Recycled Construction Materials Research Articles

Environmental Conservation by Using Recycled Aggregates: Enhancing Sustainability in Road Construction

Every day, construction and demolition waste is generated worldwide. As the road business and traffic grow, construction materials have evolved to include more unorthodox features. Road construction and maintenance rely significantly on quarried aggregates, resulting in high resource extraction demands. There is a trend toward employing secondary (recycled) materials rather than primary (virgin) ones to address this. This transformation requires the use of a variety of secondary and tertiary components, including waste byproducts. Numerous studies have been conducted to study and analyze the suitability and practical application of recycled materials in the field. Some recycled materials have better qualities than others, proving satisfactory performance in real-world circumstances. However, concerns about their incorporation persist, based on laboratory research and field observations. These concerns emphasize the necessity for more in-depth research to address potential difficulties. It is claimed that using recycled and tertiary materials in road construction can greatly help to save natural resources. This study predicts the attributes of selected materials, such as gradation, water absorption, maximum dry density, impact value, flakiness, and elongation, to establish their appropriateness for the production of Granular Sub-base (GSB) and Wet Mix Macadam (WMM).

Performance Study of Stabilized Recycled Aggregate Base Material with Two-Gray Components.

This article studies the practical road performance of recycled materials from construction waste, relying on the paving test section of the supporting project for the Qingdao Cross-Sea Bridge. The research focuses on the construction technology and road performance of using recycled construction waste materials in urban road sub-base construction. Through indoor tests such as sieving and unconfined compressive strength tests, relevant technical indicators were obtained and analyzed. Additionally, periodic core sampling, compaction tests, and rebound deflection tests were conducted on-site according to relevant standards to thoroughly investigate the specific effects of using construction waste in practice and to analyze and evaluate the actual feasibility of the materials for road use. The results indicate that the particle gradation of the construction mix in the test section aligns well with the target gradation, and the dosage of the mixing agent meets the design requirements. The 7-day unconfined compressive strength already satisfied the technical requirements for heavy and extremely heavy traffic on highways as specified in the "Technical Specifications for Construction of Highway Pavement Subbase" (JTG/T F20-2015), with the 14-day strength generally reaching 7 MPa. Core sampling revealed good aggregate gradation, smooth and straight profiles, and the thickness and strength of all parts meet the specifications. The compaction levels met the testing requirements, the surface deflection values showed a decreasing trend, and the deformation resistance was good, consistent with the general development patterns of semi-rigid sub-bases.

Predictive modeling of sustainable recycled materials for stone column construction

Climate change due to carbon dioxide emissions is one of the most significant global challenges. Sustainable recycled materials are recognized as a critical factor in mitigating climate change, representing a fundamental strategy for reducing gas emissions and preserving the environment. Promising sustainable recycled materials in construction, such as crushed asphalt, crushed concrete, crushed ceramic, and treated concrete offer numerous advantages, including reduced carbon dioxide (CO2)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{(CO}}_{2} )$$\\end{document} emissions, cost-effectiveness, increased strength, and enhanced mechanical properties. In this study, various machine learning techniques, including the support vector machine (SVM), multiple linear regression (MLR), gaussian process regression (GPR), and artificial neural network (ANN), are used to assess the effectiveness of sustainable recycled materials within stone columns. The MLR model was specifically utilized to predict the ultimate stress equation for these materials within stone columns. Forty-five constructed samples were used in developing the models. The effectiveness of each model was evaluated using various statistical assessment measures, including mean absolute error (MAE), absolute fraction of variation (R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{R}}^{2}$$\\end{document}), and root mean square error (RMSE). The predictive model’s performance was validated using the k-fold cross-validation method. The ANN model with an R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{R}}^{2}$$\\end{document} value of 0.962 and an RMSE value of 7.268 kPa, performed better compared to GPR, SVM and MLR models. In summary, the results of the study indicate that the MLR model, utilizing the identified input parameters, can accurately predict the ultimate stress for different sustainable recycled materials. Implementing such technologies within the construction sector can expedite and reduce the cost of assessing material characteristics and the influence of input parameters.

Innovations in recycled construction materials: paving the way towards sustainable road infrastructure

The expansive development of infrastructure has led to increased consumption of virgin aggregates in road construction, resulting in significant environmental impacts. To address this issue, there is a pressing need for sustainable alternatives that utilize recycled materials in pavement applications. This paper presents a comprehensive review of a decade-long research program focused on the development and evaluation of sustainable pavement materials, such as recycled and waste aggregates, industrial by-products, and natural fibers. The research encompassed a wide range of innovative materials and technologies, such as geopolymer-stabilized recycled aggregates, cement-stabilized waste materials, natural additive-modified cement stabilization, and recycled aggregate-geogrid reinforcement systems. The experimental framework employed a combination of mechanical testing, durability assessment, microstructural analysis, and environmental safety evaluation to assess the performance and sustainability of these materials. The key findings demonstrated the superior mechanical properties, improved durability, and environmental suitability of the recycled materials compared to conventional virgin aggregates. The successful implementation of these sustainable solutions in real-world projects highlights their potential to reduce the environmental footprint of road infrastructure development. Furthermore, the paper discussed the practical implications of the research outcomes for pavement design and construction, as well as future research directions to further advance the field of sustainable pavement engineering. The findings of this research report can be used as guidance for researchers, practitioners, and policymakers seeking to upcycle the widespread adoption of recycled materials in road application and contribute to the development of a more sustainable and resilient transportation infrastructure.

A Research on Fresh and Hardened Concrete Residences with Partial Replacement of Recycled Coarse Aggregates Obtained from Demolition and Construction Waste

The modern world is witnessing the development of extremely demanding structures right now. Concrete is an extremely important and widely used material. However, the reuse of construction waste is crucial when considering life cycle assessment (LCA) and the efficient recycling of construction materials. Given its potential to address sustainability and environmental challenges, using recycled materials in construction has attracted much attention. This study aims to examine what happens to concrete's compressive strength when recycled coarse aggregates (RCA) replace some of the conventional coarse aggregates. The aim is to study the impact of RCA content on the mechanical characteristics of concrete and determine its appropriateness for use in structural applications. The main objectives of this work is to determine and compare the Density, Workability, Compressive strength, split tensile strength, and Flexural strength of Recycled aggregate in relation to conventional aggregate also to ascertain the ideal percentage of aggregate replacement with recycled aggregate and to calculate the percentage change in strength for recycled aggregate at different levels of replacement. The research methodology involves carrying out laboratory experiments to examine the compressive strength, split tensile strength, and flexural strength of concrete specimens with different proportions of recycled concrete aggregate (RCA) substitutions. The typical coarse aggregates are substituted by recycled aggregates in various proportions (5%, 10%, 15%, 20%, 25%, and 30%) by weight in M25 grade concrete. The formulation of the concrete mix design is meticulously done to provide a consistent water-cement ratio and other crucial criteria. The study involves the process of casting and curing concrete specimens that contain varying amounts of recycled concrete aggregate (RCA). At certain curing ages (e.g., 7 days and 28 days), the specimens are tested for compressive strength, split tensile strength, and flexural strength in order to assess their mechanical capabilities. After that, the outcomes are contrasted with control samples made entirely of conventional coarse aggregates. Primary finding shows workability declines as the proportion of recycled trash rises, but it is kept stable with mixing.

Study on the mesoscopic mechanical behavior and damage constitutive model of micro-steel fiber reinforced recycled aggregate concrete

This study employs in-situ 4D CT experimental techniques to investigate the mesostructured changes and mechanical behavior of micro steel fiber-reinforced recycled aggregate concrete (MSF-RAC) under uniaxial compression and cyclic loading conditions. The research aims to address the scientific problem of limited understanding of how micro steel fibers affect the mesoscopic mechanical behavior and structural damage characteristics of recycled aggregate concrete. High-resolution CT scanning technology was utilized for real-time observation of crack initiation and propagation, revealing the micro-mechanisms by which micro steel fibers enhance RAC. The study found that incorporating micro-steel fibers significantly improves the density of the interfacial transition zone (ITZ), inhibits crack development, and enhances the mechanical properties of the concrete. Based on these observations, an improved stiffness degradation damage constitutive model was proposed, which comprehensively considers the distribution orientation of micro steel fibers and ITZ characteristics. The model effectively predicts the stress-strain relationship of MSF-RAC under various conditions, demonstrating high accuracy and practicality. These findings provide important theoretical support and experimental evidence for the optimal design of RAC, showcasing significant engineering application value by promoting the sustainable use of recycled materials in construction.

Automatic Detection and Isolation of Filament Width Deviation During 3-D Printing of Recycled Construction Material

Automatic Detection and Isolation of Filament Width Deviation During 3-D Printing of Recycled Construction Material

Assessing the Impact of Recycled Building Materials on Environmental Sustainability and Energy Efficiency: A Comprehensive Framework for Reducing Greenhouse Gas Emissions

In this study, we critically examine the potential of recycled construction materials, focusing on how these materials can significantly reduce greenhouse gas (GHG) emissions and energy usage in the construction sector. By adopting an integrated approach that combines Life Cycle Assessment (LCA) and Material Flow Analysis (MFA) within the circular economy framework, we thoroughly examine the lifecycle environmental performance of these materials. Our findings reveal a promising future where incorporating recycled materials in construction can significantly lower GHG emissions and conserve energy. This underscores their crucial role in advancing sustainable construction practices. Moreover, our study emphasizes the need for robust regulatory frameworks and technological innovations to enhance the adoption of environmentally responsible practices. We encourage policymakers, industry stakeholders, and the academic community to collaborate and promote the adoption of a circular economy strategy in the building sector. Our research contributes to the ongoing discussion on sustainable construction, offering evidence-based insights that can inform future policies and initiatives to improve environmental stewardship in the construction industry. This study aligns with the European Union’s objectives of achieving climate-neutral cities by 2030 and the United Nations’ Sustainable Development Goals outlined for completion by 2030. Overall, this paper contributes to the ongoing dialogue on sustainable construction, providing a fact-driven basis for future policy and initiatives to enhance environmental stewardship in the industry.

Preliminary study on the application of waste bivalve shells as biofiller for the production of asphalt concrete

The shells of molluscs are a common by-product of the aquaculture industry, and their management represents a significant environmental challenge. Although mollusc farming is considered a low-impact food production, improper shell management could make bivalve farming less environmentally efficient. To address this issue, research is exploring new approaches to reduce waste accumulation and convert shell waste into a valuable resource. The shells of bivalves are functional materials from biological waste, composed mainly of CaCO3, and can be used as secondary raw materials in various applications. In order to meet the demanding environmental target, the road sector is increasing the use of recycled materials in new construction or maintenance of old ones. The present work illustrates the results of several laboratory tests carried out to determine the physical and chemical properties of three different crushed bivalve shells waste for the application as filler in asphalt concretes. The present study highlighted the similarity of these materials with the limestone filler since no significant discrepancy between the mechanical (or technical) performance of the biofiller and the traditional limestone filler are detected through the test carried out, promoting their use in new asphalt concrete mixtures.

Study on the mechanical properties and deterioration mechanism of recycled aggregate concrete for low-grade highway pavements

This study is motivated by the imperative for sustainable construction practices, specifically focusing on recycling construction waste into low-grade highway pavements to enhance environmental sustainability and resource efficiency. The investigation explores the workability, mechanical properties, and interfacial transition zones (ITZs) of recycled aggregate concrete (RAC), emphasizing the incorporation of recycled coarse aggregate (RCA) from construction waste. The primary objective is to delineate the optimal mixture proportions of RAC that effectively balance resource utilization with the technical requisites for low-grade highway pavements. Through rigorous orthogonal testing and analysis, a mixture was identified that achieves a high RCA replacement rate while preserving workability and mechanical properties. Additionally, nanoindentation tests were employed to probe the nanomechanical properties of the ITZs in RAC, aiming to elucidate the underlying degradation mechanisms. Results reveal that the porous and rough surface of RCA significantly impacts the properties of RAC, with a marked decrease in elastic modulus and an increase in ITZ width identified as primary contributors to mechanical deterioration. Consequently, this study not only provides crucial insights for the application of RAC in low-grade highway pavements but also sets the stage for future research aimed at enhancing the sustainability and performance of recycled construction materials.

Editorial: Special Issue on Recycled Materials for Sustainable Geotechnical Construction

Infrastructure serves a vital role in resolving some of the major challenges faced by societies: supporting economic growth, meeting basic needs of citizens, and facilitating mobility and social interaction. Establishing a long-term development and maintenance plan is a critical priority for many nations. This motivates the design and construction of more resilient and sustainable infrastructure systems that are also able to overcome emerging challenges, particularly given the extreme weather conditions that have recently led to several large-scale failures on these systems. Collectively, these investments require the use of large volumes of earthen materials in construction. This has led to the rapid depletion of natural aggregate materials. Recycled materials have been used in a variety of construction applications, for example, roadways (e.g., embankment, base, subbase, asphalt, and concrete), airfields, and railways, among others. Such materials are attractive to construction and transportation industry stakeholders and taxpayers because they generate millions of dollars in savings while producing environmental benefits. Legislations are being developed/promulgated that remove barriers to large-scale beneficial use of these materials to reduce construction costs and increase sustainability. In addition, the construction industry, including the transportation systems sector, is facing ever-increasing demands to control the cost and environmental impact of waste removal and disposal. The use of recycled materials in construction would reduce energy consumption and emission of greenhouse gases, and recycling provides a means to address these demands. Recycled materials avoid energy and emissions associated with mining and processing construction materials. Energy has already been expended in the first life of recycled material. The use of recycled materials allows for the avoidance of natural materials such as sand and gravel, limestone, and oil. Often, service life can be increased by stabilization using industrial by-products as binders such as self-cementing fly ash, waste gypsum, and other ashes. Waste reuse/recycling practices can be incorporated in new construction projects, renovation/rehabilitation projects, and ongoing operations, and they can be applied to both agency and contractor activities. The evaluation of recycled materials used in construction applications has been the main focus of scientific studies over the last few decades. However, the effectiveness of waste reuse/recycling efforts in such applications still could not be implemented fully because of the lack of comprehensive reviews and evaluations of the limitations and advantages of recycled materials used in construction applications. Therefore, the collection and critical review of such information is necessary. This special issue of ASTM International’s Geotechnical Testing Journal brings together 23 papers that cover the use of a broad range of recycled materials in construction applications including steel slag, rice husk ash, ferrochrome slag, recycled concrete aggregate, recycled asphalt pavement, lignin, recycled binders, recycled plastics, and quarry fines. Moreover, the papers in this issue provide state-of-the-art information on geotechnics of recycled materials, including their material characterization, performance evaluations, and environmental suitability assessment. The field has evolved in terms of new material types and applications that must be evaluated. A variety of laboratory tests are adapted from the standards for natural earthen materials, sometimes with modifications, and there is material for the development of new testing protocols and standards. ASTM standards are particularly needed for sample preparation of recycled materials. There were not many papers on in situ testing, but an increase is expected to be seen in this area in future studies. Thus, the need continues for future investigations to increase our understanding of recycled materials that are a crucial element of sustainable construction. The editors wish to express their appreciation to all those authors who submitted their papers. Particular thanks are extended to those who contributed papers and to the reviewers of the papers and also to the publication staff in producing this special issue.

Analysis of Green Technologies in Urban Rail Transit

Transportation is an important field of carbon emissions, and promoting the green and low-carbon transformation of the transportation industry is of great significance for achieving the national carbon peaking and carbon neutrality goals. Therefore, the application of green technology in urban rail transit is receiving increasing attention. This article takes Chengdu Road Station on Tianjin Metro Line 8 as an example to analyze the technical measures to promote green and low-carbon development of urban rail transit systems from the aspects of environmental health, resource conservation, and operational services. The green and lowcarbon concept is integrated into the entire life process of the urban rail transit system, achieving green and sustainable development of rail transit from the aspects of station environment, vehicles, air conditioning, selection and recycling of construction materials, green construction, etc. And provide suggestions for the development of rail transit from four aspects: planning and design, construction and construction, equipment manufacturing, and operation and maintenance, providing reference significance for the research of green rail transit.

Tools for the Involvement of Construction and Demolition Waste in the Repeated Production Cycle

Purpose. This paper aims to analyze and classify construction and demolition waste. It is necessary that this classification not only reflects statistical data on waste generation, but also serves as an information basis for the integrated waste management system (IWMS). The main task of this system is to maximize the involvement of waste in economic recycling and to objectively reflect the technological capabilities of its processing. This is extremely important in the context of the implementation of European waste management principles and the implementation of the National Waste Management Strategy in Ukraine until 2030. Methodology. The article considers the problems of construction waste management within the framework of the National Waste Management Strategy in Ukraine until 2030, which provides for the implementation of measures and principles of waste management, including construction waste. The author analyzes the management problems in the field of construction and demolition waste, which substantiates the need to classify construction waste with the simultaneous harmonization of processing methods and technologies. Construction activities are inextricably linked to the management of various types of resources, among which secondary materials play a key role in the implementation of construction processes. The ability to effectively manage the flows of these secondary resources is critical to ensuring the sustainability and efficiency of construction production. In this context, the study of the importance of managing the flows of secondary resources becomes an integral part of strategies for optimizing construction processes. Findings. Construction waste from the demolition of buildings and structures is unique due to its size and the need to prepare it for primary crushing. This is especially true in the context of implementing the concept of renovation of the outdated housing stock. Various static and dynamic methods of destruction of building materials, in particular, impact and vibration, have been investigated, with dynamic methods being characterized by lower energy consumption. Originality. The work reflects the formation of theoretical and methodological directions based on the use of recycled materials in construction, as well as a comparative characterization of various methods of destruction of building materials. Practical value. The possibilities of recycling construction waste, in particular, their maximum involvement in recycling, which meets the goals of the Strategy of Ukraine, provides 50% of waste recycling.

Response of treated recycled aggregate concrete against low-velocity impact loading: Experimental and Weibull statistical analysis

Sustainable and ecologically friendly building practices require increased conservation and recycling of renewable resources. Because of the rise in development and demolition worldwide, using recycled construction materials as aggregate in new concrete can be an essential step towards making the material more environmentally friendly. Removing or fortifying the adherent mortar is the main technique to advance the poor standard of recycled concrete aggregate, which the adherent mortar causes. The study examines the impact performance of recycled aggregate concrete (RAC) comprising different replacement levels (10, 20, 30 and 40 %) of recycled aggregate (RA). Three concentrations (10, 15, and 20 %) of MgSO4 solution were used to pre-treat the RA and subjected to three different immersion times of 5, 10, and 15 days. For this, thirty-seven mixtures were prepared with the combination of RA contents, MgSO4 concentrations and immersion periods. The study was divided into three phases. The physical properties of RA, slump, and compressive strength tests were studied in the first phase. The best thirteen mixtures that exhibited expectational results in the first phase are put forward to the second phase. The effect of RA content, MgSO4 concentration and immersion periods on the impact strength was studied in the second phase. Besides, the differences in the impact test results were studied by Weibull distribution and results were displayed with regard to the probability of survival. The final phase studied the impact response of reinforced concrete slabs under a large mass impact. The findings reveal that the five days of immersion in a 10 % MgSO4 solution has been shown to enhance the impact strength of RAC, whereas a replacement ratio of 20 % is recommended.

Overcoming Barriers to the Adoption of Recycled Construction Materials: A Comprehensive PEST Analysis and Tailored Strategies

In the face of rampant urbanization, industrialization, and continuous advancements in construction technology, sustainable development in the construction industry becomes increasingly imperative. A promising avenue toward this sustainability is through the adoption of Recycled Construction Materials (RCMs), yet their widespread use remains complex and filled with numerous barriers, signifying an urgent need for the systematic investigation of these obstacles. This study uniquely employs a qualitative PEST (Political, Economic, Social, and Technological) analysis to illuminate the intricate impediments to the adoption and promotion of RCMs. Data for this study were collected through in-depth, semi-structured interviews with a variety of experts in the field. The research identifies substantial barriers within each PEST category. Political factors include regulatory biases and limited funding for RCM research, while economic factors involve the higher costs and limited availability of RCMs. Social aspects revolve around public awareness, safety concerns, and resistance to change within the industry. Technological issues focus on the development, performance, and compatibility of RCMs, the slow innovation pace, and the absence of standardized guidelines. Additionally, this study stands out by suggesting strategic, context-specific recommendations aimed at surmounting these obstacles and further fostering the adoption of RCMs. The solutions proposed are intimately linked to the challenges identified, highlighting the practical value and relevance of this study for guiding future research and policy development in the face of ongoing advancements in construction technology.

Stabilization of dredged clays with ternary alkali-activated materials: Towards sustainable solid wastes recycling

The primary focus of this study is to reuse dredged clay (DC) with high water content as recycled construction material by stabilizing it with a ternary alkali-activated material (AAM) based on ground granulated blast-furnace slag, fly ash, desulfurization gypsum (GGBS-FA-DG). The mechanical properties of the stabilized DC using the ternary AAM were investigated through laboratory tests, and microstructure tests were performed to reveal the stabilization mechanism of the treated DC. The results revealed that the unconfined compressive strength (UCS) of the stabilized specimens was significantly affected by the initial water content of DC and decreased with the increasing initial water content. The UCS of the stabilized DC using the ternary AAM can be increased by 1.24–4.33 times compared to using the GGBS-FA binary AAM alone. The UCS of the stabilized DC first increased and then decreased as the DG content increased. The optimal DG content was 8% for the DC with an initial water content of 1.4–2.0 times the liquid limit (1.4–2.0wL). Scanning electron microscope (SEM) and X-ray diffraction (XRD) tests reveal that geopolymer gel produced by polymerization and C-(A)-S-H gel produced by hydration can contribute to cementation strength. Needle-like ettringite (AFt) generated by the activation FA by DG can promote a denser microstructure of the stabilized DC and thus further improve the strength.

A Review on Life Cycle Assessment of Pavements in Brazil: Evaluating Environmental Impacts and Pavement Performance Integrating the International Roughness Index

This article addresses the limited understanding of the landscape regarding Life Cycle Assessment (LCA) in Brazilian pavement infrastructure. It provides an overview of LCA’s application in assessing the environmental effects of pavements while exploring the use of the International Roughness Index (IRI) as a performance criterion to assess environmental consequences and pavement performance. A comprehensive search for relevant quantitative LCA studies, published from 2013 to 2023, was conducted across several bibliographic databases, following ISO 14040 standards. A total of fourteen case studies were analyzed, providing insight into frequently used software, databases, Life Cycle Impact Assessment (LCIA) methods, and functional units. Furthermore, global warming or greenhouse gases (GHG) were the most frequently used environmental indicators, while materials, transportation, and construction were the most inventoried life cycle phases. However, the search also highlighted limitations, including the availability of Brazilian data and scope definition. Nevertheless, a quantitative comparison between conventional pavements showed a low standard deviation. The scenarios studied demonstrated that using recycled materials in pavement construction and employing high-strength materials in layers and subgrade can reduce environmental impacts. In conclusion, these findings contribute to the development of sustainable pavement practices in Brazil and highlight the need for further research to validate current findings and address existing gaps.

Life cycle analysis of the GRAND experiment

The goal of our study is to assess the environmental impact of the installation and use of the Giant Radio Array for Neutrino Detection (GRAND) prototype detection units, based on the life cycle assessment (LCA) methodology, and to propose recommendations that contribute to reduce the environmental impacts of the project at later stages. The functional unit, namely the quantified description of the studied system and of the performance requirements it fulfils, is to detect radio signals autonomously during 20 years, with 300 detection units deployed over 200km2 in the Gansu province in China (corresponding to the prototype GRANDProto300). We consider four main phases: the extraction of the materials and the production of the detection units (upstream phases), the use and the end-of-life phases (downstream phases), with transportation between each step. An inventory analysis is performed for the seven components of each detection unit, based on transparent assumptions. Most of the inventory data are taken from the Idemat2021 database (Industrial Design & Engineering Materials). Our results show that the components with the highest environmental impact are the antenna structure and the battery. The most pregnant indicators are ‘resource use’, mineral and metals’; ‘resource use, fossils’; ‘ionizing radiation, human health’; ‘climate change’; and ‘acidification’. Therefore, the actions that we recommend in the first place aim at reducing the impact of these components. They include limiting the mass of the raw material used in the antenna, changing the alloy of the antenna, considering another type of battery with an extended useful life, and the use of recycled materials for construction. As a pioneering study applying the LCA methodology to a large-scale physics experiment, this work can serve as a basis for future assessments by other collaborations.

Constructed wetlands with recycled concrete for wastewater treatment in cold climate: Performance and life cycle assessment

This study investigated the technical, environmental, and economic feasibility of using recycled construction material (concrete) as substrate in constructed wetlands for cold climate decentralized domestic wastewater treatment. The wastewater treatment efficiency was examined, and life cycle assessment (LCA) and cost benefit analysis were performed. The technical feasibility was assessed in lab-scale two-stage wetland systems with recycled concrete or lava stone as substrates, which were operated at 22 °C and 5 °C with local wild plants and vegetables. The wetlands removed ∼85 % and ∼51 % of organics and ∼67 % and ∼34 % TN at 22 °C and 5 °C, respectively; no significant difference was found between concrete and lava stone. The heavy metal contents in the cultivated vegetables met WHO standards for human consumption, showing the feasibility of nutrient recovery from the treated wastewater. A comparative LCA of septic tank standalone, septic tank + constructed wetland (with recycled concrete), and gravity-driven ceramic membrane (GDCM) system was performed. This aims to illustrate the benefits of intensifying the existing treatment process (i.e., septic tank) with the constructed wetland, with an alternative membrane-based treatment technique as benchmark. The LCA results revealed that using waste materials as the substrate in constructed wetlands could reduce the environmental impact of wetlands. Installation of the wetland as posttreatment of the septic tank (1) could reduce ∼50 % of eutrophication potential without increasing global warming impact compared to the septic tank alone; (2) had ∼90 % higher global warming impact and ∼40 % lower eutrophication impact compared to GDCM. Economic analysis revealed that the total cost of septic tank + constructed wetland (0.143 €/m3) was comparable to the septic tank alone (merely 3.5 % difference), and 49 % lower than that of GDCM (with recycled membranes). Therefore, the septic tank + constructed wetland scenario could be favorable for sensitive areas with eutrophication potential regarding its technical, economical, and environmental feasibility.

Use of Time–Temperature Superposition and Stepped Isothermal Method for Estimating Long-Term Properties of Recycled Aggregate Roller-Compacted Concrete

Abstract Although the use of recycled materials in civil engineering construction is a desirable option from a sustainability standpoint, the questionable long-term performance of these materials often hinders their widespread use in practice. The primary focus of this study was to perform accelerated aging and testing for estimating long-term properties of a roller-compacted concrete composed of crushed recycled aggregate, Type-I portland cement, and ASTM Class-F fly ash replacing up to 50 % of cement by weight. Accelerated aging was accomplished by curing cylindrical specimens at three different elevated temperature regimes for specific time durations. At the end of each time–temperature regime, the residual stiffness of the specimen was measured in a nondestructive fashion. Series of stiffness–time master curves were then constructed for each mix using the time–temperature superposition (TTS) technique and the stepped isothermal method (SIM). While the TTS method uses different sets of specimens for each elevated time–temperature regime, SIM uses a single set of specimens that are stepped up in temperature and held at each regime for a specified duration. Results indicated that for all mixes, the material stiffness degraded with time. Based on the Arrhenius equation, stiffness–equivalent age master curves were developed. Stiffness prediction was accomplished up to an equivalent age of almost 600 days, although the actual short-term test lasted only up to 6 days. It was also found that SIM and TTS provided comparable results, thus implying that the testing time and the number of specimens can be significantly reduced by using the SIM.