieving caused high glass losses and is therefore not recommended. By sensor-based sorting, the extraneous material contents were lowered from 13% and 9% in the two IBAs to below 2.2%. Four-step upgrading could even ensure extraneous material contents <0.11% and Pb contents <200 mg/kg. Although limit values for packaging glass recycling were still exceeded, this study shows that upgrading of glass recovered from fluidized bed IBAs suggests a novel opportunity to enhance closed-loop glass recycling, thereby reducing the amount of landfilled glass. Full article

This paper analyzes the effective use of a mixture of fly ash (MSWI-FA) and solid waste from flue gas treatment (MSWI-SW), which are by-products of the municipal waste incineration process. MSWI-FA (19 01 13*) and MSWI-SW (19 01 07*) are classified as hazardous waste due to their toxic metal content and leaching potential, and currently lack practical applications, unlike slag and bottom ash (19 01 12). This study tested these wastes as partial substitutes for natural sand within a range of 0–20% of cement mass. Statistical analysis of the experimental results allowed the creation of good quality models predicting the effect of substitution additives on compressive strength and flexural strength (correlation 0.91 and 0.93, respectively). The mixture with the highest share of substitution additives (40% = 20% + 20%) was characterized by a decrease in compressive strength by 1.3% and flexural strength by 25.8%. Cement mortars synthesized with the waste mixture (up to 20% of each component) showed slightly lower consistency and water absorption than the control mortars. After the frost resistance tests (25 cycles), the flexural and compressive strength showed ambiguous behavior, showing both increases and decreases, indicating that the percentage of waste components alone is an insufficient set of factors for predicting these strength properties. The concentration of metal ions, i.e., Zn, Cu, Pb, Ni, Cu, and Cr, in the eluate after the leaching tests did not exceed the legal levels of pollutants introduced into waters, with the exception of barium. However, its content did not exceed the permissible levels required for waste intended for landfill. Using the mixing plant for this waste in the amount of 20% each, we save about EUR 10 in the cost of purchasing sand (which is 13% of the production costs of 1 m³) and EUR 8 in the cost of environmental fees when producing 1 m³ of mortar. The proposed technology is compatible with the objectives of a sustainable economy. Full article

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. Full article

This study examines the strategic incorporation of various recycled materials into asphalt concrete, specifically focusing on municipal solid waste incineration bottom ash (MSWI BA), recycled asphalt shingle (RAS), and recycled concrete aggregate (RCA). Due to the high porosity of MSWI BA and RCA, and the significant asphalt binder content (30–40%) found in RAS, there is a need to increase the amount of liquid asphalt used. RAS is posited as an efficient substitute for the asphalt binder, helping to counterbalance the high absorption characteristics of MSWI BA and RCA. The research objective is to quantitatively evaluate the effect of the combined use of RAS, MSWI BA, and RCA in Hot Mix Asphalt (HMA). This study encompasses several laboratory evaluations (i.e., rutting and tensile strength tests) and a cost–benefit analysis, which is a life cycle cost analysis. The results indicate that the combined use of these materials results in a higher tensile strength and rut resistance when compared with the control (with virgin aggregate). According to the cost–benefit analysis result, when the three recycled materials are used for an HMA overlay over an existing aged pavement, it could be 60–80% more cost-effective compared to a conventional HMA overlay, thereby offering significant economical savings each year in the field of road construction. Full article

To realize the large-scale utilization of municipal solid waste incineration (MSWI) fly ash in the field of building materials and to reduce the cost of coal mine backfill mining, the effects of the mixing ratio of cementitious materials, the particle size distribution of aggregates, and the amount and mass concentration of cementitious materials on the properties of backfill materials were experimentally investigated, and the microstructure of the hydration products was analyzed. The results showed that as the mass ratio of MSWI fly ash to bottom ash increased, the rate of expansion of the cementitious system continued to increase, and the compressive strength of the cementitious system continued to decrease. The Al (aluminum) and AlN (aluminum nitride) in the fly ash reacted with water to generate gas, causing the expansion of the cementitious materials; NaOH increased the alkalinity of the solution, which promoted the formation of more bubbles, thereby improving the expansion performance of the cementitious material. When the content of NaOH was 0.9%, the sample rate of expansion could reach 15.9%. The addition of CaCl₂ promoted the early hydration reaction of the cementitious material, forming a dense microstructure, thus improving the early strength and rate of expansion of the cementitious material. The compressive strength of the backfill body increased as the fractal dimension of the aggregate particles increased, and the particle grading scheme of group S1 was optimal. The 1-day, 3-day, and 28-day strengths of the backfill body of group S1 reached 0.72 MPa, 1.43 MPa, and 3.26 MPa, respectively. It is recommended to choose a backfill paste concentration ranging between 78.5% and 80% and a reasonable amount of cementitious material between 20% and 25%. After the MSWI fly ash was prepared as a backfill material, the leaching of potentially harmful elements in the fly ash was greatly reduced, and the concentration of dioxin was reduced to 13 ng TEQ/kg. This was attributed to the dilution of the cement, the physical encapsulation of gel products, and the isomorphous replacement of Ca²⁺ in calcium aluminate chloride hydrate. Full article

This study investigated the positive effect of the combined use of recycled asphalt shingles (RASs) and municipal solid waste incineration (MSWI) bottom ash (B.A.) in asphalt concrete, which contributes to enhanced sustainability in pavement engineering. In addition, unlike traditional approaches that employ individual recycling material in hot mix asphalt (HMA), the combined use of the two waste materials maximizes the mechanical performance of the asphalt mixture. The addition of RAS (with 30–40% aged binder) as an additive generally enhances the strength/stiffness of the asphalt mixture. The high porosity/absorption of MSWI BA results in an additional amount of liquid asphalt binder in the mixture. As an admixture, RAS could supply the additional asphalt binder in the mixture when MSWI BA is used as an aggregate replacement. This research was conducted in two phases: (1) to examine the effect of MSWI BA alone and its optimal asphalt content (OAC), and (2) to assess the combined effect of B.A. and RAS in HMA. Multiple laboratory testing methods were employed for the mechanical performance investigation, including the Marshall stability test, rutting test, and indirect tensile test. The testing results show that the 20% B.A. replacement exhibits the best performance and that it requires an additional asphalt binder of 1.1%. For the combined use of MSWI BA and RAS, 5% RAS shows the best mechanical performance. All mixtures that contain the B.A. and RAS show greater strength than the control specimen (regular HMA). Full article

The cement sector is the second largest contributor to anthropogenic CO₂ emissions, and several efforts have been made to reduce its environmental impact. One alternative that has gained interest in recent years involves the use of municipal solid waste incineration (MSWI) bottom ash (BA) as clinker/cement replacement. This paper studies the application of MSWI BA in three different ways: (i) aggregate (0 to 100 v/v %), (ii) partial binder substitute (0 to 30 v/v %), and (iii) filler (5 v/v %). It stands out for its approach in characterizing seven distinct BA particle sizes and for the development and analysis of eco-cement mortars with only mechanically pre-treated BA. Hardened state properties showed that the use of BA as aggregate leads to deterioration and efflorescence formation on the surface of the mortars, making this application unfeasible. The replacement of 15 v/v % of OPC (Ordinary Portland Cement) by BA and the use of finer (<63 μm) BA as filler caused a decrease in the compressive strength of the mortar, from 15.8 to 9.3 and 11.0, respectively. However, these materials are suitable for use in walls where the minimum required mechanical resistance is 5 MPa. Furthermore, these mortars demonstrated resilience against freeze–thaw cycles and even exhibited increased compressive strength after 25 cycles. Thus, this work showed that MSWI BA can be used as an OPC substitute (up to 15 v/v %) and as a filler, promoting circular economy principles and reducing CO₂ emissions related to the construction industry. Full article

The purpose of this research is to assess the yield and reaction rate potential of carbon dioxide (CO₂) sequestration through mineralisation using readily available and inexpensive resources by exploiting waste materials. In this case, a blend of four different kinds of ashes and combustion by-products were used, namely, coal fly ash (CFA), flue gas desulphurization (FGD) residues, municipal solid waste incineration fly ashes (MSWI FA) and bottom ash (MSWI BA), produced at the same location. To highlight the impact of these materials on the carbonation process, various factors were analysed, including particle size distribution, immediately soluble contents, mineralogy, particles’ detailed structure, and chemical composition. After preparing the samples, two carbonation processes were tested: natural carbonation and accelerated carbonation. To evaluate the impact of the water content on the reaction rate and yield of the mineral carbonation, various liquid-to-solid (L/S) ratios were used. The results demonstrate that the water content and pressure play a significant role in the CO₂ sequestration during the accelerated carbonation, the higher the L/S, the greater the yields, which can reach up to 152 g CO₂/kg with MSWI FA, while no substantial difference seems to emerge in the case of the natural carbonation. Full article

A considerable amount of literature has been published on municipal solid waste incinerator (MSWI) bottom ash as a substitute for natural road materials. However, most studies are conducted in the laboratory, and as a result, very little is known about the construction of pavement structural layers from MSWI bottom ash mixtures and their performance under real conditions. Therefore, the main objective of this paper is to evaluate the bearing capacity and compaction level of the unbound base and sub-base course constructed from the MSWI bottom ash mixtures. For this purpose, three MSWI bottom ash mixtures (70–100% of MSWI bottom ash) and reference mixtures only from natural aggregates were designed and used to construct the unbound base and sub-base courses on a regional road in Lithuania. In total, five different pavement structures with MSWI bottom ash mixtures and a reference one with natural aggregates were constructed and tested. The results from this study showed that unbound mixtures with 70–100% of MSWI bottom ash are suitable to construct the unbound base and sub-base courses since the bearing capacity of those layers met the requirements (≥80 MPa for the sub-base course and ≥120 MPa for the base course) and was similar to that of the reference pavement (161 MPa for sub-base course and 212 MPa for base course). Full article

Large amounts of municipal solid waste incineration bottom ash (MSWI BA) are formed worldwide, and this quantity is growing because of the establishment of new waste-to-energy plants. This waste is generally kept in landfills but can be used for the manufacturing of cementitious building materials. This article analyzes the use of MSWI BA as a microfiller in cement mortars. The effects of MSWI BA on the properties of cement binder and mortar were analyzed by using them separately or in combination with other microfillers: milled quartz sand, metakaolin, milled glass, and microsilica. This article investigates the flowability of cement-based mixtures, the volume change as a result of the evolution of hydrogen gas, cement hydration, XRD, TG, the physical and mechanical properties of the mortar samples, and leaching. The addition of milled MSWI BA in cement mortars was found to significantly increase slump flow; therefore, MSWI BA can be used as a microfiller. The addition of metakaolin changed the kinetics of H₂, which evolved due to the reaction between Al and alkali, and had a positive effect on the mechanical properties of cement mortar. Full article

Global objectives to mitigate climate change in the construction industry have led to increasing geopolymer development as an alternative to carbon-intensive cement. Geopolymers can have similar mechanical properties and a lower carbon footprint. However, geopolymer production is not as homogeneous as cement because it is produced by synthesizing alkali solutions with different aluminosilicate precursors. This study assessed the feasibility of using conventional (fly ash, blast furnace slag, and metakaolin) and alternative precursors (steel slag, mine tailings, glass waste, sewage sludge ashes, and municipal solid waste incineration bottom ashes (MSWI BA)) in geopolymer mixes for different European regions (Belgium and Finland) from a sustainability perspective, using environmental, economic, and resource availability indicators as the criteria. A multi-objective optimization technique was applied to identify optimal precursors for geopolymer mixes using two scenarios: (1) considering both conventional and alternative precursors; (2) only considering alternative precursors. The results from the first scenario show that one of the most optimal precursor combinations for the geopolymer mix is 50% fly ash, 25% MSWI BA, and 25% sewage sludge ash for Belgium. For Finland, it is 19% fly ash, 27% mine tailings, and 45% MSWI BA. For the second scenario, one of the most optimal precursor combinations for Belgium is 87% MSWI BA and 13% steel slag. For Finland, it is 25% mine tailings and 75% MSWI BA. Subsequently, linear regression analysis was applied to predict the compressive strength of the identified optimal mixes, and the results for Belgium and Finland were between 31–55 MPa and 31–50 MPa for the first scenario and between 50–59 MPa and 50–55 Mpa for the second scenario, respectively. Full article

In order to clarify the influence of the municipal solid waste incineration bottom ash (MSWI BA) content on the pavement performance of the cement-stabilized macadam, the MSWI BA with 0%, 25%, 38% and 50% content was used instead of fine aggregates. To explore the feasibility of building pavement base with cement stabilized MSWI BA, the cement-stabilized MSWI BA mixture was prepared by mixing the MSWI BA at the mass fraction of 50%, 75% and 100% with fine crushed stuff. Subsequently, the compaction test and 7 days unconfined compression test were conducted with 4%, 5% and 6% cement dosage. The compaction test, unconfined compressive strength test, splitting strength test, compressive resilient modulus test and frost resistance tests were carried out based on the long-age samples with an optimal cement dosage of 5%. Furthermore, the unconfined compressive constitutive model was established based on the test data. Afterwards, the test road was built to measure the practical effect of MSWI BA on road construction. Meanwhile, energy-saving and emission-reduction analyses were conducted on the MSWI BA road. The results showed that under 5% cement dosage, the mechanical properties and frost resistance of the mixture with different MSWI BA content both satisfied the specification requirements; during the construction, the appropriate MSWI BA content could be selected according to the requirements of different highway grades in the specification. The established segmented constitutive model could well simulate the stress–strain relationship of the mixture in the compressive process. Using cement-stabilized MSWI BA to build the pavement base was feasible, which provided not only an important reference for the engineering design but also had positive significance for promoting carbon peaking, carbon neutrality and sustainable development of highway engineering construction. Full article

Nowadays, budget restrictions for road construction, management, and maintenance require innovative solutions to guarantee the user acceptable service levels respecting environmental requirements. Such goals can be achieved by the re-use of various waste materials at the end of their service life in the pavement structure, therefore avoiding their disposal in landfill. At the same time, significant savings are achieved on natural aggregate by replacing it with such waste materials, improving the economic and environmental sustainability of road constructions. The purpose of this study is to discuss a laboratory investigation about foamed bitumen-stabilized mixtures for road foundation layers, in which the aggregate structure was entirely made up of industrial by-products and civil wastes, namely metallurgical slags such as electric arc furnace (EAF) and ladle furnace (LF) slags, coal fly (CF) ash, bottom ash from municipal solid waste incineration (MSWI), glass waste (GW) and reclaimed asphalt pavement (RAP). Combining these recycled aggregates in different proportions, six foamed bitumen mixtures were produced and investigated in terms of indirect tensile strength, stiffness modulus, and fatigue resistance. The leaching test carried out on the waste materials considered did not show any toxicological issue and the best foamed bitumen mixture’s composition was characterized by 20% of EAF slags, 10% of LF slags, 20% of MSWI ash, 10% of CF ash, 20% of GW, and 20% of RAP. Its mechanical characterization presented a dry indirect tensile strength at 25 °C of 0.62 MPa (well above the Italian technical acceptance limits), a stiffness modulus at 25 °C equal to 6171 MPa, and a number of cycles to failure at 20 °C equal to 6989 for a stress level of 300 kPa. Full article