Recycled Material Content Research Articles

LCA-based environmental impacts outlook towards the future of construction in emerging countries

Abstract The construction sector is globally acknowledged as carbon-intensive, prompting urgent action especially in BRICS countries due to the high-contribute and continuous urban growth. Here, advocating for sustainable practices throughout the entire building life cycle is imperative, for extending building lifespans without locking in operational energy inefficiencies and using construction materials and techniques geared to resource efficiency and circularity. Following the hotspots prioritization, life cycle perspective and stepwise approach, the paper offers thus a preliminary exploration on low-carbon projection scenarios for the construction value chain, focusing on China as leading CO2 emitter. Top priority is directed towards cement/concrete supply chain, delving into the increasing recycled material content during production, the implementation of prefabrication construction, and the adoption of environmentally responsible practice for managing waste at the end of life. The percentage shares on the global carbon emissions make evidence of potential for reducing environmental impacts by switching from standard to the basic sustainable practices commonly pursued to achieve carbon neutrality targets. Findings do not pretend to be exhaustive (detailed analysis are needed), but rather prompt action towards the shift in mindset and market transition, notifying increased responsibility to stakeholders and LCA as a powerful decision-making support.

Recycling Pesticide Plastic Containers in Indonesia: An Evaluation of Technical, Economic, and Regulatory Impact Feasibility

This study explores the feasibility of recycling pesticide plastic packaging in Indonesia, focusing on technical, economic, and regulatory aspects. Technical feasibility analysis highlights challenges in material composition and pesticide residue removal, emphasizing the effectiveness of a cleaning process to ensure safety and quality of recycled materials. Economically, the study demonstrates significant cost savings when incorporating at least 40% recycled material into new packaging, enhancing market competitiveness. The regulatory analysis emphasizes the recommendation to the Indonesian government to reclassify waste pesticide containers from hazardous to non-hazardous materials following the validation of the triple rinsing trial’s effectiveness in removing pesticide residue. Reclassifying the containers as non-hazardous will reduce transportation costs from the source locations, such as plantations or farming areas, to the waste processing plant, thereby improving the economic feasibility of the pesticide plastic container recycling. Recommendations include conducting production trials with larger container sizes and adjusting the recycled material percentage, as well as exploring performance-enhancing additives for recycled plastics. Industries are advised to align with regulations by adopting best recycling practices and establishing robust compliance processes. Strengthening Extended Producer Responsibility (EPR) schemes and supporting advanced recycling infrastructure development are critical steps. These measures will improve the efficiency and effectiveness of recycling programs, ensuring regulatory compliance and promoting sustainable waste management. The study concludes that recycling pesticide plastic packaging is feasible and beneficial, provided that technical and economic challenges are effectively addressed with at least 40% recycled material content. The economic viability of recycling pesticide plastic containers will be further enhanced if the Indonesian government reclassifies the waste containers as non-hazardous, after triple rinsing process, thereby reducing transportation costs.

Circularity of new composites from recycled high density polyethylene and leather waste for automotive bumpers. Testing performance and environmental impact

New composite materials (suitable for automotive bumpers), composed of recycled high-density polyethylene (rHDPE) and leather buffing dust waste (BF) ranging from 20 to 50 wt%, were produced and investigated for mechanical properties. Optimal mechanical performance was achieved with composites containing 30 % wt BF. The environmental performance of automotive bumper production from both virgin and recycled HDPE reinforced with 30 % wt BF (HDPE-BF, rHDPE-BF) composites was compared to that of conventional polypropylene (PP) by performing a cradle to gate life cycle assessment.A component-based approach, instead of a comprehensive LCA assessment for the entire car was adopted using various functional units (FU) such as mass (FU1), volume (FU2), and volume of raw material fulfilling a specific impact strength requirement (FU3), thus enriching the paper with methodological discussions.The rHDPE-BF system provided better environmental performance compared to the virgin PP system, when considering both mass and volume-related functional units, mainly due to the avoidance of virgin polymer production. Even with the inclusion of the use phase in FU2 and a slightly higher density (+1.7 %) of composites than PP-based bumpers, the rHDPE system still provides better environmental performance (10 % less impact). The sensitivity analysis highlighted the significance of car type and final density of the bumper on the impact results. Finally, when using FU3, due to its higher impact strength, HDPE-BF system is clearly the best environmental alternative (50 % less impact) followed by rHDPE-BF system. In all cases, rising the content of recycled materials in the bumpers increases its circularity.The paper illustrates the importance of selecting a suitable functional unit, based on a specific application (i.e., automotive bumpers), to evaluate the environmental impact of new composite materials in comparison to traditional options. Expanding the assessment to encompass multiple functions provides a more accurate portrayal of reality but also introduces greater result uncertainty.

Effects of mechanical recycling on the properties of glass fiber–reinforced polyamide 66 composites in automotive components

Abstract In this study, we aimed to reveal the effective reusability of waste generated during the injection molding process of polyamide 66 (PA66) reinforced with 30 wt% of short glass fiber (PA66-GF30) widely used in the automotive industry. PA66-GF30 was subjected to the three mechanical recycling cycles, including regranulation and reinjection molding steps, and the recycled materials obtained in each of these cycles were included at the ratios of 15, 20, 25, and 30 wt% to the virgin composite. Thermogravimetric analysis and differential scanning calorimeter analyses showed that the number of recycling cycles and recycled material content in the composite had no significant change in the thermal stability and crystallinity degree of the PA66-GF30. The average fiber length determined by optical microscope analysis shifted to lower values from 300–350 to 150–250 μm by increasing the number of recycling cycles and the recycled material content. The fact that the recycled material content in the composite exceeds 25 wt% and the recycling cycle is applied three times played a key role in changing the mechanical and melt flow behaviors of the composite. Tensile strength, elastic modulus, and impact energy slightly decreased while the elongation at break and melt flow index increased.

Analysis of green certification standards related to recycled materials involving textiles based on life cycle thinking

Enterprises have been increasingly required by international brands to obtain green certification. As green certification has become an important tool for evaluating suppliers and securing environmental performance along the supply chain, and textile-related recycled materials are one of the most affected industries, this study aims to examine the differences among various certification schemes in the recycled materials industry involving textiles. We identify a set of clear and consistent evaluation metrics for the criteria in green certification, and investigate the standardized contents of green certifications for recycled materials-related industries based on life cycle thinking. It is found that “requirements on recycled material content” are required by all the green certifications examined. From the perspective of life cycle stages, the “raw material stage”, “manufacturing stage” and “disposal stage” are emphasized by the green certifications related to the recycling industry. Finally, this study combines an environmental perspective incorporating life cycle thinking (LCT) with a social and economic perspective of implementation feasibility to provide ways to strengthen certification regimes related to recycled materials and promote long-term product life cycle management and supply chain management.

Recycling of industrial and construction waste materials in roads construction

ABSTRACT Usually, aggregates used for asphalt mixtures consist mainly of natural aggregates. Sometimes the natural aggregates are substituted with limited amounts of industrial and construction wastes. The current paper deals with evaluating the mechanical performance of new developed hot asphalt mixtures made of up to 98% industrial and construction by products. In this project, different types of industrial by-products, namely, RAP, foundry sand, and steel slag in addition to biobased rejuvenators have been used to find the composition of the best asphalt mixtures made mainly of wastes that can substitute the asphalt mixtures made of natural aggregates. Fourteen selected asphalt mixtures have been evaluated using the circular road simulator test at VTI. The CRS testing program has been set up to allow different measurements, e.g. surface deterioration and wear, friction, and visual inspection. The test results demonstrated that it is possible to obtain paving mixtures with high content of recycled materials.

Additive manufacturing of recycled plastics: a ‘techno-eco-efficiency’ assessment

Plastic materials have been widely used to replace metals in functional parts due to their lower cost and comparable technical properties. However, the increasing use of virgin plastic material in consumer and industrial applications has placed a significant burden on waste management due to the volume of waste created and the potential negative effects of its end-of-life processing. There is a need to adopt circular economy strategies such as plastic recycling within industrial applications in order to reduce this significant waste management pressure. The present study used recycled polylactic acid (PLA) material as a feedstock for the 3D printing of a centrifugal semi-open pump impeller. The technical performance of 3D printed recycled PLA material and virgin PLA material was compared in this study. The environmental impacts for technically feasible impellers were assessed through the environmental life cycle assessment, while costs were evaluated by life cycle costing. The results were incorporated into a techno-eco-efficiency framework to compare the technical properties, environmental impacts, and costs. The social impacts of additive manufacturing and recycled feedstock material were also explored. The technical assessment results indicated that tensile strength, fatigue strength, density, and hardness decreased with recycled material content compared to virgin material. Microscopy of the fracture surfaces revealed the presence of slightly higher porosity and defects in recycled specimens, which could result in slightly lower technical properties. However, the recycled material was accepted for further ecological analysis as it offered higher pumping performance when compared to the original component and could reduce the burden on virgin material-based production and waste material disposal. Importantly, the results showed that 3D printed recycled PLA impellers are more eco-efficient when compared to 3D printed virgin PLA impellers.

Evaluation of Adhesion Characteristics According to Chemical Deterioration Conditions and Recycled Material Content of Butyl Rubber Compound Waterproof Sheet

This study sought to investigate the adhesion strength reduction of reclaimed butyl rubber self-adhesive waterproofing sheets after exposure to a chemical erosion environment. Ranges from 0 to 45% mixture ratio (with changing intervals of 5% ratio) of reclaimed butyl rubber replaced the new rubber content of commercial butyl rubber self-adhesive waterproofing sheets for testing, based on the optimal results for the reclaimed butyl rubber content in order to ensure performance that meets the standard criteria. The research results confirmed that performance degradation was relatively greater when exposed to an acidic environment that was responsible for chemical deterioration. It was also confirmed that, given the deterioration environment described above, the reclaimed butyl rubber content should be limited to 44% so as to ensure an adhesion performance similar to that of the untreated test sample (reclaimed butyl rubber content of 67%). Based on the above results, it was suggested that the optimal mixing range of reclaimed butyl rubber should be up to 44% of the total rubber content, considering performance degradation after field application in the production of self-adhesive waterproofing sheets.

Prediction and evaluation of rutting and moisture susceptibility in rejuvenated asphalt mixtures

Understanding the performance of rejuvenated asphalt mixtures is critical for cleaner pavement design and construction, as the use of rejuvenators lead to environmental and economic benefits with the ability to increase recycling but promote rutting and moisture susceptibility at a high recycled binder ratio. Existing models have not systematically evaluated rejuvenated asphalt mixtures in terms of rutting performance from a mechanistic approach, and there is a lack of research related to the third stage of rutting induced by high-temperature moisture damage. To overcome these shortcomings, two-stage and three-stage mechanistic-empirical models based on viscoelastic stress-strain response were proposed in this study to predict and evaluate rutting and moisture susceptibility of rejuvenated asphalt mixtures. Wheel tracking tests in wet and dry conditions were performed on a virgin asphalt mixture (without recycled materials) and on rejuvenated asphalt mixtures (with recycled materials and rejuvenator), and the cumulative rutting curves were investigated. In addition, linear viscoelastic properties at a reference temperature were used as input parameters in a finite element model (FEM) to calculate the viscoelastic response of virtual specimens under repeated loading. The FEM results were then substituted into the proposed models to determine the material parameters for wet and dry conditions separately. Two prediction results were combined to determine the proportion of rutting caused by stripping in rejuvenated asphalt mixtures. Four indices were used in the evaluation of rutting in wet conditions. Based on the wheel tracking test results, the rejuvenated asphalt mixtures with the highest recycled material content performed worst in wet conditions and best in dry conditions, which indicates that anti-stripping agent might be necessary for rejuvenated asphalt mixtures.

An Analysis of the Performance of Trolleybus Brushes Developed from Recycled Materials

The paper presents an analysis of the performance of traction brushes produced from waste materials. Brushes are used to ensure good electrical contact between the rail and the pantograph. Slides are produced by the process of hot pressing, with the parameters of heating up to max 175 °C, at the minimal pressure value of 200 MPa. Some of the developed brushes with a high (55–60%) content of recycled materials are more durable and break-resistant than their commercial counterparts.

Practical Tools for Optimizing Recycled Materials Content and Recycling Agent Dosage for Improved Short- and Long-Term Performance and Rejuvenated Binder Blends and Mixtures

The use of large quantities of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt mixtures is desirable due to environmental and economic benefits. However, recycled asphalt mixtures with high recycled materials contents are usually less workable; difficult to compact in the field; and more prone to cracking, raveling, and other durability-related pavement distresses. Recycling agents can rejuvenate the aged binders in the recycled materials to different degrees depending on type and dosage, facilitating the inclusion of increased amounts of recycled materials. Recycling agents modify the ultimate performance of the corresponding rejuvenated asphalt mixtures, thus estimating an optimum recycling agent dosage is critical to maximize its benefit without compromising the short- and long-term performance of the rejuvenated asphalt mixture. This study provides tools for estimating recycling agent dosage based on a target climate with minimum laboratory efforts by considering the type, source, and amount of recycled materials, and the source and grade of the base (virgin) binder. A total of 15 different recycled binder blends (base and recycled binders) and 32 different rejuvenated binder blends (recycled binder blends with recycling agent) were considered, including materials from eight states across the United States. Blending charts for recycled binder blends were established and verified, and later used to develop relationships to estimate the optimum dosage of recycling agent. The recycling agent optimum dosages were determined to match the continuous high-temperature performance grade (PGH) of the recycled binder blend to that required by the target climate, as this dosage yielded the best performance for rejuvenated binders and mixtures. Long-term rejuvenating effectiveness of recycling agents was verified by extensive evaluation of rejuvenated binder blends and mixtures. Discussion on optimizing RAP/RAS and base binder proportions and controlling the maximum dosage of recycling agent for economic and pavement performance considerations was also provided. Finally, practice-ready guidelines for evaluation, materials selection/optimization, and design of rejuvenated asphalt mixtures with high recycled materials contents were proposed.

Low Temperature Behavior of Asphalt Binders, Mortars, and Mixtures with High Recycled Materials Content

With the increased usage of recycled materials and various evaluation techniques being utilized to evaluate them, it is becoming increasingly important to be able to obtain consistency between the various techniques. Given the wide range of recycled materials as well as treatments or additive materials being used and the complex interactions resulting between them, it is becoming increasingly important to continually verify the field performance related to the findings of the various evaluation techniques. Therefore, this effort utilized binder blending, mortar procedure, and the uniaxial thermal stress and strain test (UTSST) to examine several mixtures containing recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS) along with example recycling agents. The methodologies were compared to each other to seek similarity in findings as well as preliminary comparisons to relevant field performance. The results indicated general agreement between certain parameters of each methodology, while the UTSST showed promising relationships to measured longitudinal and transverse cracking in the observed field test sections.

Investigation of fracture behavior of asphalt mixture composite using energy-based approach

This study aims to determine the endurance limit and macro-cracking threshold of a viscoelastic composite material using a fracture mechanics approach. Asphalt mixtures containing different recycled material contents and recycling agent doses were fabricated and long-term oven aged. Dynamic modulus tests were first conducted to obtain linear viscoelastic properties including complex modulus and phase angle, and then damage properties were determined from monotonic semi-circular bending tests. Pseudo displacement was calculated to remove the viscous effect from the total dissipated energy, and the energy balance approach and Griffith crack growth criterion were modified and used to predict the bond energy with the aid of discrete element modeling. With the bond energy computed, the endurance limit was determined to be frequency and mixture composition dependent. The macro-cracking threshold defined as the boundary between healable micro-cracks and non-healable macro-cracks was also identified to be frequency and composition dependent using a damage density concept. Both the endurance limit and the macro-cracking threshold were utilized in the asphalt mixture Black Space diagram, which is capable of illustrating the effects of aging, recycled materials content and recycling agent dose in asphalt mixtures for the prediction of fracture performance.

Total Recycled Asphalt Mixes: Characteristics and Field Performance

The use of recycled materials in asphalt concrete (AC) pavement has increased significantly because of their economic and environmental benefits. The use of recycled materials can pose risks to the performance of asphalt pavements, however. The Illinois Department of Transportation developed five total recycled asphalt (TRA) mixes in the pursuit of environmentally sustainable pavements. These mixes contain up to 60% asphalt binder replacement (ABR) obtained from reclaimed asphalt pavement (RAP) and recycled asphalt shingles. Virgin aggregates were replaced by 100% recycled aggregates including RAP, steel slag, and recycled concrete aggregate (RCA). Based on laboratory testing, all the mixes offered excellent rutting resistance because of their high ABR content. The TRA mixes were relatively less compliant and not very sensitive to field aging, whereas indirect tensile strength tests showed indistinguishable results. All mixes had comparable complex modulus |E*| and phase angle ([Formula: see text]) values at low temperatures. Laboratory-compacted specimens had relatively low flexibility index (FI) compared with field cores taken after construction. The FI values of the field cores decreased with aging, higher recycled materials content, or both. An exponential increase in transverse cracking was observed in the field cores because of their relatively high ABR, RCA/steel slag content, or both. The progression of field transverse cracking over time and FI values are well correlated. A three-dimensionally balanced mix design was introduced and used successfully to distinguish between AC mixes; it is proposed as a tool for better control mix designs and optimum field performance.

Mixture-based rheological evaluation tool for cracking in asphalt pavements

Cracking is a major distress that limits the durability of asphalt pavements. Various fatigue and fracture-based tests and analyses can be used to assess cracking resistance of asphalt mixtures in order to design more economical and durable mixtures. This mixture cracking resistance is affected by the rheological properties of the asphalt binder, both stiffness and relaxation ability as indicated by measured dynamic modulus and phase angle, respectively. One significant breakthrough involves the use of binder Black space (shear modulus versus phase angle) and the Glover–Rowe (G-R) parameter that is a function of these two rheological properties as an indication of cracking resistance. However, binder characterisation is not adequate to fully represent mixture performance and therefore there is a need for a mixture-based evaluation tool. The objectives of this study were to: (1) investigate the applicability of a representative temperature and frequency combination for mixture-based Black space evaluation; (2) evaluate the ability of mixture Black space to track the effect of aging and rejuvenation (when recycling agents are used with recycled materials); (3) explore the use of a mixture-based G-R parameter (G-Rm) for cracking resistance evaluation and (4) investigate a possible correlation between G-Rm and Flexibility Index (FI) from a semi-circular bending (SCB) test. Test results indicate a reliable temperature–frequency combination for G-Rm, which was sensitive to aging, recycled materials content, binder performance grade and recycling agent dose. Test results also indicate a good correlation between the G-Rm parameter and the FI.

Performance of asphalt mixtures with high recycled materials content and recycling agents

ABSTRACTRecycled asphalt mixtures with high amounts of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) can be excessively stiff, brittle, and prone to cracking. The use of recycling agents, or rejuvenators, can significantly reduce mixture stiffness and improve performance, specifically cracking resistance. In this study, the performance of recycled and rejuvenated asphalt mixtures from several field projects, located in different environmental zones across the United States, was evaluated considering various recycling agent dosages determined by the contractors. Field core test results and the visual distress surveys of the field projects demonstrated that using the field recycling agent dosages yielded poor mixture performance. Laboratory test results demonstrated that adding the recycling agent at the dosage to match the continuous high-temperature performance grade (PGH) of the rejuvenated binder blend (virgin/base binder, recycled binder, and recycling agent) to that of the target binder PGH specified based on climate and traffic requirements yielded improved mixture performance. The rejuvenated mixtures at this recycling agent dosage showed significant reduction in stiffness and improved cracking resistance, and facilitated the use of higher quantities of recycled materials, regardless of aging level, while maintaining rutting resistance after short-term aging.

Incorporation of Circular Aspects into Product Design and Labelling: Consumer Preferences

The transition to a circular economy requires a fundamental change in products and the way they meet consumer demands. In this context, the aim of this article is to analyse the level of importance that consumers attach to the fact that circular aspects were incorporated into a product design and to the need to communicate them on the product labelling. The aspects analysed in this study are related to durability, repairability, recycled material content, low environmental impact, fair working conditions and origin. To this end, a survey was designed and conducted with a representative sample. It was found that Spanish consumers are concerned mainly about fair working conditions during the product manufacturing and the durability of the products. A high degree of congruence was found between the level of importance attached to incorporating each aspect into the product design and including this information in the product labelling. In addition, multinomial regression models are applied to identify the consumer profiles (gender, age, household size, level of education, household income) that are more or less prone to prefer products that incorporate these aspects into their design and labelling. Household size and gender are the socio-economic variables that most affect consumer preferences.

Life cycle assessment of asphalt pavement recycling for greenhouse gas emission with temporal aspect

Abstract This paper quantifies greenhouse gas emission of asphalt pavements containing reclaimed asphalt pavement using life cycle assessment with temporal aspect. The life cycle stages include raw material acquisition, plant production, construction, maintenance, and end-of-life. The time-dependent decay function of carbon dioxide was adopted to capture time effect in life-cycle inventory assessment. The case study of runway rehabilitation demonstrates that four critical factors may affect environmental impact of pavement recycling, including recycled material content, blending efficiency of virgin and recycled binder, moisture content of recycled aggregate, and pavement performance levels. As recycled material content increases, the reduction of greenhouse gas emission increases accordingly. However, the benefits of raw material saving can be compensated by the increased moisture content of recycled aggregate and the shorter life of pavement with reclaimed asphalt pavement. As the moisture content of recycled aggregate increases, the performance of recycled asphalt pavement need reach a higher level in order to avoid environmental burden. On the other hand, the results indicate that the environmental impact of asphalt pavement recycling is overestimated if temporal aspect is not considered. This finding reinforces the importance of physical decay pattern of greenhouse gas emissions along time in life cycle assessment for global warming potential.

Development of an index to evaluate the cracking potential of asphalt mixtures using the semi-circular bending test

This study introduced a cracking parameter, called the Cracking Resistance Index (CRI), derived from the load-displacement response obtained during a semi-circular bending test, and compared it to the recently developed Flexibility Index (FI). Laboratory test results indicated that both FI and CRI are sensitive to binder Performance Grade, recycled materials content, and recycling agent dosage. The results indicated the dependency of the two indices on specimen thickness and air voids content. A reasonable correlation between FI and CRI was verified. As compared to the FI, the proposed CRI provided better distinction between different asphalt mixtures, less variability, and easier calculation.

Assessing the effects of RAP, RAS, and warm-mix technologies on fatigue performance of asphalt mixtures and pavements using viscoelastic continuum damage approach

The objective of this study was to evaluate the effects of incorporating recycled materials, i.e. reclaimed asphalt pavement (RAP) and recycled asphalt shingles, and the use of warm-mix technologies on fatigue performance of asphalt mixtures and pavement structures using the viscoelastic continuum damage (VECD) approach. Material characterisation involved dynamic modulus test and direct tension cyclic fatigue test. Two parameters, namely Material Fatigue Sensitivity (MFS) and Structure Fatigue Sensitivity (SFS), were developed to represent the fatigue resistance of asphalt mixtures and their performance in pavement structures, respectively. Validity of MFS and SFS were verified by the semi-circular bend test at intermediate temperature and the field fatigue performance, respectively. Based on the MFS results, increase in the content of recycled materials compromised fatigue resistance, implementation of warm-mix technologies brought about marginal improvements, and use of soft binder yielded pronounced fatigue benefits for hot-mix asphalt mixtures with high RAP content.