Use Of Virgin Materials Research Articles

Eco-design of airborne sound insulation in Recycled Lightweight Concrete walls for Brazilian social housing: A reliability-based approach

In Brazil, normal strength concrete (NSC) and steel bars are commonly used to construct residential buildings with concrete walls. However, recent discussions have highlighted the environmental impact of these traditional methods, particularly in terms of carbon footprint and the use of virgin materials. In response, alternative materials such as lightweight recycled coarse aggregates are promising. While Eco-design often focuses on structural and material aspects, acoustic efficiency is often neglected. This paper focuses on the airborne sound insulation of a single-story house in a Brazilian housing program constructed using a concrete wall system made of NSC. An accurate experimental validation was carried out in this house, recording a measured and simulated Weighted Standardized Level Difference (DnT,w) of 50 dB for a partition wall between two living rooms, outperforming the national standard requirement of 40 dB. With the simulation data validated, an innovative assessment using reliability methods was proposed to analyze the sensitivity of the problem in terms of the main variables, using three alternative wall materials: NSC, Lightweight Concrete (LC) and Recycled Lightweight Concrete (RLC). A sensitivity analysis using Sobol's indices identified wall thickness, density, and Young's modulus as the most critical input parameters to the model. Monte Carlo Simulation (MCS) was used to calculate the failure probability of each assumed thickness, and Reliability-Based Design Optimization (RBDO) was used to determine the optimum thickness to meet the standard requirement. Through RBDO, we determined optimal wall thicknesses for the concrete mixes studied, aiming at a sound reduction index (Rw) of 43 dB, following the Brazilian standard ABNT NBR 15575-4 and ISO 12354-1. The optimal thicknesses were 7.3 cm for NSC, 11.15 cm for LC, and 10.27 cm for RLC. Innovative acoustic-carbon efficiency indices are proposed to evaluate the studied materials: the Carbon-Acoustic Efficiency Index (CAEi) and the Recyclability-Acoustic-Carbon Efficiency Index (RACEi), which are used for a comprehensive assessment of both sustainability and acoustic performance between materials. Using these indices, the study shows that RLC can definitively replace NSC for airborne sound insulation, offering additional environmental benefits such as recyclability.

Industrial Symbiosis Practices: A Case Study of Türkiye and Denmark

The term "industrial symbiosis (IS)" refers to a cooperative strategy where industrial actors share services and exchange physical resources. This method improves resource efficiency and lessens the environmental effects of industrial operations within the network. It is a cooperative method in which businesses trade and reuse physical resources such as by-products, water, and energy, as well as share services such as waste management and infrastructure. It has several advantages, such as (i) lowering greenhouse gas emissions through energy, process, input, disposal, and transportation savings, as well as fuel substitution; (ii) cutting energy expenses; (iii) diverting waste from landfills; (iv) avoiding the use of virgin materials; (v) lowering transportation and logistics costs; (vi) lowering pollution to land, water, and air; (vii) lowering industrial water use; (viii) lowering hazardous waste; (ix) creating economic value from waste material; and (x) simplifying environmental legislation and regulation compliance. In Türkiye and Denmark, the number of industrial companies is rapidly increasing. These industries consume many resources (such as raw materials, water, electricity, natural gas, coal, etc.) and generate a large amount of solid, liquid, and gaseous waste. IS is gaining popularity as an approach for improving the sustainability of industrial systems. The efforts to develop IS have emerged as a critical issue over the last decade in these two European countries. The paper presents the current implementation of IS in Türkiye and Denmark’s process sectors, focusing on well-known IS practices.

Application of solid waste materials in cold bitumen emulsion mixtures for cleaner pavement industry: a comprehensive review.

There is a global concern with continuous waste production, and efforts are underway to use these wastes in the construction sector. The negative effects of excessive waste production and the use of virgin materials and energy in Hot Mix Asphalt (HMA) construction are challenging and require attention. The right step towards developing resilient road infrastructure is using cold bitumen emulsion mixtures (CBEMs), a cold mix asphalt (CMA). A long-term fix to issues with waste generation and the creation of flexible pavements with HMA can be found by incorporating wastes into CMA. This work reviews the utilization of numerous wastes from different sectors (agricultural, industrial, construction and demolition, and municipal) that are well-known but underutilized and could be used as potential fillers in cold asphalt mixtures. Focus is given to the critical analysis of wastes' physiochemical characteristics and how these affected the effectiveness of mixtures against primary distresses like stability, stiffness, rutting, cracking, fatigue, and moisture susceptibility. Almost all waste materials incorporation reported enhancement in the mechanical performance of CBEM mixes concerning conventional CBEM mixes. The paper sums up the impact on various mechanical properties of CBEM mixes utilizing waste material filler, presents research gaps and a way forward to inspire researchers, and serves as a guideline for using waste materials as fillers in CBEM mixes. This will improve environmental quality and promote sustainability in the paving industry.

Biochar as Alternative Material for Heavy Metal Adsorption from Groundwaters: Lab-Scale (Column) Experiment Review.

The purpose of this manuscript is to present a review of laboratory experiments (including methodology and results) that use biochar, a specific carbon obtained by a pyrolysis process from different feedstocks, as an alternative material for heavy metal adsorption from groundwater. In recent years, many studies have been conducted regarding the application of innovative materials to water decontamination to develop a more sustainable approach to remediation processes. The use of biochar for groundwater remediation has particularly attracted the interest of researchers because it permits the reuse of materials that would be otherwise disposed of, in accordance with circular economy, and reduces the generation of greenhouse gases if compared to the use of virgin materials. A review of the different approaches and results reported in the current literature could be useful because when applying remediation technologies at the field scale, a preliminary phase in which the suitability of the adsorbent is evaluated at the lab scale is often necessary. This paper is therefore organised with a short description of the involved metals and of the biochar production and composition. A comprehensive analysis of the current knowledge related to the use of biochar in groundwater remediation at the laboratory scale to obtain the characteristic parameters of the process that are necessary for the upscaling of the technology at the field scale is also presented. An overview of the results achieved using different experimental conditions, such as the chemical properties and dosage of biochar as well as heavy metal concentrations with their different values of pH, is reported. At the end, numerical studies useful for the interpretation of the experiment results are introduced.

Comparative Environmental Analysis for Using Waste Polyethylene and Steel Slag in Semi-dense Asphalt Pavements

Abstract This study presents a life cycle assessment (LCA) evaluating the use of virgin materials, waste polyethylene (PE), and electric arc furnace steel slag (EAFSS) in semi-dense asphalt (SDA) surface courses, which is primarily used for low-noise pavements. Three types of SDA mixtures with virgin materials, waste PE, and EAFSS were prepared and water sensitivity tests were conducted to determine the mechanical performance. The LCA defined three scenarios using system expansion, namely (1) the reference scenario using virgin materials in SDA and disposal of waste PE and EAFSS by municipal solid waste incineration (MSWI) and landfill, respectively; (2) the test scenario using waste PE and straight run binder in SDA, with landfilling of EAFSS; (3) the test scenario using EAFSS in SDA, with the disposal of waste PE by MSWI. The data from the experiments, Swiss industries, official reports, and standard databases were used for the inventory analysis. The results show that compared to the reference, the scenarios using waste PE and EAFSS in SDA would reduce 15 % and 36 % of greenhouse gases emissions, respectively. The reason for the improved environmental performance when waste PE is used in asphalt can be attributed to the use of straight run binder to replace polymer-modified binder and the avoided MSWI. For the EAFSS scenario, the improved environmental performance is attributable to the avoided landfilling. The results also indicate that the recycling of waste PE and EAFSS in SDA would not have benefits in nonrenewable cumulative energy demand.

In-Service Performance Evaluation of Flexible Pavement with Lightweight Cellular Concrete Subbase

The objective of engineers to improve the long-term performance of road infrastructure in changing global climate has led to the development of alternate materials for pavement construction. Lightweight cellular concrete (LCC) is a viable option for colder climates where pavements undergo several freeze-thaw cycles each year, resulting in faster deterioration of pavements. This is due to LCCs’ excellent freeze-thaw resistance, ease of placement, and potential sustainability benefits such as reduced use of virgin material and industrial by-products. However, there is a need to quantify these benefits and develop unified specifications for using LCC in the pavement structure. Therefore, this study examined the performance of flexible pavement sections that included a subbase layer, unbound granular materials for the control section, and three LCC densities (400, 475, and 600 kg/m3) for the LCC sections. Post-construction evaluation of pavement stiffness and roughness were evaluated using a Lightweight deflectometer and SurPro equipment. The results showed that LCC subbase thickness ≥ 250 mm produced over 22% smoother riding surfaces than unbound granular pavements while increasing pavement stiffness by up to 21%. Finally, this study recommends that LCC subbase thickness should not be thinner than 250 mm when using densities below 475 kg/m3 over weak subgrades.

Exploring visions and vision clusters of sustainable food packaging - The case of Finland

Food packaging faces demands to reduce its ecological footprint, e.g., plastic leakage and use of virgin materials. We collected and analyzed stakeholder visions of sustainable food packaging in Finland. The food packaging system’s complexity means that a single, tangible, transformative, and widely acceptable vision can be difficult to create. We therefore present a “vision cluster” as a concept for analyzing and presenting visions. The visions are considered from two interrelated perspectives: the breadth of the change referring to the diversity of actors involved; and the depth of change referring to the type of change, including structures, human-nature connections, and knowledge systems. Different visions complement each other and create an opportunity to discuss potential tensions between visions and actors. A vision cluster could alleviate conflict, allowing different actors to consider various sustainable futures together, and the possible tensions may be openly discussed. There were clear differences in the prominence of actors in the visions. Although the food industry is a major food packaging actor, it is less visible than the packaging industry in the visions. The changes in food packaging were often envisioned as relatively shallow or incremental. However, increasing collaboration between different actors was a recurring theme in the visions.

Reverse Chain for Electronic Waste to Promote Circular Economy in Brazil: A Survey on Electronics Manufacturers and Importers

Government requirements for the management of waste electrical and electronic equipment (WEEE) by electronics manufacturers and importers has raised some difficulties in structuring the reverse chain of WEEE in Brazil, notably due to the territorial extension of the country. The need to implement circular economy practices (CE) in the reverse chain of WEEE has been acknowledged as a key requirement for sustaining the international competitiveness of Brazilian companies. In this context, this study sets up to evaluate the flows of the reverse chain of WEEE, aiming to promote CE as well as its actions for the recycling, reuse, remanufacturing, and reduction of WEEE in Brazil. The study identifies and characterizes key manufacturing decisions for developing waste management capabilities, including the need for waste management responsibilities for installing and operating the collection points and transporting waste to recyclers. Likewise, the study highlights the relevance of the adoption of strategies for selling recycled materials to the secondary market, along with reusing and reducing the use of virgin materials. Initially, the managerial strategy is based on recycling and remanufacturing actions due to short-term monetary revaluation, in addition to the immediate resolution of the complex problem. It should be noted that the decision to outsource WEEE management does not exempt the manufacturer from reusing and reducing material consumption, an important contribution that must be taken into account in organizational practice, beyond the immediate resolution of the complex problem.

Road map for implementing circular construction practices in India: an overview

Globally, the construction industry is considered as one of the biggest consumers of natural resources and is a generator of large quantities of demolition wastes. Hence, the full-scale adoption of circular economy (CE) in the construction industry would not only conserve natural resources but also reduce environmental pollution by reusing demolition waste. Despite the recognised potential of the concept of CE, the application of CE in the construction industry is still in its infancy and is limited, particularly in developing countries such as India. Although circularity elements are applied in the construction sector in India to a certain extent, there is still a long way to go for the large-scale adoption of CE practices. Improvements in the supply chain system, incorporation of reused and recycled materials and minimisation of the use of virgin materials in construction, implementation of modular construction and use of digital tools are some of the solutions that can be adopted towards achieving CE in construction. In this context, the present study discusses the practices currently adopted in the construction sector in India towards achieving CE. Further, the methodologies adopted in other countries and limitations in implementing these technologies in India, towards circular construction, are discussed. Learning from the principles/concepts of other countries that are successfully adopting CE solutions, this study provides a road map for implementing construction practices in India to make this sector less resource intensive.

Life cycle assessment of incorporating recycled materials in pavement design

This study was set out to conduct a life cycle assessment (LCA) to explore the environmental and economic impacts of pavement design alternatives using reclaimed asphalt pavement (RAP) and recycled plastic. 25 design alternative pavement designs were considered for a four-lane 8 km-long highway section. Design mix percentages varied between 0 and 40% of RAP with 10% increments and 0–20% of recycled plastic with 5% increments. The impact was assessed based on estimating utilized energy and water resources, climate change impact in terms of CO2 equivalent, and air pollution in terms of air acidification, human health particulate (HHP), and photochemical smog. Results show that recycled plastic is superior to RAP in reducing energy consumption and GHG emissions. Both RAP and recycled plastic reduced water consumption. Recycled plastic reduced air acidification, HHP, and smog. RAP also increased HHP substantially, mainly during materials production. It was found that the RAP replacement ratio of 10% yielded the highest value of energy consumption, harmful gases emissions, air acidification, HHP, and Smog. RAP and plastic both reduced costs substantially as recycled material reduced the use of virgin materials and bitumen. In addition, using RAP eliminates the cost of moving RAP to landfills.

Applying Circular Economy to Construction Industry through Use of Waste Materials: A Review of Supplementary Cementitious Materials, Plastics, and Ceramics

Due to constant growth of waste production, recent strategies in waste management such as circular economy promote the maximum life cycle use of materials. In construction industry where structures tend to last for decades, the use of such recycled materials can have numerous benefits including overall reduction in cost, in use of virgin materials, and in CO2 production as well as providing an opportunity for a tailored concrete with specific properties. Yet, because of the stereotypical and negative image of mechanical properties reduction, as a result of using waste materials, often their vast contribution in sustainability and durability properties are not taken into consideration. In this regard, we propose viewing waste materials as secondary raw materials that in certain regards, can provide a favorably tailored property. In this regard, the following review article first provides a short description of the most commonly used waste materials such as supplementary cementitious materials (fly ash, ground granulated blast furnace slag, silica fume, metakaolin, rice husk ash, municipal solid waste ash, steel slag, copper slag), ceramics from construction and demolition (glass powder, brick and tile ceramic and porcelain), and the vastly available plastic materials (polypropylene, polyethylene terephthalate, polyvinyl chloride, and rubber). Then, by reviewing a selected environmental impact (life cycle assessment), physicochemical, durability, and finally mechanical properties discuss the limitations, future projections of newer waste materials (e.g., agricultural waste) to be used and suggest potential future study in this area.

Preliminary Study on New Alternative Binders through Re-Refined Engine Oil Bottoms (REOBs) and Industrial By-Product Additives.

Recent studies have worked towards addressing environmental issues such as global warming and greenhouse gas emissions due to the increasing awareness of the depletion of natural resources. The asphalt industry is seeking to implement measures to reduce its carbon footprint and to promote sustainable operations. The reuse of several wastes and by-products is an example of a more eco-friendly activity that fulfils the circular economy principle. Among all possible solutions, the road pavement sector encourages, on one hand, the use of recycled materials as a partial replacement of the virgin lithic skeleton; on the other hand, it promotes the use of recycled materials to substituting for a portion of the petroleum bituminous binder. This study aims to use Re-refined Engine Oil Bottoms (REOBs) as a main substitute and additives from various industrial by-products as a full replacement for virgin bitumen, producing high-performing alternative binders. The REOBs have been improved by utilizing additives in an attempt to improve their specific properties and thus to bridge the gap between REOBs and traditional bituminous binders. An even larger amount of virgin and non-renewable resources can be saved using these new potential alternative binders together with the RAP aggregates. Thus, the reduction in the use of virgin materials is applied at the binder and the asphalt mixture levels. Rheological, spectroscopic, thermogravimetric, and mechanical analysis were used to characterize the properties, composition, and characteristics of the REOBs, REOB-modified binders, and asphalt mixes. Thanks to the rheological investigations of possible alternative binders, 18 blends were selected, since they behaved like an SBS-modified bitumen, and then they were used for producing the corresponding asphalt mixtures. The preliminary mechanical analysis of the asphalt mixtures shows that six mixes have promising responses in terms of stiffness, tensile resistance, and water susceptibility. Nevertheless, the high variability of recycled materials and by-products has to be taken into consideration during the definition of alternative binders and recycled asphalt mixtures. In fact, this study highlights the crucial effects of the chemical composition of the constituents and their compatibility on the behaviour of the final product. This preliminary study represents a first attempt to define alternative binders, which can be used in combination with recycled aggregates for producing more sustainable road materials. However, further analysis is necessary in order to assess the durability and the ageing tendency of the materials.

Tinjauan Durabilitas Campuran Asphalt Concrete Wearing Course Menggunakan Aspal Tua Dengan Berbagai Bahan Peremaja

Asphalt concrete wearing course is laid on the top of road pavement so that directly exposed to ultra violet light and other environment impact. The higher temperature at the pavement surface and exposure to atmospheric oxygen accelerated aging cause asphalt to stiffen and become brittle. This aging result decrease the binding of asphalt and aggregate leads various damage of pavement. The aged asphalt rejuvenated and recycled with rejuvenating agent has been developed to reduce the use of virgin material for road maintenance. This article aims to review durability of asphalt concrete wearing course using waste cooking oil, epoxy resin, kerosene and waste engine oil as asphalt rejuvenators. Aging asphalt was prepared by heating in an oven at 85 oC for 120 hours (long term oven aging). Durability was assessed from the value of Marshall immersion which represent the resistance of asphalt mixture at water immersion. Relation between Marshall immersion and voids in mix (VIM), voids in the mineral aggregate (VMA), voids filled with bitumen (VFB) and density are also evaluated. From the analysis, it can be concluded that the use of waste cooking oil, epoxy resin, kerosene and waste engine oil as asphalt rejuvenators increase the durability of asphalt mixture containing the aged asphalt.

Eco-friendly dredged material-cement bricks

The increasing concerns about natural-resource depletion and environmental degradation have resulted in developing “green” products and switching to sustainable manufacturing processes. The conventional fired clay bricks and concrete masonry still play vital roles in the construction industry. However, the use of virgin materials and carbon emissions associated with their production have raised questions about their environmental sustainability. This study investigates the potential of using dredged material from a confined disposal facility (CDF) in Cleveland, Ohio, to fabricate eco-friendly bricks. The brick samples were made using mixtures of sand, sieved from the dredged material, with 8%, 10%, and 12%, by weight, of Type I/II cement, and compacting the samples using a pressure of 2 MPa or 4 MPa. The compressive strength, water absorption, and freeze–thaw resistance of the bricks were evaluated in the laboratory per American Society for Testing and Materials (ASTM) method C67. The compressive strength of the bricks ranged from 10.3 MPa to 17.2 MPa, whereas absorption ranged from 13% to 18%. The 50-cycle freeze–thaw (F-T) weight loss ranged from 0.1% to 0.4%, demonstrating that durable bricks, meeting the ASTM specifications (0.5% maximum F-T weight loss after 50 cycles), could be produced using the dredged material. Furthermore, a life cycle inventory of dredged material–cement brick (DM-CB) was established to compare its environmental impacts with conventional fired clay brick, concrete masonry units, and compressed stabilized brick. The DM-CB was observed to have the least embodied energy of 1.49 MJ/kg and an embodied greenhouse gas emission of 0.162 kg CO2e/kg, making it the eco-friendliest and environmentally sustainable product compared to conventional bricks.

Increasing the lifetime of products by nanomaterial inclusions—life cycle energy implications

Typically, the high energy required to manufacture nanomaterials is weighed against the benefits transferred to a product. Adequately establishing the environmental characteristics of a product that contains nanomaterials requires a complete methodology. The objectives of this study are to draw attentions on life cycle information and to demonstrate the methodology for the scientific assessment of the environmental benefits of using a nanomaterial in a product to extend the product life and to provide a real example for the calculations of the approach. About 1317 products with nanomaterials in the market were analyzed to identify the outcomes of lifetime extension by the nanomaterial additions. Five life cycle elements were quantified to establish the cradle-to-gate (CTG) life cycle footprint of a product comprised of a nanomaterial. These are the following: the life cycle of the conventional product with the usual construction and without added nanomaterial, the life cycle of the nanomaterial manufactured from CTG per kilogram of nanomaterial, the amount of nanomaterial incorporated into the product, the quantitative improvement in the product performance due to the presence of the nanomaterial (such as increased lifespan), and the incremental energy and auxiliary materials (often negligible) involved in the incorporation of the nanomaterial into the conventional product The primary challenge here is to have all five of the informational pieces in order to ensure that the environmental footprint of using a nanomaterial is complete. The results can be seen for the range of products with life extension via nanomaterials, ranging from 130 to 3100%. In these cases, the higher energy to manufacture the nanomaterial is more than offset by the avoidance of manufacturing non-nanoproducts multiple times over the life extension period. It was found that several nanoscale inclusions in the products greatly increased many properties of the final product along with the lifetime. Increasing the lifetime of products by adding nanoscale inclusions will thus reduce environmental and health concerns, as well as the use of virgin materials, energy consumption, landfill allocations in the long term, and product marketability.

Smart vs conventional motorways: Environmental impact assessment under realistic traffic conditions

This research aims at assessing the environmental impacts exerted by a smart motorway compared to those of a traditional motorway. The study has global policy implications: it takes into account the impacts due to the construction and maintenance of the infrastructure and the environmental effects produced by the traffic emissions, taking into account smart technologies and truck platooning regulation. Through a classical LCA approach, 1 km-long smart motorway with 2 m-high embankment was assumed as the functional unit for the analysis. A realistic traffic condition has been considered. A comparison between environmental effects produced by the use of virgin material and by Reclaimed Asphalt Pavement was made by assuming two maintenance plans. Thanks to C-ITS systems the greater safety featured by smart motorways has a significant effect on the environmental impact, compared to conventional motorways. The impact produced by safety barriers during the life cycle was also estimated. For smart motorways the impact categories GWP, POCP, AP and EP are observed to be considerably reduced in the maintenance phase of zinc-coated steel safety barriers and in those associated to traffic emissions. It must be noted that in smart motorways vehicle emissions are markedly influenced by the percentage of heavy vehicles travelling in Truck Platooning mode. The results show that concomitant use of lime stabilization and RAP leads to a significant reduction in energy consumption (up to 35%) and pollutant emissions (up to 34% of CO2) than in case of exclusive use of virgin material. The accidents reduction produce a 30% decrease of GWP, POCP, AP and EP related to safety barriers maintenance phase than the corresponding values of traditional motorway. Truck platooning mode generates GWP reduction close to 4%. The environmental advantages of a smart motorway increase progressively with the increase of AADT, platooning truck percentage and heavy vehicles percentage.

Use of recycled materials as mid layer in three layered structures-new possibility in design for recycling

Challenges of using recycled polymer materials in food packaging are related both to the properties of the material and demanding safety issues for food contact materials. The aim of this research was to detect possible risks using recycled post-consumer plastic waste in three-layered polyethylene (PE) films produced with virgin outer layers and a mid-layer from recycled flexible PE material. Migration tests were performed as risk assessment for identifying possible migrating substances from the mid-recycled layer. Overall migration was determined on various 3-layered structures made from virgin low-density PE (LDPE) and virgin linear low-density PE (LLDPE), respectively, with two different recycled PE from post-consumer waste (R1 and R2). 95% ethanol was used as a simulant for screening at 20, 40 and 60 °C for 10 days. Specific migration was performed using sophisticated analytical techniques (liquid and gas chromatography). Overall migration values for all temperatures were from < 2 mg/dm2 at lowest and 5.6 ± 0.1 mg/dm2 at highest temperature, thus well below the overall migration limit (OML) of 10 mg/dm2. Specific migration of intentionally and non-intentionally added substances were detected, identified and quantified. Similarly, specific migration values were under specific migration limit (SML) defined in legislation. Optical properties of the reference samples were significantly different in appearance and on cross section for samples with recycled materials R1 compared to recycled material R2 which caused only slight changes in the appearance of both reference films. This research presents a valuable study on migration from recycled flexible PE films and use of recycled materials in food packaging applications. Use of virgin materials as outer layer in combination with commercially available recycled material can increase the use of recycled materials in packaging as well as reduce the total amount of flexible plastic solid waste.

Environmental assessment of supplementary cementitious materials and engineered nanomaterials concrete

Concrete has been one of the most common building materials used in construction in the world for many centuries. The manufacturing of concrete plays an important role in the generation of global warming emissions and waste and causes non-renewable resource depletion. This research assesses the environmental impacts of the use of supplementary cementitious materials (SCMs) and engineered nanomaterials (ENMs) (i.e., by-products) as partial replacement of ordinary Portland cement in concrete. It also evaluates the structural performance of the use of construction and demolition waste as partial replacement of natural aggregate in concrete in terms of compressive strength and durability. Results show that the use of SCMs and ENMs reduces the global warming impact (GWI) and the cumulative energy demand (CED) of concrete production without reducing strength and durability. In some cases, it enhances durability and strength. However, there is a tradeoff between durability and strength improvement with the use of reengineered by-products resulting in increased GWI and CED. Although they produce almost the same GWI and CED as those of OPC concrete, improving the use of recycled aggregates as a partial natural aggregate replacement can reduce the use of virgin materials.

Carbon dioxide emissions and heavy metal contamination analysis of stone mastic asphalt mixtures produced with high rates of different waste materials

The incorporation of waste materials in asphalt mixtures has driven several studies mainly focused on improving their mechanical performance while minimizing the use of virgin materials. However, these could only be considered cleaner solutions for road paving works if their production and application do not present additional risks for human health and the environment. Therefore, this study aims at assessing the carbon dioxide emissions and possible leachates of stone mastic asphalt mixtures produced with high rates of different waste materials for binder modification or material recycling. Thus, a chemical analysis of eluates that were in contact with those mixtures and an estimation of the carbon dioxide emissions associated with their production and transportation were carried out under different scenarios. In conclusion, these mixtures comply with the established specifications for hazardous leachates. The addition of waste materials to these mixtures decreases carbon dioxide emissions, especially for recycled stone mastic asphalt mixtures with 50% reclaimed asphalt pavement material and bitumens modified with waste materials. Thus, the studied mixtures are innovative solutions for future use in pavement maintenance and rehabilitation operations, in line with the circular economy concept.

Strategies to improve performance of reclaimed asphalt pavement-recycled asphalt shingle mixtures

ABSTRACT Recycling highway construction materials and minimising the use of virgin materials can reduce the pavement life cycle costs, improve highway network condition, conserve natural resources, and protect the environment. However, aged binder in reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS) makes asphalt pavements more brittle and creates long-term durability problems. In this study, the performance benefits of using softer virgin binder grade and increased virgin binder content strategies in RAP and RAS mixture production in Oregon were quantified. Semi-circular bend and flow number tests were conducted on prepared samples in laboratory to assess their cracking and rutting performance with low or no RAP (0% and 15%), high RAP (30% and 40%), and RAP&RAS, three binder contents (total binder contents with RAP/RAS and virgin binder – 6%, 6.4%, and 6.8%), and three binder grades (PG 58-34, PG 64-22, and PG 76-22). Moreover, possible combinations of RAP/RAS content, binder content, and binder grade to produce asphalt mixtures with high cracking and rutting performances were suggested using regression modelling and sensitivity analysis. The results of this study show that increasing binder content does not create any significant impact on the cracking performance of RAP&RAS mixtures but it is an effective strategy to improve the fatigue cracking resistance of 30% and 40% RAP mixtures.