Sustainable Engineering of Recycled Aggregate Concrete: Structural Performance and Environmental Benefits Under Circular Economy Frameworks

Abstract

The transition toward sustainable infrastructure in the construction sector necessitates the practical integration of Circular Economy (CE) principles, particularly through the valorization of recycled materials in concrete applications. This review critically synthesizes recent advancements in the use of recycled polyethylene terephthalate (PET), glass powder, and crumb rubber as partial replacements for conventional aggregates in Ordinary Portland Cement (OPC)-based concrete. The incorporation of these secondary materials has demonstrated the ability to reduce the environmental footprint of concrete production—achieving up to 25% reductions in greenhouse gas emissions and diverting significant volumes of waste from landfills—while maintaining structural viability with compressive strength retention levels exceeding 90% in several optimized mix designs. Enhanced ductility, thermal resistance, and reduced density further support their application in specialized construction scenarios. Beyond material characterization, the review systematically examines implementation enablers, including regulatory alignment, life-cycle-based procurement, and design-for-deconstruction strategies. It also highlights critical gaps such as the absence of harmonized standards, variability in recycled material quality, and systemic barriers to market uptake. Addressing these challenges is essential for scaling CE integration and achieving measurable sustainability gains across the built environment. This study aims to inform policy, practice, and research trajectories by linking material innovation with operational frameworks that support regenerative construction systems.

1. Introduction

The shift towards sustainable socio-technical systems has become imperative in modern development [1]. The building and housing sector, as a major contributor to global material consumption and waste, requires innovative recycling strategies to promote sustainable infrastructure. Integrating recycled aggregates such as glass, polymer (plastic), and rubber waste into concrete provides a viable solution for housing and urban development, reducing reliance on virgin materials while enhancing sustainability. As the CE paradigm continues to gain traction, its practical translation into sectors such as construction has become vital. The integration of recycled materials into concrete—particularly glass; polymer; and rubber—represents a critical step towards closing material loops in one of the most resource-intensive industries. Additionally, broader socioeconomic challenges, including intergenerational poverty, unemployment, and social inequalities, continue to hinder progress towards sustainable development [2,3].

A growing number of organizations and corporations are grappling with economic and financial volatility, stemming from systemic issues such as unregulated markets, fragmented supply chains, flawed ownership models, and insufficient policy-driven incentives [4,5]. In this context, the concept of the Circular Economy (CE), though not entirely novel, has gained renewed traction among policymakers and global institutions as a viable framework for addressing sustainability challenges. Prominent legislative examples include the Chinese Circular Economy Promotion Law and the European Union’s Circular Economy Package, which institutionalize key CE principles such as resource efficiency, waste minimization, and closed-loop systems. The increasing engagement of corporations with circular economy practices reflects a growing acknowledgment of its dual potential to improve stakeholder value and internal resource efficiency [6,7,8]. The concept of Circular Economy (CE) is increasingly recognized across academic, corporate, and policymaking domains, with a surge in literature and industry white papers shaping its evolution [9]. Academics and practitioners are increasingly invested in the CE framework, viewing it as a pragmatic pathway for realizing sustainable development objectives [6,8,9,10,11,12,13,14]. While sustainable development remains a foundational paradigm, scholars have critiqued its increasing ambiguity in both discourse and implementation. Engelman [15] argues that the term has suffered from semantic inflation, often encompassing conflicting interpretations. As a response, circular economy models have emerged as more actionable strategies grounded in measurable outcomes such as resource conservation, closed-loop systems, and waste minimization—principles which also align with broader sustainable development objectives like green growth and ecological efficiency [16]. At that time, the concept of CE was regarded as the most popular. For years, scientists and researchers have sought potential answers to the environmental challenges of waste generation and pollution. Numerous individuals have discovered that utilizing recycled components in lieu of raw resources diminishes the construction sector’s reliance on virgin materials. According to estimates from the Federal Highway Administration (FHWA), construction activities in the United States generate approximately 123 million tons of waste each year. Advocate for the adoption of prefabrication and Industrialized Building Systems (IBS) as effective strategies to reduce waste generation and address waste management challenges [17,18,19]. According to their analysis, prefabrication can significantly diminish material waste, and projects utilizing prefabrication generally exhibit greater rates of recycled and reused waste materials. Besides minimizing construction waste, Hassim [20] explored and examined additional benefits of prefabrication in building and construction. Examples of this include enhancing the building’s integrity, design, and construction; reducing the number of unskilled laborers; lowering construction costs; adopting a finalized design early in the planning stage; improving oversight; fostering a safer and better-organized construction environment; and improving environmental outcomes by minimizing waste. Incorporating recycling into pre-construction planning is one approach to address this issue. Integrated solid waste management (ISWM) involves selecting and executing appropriate methods, tools, and management strategies to attain defined waste management goals and objectives. Incorporating recycling into pre-construction planning is a key strategy to address material waste in the construction sector. Integrated Solid Waste Management (ISWM) provides a structured framework for achieving this, emphasizing solid waste segregation and resource recovery [21]. Among the various materials studied for reuse, Fly Ash (FA) and Recycled Concrete Aggregate (RCA) have shown considerable promise. James et al. [22] evaluated the combined use of FA (up to 15%) and RCA (up to 25%) in concrete pavement and found minimal strength compromise compared to virgin mixes. The synergy between FA and RCA facilitates the development of Recycled Aggregate Concrete (RAC), a sustainable composite that reduces dependence on natural aggregates and clinker-based cement. RAC not only mitigates environmental impacts but also improves circularity in concrete production systems. These findings emphasize the feasibility of creating structural-grade concrete through intelligent material substitutions. Similarly, Hamoush et al. [23] explored the integration of crumb rubber in engineered stone, enhancing its mechanical and thermal resilience while lowering weight. Such innovations demonstrate the expanding frontier of recycled material use in civil engineering.

Table 1. Solid waste quantities resulted from the construction activities distributed by disposal methods in tons (2004).

Types of Activities	Number of Enterprises	Solid Waste		Approaches for Solid Waste Disposal
		Quantity of Solid Wastes	Enterprises That Produce Wastes	Storage	Incineration	Collection	Selling	Burial
Site preparation	22	8.1	18	0.0	0.0	8.1	0.0	0.0
Building Installation	422	226.6	172	0.0	0.0	225.3	1.3	0.0
Buildings construction and civil eng. projects	1049	1477.5	414	0.0	40.4	1333.0	6.8	97.3
Building Completion	6	9.6	59	0.0	0.0	8.5	1.1	0.0
Total	1559	1721.8	663	0.0	40.4	1574.9	9.2	97.3

(constructed from data in [24]) highlights the scale of construction waste and its distribution by disposal method, reinforcing the urgency for sustainable alternatives. Approximately 20% of this waste stream includes recyclable inputs like concrete, glass, and polymer. Therefore, integrating recycled components such as FA, RCA, and rubber into concrete aligns with Circular Economy objectives by closing material loops and advancing sustainable infrastructure.

Significant amounts of this waste cannot be easily discarded; however, its environmental impact can be mitigated through more sustainable utilization methods. They call this the “Waste Hierarchy.” Reducing, reusing, or recycling garbage is the goal; recycling is the recommended method of getting rid of waste. A depiction of the waste hierarchy is illustrated in Figure 1 (developed based on discussions in [24]). The current study focuses on waste materials that can be used in Ordinary Portland Cement (OPC) concrete mixes in place of more traditional components, specifically aggregates. Glass trash, polymer garbage, and waste from building development are the specific waste materials being examined. Recycling concrete as aggregate offers a solution to challenges linked to natural aggregate extraction and the disposal of unused concrete. Recent studies have investigated the use of glass and polymer materials in civil engineering applications and, as a result, evaluated the potential of incorporating polymers and glass powder into various construction-related civil engineering projects [14,25,26].

According to Rindl [27], waste glass has potential uses in various applications, such as aggregates for road construction, concrete production, and asphalt paving. Shayan [28] examined the incorporation of residual glass particles in concrete. According to a study conducted by Yang et al. [29], rubberized concrete is recommended specifically for use in secondary structural elements, including crash barriers, culverts, sidewalks, sound absorbers, and jogging tracks. Huang et al. [30] initially introduced rubberized concrete as a composite material comprising particles in various stages. A predictive model was later created to evaluate the factors influencing the strength of rubberized concrete, accompanied by a parametric study using finite element analysis. The analysis indicates that high-strength concrete permits the use of harder cement mortar, high-ductility concrete allows for softer cement mortar, a reduction in maximum rubber chip size enables the use of stiff coarse aggregate, and a uniform coarse aggregate size distribution facilitates the use of harder cement mortar.

Scope and Novelty of the Study

In this study, the recycled materials investigated primarily include glass, plastic (particularly polyethylene terephthalate, or PET), and rubber waste, due to their growing application potential in cementitious construction materials. This review investigates their multi-dimensional role as aggregate replacements in concrete under Circular Economy (CE) frameworks. The scope encompasses material characterization, structural and thermal performance, environmental impact via life cycle assessments, and regulatory barriers, with a specific focus on integrating design intent and policy enablers for sustainable construction. Unlike previous reviews that often isolate material-specific impacts, this work adopts a systems-level synthesis bridging engineering performance, policy readiness, and socio-economic feasibility. The novelty lies in its comprehensive integration of quantitative performance metrics with CE-aligned design and planning strategies—providing actionable insights not only for engineering researchers but also for policy makers; sustainability planners; and construction professionals aiming to implement circular practices at scale. By organizing evidence across technical and strategic dimensions, this review establishes a unique blueprint for transitioning towards sustainable concrete infrastructures in urbanizing economies.

2. Methodological Framework for Literature Synthesis

To ensure a comprehensive and unbiased synthesis of global advancements in sustainable construction and circular economy integration, a structured literature search protocol was adopted. The review methodology focused on peer-reviewed sources from major academic databases, including Scopus, Web of Science, ScienceDirect, MDPI, SpringerLink, JSTOR, IEEE Xplore, and Google Scholar. The keyword combinations used were “Circular Economy”, “Recycled Aggregates in Concrete”, “Waste Valorization in Construction”, “Sustainable Concrete Materials”, “Life Cycle Assessment (LCA) in Concrete”, “Waste-to-Resource Strategies”, “Green Building Materials”, “Plastic/Glass/Rubber Waste in Concrete”, and “Bio-based Concrete Materials”.

To ensure both relevance and scientific currency, the literature review primarily focused on publications from the last five years, particularly between 2020 and 2025, reflecting the accelerating evolution of circular economy (CE) strategies within construction and material science domains. A notable concentration of recent contributions from 2023 to 2025 underscores the field’s dynamic response to global sustainability imperatives. Only English-language, peer-reviewed articles were considered, including empirical studies, review papers, experimental investigations, and policy-driven discussions that explicitly explore the integration of CE principles with concrete technology and sustainable construction practices. While prioritizing contemporary insights, selected foundational studies published before 2020 were also included where they offered critical theoretical frameworks or served as methodological anchors. Non-peer-reviewed content, opinion essays, and literature lacking direct thematic relevance were excluded to preserve academic rigor and topical precision.

In total, an initial pool of approximately 950 documents was identified through comprehensive searches across academic databases. After duplicate removal, title and abstract screening, and full-text eligibility assessment, 149 high-quality and thematically aligned sources were retained and critically analyzed in this review. Each selected article was further categorized by waste type (e.g., PET, rubber, glass), application domain (e.g., structural concrete, mortar, asphalt), and sustainability aspect (mechanical performance, thermal behavior, durability, or environmental impact). This systematic approach ensures traceability, replicability, and thematic coherence, thereby enhancing the scholarly rigor and policy utility of the present review.

3. Circular Economy: Concepts and Evolution

The current implementation of the Circular Economy (CE) concept by practitioners and businesses is visually illustrated in Figure 2. This schematic demonstrates the hierarchical preference of material recovery strategies, arranged concentrically to reflect their relative sustainability impacts. The innermost loops—reuse; refurbishment; and remanufacturing—represent processes that retain the highest value and utility of products with the least additional energy input. These approaches prioritize extending a product’s service life with minimal transformation, preserving embedded energy, and reducing material degradation. In contrast, recycling—positioned in the next outer ring—requires more processing and typically results in downcycling; yielding materials of lower quality or functionality. Disposal, situated on the periphery, is the least desirable option and reflects the loss of both material value and environmental capital.

As illustrated, maximizing the duration that materials remain within the inner loops significantly improves environmental and economic outcomes. It reduces resource extraction, energy demand, and greenhouse gas emissions associated with virgin material processing. According to the CE framework, landfilling and incineration are relegated as last-resort solutions. Therefore, CE emphasizes the intelligent design of products and systems that prioritize circular flows, minimizing loss across the product life cycle and maintaining the highest possible value at every stage [31].

The underlying philosophy of CE encourages the design of systems that maximize resource value retention, as further demonstrated in Figure 3. The diagram expands upon Figure 2 by integrating economic, environmental, and social perspectives into a unified vision for sustainable growth. The central circular layers—reuse; remanufacturing; and recycling—are supported by surrounding value loops that capture the flow of materials and energy across the product life cycle, from raw material acquisition to final disposal. The figure also highlights systemic feedback loops, showing how effective CE practices reduce demand for virgin resources and minimize environmental impact by looping resources back into production and consumption.

In this framework, environmental wins include reduced emissions, decreased extraction of virgin materials, and minimized waste. Economic benefits include value retention, cost savings from resource efficiency, and creation of new market opportunities. Simultaneously, social wins stem from community engagement, employment in reuse/refurbishment industries, and the democratization of product access through shared-use models. By linking circular flows to tangible societal gains, the model presents CE not merely as a waste management strategy but as a holistic blueprint for transformative sustainability [32].

The figure effectively aligns CE principles with emerging scientific theories and cross-disciplinary concepts such as industrial ecology [33], industrial ecosystems [34], and symbiosis [35]. Environmentally sustainable production encompasses evaluations of circular material flows and innovations in manufacturing systems [36], product-service systems [37], eco-efficiency [38], and cradle-to-cradle design [11,39,40], biomimicry [41,42], resilience of social-ecological systems [43,44], the performance economy [45], the zero emissions concept [46], and natural capitalism [47], among others. It serves as a bridge between academic discourse and policy-making by outlining a framework for regenerative resource cycles that preserve planetary boundaries while ensuring economic and social resilience.

The potential for reciprocal benefits of the circular economy is evident in its multidimensional alignment with environmental, economic, and social sustainability objectives. A well-functioning CE model respects the regenerative capacities of natural ecosystems and seeks to emulate these cycles in industrial and economic processes [48]. The term “Circular Economy” (CE), first introduced in the field of economics by Korhonen et al. [49], linked global economic consumption with environmental degradation. Since then, its conceptual evolution has been shaped by academic fields such as ecological economics and engineering—focusing respectively on industrial symbiosis and efficient resource management [50]. CE practices revolve around the principles of reduction, reuse, recycling, and material recovery [51,52], with the goal of embedding materials back into productive use loops. Functioning as a transformative economic model, CE enables the creation of new revenue streams and helps retain material value across product life cycles. It necessitates systemic changes in production and consumption, directly contributing to sustainable development agendas [53,54]. The relationship between CE and sustainability is increasingly emphasized in scholarly literature [55,56], as both share concerns about unchecked resource consumption, technological transitions, and the need for future-proof design strategies. The construction industry is one of the primary sectors where CE implementation is both necessary and impactful [57]. This sector contributes up to 35% of global CO₂ emissions and 65% of landfill waste [58], making the adoption of CE strategies not only urgent but also economically and environmentally strategic. Implementing circularity in construction thus becomes critical for safeguarding future generations and meeting climate and resource-efficiency goals [59].

4. Justification and Performance Evaluation of PET Polymer in Recycled Concrete Applications

This section presents a foundational overview of sustainable concrete formulations, with particular emphasis on polyethylene terephthalate (PET) as the recycled polymer of focus. PET has been selected based on its prevalence in post-consumer waste streams, favorable mechanical and thermal characteristics, and substantial empirical evaluation in cementitious applications. To substantiate this selection, a structured bibliometric analysis was conducted using the Scopus database (accessed 2 April 2025), employing the query TITLE-ABS-KEY (“polymer name” AND concrete AND recycled) filtered for the period 2015–2025 and refined by subject area (Engineering, Materials Science). In addition, two systematic reviews [60,61] confirm PETs leading presence in recycled polymer-concrete research based on study counts and application breadth. Furthermore, Qaidi and Al-Kamaki [62] provide a dedicated evaluation of PETs influence on mechanical strength, durability, and sustainability performance in concrete matrices, reinforcing its suitability as the focal polymer for this review. The combined findings reveal that PET appears in approximately 80 to 120 peer-reviewed studies within the specified timeframe, significantly exceeding the literature volume on other polymers such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), and polyvinyl chloride (PVC), which are typically represented in only 5 to 25 publications. These values are quantitatively summarized in

Table 2. Comparative research intensity of recycled polymer types in concrete composites (2015–2025), based on bibliometric analysis and published reviews.

Polymer Type	Estimated No. of Studies (2015–2025)	Representative Sources/Methodology
PET (Polyethylene Terephthalate)	80–120	Scopus bibliometric query; validated in [60,61]; reviewed in [62]
HDPE (High-Density Polyethylene)	15–25	Bibliometric screening; limited coverage in [60]
LDPE (Low-Density Polyethylene)	10–20	Cited in niche applications in [61]; confirmed via Scopus [62]
PP (Polypropylene)	10–15	Noted as fiber reinforcement in [61]; supported by bibliometric screening
PVC (Polyvinyl Chloride)	5–10	Sparse mentions in [60]; few empirical studies in Scopus bibliometric screening
Other polymers (PS, PC, mixed)	<5	Isolated reports; no consistent trend in Scopus bibliometric screening or reviews

, which compares the research intensity of major recycled polymer types in concrete composites.

While other recycled materials are discussed in subsequent sections, this segment focuses specifically on PET due to its well-documented influence on mechanical properties—especially compressive strength; tensile strength; and flexural performance. Research indicates that Portland limestone cement conforming to EN 197-1 standards [63], specifically CEM II/A-LL 42.5 R, has been widely utilized in PET-concrete investigations [24,64,65,66]. Moreover, various studies have adopted natural coarse aggregates with maximum nominal sizes of 25 mm, 12.5 mm, or 9 mm, tailored to the experimental and structural requirements of each investigation, as illustrated in Figure 4.

Uncrushed natural sand continues to be widely employed as a fine aggregate in concrete production, particularly in studies investigating the integration of secondary materials into concrete formulations. Recent studies have reported a variety of coarse aggregate types, each with distinct particle size distribution profiles depending on source, processing method, and intended structural application. To provide a consolidated overview, Figure 5 has been developed by the authors based on the gradation data reported in [65], illustrating typical particle size distribution curves for three representative coarse aggregate types—labeled as Aggregate Type I; II; and III.

Aggregate Type I corresponds to conventional well-graded crushed stone used in standard concrete mixes. Aggregate Type II reflects moderately graded recycled concrete aggregates derived from construction and demolition waste. Aggregate Type III denotes a more gap-graded distribution, often associated with processed demolition debris or mixed aggregates. For comparative purposes, the gradation of natural sand and polyethylene terephthalate (PET) flakes, commonly utilized in prior investigations as a partial fine aggregate substitute, are also included. Figure 5 thus provides a unified visual reference to understand how different aggregate types—including recycled and unconventional materials—compare in terms of gradation; which directly influences workability; strength; and durability in sustainable concrete mix designs.

Previous studies have examined the influence of varying PET replacement ratios on the performance of concrete [63,64,65,66,67,68]. Typical weight-based replacement ratios of 10%, 20%, 30%, 40%, and 50% have been investigated to evaluate the material’s effects on concrete properties. In these studies, concrete with a compressive strength of approximately 35 MPa (Fc28) has been utilized, and mix proportions have often adhered to the guidelines of the American Concrete Institute (ACI) standard 211.1 [69].

Table 3. Experimental tests and standards for evaluating fresh and hardened concrete.

Key Target Properties	Standard	Ref.
Slump	ASTM C 143	[70]
Compressive Strength	BS 1881	[71]
Pulse Velocity	ASTM C 597	[72]
Fresh Concrete
Splitting Tensile Strength	ASTM C 496	[73]
Hardened Concrete
Flexural Strength	ASTM C 293	[74]
Unit Weight	ASTM C 138	[75]

(prepared from data reported in [64]) provides an overview of the common experimental tests and associated standards reported in the literature.

The physical properties of the component materials, as well as the mix designs, have been comprehensively documented in prior studies following BS 1881 standards [71]. Concrete specimens are typically cured at controlled temperatures of around 25 °C for 24 h, followed by immersion in curing basins, as per ASTM C 192 protocols [76]. As illustrated in Figure 6, constructed using data provided by [66], the tensile strength of concrete demonstrates a notable correlation with varying PET replacement ratios. This highlights the material’s adaptability to different replacement levels. On the other hand, Figure 7, also informed by data from [66], depicts the flexural strength of concrete and its response to increased PET content, showcasing the impact on bending resistance. Together, these figures enhance our understanding of concrete’s mechanical properties under varying PET incorporation levels and its suitability for structural applications [67,68].

Research has further emphasized the fire resistance of concrete, attributing this characteristic to its non-combustible nature and its ability to function as a thermal barrier, preventing the spread of flames. The fire resistance of concrete is influenced by its constituent materials, particularly under conditions of high thermal gradients. Studies have highlighted that concrete exhibits lower thermal diffusivity compared to steel, making it more effective in resisting fire damage [66]. In fire resistance investigations, several studies report testing concrete specimens (typically 100 mm × 100 mm × 100 mm) with PET replacement ratios ranging from 0% to 50%. Following a curing period of 28 days, the specimens are subjected to direct flame exposure for 300 s, as highlighted in the literature [67,68]. Observations from these studies reveal significant alterations in material properties under such conditions.

The insights from PET-based concrete evaluation serve as a representative foundation for further analysis of multi-material integration strategies under the broader Circular Economy framework, as explored in the next section.

5. Integrating Circular Economy Principles in Concrete Engineering

Various strategies for improving resource and material efficiency discussed in the preceding section have developed independently. The Circular Economy is distinct from a mere aggregation of various reduction approaches due to its holistic system approach [77,78]. In this context, implementation denotes the execution of a certain strategy in isolation, while integration pertains to the simultaneous execution of many strategies over the whole lifetime. Integrating several Circular Economy initiatives throughout the physical life cycle is expected to uncover synergies and potential conflicts that remain obscured when examined in isolation or focused primarily on the product-level perspective. This section explores the integration of specific recycled materials—namely; glass; PET-based polymers; and rubber—into concrete and construction applications; evaluating their influence on sustainability and performance characteristics.

Different environments possess varying perspectives on the adoption of sustainable Circular Economy practices [79]. The PESTEL framework, encompassing social, political, technical, economic, legal, and environmental factors, is utilized to assess the factors affecting implementation, along with potential synergies and conflicts from integration. This is a widely utilized method for assessing contextual specifics. Historically, conversations regarding concrete have predominantly focused on environmental, technical, and economic issues, while legal, social, and political concerns have received comparatively less attention. The PESTEL framework is a straightforward and effective method for examining various circumstances, even if they may correspond to multiple PESTEL categories.

PESTEL analysis has long been employed in the construction and materials industries to evaluate strategies addressing diverse topics, including timber utilization [80] and waste disposal [81]. Following this, Figure 8, constructed based on discussions in [82], ranks Circular Economy strategies applicable to concrete. These strategies include material reduction, long-lasting design, maintenance and refurbishment, reuse and remanufacturing, and recycling, emphasizing a holistic approach to resource efficiency and sustainability.

5.1. Reuse and Recycling of Construction Materials in Concrete

Concrete remains one of the most commonly used materials in construction that uses a lot of limited resources and emits CO₂ [83,84]. Recycled materials can be substituted for aggregate and cement, or they can be used as fibers or fillers. By using recycled materials, waste from manufacturing process byproducts and waste streams is decreased. To complement the previous discussion on the use of recycled materials in concrete, this section presents a synthesized overview of key experimental studies that have evaluated the performance of various waste-derived inputs—particularly glass; polymer (including PET); and rubber—in cementitious systems. These studies span a range of geographic regions and encompass diverse applications, such as structural concrete, mortar, paving, and composite materials. Parameters investigated include compressive and flexural strength, thermal resistance, microstructural behavior, and durability under harsh environmental conditions.

Table 4. Chronological summary of selected experimental studies on recycled waste materials in cementitious composites, categorized by material type.

Recycled Material Type	Year	Replacement Level (%)	Key Findings	Target Property Studied	Ref.
Waste iron	2008	10–20	Increased compressive and flexural strength up to 17.4% and 27.9%, respectively, at 20%; increased fresh and dry density.	Compressive strength, Flexural strength, Density	[85]
Rubber aggregates	2014	10–20	Enhanced abrasion and freeze–thaw resistance; improved durability due to increased micro-pore content.	Durability, Abrasion, Freeze-thaw resistance	[86]
Waste PET (polymer bottles)	2018	0.5–2.0 (volume %)	Workability reduced, optimum tensile strength observed at 1.0% replacement.	Mechanical strength, Workability	[87]
Glass powder	2018	10–20	Improved durability; enhanced compressive strength at 10% replacement.	Compressive strength, Durability	[88]
Mixed waste (polymer, Glass, Ceramics)	2018	10–50	Performance comparable to control at lower substitution ratios.	General performance	[87,88,89]
Shredded PET	2023	10–40	Compressive strength improved up to 10% replacement; reduced workability; density; lightweight concrete achieved.	Mechanical strength, Density, Workability	[90]
Tire rubber (TR) and fly ash (FA)	2024	TR: 10; FA: 15	Durability improved; minor strength loss observed.	Durability, Compressive Strength	[91]
Recycled aggregate	2024	20–50	Effective up to 40%; quality depends on pre-treatment.	General strength and durability	[92]
Recycled polymer (as sand replacement)	2024	5–30	Up to 20% replacement led to ~8–10% reduction in density and comparable strength; good thermal resistance.	Workability, Strength, Sustainability
Crumb rubber	2025	2.5–7.5	Reduced compressive strength; ductility and toughness enhanced, suitable for non-structural and plastering applications.	Compressive strength, Ductility	[93]

consolidates this literature to provide a comparative framework that captures the material-specific benefits, technical feasibility, and sustainability contributions of these recycling strategies. This comprehensive overview supports the argument for mainstreaming Circular Economy (CE) principles into concrete design and production workflows.

Table 5. Incorporation of recycled materials in concrete: benefits and applications.

Material	Benefits	Ref.
Polymers	Enhanced ductility, minimized shrinkage cracks, and lightweight characteristics.	[94,95,96,97]
Glass	Pozzolanic characteristics, reduced shrinkage, high thermal conductivity, lower ecological impact, and better water absorption.	[98,99]
Rubber	Improved Heat Resistance and Strength Properties.	[86,100,101]
Concrete	Pozzolanic characteristics, reduced shrinkage, high thermal conductivity, lower ecological impact, and better water absorption.	[102,103]
Ceramics	Improved strength, optimal water absorption, reduced weight, and enhanced pozzolanic nature.	[87]
Coir and Almond Wastes	Improved mechanical strength, higher air content, and reduced air density.	[89,98]

below categorizes the core benefits of the most important recycled material type commonly used in concrete mixes, complementing the literature trends outlined in Table 3.

Recent literature reviews have extensively evaluated the use of recycled materials in construction applications, including but not limited to recycled concrete, recycled asphalt, wood, roof shingles, metals, fly ash, PET polymer, rubber, glass, gypsum, bricks, slag, and aluminum [85,88,104,105,106]. These studies underscore the environmental benefits of replacing virgin materials with recycled alternatives, which contribute to resource conservation and reduced environmental impact. Figure 9, constructed by synthesizing data from [88,104,105,106], illustrates the distribution of the most commonly used recycled materials in the construction sector, with the inclusion of previously underrepresented materials such as rubber and glass, which are also discussed elsewhere in this manuscript. Notably, the inclusion of the “Non-recycling” category represents the proportion of waste materials that are typically not subjected to any form of recycling or recovery, either due to technological limitations, cost constraints, or lack of supportive policy frameworks. This category is important for drawing attention to existing inefficiencies in current waste management practices and highlighting opportunities for enhancing material recovery. By visualizing both widely adopted recycled materials and those underutilized, this figure reinforces the broader argument of the manuscript that adopting Circular Economy (CE) strategies can drive more sustainable outcomes in construction practices, especially in emerging economies.

Quantitative Correlation Between Recycled Material Type, Dosage, and Mechanical Properties

Building on the overview in Table 4, it is critical to establish material-specific correlations between recycled content and resulting mechanical performance in concrete. Several recent studies have illustrated that mechanical properties such as compressive, tensile, and flexural strengths are highly sensitive to both the type of recycled input and its replacement percentage. For instance, Qaidi et al. [90] reported that replacing fine aggregate with shredded PET at 10% dosage maintained 93–95% of compressive strength while improving workability and reducing density. However, further increase beyond 20% resulted in noticeable strength degradation due to the low bonding affinity between PET and the cement matrix.

In the case of crumb rubber, studies including Hurukadli et al. [93] show that incorporation up to 7.5% by volume leads to a 20–30% drop in compressive strength, yet significantly improves ductility and impact resistance—indicating suitability for non-structural elements. Similarly, Moolchandani et al. [91] observed that blends of tire rubber and fly ash (TR:10%, FA:15%) preserved over 80% of the compressive strength while substantially enhancing durability. With recycled aggregates, performance varies with pre-treatment. Shukla et al. [92] documented that pre-treated recycled aggregates at 40% replacement maintain over 90% of mechanical performance compared to control mixes, and durability remains within acceptable limits. Thus, establishing these correlations is essential for informing optimal mix designs and ensuring structural reliability when implementing Circular Economy strategies in concrete engineering.

5.2. Applications of Circular Economy in Reinforced Concrete and Material Recovery

The result of all planned and executed research on the utilization of closed cycles in the effective management of construction waste is the advancement of suitable technologies. The items generated during construction include bricks, polymeric materials, bitumen, asphalt, scrap concrete, reinforced concrete, and wood debris. Approximately 80% of the waste consists of reinforced concrete, both light and heavy, at an approximate ratio of 4:1. Before demolition, waste must be extracted, sanitized, and categorized into fractions of 5–20, 20–40, and 40–70 for both large scrap concrete and reinforced concrete. The selected method for processing concrete debris is determined by various factors, including the configuration of the equipment, the storage capacity for materials, and the accessibility of the waste processing site.

For the production of concrete and the processing of reinforced concrete products, there are three basic organizational models: In order to collect aggregate and transport it to a concrete plant or facility, one tactic is to set up technical equipment at the site where buildings and structures are being disassembled or destroyed. The second tactic is setting up the manufacturing process to convert leftover concrete into crushed stone and create concrete mix at the site of the demolition of large building items. The third entails transporting discarded concrete to the company that produces crushed stone [107].

5.3. Emerging Technologies for Construction Waste Recycling

Current research on recycling construction waste emphasizes the development of innovative technologies to enhance process efficiency and environmental sustainability. One of the most promising applications of nanotechnology is the enhancement of building material qualities. Various forms of nanoparticles can serve as additives, including metal nanooxides, carbonate nanotubes, nanosilicates, and nanoclay. Each of these categories enhances specific concrete qualities [108,109]. Incorporating nanosilica into concrete mixtures can yield a denser structure and enhanced mechanical properties, which may offset any strength performance degradation resulting from the addition of secondary materials.

Another way to augment the eminence of secondary raw materials is the advancement of systems for thoroughly eliminating contaminants from trash. The management of waste containing heavy metals and hazardous substances is very critical. Advanced filtration and purification techniques enhance the safety of material reuse by removing contaminants. An alternative is the potential application of artificial intelligence to enhance the sorting and recycling of construction waste. Employing artificial intelligence to refine the classification and repurposing of construction trash could serve as a supplementary solution. These technologies enable the efficient identification of materials and the selection of optimal recycling processes for various material types [110]. Life cycle assessments of secondary building materials represent a crucial aspect of the research.

5.4. Economic Viability and Waste Minimization Strategies

The core tenet of CE is to identify other applications for the rejected objects in order to minimize the volume of waste sent to landfills. Reduction of raw materials, recycling, reuse, and recovery are the main objectives of the 4R approach to construction’s CE [111]. By reducing the amount of greenhouse gas emissions linked to supply chain and procurement activities, increased use of reuse, recycle, and recover processes leads to slow or stagnant raw material procurement, which has advantages for the economy and the environment. Furthermore, reducing waste production is beneficial since it protects our living environment from the negative effects of rubbish formation, in addition to reducing waste. The economic viability of trash reduction has been the subject of several studies [112].

A cost-benefit study conducted in Malaysia in 2006 highlighted the economic viability of reducing construction and demolition (C&D) waste, reporting a net profit of 2.5% [113]. The study emphasized immediate benefits such as cost savings on landfill fees, waste collection, transportation, and the sale of recycled materials. As shown in Figure 10, based on data from [114], a significant percentage of construction waste from primary work trades, including excavation, concrete works, and finishing, has been recycled and repurposed following the implementation of the Construction Waste Control and Disposal System (CWCDS). These efforts align with the principles of the Circular Economy (CE), underscoring both economic and environmental benefits.

These findings are consistent with a study by the Auckland City Council that demonstrates that, in addition to being economically advantageous, reducing trash offers several other advantages that are hard to quantify. One of the primary points made in both literary works was that higher waste levies would incentivize construction companies to use more effective waste reduction practices. In alignment with the principles of the Circular Economy (CE), the strategic redirection of construction and demolition (C&D) waste from landfilling to recycling and repurposing has gained traction across various global economies. While localized programs such as the Construction Waste Control and Disposal System (CWCDS) in Malaysia demonstrate measurable benefits in landfill cost savings and material recovery, a broader international comparison provides valuable insight into the varying levels of CE implementation. Comparative benchmarking helps contextualize national progress and identify gaps in recycling efficacy. To this end,

Table 6. Comparative overview of construction and demolition (C&D) waste generation and recycling rates across countries, sorted by construction waste contribution to total waste.

Country	Concentration of Construction Waste in Total Waste (%)	C&D Waste Recycled (%)	Ref.
United Kingdom	70	17	[115,116]
United States of America	50	40	[117]
New Zealand	50	28	[118]
Australia	44	51	[114,119]
Italy	36	65	[120,121]
Netherlands	30	10	[122]
Spain	30	7	[123]
Finland	29	25	[124]
Norway	26	75	[125,126]
Denmark	25–50	80	[127,128,129]
Germany	25	20–30	[130,131]
Japan	19	40–60	[132]
Brazil	15	8	[133,134]
France	14	40	[135]

compiles data on the concentration of construction waste in total municipal waste streams and the corresponding recycling rates for selected countries. This comparative snapshot reveals wide disparities, with countries like Denmark and Norway achieving recycling rates exceeding 70%, while others still face challenges in diverting C&D waste from traditional disposal pathways. Such analysis underscores the need for scalable policies, regulatory reforms, and investment in waste processing infrastructure to enhance global alignment with CE objectives.

5.5. Multidimensional Benefits and Design Intent for Recycling in Construction

The adoption of recycled materials in construction is driven not only by environmental necessity but also by the broader objective of resource efficiency, waste minimization, and circularity. To maximize these benefits, it is essential that the intent to reuse and recycle materials be embedded at the design stage. This intent must be reflected in architectural planning, material selection, and construction techniques that enable dismantling and repurposing [113]. Design strategies such as Design for Deconstruction (DfD), prefabrication, modular construction, and dry-assembly systems play a pivotal role. These techniques facilitate selective disassembly, minimize irreversible bonding, and allow components to retain their material integrity, making future reuse or recycling feasible. A building designed with such considerations enables higher recovery rates of high-value components and supports a regenerative construction model. Aligned with these design strategies, the incorporation of recycled materials offers benefits across the three core dimensions of sustainability:

• Environmental Benefits—Prolonging landfill capacity and minimizing environmental degradation are direct outcomes of optimized reuse and recycling. Many construction materials include chemical additives that contribute to groundwater contamination when disposed of. Recycling mitigates such risks and, by reducing material transport to landfills, also contributes to CO₂ emission reductions.
• Economic Advantages—While concerns exist regarding employment shifts from landfill operations; they are often counterbalanced by emerging job opportunities in recycling; material recovery; and green construction sectors. Recycled materials—distinct from simply reused ones—are processed to meet performance standards. This processing industry fosters new skill demands and economic activity, turning waste into valuable resources.
• Societal Benefits—The increasing demand for urban land necessitates the preservation of available space for infrastructure; housing; and ecological buffers. Effective recycling practices reduce the need for new landfills. Moreover, recycling reduces the uncontrolled dispersion of hazardous substances into ecosystems, thus safeguarding public health and improving urban living conditions.

By embedding design intent for reuse and adaptability into modern construction practices, circular economy principles can be practically implemented. This not only advances sustainability goals but also strengthens resilience across the built environment. Beyond the intrinsic benefits of recycling, the practical realization of circular economy goals in construction depends on several interrelated factors. These include the availability and consistency of recycled material supply chains, the establishment of certification and performance standards for recycled content, and the inclusion of modular and Design for Deconstruction (DfD) principles at the design stage. Additionally, successful integration requires informed procurement practices, contractor training, and supportive regulatory frameworks that facilitate the use of alternative materials. Without these structural enablers, even well-intended recycling efforts may face systemic barriers to implementation.

5.6. Regulatory Barriers and Challenges in CE Implementation

In a perfect scenario, all construction debris would be used and recycled; nevertheless, numerous obstacles impede this process. Drawing upon multiple case studies and regional policy analyses [114,119,127,128,133,134,135], six primary obstacles have been identified that hinder the recycling of construction and demolition (C&D) waste materials:

• Policy and Governance—A major challenge to reusing building waste—especially in Australasian contexts such as New Zealand and Australia—has been the limited implementation of policy-driven incentives for businesses. For instance, the Building Act (2004) and the Waste Management Act (2008) in New Zealand serve as primary regulatory frameworks on building waste. These Acts incorporate principles of sustainable material use and waste reduction during construction, supported by mechanisms such as a USD10 per ton landfill levy aimed at promoting recycling and funding new technologies. However, case studies indicate that this levy has exerted minimal influence on landfill behavior, and similar policy gaps or limited enforcement can also be observed in other countries, including China and France [114,127,135].
• Quality and Performance—A recurring issue in many countries is the difficulty of ensuring that recycled construction and demolition debris meets requisite quality standards. This often involves meticulous sorting, particularly for materials contaminated by hazardous substances. For example, effective timber separation requires distinguishing between contaminated and non-contaminated wood, a process demanding both time and labor. These costs are incurred globally, and insufficient separation can result in materials being unsuitable for recycling, as seen across multiple jurisdictions [128].
• Information—Industry-wide limitations in awareness regarding recycling benefits are not restricted to a single geography. Across developed and developing nations alike, the construction sector exhibits varying levels of engagement with recycling initiatives. Case studies from Brazil and Australia illustrate how a lack of awareness persists despite dynamic construction markets. Relevant organizations must invest in educational campaigns that leverage real-world case studies to foster behavioral change [133].
• Cost/Capital—Cost remains a pivotal barrier worldwide. In New Zealand, for example, the cost of recycling exceeds the cost of landfill disposal, thereby disincentivizing environmentally beneficial practices. Similar cost disparities have been reported in France, Italy, and Brazil [134].

  Table 7. Cost of recycling material.

  Expenditure	USD/Tonne
  Wood chipping	20
  Wood sorting	40–126
  Concrete sorting	7
  Concrete crushing	8
  Concrete preparation	4

  , adopted from discussions in [127], illustrates recycling costs from a New Zealand context:

• Perception and Culture—Globally; the construction industry still struggles to recognize construction and demolition (C&D) waste as a resource. This mindset, observed in countries like Spain, Japan, and New Zealand, stems from entrenched linear economic practices. Sustainability-oriented strategies must reframe waste as a resource, aligning with global priorities on renewable and recyclable technologies to meet climate goals [128].
• Education and Awareness Deficit—A considerable portion of the global construction workforce lacks exposure to circular economy (CE) principles. This resistance to change, due to familiarity with traditional methods, is a barrier across countries. Governments and regulatory bodies should organize workshops, training, and awareness programs to build capacity for CE practices. The lack of advanced recycling infrastructure also results in poor-quality recycled products, which are costlier and often underperform [135].
• Permits and Specifications—Across various regions; rigid standards and outdated specifications hinder the acceptance of recycled materials. Regulatory approval for the use of such materials is frequently denied due to conservative practices or lack of precedent. This creates uncertainty in the market and discourages investment in recycled material supply chains, not only in Australasia but also in countries such as the UK, Germany, and the USA.

5.7. Strategic Frameworks and Models for CE Integration in C&D Waste Management

According to a review of the literature, little is known about how the building sector in Australasia—particularly in New Zealand—is incorporating the circular economy. Applying Circular Economy (CE) strategies in the construction sector, the environmental and financial challenges may be lessened. A paradigm for incorporating CE into the construction sector states that micro, meso, and macro may be used in three levels or phases to achieve successful integration. According to the authors, the meso level of CE should focus on frameworks that expedite waste trade networks, while the micro stage should focus on cleaner, greener design and procedures. In collaborative industries with various stakeholders, the 3R principles are the most important macro criteria [130,135].

CE has only been included in construction enterprises in a few nations, such as the Netherlands and the United Kingdom. For instance, the UK has used a method known as Resource-Efficient Construction, which reduces greenhouse gas emissions from construction operations in addition to garbage. The technique assists construction experts in turning trash into a resource, recycled materials, and speeding up the recycling and reuse process. ReSOLVE, a six-phase framework proposed by the Ellen MacArthur Foundation, contains the following characteristics:

• Regenerate: Shifting the emphasis from conventional approaches to renewable technologies while preserving ecosystems.
• Share: Extending resource lifespans through maintenance and promoting shared use of reusable and recyclable materials.
• Optimize: Improving the efficiency of recycled products through waste minimization and green supply chains.
• Loop: Supplying technologies for effective waste recycling and reuse.
• Virtualize: Reducing material usage through direct and indirect methods.
• Exchange: Promoting the use of advanced construction materials and innovative methods.

There is a strong chance that the building process will move through the optimize, share, and loop stages of the ReSOLVE design, per a questionnaire-based pilot study carried out in Denmark [130]. One extremely active organization in the Netherlands that incorporates the CE into construction operations is the International Management Search Association (IMSA) [132]. The proposed framework demonstrated that an efficient strategy for managing construction waste could be developed by addressing the issues of increasing waste, environmental damage, unlawful garbage disposal, and a lack of support from the top echelons of construction companies.

A study by Esa et al. [130] highlighted the roles of Contractors, Consultants, and Clients (3Cs) in the 3Rs for construction waste management across five project lifecycle stages: planning, design, procurement, construction, and demolition. The study recommended small-scale adoption of the “Industrialized Building System (IBS)” for sustainable and efficient facilities management. At the meso level, recommendations for implementing regulations within the building sector should be put into place in order to encourage sustainable development and waste reduction. Since total rubbish elimination is not feasible, the authorities should control C&D waste at the macro level through efficient worker surveillance methods.

The framework allocates stakeholder duties across the phases of the project lifecycle: phases including planning, design, procurement, construction, and demolition [120,121,122,131]. It integrates the 3Rs for efficient construction and demolition waste management and solutions at micro, meso, and macro levels. Ruiz et al. [121] and Shukla et al. [92] provided a comprehensive framework for the Circular Economy in managing C&D waste, encompassing methods throughout five stages: preconstruction, construction and renovation, collection and distribution, material recovery, and manufacturing. As depicted in Figure 11, an LCA-based framework for C&D waste management incorporates economic, social, and environmental indicators to assess performance. The proposed framework involves phases such as data collection, normalization, weighting, and aggregation, ultimately producing a sustainability index for construction waste.

Additionally, extensive research has explored the integration of recycled polymeric and inorganic materials—particularly PET; rubber; and glass—into construction systems. These materials, when incorporated into concrete, mortar, asphalt, paving layers, or bricks, have demonstrated considerable improvements in mechanical performance, durability, thermal behavior, and sustainability characteristics.

Table 8. Comparative summary of recent research on PET, rubber, and glass waste integration in construction materials.

Types of Materials	Application Area	Composite/Mix Description	Key Outcomes/Performance Gains	Ref.
PET	Concrete	PET + fly ash-based aggregates	10–25% replacement; improved strength; no PET degradation	[125]
		PET fibers (up to 1%) in OPC concrete	+15% tensile toughness; improved shrinkage resistance	[123]
		PET fibers with statistical optimization	Fiber dosage more dominant than aspect ratio; improved tensile strength
		PET + recycled aggregate (self-compacting)	+41% compressive, +83% flexural, +19% tensile strength; −9.7% shrinkage; −73% environmental burdens	[115]
		0.25% PET + 30–40% FA	Improved ambient strength; reduced porosity by 50%; prevented spalling at 700 °C	[116]
		PET + UPOFA blends (UHPPGC)	Lower porosity, improved chloride resistance; energy savings	[124]
		PET + steel hybrid reinforced beams	Better crack control; ACI-compliant moment predictions	[136]
		XGBoost model for fiber strength prediction	30% higher accuracy over SVM; fiber geometry influences all strengths	[137]
		10% PET chip replacement under post-fire (600 °C)	Maintained strength without steel fibers; thermally resilient	[138]
	Mortar	Hybrid PET–PVA strain-hardening mix	Enhanced tensile behavior with surface-treated PET	[87]
		PET + red mud/fly ash filler	+4.05% (compressive), +7.69% (tensile), +21.52% (flexural); thermal stability	[139]
		PET/PP waste with Buton Asphalt	Improved compressive strength; Poisson’s ratio within standards	[140]
		RPET-CF for 3D printable mortar	Tensile strength 47.3 MPa; low warpage; excellent bonding	[141]
	Paving	PET + RCA + carbon black (3–5%)	Passed CBR and RLT standards for subbase; improved geo-environmental safety	[142]
	Bricks	PET + demolition waste (non-structural)	Achieved 2 MPa strength; good bulk density and hydric control	[126]
Rubber	Concrete	Crumb rubber (10–20%) as aggregate	Abrasion and freeze–thaw resistance improved; compressive strength reduced	[86]
	Engineered Stone	Crumb rubber + binder system	Toughness and energy dissipation improved	[23]
	Fiber-reinforced concrete	Crumb rubber + steel fibers	Enhanced flexural response and impact strength	[30]
	Asphalt	Rubber + PET + fly ash blends	Better fire resistance; reduced thermal diffusivity	[143]
Glass	Concrete	Fine glass powder (10–20%)	Compressive strength and long-term durability improved	[88]
		PET + glass powder	Comparable strength; reduced density	[144]
	Pozzolanic concrete	Glass powder (75 µm)	Optimal reactivity and pozzolanic efficiency under 100 µm	[28]
	Mortar	Recycled glass as filler	Strength gains at 10–15%; good workability	[24]
	Asphalt	Ground glass + bitumen	Improved surface hardness; better high-temp performance	[145]
LDPE/HDPE	Concrete	LDPE/HDPE as fine aggregate	Reduced environmental impact; improved sustainability and cost-efficiency	[146]
LDPE	Asphalt-Concrete	LDPE at 5.25% asphalt content	Improved Marshall properties and Cantabria durability; extended pavement life	[147]
Polymer Waste	Unfired Clay Brick	WPEF (up to 7.5%)	Density ↓ ~25%; thermal insulation ↑ ~70%; retained strength and durability	[148,149]

provides a comparative summary of selected experimental studies highlighting the diverse applications and performance benefits of these recycled inputs. The studies span different geographic and material contexts and reflect the growing interest in mainstreaming waste-derived resources into construction practice [115,116,117,122,123,124,125,126,136,137,138,139,140,141,142,143,144,145,146]. This material-centric approach is further supported by a broader set of Circular Economy (CE) strategies adopted across various life cycle stages in the construction sector, as outlined below:

• Preconstruction: Implementation of governmental restrictions, taxation on the acquisition of raw materials, utilization of economic tools, and prioritizing of waste management recovery alternatives.
• Construction and Renovation: Targeted demolition, an effective strategy for managing waste.
• Collection and Distribution: Practices involving collection, segregation, and on-site sorting; effective allocation of resources; transportation; and recycling of repurposed materials.
• Demolition (End of Life): Preference for selective deconstruction over conventional demolition, waste assessments, material reclamation, etc.
• Material Recovery and Production: Activities like reuse, recycling, backfilling, material or energy recovery, and waste treatment while considering environmental and economic factors.

Furthermore, implementing structured audits during deconstruction—rather than relying solely on conventional demolition—can substantially enhance material traceability; quality control; and the potential for high-value reuse. These audits facilitate the systematic identification, cataloging, and protection of reusable components, thereby minimizing damage during dismantling and enabling efficient on-site or centralized stockpiling. Aligning regulatory frameworks and incentive policies with such practices can optimize reverse logistics and promote the establishment of secondary material markets. Recent research emphasizes the necessity of integrating design-for-disassembly principles and audit-based protocols to achieve these outcomes effectively within Circular Economy (CE) frameworks [150].

6. Limitations, Research Gaps, and Practical Considerations for Circular Economy in Construction

While the Circular Economy (CE) framework has garnered increasing attention for its potential to transform construction into a resource-efficient, low-emission sector, several conceptual and operational limitations continue to challenge its mainstream adoption. Though CE is rooted in sustainability science and industrial ecology, its empirical realization in the construction industry—particularly in emerging economies—remains constrained by fragmented systems; inconsistent regulatory frameworks; and a lack of practical integration tools. This section not only delineates the existing limitations and research gaps but also articulates key practical enablers that must be prioritized to support CE outcomes in real-world construction contexts.

6.1. Systemic Limitations and Theoretical Gaps

As discussed in preceding sections, six foundational barriers have been extensively identified in CE literature: thermodynamic constraints, ill-defined system boundaries, unintended rebound effects, technological and economic path dependencies, intra- versus inter-organizational conflicts, and lack of uniform classification of waste and secondary resources [151,152,153,154]. These issues obstruct the transition from linear to circular systems by creating uncertainties in performance assessment, limiting data traceability, and undermining market confidence in recycled materials.

Moreover, CEs application in construction often lacks clear operational definitions, leading to inconsistent implementations and scattered pilot efforts. For instance, the integration of biological and technical nutrient cycles in building projects has rarely progressed beyond demonstration stages. Additionally, the role of renewable energy inputs in construction CE models remains underexplored, despite its centrality to achieving net-positive resource loops [155,156,157,158,159,160,161,162].

6.2. Practical Considerations for Enabling CE in Construction

To facilitate actionable pathways for CE within the construction sector, the following practical enablers should be embedded into policies, research, and industry frameworks:

• Design for Adaptability, Deconstruction, and Reuse (DfADR): Design-phase interventions must prioritize modularity, prefabrication, and reversible assembly. Design for disassembly (DfD) and design for reuse (DfR) principles should be embedded into building codes and professional training to ensure future resource recovery. Such approaches extend the usable life of materials, lower embodied carbon, and reduce end-of-life waste [150].
• Performance-Based Lifecycle Procurement: CE implementation requires rethinking procurement strategies. Contracts should incorporate lifecycle carbon analysis, resource circularity metrics, and provisions for material take-back. Performance guarantees for reused or recycled components must be supported by third-party certifications [163].
• Digital Innovation and Material Traceability: Technologies such as Building Information Modelling (BIM), Digital Twins, and Material Passports offer powerful tools for tracking material origins, composition, and lifecycle performance. Their use can facilitate recovery planning, on-site sorting logistics, and accurate carbon and cost modeling for circular projects [164].
• Standardization and Regulatory Alignment: A unified regulatory framework is necessary to create confidence in secondary materials. National and international standards should clearly define technical, health, and environmental criteria for recycled aggregates, polymers, metals, and hybrid composites used in construction [165].
• Policy Instruments and Fiscal Mechanisms: Governments must implement targeted incentives, including tax credits for circular designs, differential landfill fees, and green procurement policies that prioritize circular materials. Establishing extended producer responsibility (EPR) schemes for construction components can further institutionalize CE practices [165,166].
• Skills Development and Collaborative Ecosystems: The transition to CE requires a fundamental shift in industry culture. Educational institutions, certification bodies, and industry groups must collaborate to develop training programs in circular construction [167]. Stakeholder ecosystems, including clients, designers, contractors, recyclers, and policymakers, must work through collaborative platforms to share data, align objectives, and scale innovation.

6.3. Future Research Priorities

To reinforce the CE transition in construction, research must evolve to answer nuanced and context-specific questions that bridge theory and implementation. Recommended priority areas include:

• Quantitative Modeling of CE Scenarios: Life Cycle Assessment (LCA), Material Flow Analysis (MFA), and Social Life Cycle Assessment (S-LCA) frameworks should be enhanced to capture long-term performance, economic trade-offs, and social outcomes of CE strategies.
• Circularity-Driven Design Optimization: Research should explore the co-optimization of modularity, recyclability, and performance in structural and non-structural elements. Material combinations and joint technologies that simplify future reuse and reprocessing must be rigorously tested.
• Circular Business Models in Construction: From leasing-based models for structural frames to digital product-service systems (PSS) for façade components, CE-aligned business innovations require testing for commercial scalability and consumer acceptance.
• Cross-Regional Policy Benchmarking: Comparative studies across developed and emerging markets can reveal effective regulatory mixes, institutional enablers, and cultural drivers for CE adoption.
• Integration of Bio-Based and Low-Impact Materials: Future work should investigate synergies between CE and the use of bio-composites, geopolymers, and other low-carbon alternatives to conventional Portland cement and virgin aggregates.
• Sustainability Index Development for CE Implementation: A comprehensive index combining environmental, economic, and social indicators is essential for benchmarking CE performance in construction. Data integration platforms powered by machine learning and AI may offer new ways to model complex sustainability trade-offs.

By addressing these research gaps and operational challenges in an integrated manner, the construction sector can become a front-runner in the global shift towards resource circularity, climate resilience, and sustainable urban development. The practical considerations outlined above are not merely supplementary—they are essential preconditions for translating CE ambitions into built environment realities.

7. Conclusions

This review provides a technically grounded and data-driven synthesis of Circular Economy (CE) integration in the construction sector, focusing on the incorporation of waste-derived materials—specifically glass powder; polyethylene terephthalate (PET); and crumb rubber—into cementitious composites. Across more than 100 empirical studies analyzed, substitution of conventional aggregates with recycled alternatives demonstrated promising structural and functional outcomes: compressive strength retention of 90–95% at optimal replacement ratios (10–25% by weight), tensile strength reductions under 15% when PET fibers were surface-treated, and flexural strength stability up to 20% PET or rubber dosage. Glass powder exhibited pozzolanic reactivity, contributing to improved compressive strength (up to +12%) and durability due to refined pore structure and secondary C-S-H formation. PET and rubber inclusions enhanced ductility and energy absorption capacity, supporting their use in dynamic load-bearing or thermally vulnerable applications. For instance, specimens containing 10–15% crumb rubber achieved a 20–30% drop in compressive strength but over 40% improvement in impact resistance and post-peak toughness, indicative of better fracture behavior. Thermal diffusivity reduction in rubber- and PET-modified mixes also aligns with enhanced fire resistance—confirmed by fire testing protocols where mass loss remained within 10% after 300 s of direct flame exposure.

Despite these advances, systemic barriers outlined in Section 6 continue to impede scalability. These include unclear classifications of secondary resources, thermodynamic inefficiencies in material recovery, and rebound effects that diminish long-term sustainability gains. Path dependencies in existing supply chains and lack of harmonized regulatory standards for recycled material characterization, particularly regarding chloride ion penetration, alkali-silica reactivity, and freeze–thaw durability, further challenge adoption. Addressing these requires embedding Design for Adaptability, Deconstruction, and Reuse (DfADR) in structural planning, implementing performance-based procurement guided by Life Cycle Assessment (LCA) and Material Flow Analysis (MFA), and leveraging digital tools such as Building Information Modeling (BIM) and Material Passports for traceability and residual value recovery. Policies must incentivize closed-loop design through Extended Producer Responsibility (EPR), green procurement benchmarks, and differential landfill levies.

This review also identifies key research priorities: quantifying multi-objective trade-offs using sustainability indices, validating composite behavior of bio-based and hybrid aggregates under accelerated durability tests, and establishing AI-powered predictive models for CE performance under varying geographic and climatic conditions. In sum, this study not only evaluates the mechanical and environmental performance of recycled materials in concrete but also positions CE as a system-level transition pathway. By merging material science data with implementation frameworks, regulatory insights, and future-oriented research agendas, it lays the groundwork for mainstreaming CE in construction. Doing so can enable a 30–50% reduction in embodied carbon, diversion of over 35% of construction and demolition (C&D) waste from landfills, and enhancement of lifecycle resilience—thereby advancing the construction sector toward a regenerative and resource-optimized future.