Solid Waste Recycling Research Articles

Immobilization enhancement of heavy metals in lightweight aggregate by component regulation of multi-source solid waste

Integrated recycling of solid waste containing heavy metals is a critical environmental challenge. In this study, a green solution to reduce heavy metal leaching from solid waste is demonstrated by combining contaminated soil, industrial sludge and lithium slag in pairs to produce lightweight aggregates (LWAs). The physical properties and heavy metal leaching behavior of LWA samples were systematically investigated and characterized. The results showed that industrial sludge reduced the density and water absorption of LWA, while the high content of lithium slag was detrimental to the physical properties. LWA containing 80% contaminated soil and 20% lithium slag had the lowest particle density of 1.47 g/cm3 due to the hollow structure caused by the low viscosity and violent generation of SO2. LWAs with lithium slag leached excessive Cu and Cr relatively, while heavy metals were immobilized well in LWAs with contaminated soil and industrial sludge as the main components. Because the flux components of industrial sludge could enhance the encapsulation of heavy metals by glass phase. In addition, the co-immobilization of multiple heavy metals was observed in the spinel phase. This study provides an efficient and safe method for the synergistic recycling of solid waste.

A survey of knowledge, attitude, and performance of Kerman residents on segregation and recycling of household solid wastes during COVID-19 period

Background: Awareness, knowledge, and attitude towards waste management, environmental factors of waste disposal sites and citizens’ as well as waste generators’ behaviors should be considered for implementing a waste segregation plan at the source. Methods: The statistical population of this cross-sectional study includes 150 000 households living in Kerman. The sample size is calculated as 444 individuals using a stratified sampling method considering a 15% withdrawal probability. The correlation between Kerman citizens’ demographic data (age, gender, mean income, and household head’s educational level) and behavioral patterns (knowledge and awareness, attitude and behavior) regarding waste management and environmental factors of waste disposal sites was evaluated using SPSS software. Results: Examining the variables indicates that attitude, environmental factors, behavior, awareness, and knowledge have the highest mean and standard deviation, respectively. The highest mean score of awareness and knowledge was observed among individuals who earned 40 million IRR and higher income (2.55±0.24) and those who had a PhD degree (2.63±0.27). The results show that one unit increase in the score of awareness and knowledge, attitude and environmental factors could increase the mean behavior score. Conclusion: Teaching the households waste-related environmental issues and how to properly separate recyclable waste as well as providing correct information regarding the current (COVID-19 period) and future plans and policies of the waste management organization, and developing suitable motivational mechanisms could improve the performance level of a society.

Diffusion mechanism of solid waste product utilization pulping and fracture network grouting

China's commitment to achieving carbon neutrality by 2060 has highlighted the pressing need for effective solid waste recycling. The reinforcement of mine water hazards has led to increased production costs due to the significant consumption of slurry. This study focuses on the development of mine crack grouting sealing and reinforcement materials using mine slag powder and waste rubber particles, along with cement reinforcement and alkali slag stimulation. The impact of water-cement ratio, rubber particle content, and slag mass fraction on slurry performance is analyzed, and the optimal values for these parameters are determined. A two-phase seepage simulation using COMSOL is conducted to investigate the flow and diffusion of slurry in a fractured network rock mass. The findings indicate that a water-cement ratio of 0.7 and a slag and rubber particle mass fraction of 70% and 30% respectively result in the slurry with favorable fluidity and mechanical properties. The diffusion pattern of the slurry in the fractured rock mass is characterized by vortex-like diffusion. The stability of the fractured rock mass is influenced by both grouting time and pressure, which should be carefully considered during on-site operations. This research has significant implications for the integrated prevention and control of mine water hazards and the large-scale utilization of high-dosage solid waste, thereby ensuring production safety, ecological environment safety, and sustainable development in mining areas.

Local Market Institutions and Solid Waste Management in Accra’s Open-Air Markets

ABSTRACT Solid waste management is a global concern that has been handled in several ways in different parts of the world. In cities of the Global North, measures meant to prevent or minimise solid waste generation and its associated challenges are based on the waste management hierarchy, whereas in cities in the Global South, the active involvement of the public and private sectors is well documented. Existing studies cover practices of solid waste collection, reuse, recycling and landfilling by private formal and private informal actors. The term informal actors has often been used to refer to itinerant waste buyers, waste pickers and recyclers. Local African institutions existing in marketplaces – such as women known as ‘market queens’ or ‘commodity queens’ and market chairmen, whose management roles are not necessarily geared towards livelihood creation – have, however, been neglected. This lack of attention to the roles of local institutions in solid waste management potentially undermines efforts aimed at waste minimisation and the achievement of policy measures such as the 2030 Agenda for Sustainable Development (Sustainable Development Goal 11) that seeks to make cities inclusive, safe, resilient and sustainable. Hence, based on the cases of the Kaneshie, Kantamanto and Madina markets in Accra, empirical evidence of the role that local market institutions play in solid waste management is provided. Based on this, an argument is made for removing structural barriers impeding local market institutions’ participation in existing systems for managing urban market environments.

Influence of Coal Gangue Powder on the Macroscopic Mechanical Properties and Microstructure of Recycled Aggregate Concrete.

The construction and coal industries generate substantial industrial waste, including coal gangue and construction and demolition (C&D) waste, leading to environmental pollution and high disposal costs. Integrating recycled aggregates (RAs) and coal gangue powder (CGP) into concrete is an effective approach for waste management. However, CGP can affect the performance of traditional recycled concrete. This study primarily aims to optimize the utilization of RAs and CGP while maintaining concrete performance. They utilized orthogonal experimental designs and microscopic characterization techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Orthogonal experimental analysis indicated that with a water-cement ratio (WCR) of 0.5 and replacement rates of 10% for CGP and 60% for RA, compressive and splitting tensile strengths reached 73.6% and 77.4% of ordinary C30 concrete, respectively. This mix proportion minimizes strength decline in coal gangue powder-recycled aggregate concrete (CGP-RAC) while maximizing recycled material replacement. Microscopic analysis revealed that CGP increased the Ca/Si ratio in cement paste, impeding hydration reactions, resulting in a looser internal structure and reduced concrete strength. These findings are anticipated to provide fresh theoretical insights for solid waste recycling and utilization.

The Role of Leadership and Collaboration in Innovative Changes in the Solid Waste Recycling Industry: Corporate and Regional Levels

Transition to a circular economy and growing popularity of "green" behavior rising the question of how to bring relevant innovative changes to the solid waste recycling industry. Finding the right answer to this question becomes a priority in the different regions of the world. The best examples of innovative changes in this industry can be found in the theoretical sources, but their effective implementation in practice is sometimes a challenge due to poor management or low level of staff involvement. The aim of this article is to analyse and evaluate the influence of leadership and collaboration on the innovative processes and advanced economic and environmental performance of solid waste recycling enterprises. Primary and secondary data collection and analysis methods were used to provide the evidence for the research findings. The results show that motivated team with a professional leader can make a difference in the process of development and implementation of innovations allowing improving the efficiency and increasing the capacity of solid waste recycling industry. This difference include approach for setting up goals and using resources in the process of their achievement. The scientific novelty of the article lies in the disclosure of the specifics of various types of innovative changes in the solid waste recycling industry, as well as the impact of leadership and cooperation on innovative processes. Authors concluded that leadership and teambuilding skills should be a part of education and training in the solid waste recycling industry due to their significant influence on the industry success.

Degradation of imidacloprid via the activation of peroxymonosulfate and peroxydisulfate using a Fenton-sludge-derived Fe0/Fe3C composite

The Fenton process is a commonly employed advanced oxidation process for industrial wastewater treatment. However, large volumes of iron-containing sludge are generated in the Fenton reaction, causing secondary pollution. In the present study, we report a Fenton-sludge-derived biochar (FSB) designed to degrade the neonicotinoid pesticide, imidacloprid (IMD) via activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS). The effect of pyrolysis temperature on the transformation of the crystal phase and surface functional groups of samples was monitored using X-ray diffraction, Fourier transformation-infrared spectroscopy, and scanning electron microscopy. The use of FSB treated at 900 °C (FSB 900) containing the iron phase Fe0/Fe3C led to the highest IMD degradation efficiency with both PMS and PDS (92.7 ± 0.5 % and 100.0 ± 0.0 %, respectively; [IMD]0 = 20 mg/L, [persulfate]0 = 2 mM, [FSB]0 = 0.2 g/L, reaction time = 60 min). The main reactive species involved in IMD degradation via PMS and PDS activation using FSB 900 were identified with scavenger tests. The effects of solution pH and the additional anions on the performance of IMD removal efficiency were also investigated. This study provides insights into the recycling of solid waste derived from the Fenton process and the degradation of recalcitrant organic pollutants in wastewater.

Induction Heating and Cooling Performance of Asphalt Mixture as Recycling Rap and Steel Slag

Recycling reclaimed asphalt pavement (RAP) for asphalt pavement construction is of interest due to its potential to mitigate environmental impact and resource consumption; however, the addition of RAP limits the induction heating behavior of asphalt mixtures, hindering the further application of RAP in sustainable and functional asphalt pavement. This study prepared recycled asphalt mixtures with high contents of steel slag aggregate and RAP, and optimized the rejuvenator dosage and composition design to investigate the induction heating rate. The effect of the steel fiber content, heating time, and heating distance on the induction capacity were verified for the recycled asphalt mixture. Moreover, the cooling curves of the recycled asphalt mixture were explored using a constant temperature chamber and infrared camera. The results showed that 6 wt% of rejuvenator in aged asphalt could evidently restore the physical properties and surface morphology, the highest heating rate of 1.204 °C/s could be reached with 2 wt% of steel fiber content, and the effective intervals of heating time and heating distance were set as 60–120 s and 10–20 mm, respectively. This study could be a significant reference in promoting solid waste recycling and sustainable asphalt pavement construction.

Fabrication of biodegradable kraft paper from buffing dust and jute fiber: Green solutions for packaging

AbstractAddressing solid waste recycling, this study aims to develop biodegradable kraft paper from buffing dust (BD) and post‐consumed jute fiber (JF). Employing a simple solution casting method with a polyurethane binder, the kraft paper was fabricated and characterized using UV–Vis spectroscopy, FTIR, XRD, SEM, TGA, OTR, biodegradability, and tensile tests. The findings revealed covalent and hydrogen bonding between BD and JF, forming a uniform surface. Notably, the composite exhibited improved thermal stability, enhanced gas barrier properties, and biodegradability compared to individual components. Furthermore, the composite also showed 57% higher tensile strength, 38% greater elongation, 20% increased hardness, and 9% higher density compared to buffing dust. Compared to jute fiber, the increases were 125%, 91%, 30%, and 19% respectively. Moreover, the composite excelled in gas barrier performance, surpassing BD and JF by a remarkable 61% and 73% increase respectively. These significant findings underscore the vast potential of the composite kraft paper as a versatile material suitable for various applications, including packaging, interior furnishing industries, and reinforcing elements in the footwear industry. By addressing waste management and promoting sustainability, this research contributes to the development of eco‐friendly materials that align with contemporary environmental concerns.Highlights Covalent and hydrogen bonding enhance uniformity. Biodegradable kraft paper with improved properties. Impressive tensile strength, elongation, and hardness. Versatile material for eco‐friendly applications. Promotes sustainability and waste management.

Stakeholder Participation and Solid Waste Management in Lira City East Division

Purpose: this study examined the contribution of stakeholder participation to SWM in Lira City East division. Specifically, the study determined the effect of stakeholder participation on solid waste reduction, solid waste recycling and on waste reuse.
 Methodology: The study adopted a cross-sectional study design, which employed a mixed methods approach of both quantitative and qualitative methods. The study population consisted of 195 respondents, which included political leaders and civil servants of Lira City East division and heads of household in Lira City East. Both the Simple random sampling technique and purposive sampling technique were used to select a sample of 132 participants. The researcher adopted Self-Administered Questionnaires to collect quantitative data and an interview guide to collect qualitative data. Both descriptive statistics (mean, and standard deviation), and inferential statistics (correlation and regression) were used to analyse numerical data. Content analysis was used to analyse qualitative data.
 Findings: The findings revealed a statistically significant positive relationship between stakeholder participation and SWM. Further, it was revealed that stakeholder participation yields a significant effect on waste reduction, waste recycling and waste reuse.
 Unique contribution to theory, practice and policy: It is concluded that stakeholder participation affects SWM in Lira City East division. This study contributes an original and empirical-evidence of the contribution of stakeholder participation on SWM in Lira City East division. It is recommended that, for better management of solid waste in Lira City division, the authorities of Lira City east division should sensitise the residents on the possible mechanisms of reducing the amount of waste generated at homestead, how the waste generated can be recycled to other useful forms and how the waste generated can be reused. This study contributes to the reawakening of the urban stakeholders in Lira city and Uganda, as a whole, on the magnitude of the solid waste challenge and how this calls for instantons effort to achieve healthy and cleaner cities/urban centers

Polypropylene fiber reinforced alkali-activated ultra-light foam insulation material: Performance study and mechanism analysis

Reducing building energy consumption has become an important measure to achieve sustainable development in urban construction worldwide, and installing insulation materials on building envelopes has been proven to be an effective means of reducing building energy consumption. This study developed a high toughness ultra-light foam insulation material (FIM) by combining polypropylene (PP) fiber, expanded polystyrene (EPS) lightweight aggregates, and alkali-activated multiple cementitious materials. Its purpose was to reduce building energy consumption while promoting the recycling of solid waste. The effects of PP fiber length and content on the dry density, flexural strength, compressive strength, thermal conductivity, and volumetric water absorption of FIM were studied, and the improvement mechanism of PP fiber was revealed. Scanning electron microscopy was used to observe the microscopic morphology of FIM. It was exciting to note that all developed FIM had a dry density of less than 150 kg/m3, and a minimum thermal conductivity of only 0.0423 W/(m·K). PP fiber with a length of 9 mm played a key role in improving the flexuralperformance of FIM, which increased by 21.05% compared to the control group. PP fiber with a length of 3 mm showed the most significant improvement in the thermal conductivity of FIM, which was 13.5% lower than the control group. A response surface methodology (RSM) was used to propose a prediction model for five performance indicators of FIM, with PP fiber length and content as variables. The results showed a high correlation between the predicted value and test value, which verifies the validity of the prediction models. The proposed models can provide important reference basis for mix proportion design.

Cytotoxic and oxidative changes in individuals occupationally exposed to recyclable municipal solid waste

ABSTRACT aste collectors are exposed to a wide variety of bacteria, endotoxins, fungi, allergens, particulate matter, irritating inhalants, and vehicle exhaust, making them more prone to development of chronic diseases. Although several studies described the impact of occupational exposure on the overall health of waste collectors, few investigations were conducted regarding cellular and molecular changes that may occur due to exposure. The aim of this study was to assess biomarkers of oxidative stress such as levels of reactive oxygen species (ROS), lipoperoxidation, total antioxidant capacity (TAC), apoptosis, butyrylcholinesterase (BChE) activity and mitochondrial function (MitoTrackerTM Green FM and MitoTrackerTM Red) using the peripheral blood from individuals occupationally exposed to recyclable solid waste in Southern Brazil. The study included 30 waste collectors and 30 control individuals, who did not perform activities with recognized exposure to biological and chemical substances. Waste collectors were found to exhibit in peripheral blood leukocytes (PBL) higher rates of apoptosis, increased production of ROS, and reduced mitochondrial membrane potential (MMP), associated with decreased total antioxidant capacity (TAC) and elevated activity of BChE in plasma. Therefore, evidence indicates that cytotoxicity, oxidative stress, and inflammatory responses may be involved in the multiplicity of adverse health outcomes related to contaminant exposure in waste collectors. It is thus necessary to implement and/or improve occupational health programs aimed at workers as well as mandatory inspections for the use of personal protective equipment.

Recycling of Municipal Solid Waste in Construction

This article discusses a promising direction focused on the use of recycled municipal solid waste in construction. In Russia, there are problems related to municipal solid waste management, which necessitates the modernization of this process and confirms the relevance of the issues raised. Analysis and use of the experience of foreign countries in the processing of municipal solid waste and its secondary use in Russia contributes to the search for a more environmentally responsible approach that entails both economic and social benefits. The use of solid municipal waste recycling products in construction is aimed at minimizing the negative impact on the environment and is a step towards the transition to a circular economy, where waste is turned into valuable resources. The article reflects on the various methods of recycling municipal waste and analyzes the priority areas for the processing of municipal solid waste. In addition, examples of successful building projects using recycled products are given, and the challenges and prospects of this approach, as well as its significance for sustainable development and environmental responsibility in the construction industry, are revealed.

Performance optimization design of high ductility cement-based alkali-activated municipal solid waste incineration fly ash composite for rapid repair material

As a residue that results from the high-temperature incineration of urban household waste, municipal Solid Waste Incineration Fly Ash (MSWIFA) contains various harmful organic pollutants like dioxins and heavy metals. These contaminants pose significant health risks to humans, including deformities and carcinogenic effects. The focus of this study is the development of a High Ductility SAC Rapid Repair Material (HD-SACRRM) through MSWIFA as a partial replacement for Sulphate Aluminate Cement (SAC), so as to achieve high ductility, rapid hardening, and the strength required for pavement layers. The reactivity of MSWIFA is investigated by adjusting its content and the type and dosage of alkali-activators. X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) tests are conducted to analyze the variety and microstructure of alkali-activated MSWIFA-SAC hydration products. Also, the efficiency of immobilizing heavy metal ions within the alkali-activated system is examined. Based on these findings, the proportions of HD-SACRRM are optimized. The experimental results demonstrate that the optimal conditions for MSWIFA reactivity are met when the MSWIFA content is 20% and the 30% soluble silicate with a modulus of 1.8 is present. The optimized conditions of HD-SACRRM are as follows: a 20% MSWIFA content, 30% soluble silicate with a modulus of 1.8, a water-cement ratio of 0.30, a 2.0% fiber volume fraction, a sand-cement ratio of 0.30, and 5% Li2CO3 as an early strength agent. After 48 h of curing as standard, the material exhibits a compressive strength of 45.7 MPa, an ultimate elongation of 2.70%, and an average crack width of 127.59 μm. The alkali-activated MSWIFA-SAC system generated more gels such as C-S-H and C-A-H, thus resulting in a dense microstructure that enhances both the capacity of heavy metal immobilization and mechanical strength. These findings shed some light on the recycling of MSWIFA solid waste and the repair of asphalt concrete road surfaces.

Analysis of Carbon Storage Potential of CO2 Foamed Concrete

The technology of carbon capture, utilization, and storage (CCUS) is an important component of carbon neutral technology systems. To confirm the carbon storage potential of CO2 foamed concrete (CFC), this study addressed the principle of carbon storage in CFC materials. It is apparent that carbon storage of CFC materials includes carbon fixation in concrete skeletons and carbon storage in CFC bubbles. The carbon fixation of CFC skeletons is realized by CO2 mineralization. As the concrete skeleton in CFC is in the CO2 atmosphere, the carbonation of CFC materials or CO2 mineralization is more complete. Research shows that the carbonation rate of CFC materials can reach almost 30% after acidification, foaming with high CO2 pressure and curing in the atmosphere. The carbonation rate is higher than the rate in concrete curing with CO2. A mathematical model was established to calculate carbon fixation capacity in CFC materials, and the carbon fixation and storage capacity in CFC material were estimated. The results showed that more than 99% carbon storage of CFC was realized by the chemical carbonization of the concrete skeleton. Comparatively, the potential of carbon storage in the bubble of CFC was small. In this study, carbon storage capacity was divided into three categories, i.e., theoretical maximum capacity, relative reliable capacity, and expected capacity or potential. The carbonation rate for theoretical maximum capacity was 100%, when all the concrete was considered to be carbonated. As the carbonation rate of concrete during the whole life cycle is approximately 55% all over the world, 50% was set as the carbonation rate for relative reliable capacity calculation. If at high temperatures, CO2 curing with high pressure or accessory ingredients applied to silicate concrete can improve carbonation rate to be over 80%, when the carbon storage capacity is considered to be expected capacity or potential. In 2017-2021, the theoretical maximum capacity of carbon storage was 3.623×109 t CO2 in China, with 7.25×108 t·a-1. The relative reliable capacity was 3.75×108 t·a-1, and the expected capacity was 5.80×108 t·a-1. If the carbonation rate was 30%, the carbon storage of concrete produced annually in China during the whole life cycle reached 2.18×108 t, which was more than the carbon sink of Daxing'anling forest for one year. In coal electricity integrated mining areas and large thermal, metallurgical, cement chemical, and other high-energy consuming enterprises, CFC has a good prospect of development to promote the recycling of solid waste and waste gas. Meanwhile, it is pointed out that the stability of CFC before solidification is a technical problem to be solved in the next step.

Recyclable waste in Brazilian municipalities: A spatial-temporal analysis before and after the national policy on solid waste

In 2010, the Brazilian authorities approved the National Policy on Solid Waste (NPSW) with the aim of promoting the recycling and reuse of solid waste. However, assessing the distribution and progress of recyclable material recovery following the implementation of this key government policy remains a challenging task. Therefore, this study employs a spatial-temporal analysis to investigate the impact of the NPSW on the recovery of recyclable waste in Brazil. We employed spatial statistical techniques such as Getis-Ord Gi* and Global Moran's I. The results revealed significant and heterogeneous clustering of recycled materials among municipalities, both before and after the implementation of the NPSW. The analysis demonstrated that recycled waste tended to cluster in more developed and urbanized areas, while a considerable number of cold spots were observed in less developed regions or densely populated areas, indicating low recycling rates. These findings raise environmental concerns for policymakers and emphasize the need for interventions to enhance recycling efforts. The study highlights the urgency of improving municipal solid waste management and raising awareness among local communities about the economic and environmental benefits of recycling, particularly in areas characterized by unsanitary living conditions, poverty, and low-income disparities. Therefore, it is recommended to tailor the legal framework to local realities, considering the vast and socioeconomically diverse landscape of Brazil.

A sustainable green reverse logistics plan for plastic solid waste management using TOPSIS method.

Recycling solid plastic waste is helpful for resource utilisation in a sustainable manner, and this can lead to reverse logistics to recover waste in supply chain management. In developing economies, it is very essential to recover waste and recycle it, as mismanagement of it could hasten the development of negative socioeconomic and environmental issues. This paper investigates plastic waste recycling by means of reverse logistics management. We feature Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), which is a multi-criteria decision-making approach to selecting a suitable warehouse that will assist the decision-maker and supply the product to the re-manufacturing cell by inspecting the waste. The paper also focuses on the carbon emissions that are emitted during re-manufacturing through a mathematical model that minimises the total cost and total carbon emissions. A case study of the plastic re-manufacturing industry in Tripura, India, is shown here to present the steps of the decision support system. The model is programmed with real-life data from the case study and yields a total cost of Rs. 2894.37 and total emissions of 414.15 gm/lt, when the disposal cost is considered; without it, the total cost is Rs. 2668.69 and the total emissions are 413.54 gm/lt. The results obtained are promising for reducing carbon emissions from the recycling process of plastic waste at a lower cost. This research will also help the environment cope with plastic waste, which has become a threat to nature, as well as carbon emissions that come from the industry. Finally, some managerial insights and suitable analyses with pictorial representation are proposed.

Test study on mechanical properties of compound municipal solid waste incinerator bottom ash premixed fluidized solidified soil

In this paper, the municipal solid waste incineration bottom ash (MSW-IBA) is used as the fine aggregate and firming agent component of the premixed fluid stabilized soil (PFSS). Through the mechanical strength test, and the hydration products and microstructure characterization, the effects of the NaOH content for MSW-IBA pre-aging treatment and activator content on the mechanical properties of the PFSS are studied. The results show that the mechanical strength of the prepared PFSS is closely related to the amount of NaOH and the activator. The increase in the amount of NaOH and activator can affectthe formation of early hydration product Aft, and reduce the early strength. However, it can promote the depolymerization of glass phase in MSW-IBA and slag to form C-(A)-S-H and Mg-(A)-S-H gel, increase the microstructure density, and thus improve the late strength. The application of MSW-IBA in PFSS can achieve the recycling of solid waste.

Design and performance evaluation of a new green pavement: 100% recycled asphalt pavement and 100% industrial solid waste

In order to achieve sustainable development of road construction while addressing the occupation of land resources and the environmental impact of recycled asphalt pavement (RAP) and industrial solid waste, as well as the problem of insufficient resistance to permanent deformation and durability of conventional asphalt pavement, this study designed a new type of green pavement, which uses 100% RAP to form a large void matrix skeleton and 100% solid waste to prepare grouting materials. Research has found that green pavement has significantly higher high-temperature stability and durability than conventional asphalt pavement. The green pavement formed with a continuous gradation RAP matrix skeleton can be 100%–1000% higher than the green pavement formed with a single particle size gradation RAP matrix skeleton under the same fatigue stress ratio and load. At the same time, it also has significantly higher low-temperature bending characteristics, strength characteristics, and crack resistance. The above indicates that the green pavement designed in this study has good pavement performance, mechanical properties, and durability, especially the green pavement formed with a continuous gradation RAP matrix skeleton.

Development and application of lead smelting slag eco-cementitious material: Synergistic excitation regulation and heavy metal solidification

In order to realise the resource reuse and safety of lead smelting slag (LSS) that contains several harmful heavy metals, LSS eco-cementitious materials (LSSEM) were prepared in this study using calcium and magnesium sources to excite high-volume LSS (78.125%). The results show that the synergistic effect of dual excitation sources can significantly increase the compressive strength of LSSEM from 13 MPa to 34.44 MPa. Performance enhancement mechanisms were investigated using X-Ray Diffraction (XRD), Fourier Transform Interferometric Radiometer (FTIR), Thermal Gravimetric Analysis (TG), Scanning Electron Microscope (SEM), and Mercury Intrusion Porosimetry (MIP). Introduction of calcium and magnesium sources facilitated dissolution of the active components in the LSS to achieve greater excitation. Leaching experiments showed that LSSEM could significantly solidify heavy metals based on the synergistic action of the dual excitation sources. The solidification ratio for each heavy metal exceeded 70%, and the leaching of heavy metals conformed to drinking water quality standards. The slump of pavement concrete prepared with LSSEM was 130 mm, and its 28-d flexural tensile strength and compressive strength were 6 MPa and 49 MPa, respectively, meeting the requirements for pavement concrete design with light traffic load. A conceptual model of the synergistic stimulatory effect of calcium and magnesium sources on LSS excitation was developed. This study promotes solid-waste recycling and provides complementary cementitious materials with lower energy consumption and CO2 emissions for the construction industry.