Bird’s-eye view of recycled solid wastes in road engineering

Recent trends in road engineering have explored the potential of incorporating recycled solid wastes into infrastructures that including pavements,bridges,tunnels,and accessory structures.The utilization of solid wastes is expected to offer sustainable solutions to waste recycling while enhancing the performance of roads.This review provides an extensive analysis of the recycling of three main types of solid wastes for road engineering purposes:industrial solid waste,infrastructure solid waste,and municipal life solid waste.Industrial solid wastes suitable for road engineering generally include coal gangue,fly ash,blast furnace slag,silica fume,and steel slag,etc.Infrastructure solid wastes recycled in road engineering primarily consist of construction&demolition waste,reclaimed asphalt pavements,and recycled cement concrete.Furthermore,recent exploration has extended to the utilization of municipal life solid wastes,such as incinerated bottom ash,glass waste,electronics waste,plastic waste,and rubber waste in road engineering applications.These recycled solid wastes are categorized into solid waste aggregates,solid waste cements,and solid waste fillers,each playing distinct roles in road infrastructure.Roles of solid waste acting aggregates,cements,and fillers in road infrastructures were fully investigated,including their pozzolanic properties,integration effects to virgin materials,modification or enhancement solutions,engineering performances.Utilization of these materials not only addresses the challenge of waste management but also offers environmental benefits aiming carbon neutral and contributes to sustainable infrastructure development.However,challenges such as variability in material properties,environmental impact mitigation,secondary pollution to environment by leaching,and concerns regarding long-term performance need to be further addressed.Despite these challenges,the recycled solid wastes hold immense potential in revolutionizing road construction practices and fostering environmental stewardship.This review delves into a bird’seye view of the utilization of recycled solid wastes in road engineering,highlighting advances,benefits,challenges,and future prospects.

Household Solid Waste Awareness and Practices among Residents of Windhoek, Namibia

This study explores household solid waste management (HSWM) practices and awareness among residents of Windhoek West, a rapidly urbanizing constituency in the Khomas Region of Namibia. Employing a descriptive methodology, the research investigates the interplay between public awareness, regulatory frameworks, and the availability of waste management facilities to assess their impact on waste management behaviors. Our findings indicate significant gaps in both knowledge and infrastructure that hinder effective waste management. The study reveals that while there is a high willingness among residents to engage in recycling and waste reduction, actual practices are limited due to inadequate facilities and lack of stringent enforcement of waste policies. This research identifies key factors that influence waste management practices, including demographic characteristics and access to waste management facilities. It also proposes actionable strategies such as expanding recycling and sorting facilities, enhancing educational campaigns tailored to local needs, and implementing regular enforcement mechanisms. These strategies are aimed at improving compliance with waste management protocols and fostering a culture of environmental responsibility. The results of this investigation show the critical role of ongoing education and infrastructural improvement in bridging existing knowledge gaps and facilitating effective waste management practices. This research lays a foundational step toward enhancing sustainable urban development and effective waste management in Windhoek, providing valuable insights for policymakers, community leaders, and stakeholders engaged in urban environmental management.

Production Practice of Solid Waste Desulfurizer Disposal in European Metallurgical Furnace

In order to realize the OY Smelting Furnace disposal of solid waste,municipal waste,form a model of steel enterprises and urban integration,through the production practice of smelting furnace,analyzes the mechanism of solid waste disposal,and proposed the disposal of solid waste desulfurization agent and disposal method:According to the theory to guide the actual production process,the test ton of iron with 10-15kg of desulfurizer in the production process does not affect the quality of molten iron and slag quality.

Current Situation Analysis and Suggestions for Solid Waste Management Practices among Households in Freetown

Freetown which is the capital city of Sierra Leone is facing challenges with population growth, urbanization, and industrialization, leading to an increase in municipal solid waste (MSW) generation. The study aims to evaluate MSW generation, composition, and disposal methods, as well as the impact of collection fees, policy implementation, and women’s participation in municipal solid waste management (MSWM). The study used both qualitative and quantitative methods for data collection and analysis. The study administered 393 structured questionnaires in three selected sections to collect data on variables such as family size, education, level of knowledge, etc. The study used door-to-door data collection to determine the rate of solid waste generation, composition, and disposal in 66 households from two of the selected sections and 34 households from the other section to evaluate the current situation of MSWM practices among households in Freetown. The study used a descriptive statistic to analyze the data collected using Origin-Pro9 and MS Excel software. The findings showed that with a 4.2% urban growth rate, Freetown had a population of 1,467,543 in 2023, generating 851 tons of MSW per day, with organic waste accounting for 78% of the total MSW generated. Plastic waste generation also increased from 7.6% in 2020 to 13% in 2023. The study emphasizes the need to sustain the MSWM system by prioritizing solid waste collection fees, policy enforcement, and women’s participation in the MSWM sector. It further suggests and provides recommendations for developing an efficient and sustainable MSWM system in Sierra Leone, including knowledge transfer from countries like China and the US.

Assessment of Municipal Solid Waste Management in the Farmgate Area of Dhaka North City Corporation

This investigation is focused on conducting a thorough analysis of Municipal Solid Waste Management (MSWM). MSWM encompasses a range of interdisciplinary measures that govern the various stages involved in managing unwanted or non-utilizable solid materials, commonly known as rubbish, trash, junk, refuse, and garbage. These stages include generation, storage, collection, recycling, transportation, handling, disposal, and monitoring. The waste materials mentioned in this context exhibit a wide range of items, such as organic waste from food and vegetables, paper, plastic, polyethylene, iron, tin cans, deceased animals, byproducts from demolition activities, manure, and various other discarded materials. This study aims to provide insights into the possibilities of enhancing solid waste management in the Farmgate area of Dhaka North City Corporation (DNCC). To accomplish this objective, the research examines the conventional waste management methods employed in this area. It conducts extensive field surveys, collecting valuable data through interviews with local residents and key individuals involved in waste management, such as waste collectors, dealers, intermediate dealers, recyclers, and shopkeepers. The results indicate that significant amounts of distinct waste categories are produced daily. These include food and vegetable waste, which amount to 52.1 tons/day;polythene and plastic, which total 4.5 tons/day;metal and tin-can waste, which amounts to 1.4 tons/day;and paper waste, which totals 5.9 tons/day. This study highlights the significance of promoting environmental consciousness to effectively shape the attitudes of urban residents toward waste disposal and management. It emphasizes the need for collaboration between authorities and researchers to improve the current waste management system.

Development of Wet Shotcrete with Solid Waste as Aggregate:Strength Optimization and Mix Proportion Design

The super-fine particle size of tailings is its drawback as a recycled resource,which is reflected in the low strength of the new construction and industrial materials formed when it is mixed with cement and other cementitious materials.Therefore,it is crucial to study the effect of tailings particle size and cementitious material on the strength of tailings wet shotcrete(TWSC)and to investigate the optimal mix proportion.In this paper,a multivariate nonlinear response model was constructed by conducting central composite experiments to investigate the effect of different factors on the strength of TWSC.The strength prediction and mix proportion optimization of TWSC are carried out by machine learning techniques.The results show that the response model has R^(2)>0.94 and P<0.01,which indicates that the model has high reliability.Moreover,the strength of TWSC increases with the increase of tailings fineness modulus and decrease of water-binder ratio,while it also increases and then decreases with the increase of replacement rate of slag powder to cement(SRC rate).The extreme learning machine(ELM)constructed in this paper predicts the strength of TWSC with an accuracy of more than 98%and achieves rapid prediction under multi-factor conditions.It is worth mentioning that the ELM combined with the genetic algorithm(ELM-GA)collaboratively solved to obtain the mix proportion for C15 and C20 strength grades of TWSC and the maximum error is verified by experiments to be less than 2%.

Preparation and characterization of high-strength calcium silicate boards from coal-fired industrial solid wastes

To realize the comprehensive utilization of coal-fired industrial solid wastes, a novel high-strength board was prepared from calcium silicate slag, fly ash, and flue gas desulfurization(FGD) gypsum. The changes in mineral phases, chemical structure, and morphology during hydration were investigated by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), and scanning electron microscopy(SEM). A traditional board made from quartz and lime was prepared as a reference. The novel board not only consumes a lot of solid wastes, but also meets the strength requirement of the class-five calcium silicate board according to the Chinese Standard JC/T 564.2—2008. Microanalysis showed that hydrated calcium silicate gel(C-S-H(I)), ettringite, tobermorite, and xonotlite were successively generated in the novel board by synergistic hydration of the mixed solid wastes. The board strength was improved by the formation of tobermorite and xonotlite but decreased by unhydrated quartz. It was demonstrated that quartz was not completely hydrated in the traditional board. As a result, the flexural strength of the traditional board was much lower than that of the novel board.

Environmental and Health Impact of Solid Waste Disposal in Developing Cities: A Case Study of Granville Brook Dumpsite, Freetown, Sierra Leone

Indiscriminate disposal of solid waste in dumpsites located within urban areas has proved to be a problem to nearby residents in most developing cities of the world, Freetown is no exception. Open dumps have environmental safeguards;they can pose major public health threats and environmental effects in urban cities. Therefore, this paper presents the findings of a research carried out in Freetown municipal area in Sierra Leone to determine the environmental and health impacts of solid waste disposal at Granville Brook dumpsite on the surrounding human settlements. Data were collected from three hundred and ninety eight nearby dumpsite household residents (less than fifty metres) and two hundred and thirty three far away household residents (more than fifty metres) through the use of structured self-administered questionnaires. Interviews and personal observations were also used to collect some of the data. Descriptive statistics involving tables, graphs and figures were used to present and analyze the data. Results show that both nearby residents and far away residents suffered from related diseases such as malaria, chest pains, diarrhea and cholera, due to the location of the dumpsite closer to their settlements. As a result, this study highlights the need for the Freetown City Council to properly manage and relocate the dumpsite to a safe distance from all human settlements, and provide resettlement and environmental education programmes for all persons living less than fifty metres away from the dumpsite as interim measures.

Exploration on the Recycling of Waste Building Materials in Comprehensive Land Consolidation from the Perspective of Ecological Civilization

The necessity and difficulties of waste building material utilization in comprehensive land consolidation are put forward by analyzing the source,quantity and harm of waste building materials.Combined with the practice of Shanghai,the mechanism and pattern of waste building materials recycling are explored,in order to provide the reference for recycling of waste building materials and efficient promotion of land consolidation.

Study on Strength Reduction Law and Meso-Crack Evolution of Lower Layered Cemented Tailings Backfill

The green disposal of tailings solid waste is a problem to be solved in mine production.Cemented tailings filling stoping method can realize the dual goals of solid waste resource utilization and mined-out area reduction.However,the volume of the mined-out area of the open-pit method is larger than the filling capacity,resulting in the complex stratification of the underground backfill,and the strength of the backfill cannot meet the requirements.In this paper,according to the delamination situation,the specimens of horizontal and inclination angle layered cemented tailings backfill(LCTB)is made for a uniaxial compression test,and the failure process of delamination backfill is reduced by PFC.The results show that the corresponding reduction factorφof horizontal LCTB is 0.560–0.932,and the correspondingφvalue of inclination angle LCTB is 0.338–0.772.The failure mode of backfill in different layers is mainly manifested as a tensile failure.The PFC numerical simulation results are consistent with laboratory test results,which verifies the correctness of backfill failure.The research results provide a reliable theoretical basis for the strength design of backfill in goaf,which is of great significance for solid waste utilization and environmental protection.

Environmental and economic benefit of recycling model of packaging waste:a case study on aluminum

In order to achieve sustainable utilization of natural resources, save energy and protect environment and ecosystem, it is important for a region or a nation to develop and implement a viable waste recycling model from both theoretical and practical point of view. Some packaging recycling models operated in developed countries are introduced in this article. Aluminium can recovery and recycling is emphasized. Cost effective, economic and environmental benefit of different models are compared and analyzed. The result shows that all recycling models have their characteristics due to the initial purpose of recovery and the situation of the implementing country. However, all the models contribute to the reduction of municipal solid waste disposal and resources conservation.

The Legal Framework for Solid Waste Disposal and Management in Kwara State, Nigeria

Solid waste such as “garbage” “trash” “refuse” “slug” and “rubbish” is disposed off or is required to be disposed off in accordance with national law. The study relies on primary and secondary sources of information. The primary sources include the Constitution, statutes and subsidiary legislation. The secondary sources of information include books, journals, conference proceedings, newspapers, magazines and internet materials. The information obtained from these sources is subjected to content and contextual analysis. The study examines the Kwara State Environmental Protection Agency Law, 1992 and other laws on waste disposal and management in Kwara State, Nigeria. The study also examines the regulations and the agency i.e. the Kwara State Environmental Protection Agency created by the law with a view to determine the inadequacies in the law.

An Appraisal of Spatial Distribution of Solid Waste Disposal Sites in Kano Metropolis, Nigeria

This paper describes a research project that has been conducted as part of the Kano Municipal waste management strategy. The aim is to quantify and to identify the existing locations of waste disposal sites by mapping their spatial distribution within the metropolitan Kano. QUICKBIRD satellite imageries;locations of existing waste disposal sites collected using Global Positioning System (GPS);and topographical map (1:5000 scale) of Kano metropolis were used to generate data for the study. The data were prepared and analysed using ArcMap 10.2.1 and Erdas Imagine 11 software to produce the spatial distribution maps for solid waste disposal sites within the metropolis. The result shows that out of the 300 existing waste disposal sites assessed, the city has fairly well-distributed waste disposal sites. Conversely, the disposal sites are more clustered in the centre of the metropolis than the outskirts. However, about 80 percent of the sites are either located very close to roads, settlements or water bodies. Also, while about 92 percent of the existing waste disposal locations are open space, only about 7 percent are containers (closed dumping sites). Correspondingly, about 89 percent are authorised dumping sites and only about 11 percent are unauthorised illegal. The study recommends that policymakers should intervene and relocate the existing unauthorized dump sites to more suitable areas.

Contributions on Selective Waste Collection and Recycling Cooperatives in Municipalities in the State of São Paulo,Brazil

The collection and proper disposal of MSW(Municipal Solid Waste)is one of the biggest challenges faced by Brazilian public managers.Dry recyclable waste represents about 33.6%of the gravimetric composition of MSW,with a tendency to increase in the next few years,due to the increasing consumption of processed products,with short life cycles and excess packaging.The inadequate management of these residues results in a series of social,environmental and economic problems.In recent years,there has been a great advance in Brazilian laws,assigning responsibilities and regulating waste management in the country,optimizing the use of infrastructure and human and financial resources.Scarce resources and insufficient infrastructure demand actions based on a lot of planning.One of the main limiting factors for the planning and development of public policies for the sector is the lack of reliable data and information on the generation and management of waste,that allow the creation of future scenarios and the definition of adequate strategies for minimization,valorization of waste and final disposal of waste that no longer can be processed.Thus,this work sought to analyze the current situation of selective waste collection and recycling cooperatives in 211 municipalities in the State of São Paulo,evaluating the issues and opportunities for the applicability of Law n.12,305/2010,Brazilian PNRS(in Portuguese)(National Policy of Solid Waste)in the management of this waste in small,medium and large cities.A bibliographic research was carried out on the panorama of solid waste management in Brazil and in the State of São Paulo,as well as a contextualization on selective waste collection and recycling cooperatives.Following that,data from 211 municipalities taking part in the survey Solid Waste Management—Municipalities of the State of São Paulo were analyzed,focusing on answers that correlated with the topics covered in this research.For this work,questions were used in order to obtain a basic overview of solid waste management in the municipalities,identifying the characteristics of selective waste collection and recycling cooperatives in the municipalities and to verify the similarity,benefits and difficulties of selective waste collection and waste cooperatives in the municipalities studied.After tabulating and analyzing the data,a matrix was prepared to compare the results obtained in relation to selective waste collection and recycling cooperatives and the guidelines of the PNRS(National Solid Waste Policy)in urban environmental management,which allowed the conclusion that all municipalities participating in the research have a good understanding of solid waste management practices,as well as seek to comply with the guidelines of the PNRS.However,the results of this matrix indicated that there are important points that need to be considered in the planning of actions for a better management of recyclable waste,such as the implementation of inter-municipal consortiums in the management of solid waste,investment in environmental education,stimulation to create recycling cooperatives and adoption of social inclusion regulations for informal waste collectors.

Reduction process and zinc removal from composite briquettes composed of dust and sludge from a steel enterprise

In this study, composite briquettes were prepared using gravity dust and converter sludge as the main materials; these briquettes were subsequently reduced in a tube furnace at 1000-1300℃ for 5-30 min under a nitrogen atmosphere. The effects of reaction temperature, reaction time, and carbon content on the metallization and dezincification ratios of the composite briquettes were studied. The reduced com- posite briquettes were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and energy-dispersive spectroscopy （EDS）. The results show that the gravity dust and converter sludge are combined into the composite briquettes and a reasonable combination not only improves the performance of the composite briquettes, but also leads to the reduction with no or little reductant and flux. As the re- action temperature is increased and the reaction time is extended, the metallization and dezincification ratios of the composite briquettes in- crease gradually. When the composite briquettes are roasted at 1300℃ for 30 rain, the metallization ratio and dezineification ratio reaches 91.35% and 99.25%, respectively, indicating that most of the iron oxide is reduced and the zinc is almost completely removed. The carbon content is observed to exert a lesser effect on the reduction process; as the C/O molar ratio increases, the metallization and dezincification ra- tios first increase and then decrease.

Microstructure and Properties of Silty Siliceous Crushed Stone-lime Aerated Concrete

The clayish crushed stone was used for making aerated concrete. Through studying hydro-thermal synthesis reaction, mix ratio, gas-forming and performance analysis, Grade-B05 and Grade-B06 aerated concrete were prepared successfully. The proper mix ratio and key processing parameters were achieved. The microstructure of aerated concrete with crush stone was analyzed by means of XRD and SEM. The experimental results indicate that the hydration products are poorly crystalline C- S- H （ B ）, tobermorite and hydrogarnet. No componeat of clay was found. Unreacted SiO2 cart be in existence, and the structure system of aerated concrete is homogencous and dense.

Synthesis of steel slag ceramics: chemical composition and crystalline phases of raw materials

Two types of porcelain tiles with steel slag as the main raw material （steel slag ceramics） were synthesized based on the CaO-A1203-SiO2 and CaO--MgO-SiO2 systems, and their bending strengths up to 53.47 MPa and 99.84 MPa, respectively, were obtained. The presence of anorthite, a-quartz, magnetite, and pyroxene crystals （augite and diopside） in the steel slag ceramics were very different from the composition of traditional ceramics. X-ray diffraction （XRD） and electron probe X-ray microanalysis （EPMA） results illustrated that the addition of steel slag reduced the temperature of extensive liquid generation and further decreased the firing temperature. The considerable contents of glass-modifying oxide liquids with rather low viscosities at high temperature in the steel slag ceramic adobes promoted element diffusion and crystallization. The results of this study demonstrated a new approach for extensive and effective recycling of steel slag.

Present Status of Solid Waste Management at Babylon Governorate, Iraq

Babylon Governorate covers an area of 5315 km2 with a population that reaches about 1,974,490 inhabitants in the central part of Iraq. Iraq produced 31,000 tons/day solid waste in 2013. The Governorate of Babylon produces annual 483,221 tons of solid waste. Management of collection and disposal of waste in Babylon Governorate is done through open dumping of waste and poor collection process. These sites do not conform to the scientific and environmental criteria applied in the selection of landfill sites. To find out how much solid waste is expected in the future, two methods were used to calculate the population growth in Babylon Governorate to the year 2030. The results showed that the total waste in 2030 will be 761,104 tons and 943055 tons while the cumulated quantity of solid waste expected till 2030 was 12,494,521 tons and 14,095,437 tons according to the first and second methods respectively.