Performance Comparison of Recycled HDPE, PET, and LDPE in Construction Materials: A Systematic Review

Performance Comparison of Recycled HDPE, PET, and LDPE in Construction Materials: A Systematic Review | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Systematic Review Performance Comparison of Recycled HDPE, PET, and LDPE in Construction Materials: A Systematic Review Edward Remijus Lutego, Jacob Kihila, Minza Selele This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9091978/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This systematic review examines the use of three common recycled plastics, which are: high-density polyethylene (HDPE), polyethylene terephthalate (PET), and low-density polyethylene (LDPE), for the manufacturing of bricks and blocks, focusing on their mechanical and physical properties. The study addresses two major industry challenges: managing increasing plastic waste and developing sustainable alternatives to conventional building materials. Following PRISMA 2020 guidelines, a comprehensive search was conducted across five academic databases for peer-reviewed studies published between 2014 and 2025. After careful screening and quality assessment, 26 studies were included in the analysis, covering plastic type, replacement ratios, mechanical and physical properties, and manufacturing methods. The common manufacturing methods used are melt and bind, dry mixing, binder addition, aggregate substitution and small percent incorporation. The results show that HDPE consistently provides the highest compressive strength, often exceeding 20 MPa at optimal replacement of around 7.5% and 75:25 for the melt and bind method. Polyethylene terephthalate showed moderate strength but excellent flexural performance, with optimal ratios from 15% to 30%. Low-density polyethylene produced highly variable results, with peak compressive strength of 24.83 MPa at only 0.5% replacement, and reduced strength at higher levels. For all plastic types, density decreased by about 5% to 15%, such as from 1.67 to 1.58 grams per cubic centimetre in bricks containing polyethylene terephthalate. Water absorption trends were varying, such as polyethylene terephthalate often lowering absorption by up to 20%, while higher low-density polyethylene contents tended to increase it. Civil Engineering Environmental Engineering Thermoplastics (HDPE LDPE PET) Sustainable Building Materials Tensile strength Flexural Strength Compressive Strength Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction This systematic review aims to address the escalating plastic waste problem by systematically comparing the performance of the three most researched plastic waste types; high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polyethylene terephthalate (PET), to evaluate how plastic type selection, material application, and mixture design influence the performance of construction materials. Plastic waste has become one of the most pressing environmental challenges of the 21st century, where by globally the plastic production has reached about 400 million metric tons annually, but due to inadequate management systems, an estimated 8 to 10 million tons entering marine environments each year [ 1 ]. A single-use plastic accumulates in landfills and natural environments, where they persist for centuries, turning into microplastics that contaminate soil and water systems. Therefore, identifying alternative uses of plastic waste is essential for mitigating environmental pollution and supporting sustainable development goals. The construction industry is among the potential sectors for plastic waste utilisation because of its high material consumption, which replaces cement, whose manufacturing process contributes substantially to global carbon dioxide emissions. Due to that, researchers have continuously investigated the use of recycled plastic waste, particularly polyethylene-based plastics, as partial substitutes for cement or aggregates in construction materials such as bricks, blocks, and paving units [ 2 ], [ 3 ], [ 4 ]. This approach offers a dual benefit by diverting plastic waste from landfills and natural environments while reducing reliance on conventional construction materials. Different studies have demonstrated that plastic waste containing PET, HDPE, and LDPE can be mixed with sand or cementitious materials at varying ratios to produce lightweight construction materials with acceptable mechanical and physical properties [ 5 ]. Each plastic type possesses distinct physical and chemical characteristics that influence its performance in construction applications. HDPE is characterised by high density, good chemical resistance, and a melting point between 120°C and 180°C, with common sources including food containers and pipes [ 6 ]. PET exhibits high tensile strength, dimensional stability, and a higher melting point of approximately 250–260°C, making it one of the most widely recycled plastics globally [ 7 ]. LDPE, by contrast, has lower density and strength but greater flexibility, with a melting point between 105°C and 115°C, and is commonly derived from plastic bags and flexible packaging materials [ 8 ]. Differences in molecular structure, crystallinity, and thermal behaviour among these plastics significantly affect their interaction with sand or cement materials and their resulting physical and mechanical performance [ 9 ]. Despite many research activities done on this technology, critical knowledge gaps still exist that limit practical implementation. While previous reviews have examined plastic waste utilisation in construction, comprehensive analysis specifically comparing HDPE, PET, and LDPE effects on building materials remains limited, with most studies focusing on single plastic types or excluding systematic comparison [ 10 ]. Different plastic types, mix ratios, and manufacturing methods across studies, including heat compression moulding, melt-and-bind, extrusion processes, and conventional concrete mixing has generated widely varying findings regarding optimal patterns and performance outcomes. Thus, several critical questions remain unanswered on which plastic type provides optimal performance for specific applications, what substitution ratios effectively balance waste utilisation with structural integrity, and what manufacturing method influences better final product properties. This incomplete knowledge base creates substantial barriers towards creating an evidence-based guidance on plastic type selection, mixture design, processing methods and parameters, and quality assurance protocols necessary for commercial implementation. This systematic review addresses these critical gaps by synthesising and critically evaluating existing research on HDPE, PET, and LDPE incorporation in construction materials, specifically bricks, blocks, and paving materials published between 2014 and 2024. The review systematically evaluates which plastic types provide optimal mechanical and physical performance across different contexts, what replacement ratios effectively balance structural requirements with waste utilisation objectives, how manufacturing processes influence material properties and consistency, and what research gaps require future investigation. By providing comprehensive, evidence-based answers, this review supports researchers in identifying priority areas for investigation, guides material developers on plastic type selection and processing parameters, informs policymakers in developing standards and regulations, and helps stakeholders understand the potential scale of plastic waste diversion through construction applications. Ultimately, this review aims to accelerate the transition from fragmented research findings to clear knowledge that enables evidence-based decision-making and supports the development of commercially viable, environmentally beneficial building products that simultaneously address plastic waste accumulation and construction industry sustainability challenges. The Research question of this systematic review is dedicated to understanding “How do different types of plastic, specifically, high-density polyethylene (HDPE), polyethylene terephthalate (PET), and low-density polyethylene (LDPE) affect the mechanical and physical strength of construction materials?” such as compressive strength, tensile strength, flexural strength and water absorption. Analysing these differences and the underlying mechanisms provides the necessary empirical foundation for selecting the optimal plastic type and ratio. 2. Methodology 2.1 Review Design and Protocol Development This systematic review followed the PRISMA and Meta Analyses 2020 guidelines, which are widely used international guidelines that help make systematic reviews clear, transparent, and easy for others to follow and reproduce [ 11 ]. The review plan was first developed, it was set to clearly explain how the database search would be done, which studies would be included or excluded during screening, how information would be collected, and how the results from different studies would be combined. A comprehensive search strategy was developed and refined through several stages of testing, starting with exploratory searches to identify the most relevant keywords and subject terms. 2.2 Information Sources and Search Strategy This research searched five academic databases to gather as much relevant information as possible from different fields. Web of Science and Google Scholar were used as the main sources because they contain many resources and publications on plastic recycling to produce building materials. Scopus was used because it offers broad coverage and is regularly updated. The study also used two other sources, which are; reseach4life and EBSCOhost. A comprehensive search strategy was used across all databases, combining Boolean operators, controlled vocabulary, and natural language terms to capture relevant studies on recycled plastics in building materials. The search focused on three main concepts: plastic types (e.g., HDPE, PET, LDPE, plastic waste), building materials (e.g., bricks, blocks, concrete, construction materials), and material properties (e.g., strength, durability, mechanical properties). The format used include: AND operator: plastic types (HDPE OR “high density polyethylene” OR PET OR “polyethylene terephthalate” OR LDPE OR “low density polyethylene” OR “plastic waste” OR “recycled plastic”), building materials (bricks OR blocks OR “building materials” OR “construction materials” OR concrete OR masonry OR paving), and properties (strength OR “compressive strength” OR “mechanical properties” OR “physical properties” OR “tensile strength” OR “flexural strength” OR water absorption) [ 12 ]. The database search initially retrieved 181 articles, which were then imported into Zotero and Publish or Perish software to identify and remove duplicates. 2.3 Inclusion and Exclusion Criteria Studies were included if they investigated sand-plastic bricks or blocks using thermoplastic waste, focusing on HDPE, PET, or LDPE as the binding material, reported at least one measurable mechanical or physical property, and were experimental, comparative, or optimisation studies which was published in English between 2014 and 2025. Eligible studies compared plastic-containing materials with controls or other plastic types and provided quantitative data on mechanical strength, specifically compressive strength, tensile strength, and flexural strength, physical properties including density measured in grams per cubic centimetre or kilograms per cubic meter and water absorption measured in percentage [ 13 ]. Studies on plastic types other than HDPE, PET, and LDPE, including polypropylene, polystyrene, polyvinyl chloride, or mixed plastics of unspecified composition, was excluded unless these materials were studied in direct comparison with the three focal plastic types, also if they focused solely on plastics as aggregates, road construction applications, non-target plastics, or lacked quantitative data or clear methodology. Non-peer-reviewed reports, duplicates, inaccessible full texts, and non-English publications without translation were also excluded. 2.4 Screening procedure All 181 records identified were imported into Publish or Perish and Zotero for systematic deduplication and screening. Using the software’s automated algorithms, duplicates were detected based on titles, authors, publication years, and DOIs. Manual verification of automatically detected duplicates was performed to make sure only the duplicates are removed. Title and abstract screening were conducted to identify studies meeting the inclusion criteria. Key factors considered included the study materials type or interventions, outcomes, and study design, with priority given to studies reporting quantitative data. Records clearly not meeting the criteria were excluded, while those with uncertain relevance were retained for full-text review. 3. Results 3.1 Study Selection and Flow From the initial search, a total of 181 records were identified. After removing 36 duplicates, 145 unique records remained. Title screening excluded 27 papers, leaving 118 studies for further evaluation. Abstract screening of the remaining 118 studies led to the removal of 79 records due to non-target plastics, irrelevant applications, publications before 2014, or lack of quantitative data. The full-text assessment then examined 39 studies for methodological precision and quality assurance, leading to the exclusion of 9 reports that did not meet all criteria and 4 that lacked sufficient quantitative data. After this comprehensive screening, 26 studies met all inclusion and quality standards and were included in the detailed analysis, a search on Google Scholar returned 10 references, Web of Science 8 references, Scopus 4 references, Research4Life 3 references, and EBSCOhost 1 reference. 3.2 Characteristics of Included Studies 3.2.1 Geographic Distribution and Regional Research Patterns The 26 studies reviewed on the three plastic materials of HDPE, LDPE, and PET on building material performance reveal a geographically diverse set, which is thematically aligned with the purpose of the research. Asia accounts for the largest number with 13 papers, covering Southeast Asia, South Asia, and East Asia, including Malaysia, Indonesia, Thailand, India, Pakistan, Bangladesh, and China. Research from this region is predominantly experimental and application-oriented, focusing on compressive strength, density, water absorption, and durability of bricks, paving blocks, and interlocking blocks incorporating HDPE, LDPE, and PET. Africa contributes 7 papers, mainly from Nigeria, Ghana, Burkina Faso, and South Africa, with a strong emphasis on plastic-bonded sand bricks, interlocking blocks, and low-cost masonry units aimed at addressing housing shortages and plastic waste challenges. Latin America is represented by 3 papers, mostly from Brazil, focusing on PET-modified soil-cement bricks and pavers with attention to mechanical performance and practical applicability. The remaining 3 papers originate from Europe and other developed regions, consisting mainly of foundational reviews and methodological contributions on plastic recycling, polyethylene properties, and systematic review frameworks, which provide the theoretical and scientific basis for experimental studies elsewhere. Across all regions, PET is the most widely investigated plastic type, reflecting its global availability, while HDPE and LDPE studies are more regionally concentrated, shaped by local waste streams and processing practices. Overall, the literature indicates that developing regions dominate applied experimental research, targeting sustainable construction and material performance, whereas developed regions contribute critical conceptual, recycling, and methodological foundations that support the plastic waste management challenge. 3.2.2 Temporal Distribution and Research Evolution The temporal distribution of the 26 references indicates a clear and progressive evolution of research on plastic-modified building materials from foundational knowledge to applied engineering solutions. Early studies (2000–2006) are limited in number and largely theoretical, focusing on the fundamental properties of polyethylene and plastic recycling technologies [ 7 ], [ 8 ], [ 24 ], [ 25 ], providing the material-science and concrete-technology baseline. Between 2014 and 2016, research activity began to shift toward construction applications, with early experimental investigations and predictive models examining PET, HDPE, and LDPE as partial aggregate replacements in concrete and bricks [ 9 ], [ 23 ], [ 26 ]. From 2017 to 2019, a noticeable expansion occurred, marked by increased experimental validation and global contextualization of plastic waste issues, including performance testing of plastic-containing masonry units and global plastic flow assessments [ 1 ], [ 14 ], [ 17 ]. The period from 2020 to 2022 represents a consolidation phase, with a growing number of comparatives, durability-focused, and review studies evaluating different plastic types and mix proportions, often framed within sustainability and circular economy narratives [ 13 ], [ 27 ], [ 28 ]. The most recent phase (2023–2025) shows a mature and sophisticated research direction, characterised by advanced experimental designs, optimisation techniques, microstructural analysis, thermal performance assessment, and region-specific construction solutions such as interlocking blocks and lightweight systems [ 15 ], [ 18 ], [ 21 ], [ 29 ], [ 30 ]. Overall, the temporal trend reflects a transition from material characterisation to performance-driven, sustainability-oriented construction applications, with increasing methodological consistency and contextual relevance in recent years. 3.3 Plastic Types and Replacement Ratios 3.3.1 Distribution of Plastic Types Studied The analysis of the 26 included studies shows that polyethylene terephthalate (PET) is the most commonly investigated plastic, either individually or in combination with other plastics, appearing in 13 studies. This is due to its availability from beverage containers [ 7 ], used as fibres, shredded aggregates, or molten binders in concrete, bricks, paving blocks, and interlocking units. High-density polyethylene (HDPE) was examined in 7 studies, typically collected from water sachets, especially in West African cases, milk jugs, and detergent bottles [ 28 ], [ 31 ], used as a partial replacement for fine or coarse aggregates in cement-based materials, with research focusing on compressive strength, density variation, and water absorption characteristics, while low-density polyethylene (LDPE) appeared in 6 studies, usually sourced from plastic bags and flexible packaging [ 26 ], [ 32 ], mainly used in plastic-sand composites, lightweight bricks, and paving applications, taking advantage of its low melting temperature and binding capability Some investigations also used mixed plastics, including a blend of either PET, HDPE, and LDPE or combinations incorporating polypropylene, in about 8 studies, reflecting a variety of mixed waste streams and possible advantages from polymer blending [ 30 ], [ 33 ]. Different comparative studies evaluating performance between different plastic types provided particularly useful evidence for selecting a suitable plastic material for construction applications [ 19 ], [ 34 ]. 3.3.2 Material Ratio Ranges Some studies tried different amounts of plastic to see how it could affect the strength of a construction material. While other studies tried very large amounts to test how far plastic could be used as the main binder, especially in sand-plastic bricks. For high-density polyethylene the majority of studies concentrate in the 10% to 40% range for sand-plastic brick and as low as 2.5% by weight for partial cement substitution, where the balance between mechanical performance and waste utilisation becomes optimum [ 34 ], [ 35 ]. For polyethylene terephthalate, replacement ratios ranged from 3% by volume to 70% in PET-sand binder systems, with many studies focused on 10% to 30% for concrete applications and 40% to 60% for sand-plastic brick applications [ 22 ], [ 36 ]. For low-density polyethylene, replacement ratios ranged from very small additions of 0.5% by weight in cement-based systems to 60% by volume in pavement block applications [ 26 ], [ 32 ], and 30% to 50% for sand-plastic bricks [ 30 ], [ 33 ]. 3.3.3 Manufacturing Method Categories The most commonly used method is the melt and bind approach, which involves melting or softening thermoplastics and combining them with sand or other aggregates so that the plastic itself becomes the binder. This produces lightweight bricks and can incorporate relatively high plastic contents (around 25–75%), [ 31 ], [ 37 ], [ 38 ]. Second, the shredding and dry-mixing approach whereby plastic waste are grinded into flakes and mixed with cement using standard concrete equipment so the plastic replaces part of the aggregate [ 18 ], [ 34 ]. Third, the binder-addition approach, the method combines shredded plastic with additional polymer binders such as polyurethane to form composite bricks [ 39 ]. Fourth, the foundry-sand substitution approach, incorporating the shredded plastic with waste foundry sand, as a partial substitute for fine aggregate [ 14 ], [ 30 ], [ 33 ], [ 40 ]. The last is the small-percentage incorporation approach, which adds only 0.5 to 5 percent plastic into cementitious mixtures, where the plastic mainly acts as a filler rather than a replacement aggregate [ 22 ], [ 32 ], [ 37 ]. 3.4 Mechanical Properties 3.4.1 Compressive Strength pattern of different plastic materials High-density polyethylene (HDPE) shows good compressive strength, especially when the amount of plastic used is at an optimum level. Studies show that strength can be improved further by using construction additives. For example, one study found that a sand-HDPE mix attained very high strength when kaolin clay was added, whereby a sand to HDPE ratio of 75:25 produced baseline compressive strength of 21.4 MPa and 52.76 MPa with the addition of 5% kaolin clay, mainly because the clay improved bonding between the sand and plastic [ 25 ], [ 31 ]. Other researchers also found that small or moderate amounts of HDPE can sometimes increase strength compared with normal concrete or bricks, due to better particle packing and the filler effect [ 21 ], [ 34 ]. Even when higher HDPE percentages are used, strength generally decreases gradually rather than suddenly, which means HDPE can be used at optimum levels while still meeting desirable building strength requirements [ 6 ], [ 14 ], [ 19 ], [ 19 ], [ 40 ], where it can maintain a compressive strength of at least 13.8 MPa for the addition of up to 35% HDPE content [ 28 ]. Polyethylene terephthalate (PET) shows a wide variation of results. In many different sand-plastic or cement-plastic ratios, PET gives lower compressive strength than HDPE at the same percent of material used [ 15 ]. For example, interlocking PET-sand bricks show lower compressive strength with a 70:30 PET to sand ratio, achieving compressive strength of 7.86 MPa, lower than HDPE strength; however, showed a very good bending strength [ 36 ]. Some designs, such as sand-filled PET bottle bricks, achieved compressive strength similar to or even higher than normal concrete, where by it give a compressive strength ranging from 17.44 to 35 MPa [ 41 ]. Moderate PET replacement inside cement mixes can also increase strength in some cases, while very small additions in soil-based bricks reduce strength slightly but still remain acceptable for non-structural uses [ 22 ], [ 42 ]. According to [ 20 ], [ 43 ], [ 44 ] increasing PET content to a ratio of 72:25 resulted in improved compressive strength. Low-density polyethylene (LDPE) shows a broad range of results. In some mixes, a very small amount leads to the highest strength, but slightly higher amounts cause a large drop. This means LDPE is very sensitive to how much is added, example 0.5% LDPE by weight of sand produced a maximum compressive strength of 24.83 MPa, while 1.5% LDPE produced only 12.32 MPa, representing a 50% reduction [ 32 ]. When LDPE replaces sand at higher levels, studies show a steady fall in strength, example range from 10% to 60%, reporting compressive strengths ranging from 14.70 to 47.29 MPa [ 17 ], [ 26 ]. Overall, LDPE perform good for very small additions that are carefully controlled, or for construction products where lower strength is acceptable in exchange for other benefits such as lighter weight or lower cost [ 16 ], [ 23 ]. 3.4.2 Tensile and Flexural Strength Patterns Tensile and flexural properties are important because they determine how the recycled plastic materials respond to cracking, bending, and different failure modes [ 24 ]. From the studies, the results of the two properties obtained deviate from compressive results [ 13 ]. The analysis from different studies showed that incorporating plastics, especially PET or mixed plastic blends, can significantly improve tensile and flexural performance even when compressive strength does not increase. For example, PET-sand bricks have shown a higher flexural strength due to PET’s ability to bond microcracks and enhance ductility, while mixed plastic bricks have demonstrated higher tensile and flexural values than clay bricks despite having almost similar compressive strength [ 27 ], example, a 70:30 ratio achieved exceptional flexural strength of 21.94 MPa, [ 33 ], [ 36 ]. These results indicate a shift from brittle compression failure toward more ductile behaviour, which may offer advantages in applications exposed to seismic loads or impact conditions [ 9 ]. Some studies have also shown the improvements in cement-based systems at low replacement levels, they found that PET particles can enhance the bond at the microscale and improve crack control, leading to higher flexural strength in both plain and reinforced concrete mixes example; 10% PET granule replacement in concrete demonstrated positive impacts on flexural and cracking performance [ 18 ], [ 45 ]. The pattern has also been observed for HDPE when additives such as kaolin are used, leading to higher impact and shear resistance [ 31 ]. Overall, while compressive strength may decrease in some cases, tensile and flexural behaviours often remain stable or improve, suggesting that plastic incorporation could be advantageous in applications where bending, ductility and crack resistance are critical [ 46 ] 3.5 Physical Properties 3.5.1 Recycled Plastic Material Density Properties Incorporating plastics into construction materials consistently reduces the density of a construction material, with the extent of reduction being highly influenced by the type of plastic, replacement ratio, and composition. This is because plastic material has a lower specific gravity than building materials like sand (≈ 2.65 g/cm 3 ) and cement (≈ 3.15 g/cm 3 ). Whereby, LDPE (0.91–0.93 g/cm 3 ), HDPE (0.93–0.97 g/cm 3 ), and PET (1.38–1.40 g/cm 3 ) [ 24 ], [ 25 ]. Studies have quantified the density reduction effect, where Tamboura et al. reported that adding PET at 3–7% by volume in cement-stabilised laterite bricks reduced bulk density from 1.67 g/cm 3 to 1.58 g/cm 3 , representing a 5.4% reduction [ 22 ]. Mydin et al. found that 25% PET replacement in foamed mortar led to a 15% decrease in density, demonstrating substantial benefits for lightweight construction applications [ 29 ]. Similarly, increasing HDPE content in concrete lowered density, affecting both structural loading and thermal performance [ 35 ]. Nursyamsi et al. observed that 20% LDPE replacement produced lighter bricks compared to the original product [ 17 ]. These results indicate that recycled plastic materials are particularly good for lightweight construction, such as high-rise buildings, where reductions in dead load provide structural and economic advantages [ 13 ]. 3.5.2 Water Absorption Behaviour Water absorption in recycled plastic construction materials shows varying trends, which are influenced by plastic type, composition, interfacial bonding quality, porosity and the production method [ 13 ], [ 24 ]. For polyethylene terephthalate (PET), several studies report reduced water absorption with increasing plastic content. For example, Mydin et al. found that replacing 0–25% of foamed mortar with PET reduced water absorption by 20%, due to PET’s hydrophobic surface nature that blocks the connected pore networks [ 29 ]. Similarly, PET-sand bricks showed nearly negligible water absorption (0-0.35%), offering excellent moisture resistance [ 23 ], [ 46 ], [ 47 ]. Nnorom et al. reported that interlocking PET-sand bricks with a 3:1 sand-to-plastic ratio absorbed only 0.5% water, making it lower than other common masonry building materials [ 38 ]. The trend is different for low-density polyethylene (LDPE), which shows more variable results. Some studies report increased absorption with plastic addition due to poor interfacial bonding, while others find non-monotonic trends depending on formulation. Ohemeng et al. observed higher water absorption in concrete pavement blocks with increasing LDPE content, which is caused by interfacial voids that allowed water penetration [ 26 ]. Aryasatiani & Alfiah reported a non-linear pattern, with water absorption lowest to 4.65% at 1% LDPE but increasing to 6.45% at 2%, showing the complex relationship between packing density and bonding quality [ 32 ]. For HDPE, a small addition of a material shows good results on the performance of a recycled construction material, for example, using 1% of HDPE can significantly reduce water absorption [ 48 ]. By comparison, when different types of plastics are combined, the results are usually positive. Jajere, Nwufo and Subhani et al. showed that plastic-foundry sand bricks absorbed water at a rate lower than conventional clay bricks, due to hydrophobic plastic coating eliminating connected porosity [ 33 ], [ 37 ]. Rajan et al. reported water absorption below 7% for optimised plastic-sand paver blocks, meeting standard performance criteria [ 30 ]. Similarly, Yadav found 3.7% absorption for concrete pavers with 7.5% plastic replacement, indicating suitability for exterior applications [ 49 ]. Ali et al. found that bricks with HDPE show competitive moisture resistance characteristics, with absorbency influenced by voids [ 14 ]. Table 1 Water Absorption Trends for Different Plastic Materials Plastic Type Material / Application Plastic Content Water Absorption Reference PET Foamed mortar 0–25% replacement ↓ 20% [ 29 ] PET Sand bricks ---- 0-0.35% [ 46 ] PET Interlocking sand bricks 3:1 sand: plastic 0.5% [ 38 ] LDPE Concrete pavement blocks Increasing replacement ↑ [ 50 ] LDPE Concrete blocks 0.5-2% 4.65–6.45% [ 32 ] Mixed plastics Foundry sand bricks ---- ≈ 1/10 of clay bricks [ 33 ] Mixed plastics Paver blocks Optimized < 7% [ 30 ] Mixed plastics Concrete pavers 7.5% replacement 3.7% [ 49 ] 4. Discussion 4.1 HDPE exhibits superior mechanical performance Construction material made up of HDPE generally has the highest mechanical strength compared to PET or LDPE at similar mixing ratios. HDPE-based bricks and blocks maintain high compressive strength across moderate replacement levels, making them suitable for structural applications. The material also supports improved workability and durability without excessively increasing density, providing a reliable option for sustainable construction materials. Its consistent performance across different production methods and mix designs highlights its practical potential for wider adoption in construction projects. HDPE also performs very well when combined with other construction materials. Even small amounts of additives can significantly enhance bonding and increase compressive and flexural strength. This demonstrates HDPE’s versatility for producing stronger and more durable construction materials. HDPE-based construction materials are suitable for applications such as paving blocks, lightweight masonry, partition walls, and outdoor structures due to their high compressive strength, durability, and workability; however, they have limitations including lower fire resistance, potential thermal deformation at high temperatures, and variable long-term bonding with mineral aggregates, which require careful design and testing before structural use. 4.2 PET is strong in bending, has good insulation, and is widely available PET generally shows lower compressive strength than HDPE but offers advantages that make it suitable for non-structural construction applications. PET-based composites exhibit strong flexural performance and improved crack resistance, providing good bending capacity and dimensional stability. These properties make PET appropriate for interior partitions, façade panels, cladding systems, and other lightweight building elements. PET performs particularly well in plastic-sand composites at higher plastic contents, where its flexibility enhances material behavior. In cement-based mixes, lower PET replacement levels are more effective in maintaining adequate strength. The hydrophobic nature of PET improves moisture resistance, supporting durability in humid or wet environments. Its wide availability supports large-scale plastic waste utilisation. Overall, PET is best applied where bending resistance, insulation, and durability are prioritised over compressive strength. 4.3 LDPE most variable behaviour and a more limited use LDPE exhibits highly variable mechanical performance, with compressive strength strongly dependent on its dosage and processing conditions. Small LDPE additions can occasionally improve strength by filling voids and enhancing particle packing, but higher replacement levels typically lead to significant strength reductions. This sensitivity is mainly due to LDPE’s low density, softness, smooth surface texture, and weak bonding with cementitious and mineral materials. Its low melting temperature further influences performance, making processing conditions critical. As a result, LDPE strength outcomes vary widely across mixture designs and manufacturing methods. LDPE is most suitable at very low replacement levels under controlled production conditions. Alternatively, it can be applied in non-structural or low-load elements where compressive strength is not a primary design requirement. Overall, LDPE functions better as a secondary modifier rather than a structural material in construction applications. 5. Conclusion Findings from this review suggest that recycled plastics can be used effectively in construction materials only when they are carefully selected and designed to meet specific performance requirements, it also reveals that the effectiveness of recycled plastics in construction materials is determined mainly by plastic type, processing method, and mix design, rather than the amount of plastic used alone. Treating all plastic waste as the same material during production leads to inconsistent performance and unsafe use of plastic material; instead, material selection should be guided by performance needs such as load bearing and water resistance, production method, and availability of plastic waste materials. HDPE is the best choice when high compressive strength and consistent performance are required, especially for structural or load-bearing uses and when melt-and-bind processing is available. PET is more suitable when flexibility, bending resistance, and moisture resistance are important, making it ideal for lightweight, non-structural applications, particularly where bottle waste is readily available. LDPE is most suitable for simple, lightweight applications where performance demands are low. It is a practical choice when low processing temperatures for melt-and-bind processing and reduced costs are important, but it is limited to non-structural uses. To move this technology into practical use and beyond laboratory-scale experiments, future research needs to focus on standardisation and practical validation, which includes improving production methods to reduce product failures. Key priorities include understanding long-term durability of a material, evaluating fire performance, assessing environmental and economic impacts, and developing clear testing and design guidelines. 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Sustainability 15(24):16602. https://doi.org/10.3390/su152416602 Tamboura S, Sanou I, Ouedraogo M, Kam S, Messan A, Ouedraogo E (2023) Influence of waste PET on the properties of laterite-based compressed earth blocks stabilized with cement. Materials 16(8). https://doi.org/10.3390/ma16083140 Paschoalin Filho JA, Storopoli JH, Dias A (2016) Evaluation of compressive strength and water absorption of soil-cement bricks manufactured with addition of pet (polyethylene terephthalate) wastes. Acta Scientiarum Technol 38(2):163–171. https://doi.org/10.4025/ACTASCITECHNOL.V38I2.28458 Mehta PK, Monteiro PJM (2006) Concrete: Microstructure, properties, and materials, 3rd edn. McGraw-Hill Peacock AJ (2000) Handbook of polyethylene: Structures, properties, and applications. Marcel Dekker Ohemeng EA, Ekolu SO, Quainoo H (2014) Strength prediction model for concrete containing LDPE plastic waste as fine aggregate. J Sustainable Dev 7(5):169–179. https://doi.org/10.5539/jsd.v7n5p169 Aneke FI, Naghizadeh A (2022) Utilization of Plastic Waste Material in Masonry Bricks Production Towards Strength, Durability and Environmental Sustainability. J Sustainable Archit Civil Eng 30(1):228–241. https://doi.org/10.5755/j01.sace.30.1.29495 Sarwar W, Ghafor K, Qadir MG (2022) Utilization of plastic waste in concrete: A review. Journal of Cleaner Production , 380 . https://doi.org/10.1016/j.jclepro.2022.135042 Mydin MAO, Rozlan NA, Ganesan S, Sani NM (2025) Thermal and mechanical performance of lightweight foamed concrete integrated with polyethylene terephthalate (PET) fiber waste. J Adv Res Fluid Mech Therm Sci 93(1):16–28. https://doi.org/10.37934/arfmts.93.1.1628 Rajan M, Rajalinggam D, Narayanan K, Sivamani J (2025) Eco-friendly paver blocks: Repurposing plastic waste and foundry sand. Materia. https://doi.org/10.1590/1517-7076-rmat-2024-0707 Gounden T, Chetty M, Rorke D (2023) Development of sand-plastic composite bricks reinforced with kaolin clay. J Compos Sci 7(11). https://doi.org/10.3390/jcs7110467 Aryasatiani N, Alfiah N (2022) The effect of low-density polyethylene (LDPE) plastic waste on the compressive strength of paving blocks. Journal of Physics: Conference Series , 2193 (1). https://doi.org/10.1088/1742-6596/2193/1/012077 Subhani SM, Manipal S, Sekar SK, Chandrasekaran K (2024) Sustainable interlocking bricks from plastic waste and foundry sand: An experimental investigation. Materials Today: Proceedings , 92 , 1247–1253. https://doi.org/10.1016/j.matpr.2023.05.162 El-Metwally SE, El-Sayed TA, Abd-Elrahman SE (2023) Utilization of waste high-density polyethylene in concrete mixes. Journal of Building Engineering , 68 . https://doi.org/10.1016/j.jobe.2023.106083 Chusilp N (2022) Effect of recycled plastic content as fillers on mechanical and durability properties of concrete. Int J GEOMATE 22(92):146–153. https://doi.org/10.21660/2022.92.3154 Garbati AA, Imran MA, Chike CC, Nwaka EN, Akomah UC, Ogueri IJ, Olaremi SO, Ige AS, Marcellinus AC, Osasona CO (2024) Evaluating the Structural Integrity and Performance of Polyethylene Terephthalate and Low-Density Polyethylene-Based Interlocking Bricks for Sustainable Construction. Archives Adv Eng Sci, 1–12. https://ojs.bonviewpress.com/index.php/AAES/article/view/4198 Jajere FA, Nwufo BT (2024) Preparation and evaluation of physio-chemical properties of plastic wastes pavement blocks. J Chem Soc Nigeria 49(6):981–1000. https://www.ajol.info/index.php/jcsn/article/view/291263 Nnorom OO, Onuegbu GC, Nwanonenyi SC (2024) Physico-mechanical properties of sand-plastic interlocking paving brick. J Thermoplast Compos Mater 37(1):192–205. https://doi.org/10.1177/08927057231171525 Alaloul WS, Musarat MA, Rabbani MBA, Iqbal Q, Maqsoom A, Farooq W (2020) Construction sector contribution to economic stability: Malaysian GDP distribution. Sustainability 12(12). https://doi.org/10.3390/su12125146 Mg T (2025) HDPE plastic waste as a fine aggregate substitute in the production of CLC lightweight bricks: An experimental study. Teknisia 30(1):54–59. https://journal.uii.ac.id/teknisia/article/view/40509 Muyen Z, Hoque MN, Barna A (2016) Strength properties of plastic bottle bricks and their suitability as construction materials in Bangladesh. Progressive Agric 27(3):362–368. https://doi.org/10.3329/pa.v27i3.30852 Barreto EDS, Stafanato KV, Marvila MT, Azevedo ARG, Ali M, Pereira RML, Monteiro SN (2019) Clay ceramic waste as pozzolan constituent in cement for structural concrete. Materials 14(11). https://doi.org/10.3390/ma14112917 Maddodi BS, Lathashri UA, Devesh S, Gowrishankar MC (2022) Repurposing Plastic Wastes in Non-conventional Engineered Wood Building Bricks for Constructional Application – A Mechanical Characterization using Experimental and Statistical Analysis. Eng Sci 18:180–191. https://doi.org/10.30919/es8d696 Udhaya KT, Jayadurgalakshmi M (2025) Development of Light Weight Green Efficient Interlocking Blocks Using Waste Plastics and Industrial Wastes for Low Cost Housing Construction. Mater Sci Forum 1144:71–76. https://www.scientific.net/MSF.1144.71 Kangavar ME, Lokuge W, Manalo A, Karunasena W, Frigione M (2023) Investigation on the properties of concrete with recycled Polyethylene Terephthalate (PET) granules as fine aggregate replacement. Case Studies in Construction Materials , 18 . https://doi.org/10.1016/j.cscm.2022.e01790 Ashraf MA, Bhat AH, Rashid S (2024) Recycling of plastic waste into construction materials: A step towards sustainable development. Materials Today: Proceedings , 93 , 245–251. https://doi.org/10.1016/j.matpr.2023.07.298 Gupta A, Chandrakar V (2023) A Review Paper on Reuse of Plastic Waste as Pavement Construction Material. Int J Sci Technol Eng 11(2):1–6. https://doi.org/10.22214/ijraset.2023.49291 Nwankwo CO, Bamigboye GO, Davies IEE, Michaels TA (2023) High density polyethylene (HDPE) waste as aggregate in concrete production: A sustainable approach for construction and waste management. Heliyon 9(1). https://doi.org/10.1016/j.heliyon.2022.e12681 Yadav K (2024) Transforming waste into innovation: A review of plastic bricks. Emerg Mater Res / Springer. https://doi.org/10.1007/s44290-024-00040-8 Ohemeng EA, Ekolu SO, Quainoo H (2014) Strength prediction model for concrete containing LDPE plastic waste as fine aggregate. J Sustainable Dev 7(5):169–179. https://doi.org/10.5539/jsd.v7n5p169 Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9091978","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Systematic Review","associatedPublications":[],"authors":[{"id":604284055,"identity":"fbc37ca8-a1e2-4327-a3ff-653f4a610292","order_by":0,"name":"Edward Remijus 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Diagram\u003c/em\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9091978/v1/4bef95b8fa40e7f3ac21f626.png"},{"id":104492531,"identity":"ba40a9d1-6a83-41ff-9d7c-7ad756022c7e","added_by":"auto","created_at":"2026-03-12 11:57:24","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":14367,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eGeographic Distribution of Plastic- Based Building Material Studies (n=26)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9091978/v1/5caf9eb351e9dd5a5f269973.png"},{"id":104492520,"identity":"250ff43a-7414-4284-a1df-da867d54325d","added_by":"auto","created_at":"2026-03-12 11:57:20","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":60012,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eIllustrative compressive strength with increasing plastic content\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9091978/v1/b2f476eeeef25d64bc99d4fe.png"},{"id":104492530,"identity":"7a8f02b5-bca8-45e7-933f-5f28592d2c2a","added_by":"auto","created_at":"2026-03-12 11:57:23","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":80666,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eEffect of Plastic Type on Combined Tensile- Flexural Performance\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9091978/v1/2a392c6e2a2f53d176d61e9e.png"},{"id":104492571,"identity":"281ddc26-743f-48da-8493-9750d43f8a79","added_by":"auto","created_at":"2026-03-12 11:57:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1275568,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9091978/v1/73c3bc3b-2dae-4ee0-97ae-f7dc18b4d611.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003ePerformance Comparison of Recycled HDPE, PET, and LDPE in Construction Materials: A Systematic Review\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThis systematic review aims to address the escalating plastic waste problem by systematically comparing the performance of the three most researched plastic waste types; high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polyethylene terephthalate (PET), to evaluate how plastic type selection, material application, and mixture design influence the performance of construction materials. Plastic waste has become one of the most pressing environmental challenges of the 21st century, where by globally the plastic production has reached about 400\u0026nbsp;million metric tons annually, but due to inadequate management systems, an estimated 8 to 10\u0026nbsp;million tons entering marine environments each year [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. A single-use plastic accumulates in landfills and natural environments, where they persist for centuries, turning into microplastics that contaminate soil and water systems. Therefore, identifying alternative uses of plastic waste is essential for mitigating environmental pollution and supporting sustainable development goals.\u003c/p\u003e \u003cp\u003eThe construction industry is among the potential sectors for plastic waste utilisation because of its high material consumption, which replaces cement, whose manufacturing process contributes substantially to global carbon dioxide emissions. Due to that, researchers have continuously investigated the use of recycled plastic waste, particularly polyethylene-based plastics, as partial substitutes for cement or aggregates in construction materials such as bricks, blocks, and paving units [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. This approach offers a dual benefit by diverting plastic waste from landfills and natural environments while reducing reliance on conventional construction materials.\u003c/p\u003e \u003cp\u003eDifferent studies have demonstrated that plastic waste containing PET, HDPE, and LDPE can be mixed with sand or cementitious materials at varying ratios to produce lightweight construction materials with acceptable mechanical and physical properties [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Each plastic type possesses distinct physical and chemical characteristics that influence its performance in construction applications. HDPE is characterised by high density, good chemical resistance, and a melting point between 120\u0026deg;C and 180\u0026deg;C, with common sources including food containers and pipes [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. PET exhibits high tensile strength, dimensional stability, and a higher melting point of approximately 250\u0026ndash;260\u0026deg;C, making it one of the most widely recycled plastics globally [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. LDPE, by contrast, has lower density and strength but greater flexibility, with a melting point between 105\u0026deg;C and 115\u0026deg;C, and is commonly derived from plastic bags and flexible packaging materials [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Differences in molecular structure, crystallinity, and thermal behaviour among these plastics significantly affect their interaction with sand or cement materials and their resulting physical and mechanical performance [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDespite many research activities done on this technology, critical knowledge gaps still exist that limit practical implementation. While previous reviews have examined plastic waste utilisation in construction, comprehensive analysis specifically comparing HDPE, PET, and LDPE effects on building materials remains limited, with most studies focusing on single plastic types or excluding systematic comparison [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Different plastic types, mix ratios, and manufacturing methods across studies, including heat compression moulding, melt-and-bind, extrusion processes, and conventional concrete mixing has generated widely varying findings regarding optimal patterns and performance outcomes. Thus, several critical questions remain unanswered on which plastic type provides optimal performance for specific applications, what substitution ratios effectively balance waste utilisation with structural integrity, and what manufacturing method influences better final product properties. This incomplete knowledge base creates substantial barriers towards creating an evidence-based guidance on plastic type selection, mixture design, processing methods and parameters, and quality assurance protocols necessary for commercial implementation.\u003c/p\u003e \u003cp\u003eThis systematic review addresses these critical gaps by synthesising and critically evaluating existing research on HDPE, PET, and LDPE incorporation in construction materials, specifically bricks, blocks, and paving materials published between 2014 and 2024. The review systematically evaluates which plastic types provide optimal mechanical and physical performance across different contexts, what replacement ratios effectively balance structural requirements with waste utilisation objectives, how manufacturing processes influence material properties and consistency, and what research gaps require future investigation. By providing comprehensive, evidence-based answers, this review supports researchers in identifying priority areas for investigation, guides material developers on plastic type selection and processing parameters, informs policymakers in developing standards and regulations, and helps stakeholders understand the potential scale of plastic waste diversion through construction applications. Ultimately, this review aims to accelerate the transition from fragmented research findings to clear knowledge that enables evidence-based decision-making and supports the development of commercially viable, environmentally beneficial building products that simultaneously address plastic waste accumulation and construction industry sustainability challenges.\u003c/p\u003e \u003cp\u003eThe Research question of this systematic review is dedicated to understanding \u003cem\u003e\u0026ldquo;How do different types of plastic, specifically, high-density polyethylene (HDPE), polyethylene terephthalate (PET), and low-density polyethylene (LDPE) affect the mechanical and physical strength of construction materials?\u0026rdquo;\u003c/em\u003e such as compressive strength, tensile strength, flexural strength and water absorption. Analysing these differences and the underlying mechanisms provides the necessary empirical foundation for selecting the optimal plastic type and ratio.\u003c/p\u003e"},{"header":"2. Methodology","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Review Design and Protocol Development\u003c/h2\u003e \u003cp\u003eThis systematic review followed the PRISMA and Meta Analyses 2020 guidelines, which are widely used international guidelines that help make systematic reviews clear, transparent, and easy for others to follow and reproduce [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The review plan was first developed, it was set to clearly explain how the database search would be done, which studies would be included or excluded during screening, how information would be collected, and how the results from different studies would be combined. A comprehensive search strategy was developed and refined through several stages of testing, starting with exploratory searches to identify the most relevant keywords and subject terms.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Information Sources and Search Strategy\u003c/h2\u003e \u003cp\u003eThis research searched five academic databases to gather as much relevant information as possible from different fields. Web of Science and Google Scholar were used as the main sources because they contain many resources and publications on plastic recycling to produce building materials. Scopus was used because it offers broad coverage and is regularly updated. The study also used two other sources, which are; reseach4life and EBSCOhost.\u003c/p\u003e \u003cp\u003eA comprehensive search strategy was used across all databases, combining Boolean operators, controlled vocabulary, and natural language terms to capture relevant studies on recycled plastics in building materials. The search focused on three main concepts: plastic types (e.g., HDPE, PET, LDPE, plastic waste), building materials (e.g., bricks, blocks, concrete, construction materials), and material properties (e.g., strength, durability, mechanical properties). \u003cb\u003eThe format used include: AND operator: plastic types (HDPE OR \u0026ldquo;high density polyethylene\u0026rdquo; OR PET OR \u0026ldquo;polyethylene terephthalate\u0026rdquo; OR LDPE OR \u0026ldquo;low density polyethylene\u0026rdquo; OR \u0026ldquo;plastic waste\u0026rdquo; OR \u0026ldquo;recycled plastic\u0026rdquo;), building materials (bricks OR blocks OR \u0026ldquo;building materials\u0026rdquo; OR \u0026ldquo;construction materials\u0026rdquo; OR concrete OR masonry OR paving), and properties (strength OR \u0026ldquo;compressive strength\u0026rdquo; OR \u0026ldquo;mechanical properties\u0026rdquo; OR \u0026ldquo;physical properties\u0026rdquo; OR \u0026ldquo;tensile strength\u0026rdquo; OR \u0026ldquo;flexural strength\u0026rdquo; OR water absorption)\u003c/b\u003e [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The database search initially retrieved 181 articles, which were then imported into Zotero and Publish or Perish software to identify and remove duplicates.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Inclusion and Exclusion Criteria\u003c/h2\u003e \u003cp\u003eStudies were included if they investigated sand-plastic bricks or blocks using thermoplastic waste, focusing on HDPE, PET, or LDPE as the binding material, reported at least one measurable mechanical or physical property, and were experimental, comparative, or optimisation studies which was published in English between 2014 and 2025. Eligible studies compared plastic-containing materials with controls or other plastic types and provided quantitative data on mechanical strength, specifically compressive strength, tensile strength, and flexural strength, physical properties including density measured in grams per cubic centimetre or kilograms per cubic meter and water absorption measured in percentage [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eStudies on plastic types other than HDPE, PET, and LDPE, including polypropylene, polystyrene, polyvinyl chloride, or mixed plastics of unspecified composition, was excluded unless these materials were studied in direct comparison with the three focal plastic types, also if they focused solely on plastics as aggregates, road construction applications, non-target plastics, or lacked quantitative data or clear methodology. Non-peer-reviewed reports, duplicates, inaccessible full texts, and non-English publications without translation were also excluded.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Screening procedure\u003c/h2\u003e \u003cp\u003eAll 181 records identified were imported into Publish or Perish and Zotero for systematic deduplication and screening. Using the software\u0026rsquo;s automated algorithms, duplicates were detected based on titles, authors, publication years, and DOIs. Manual verification of automatically detected duplicates was performed to make sure only the duplicates are removed. Title and abstract screening were conducted to identify studies meeting the inclusion criteria. Key factors considered included the study materials type or interventions, outcomes, and study design, with priority given to studies reporting quantitative data. Records clearly not meeting the criteria were excluded, while those with uncertain relevance were retained for full-text review.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Study Selection and Flow\u003c/h2\u003e \u003cp\u003eFrom the initial search, a total of 181 records were identified. After removing 36 duplicates, 145 unique records remained. Title screening excluded 27 papers, leaving 118 studies for further evaluation. Abstract screening of the remaining 118 studies led to the removal of 79 records due to non-target plastics, irrelevant applications, publications before 2014, or lack of quantitative data.\u003c/p\u003e \u003cp\u003eThe full-text assessment then examined 39 studies for methodological precision and quality assurance, leading to the exclusion of 9 reports that did not meet all criteria and 4 that lacked sufficient quantitative data. After this comprehensive screening, 26 studies met all inclusion and quality standards and were included in the detailed analysis, a search on Google Scholar returned 10 references, Web of Science 8 references, Scopus 4 references, Research4Life 3 references, and EBSCOhost 1 reference.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Characteristics of Included Studies\u003c/h2\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 Geographic Distribution and Regional Research Patterns\u003c/h2\u003e \u003cp\u003eThe 26 studies reviewed on the three plastic materials of HDPE, LDPE, and PET on building material performance reveal a geographically diverse set, which is thematically aligned with the purpose of the research. Asia accounts for the largest number with 13 papers, covering Southeast Asia, South Asia, and East Asia, including Malaysia, Indonesia, Thailand, India, Pakistan, Bangladesh, and China. Research from this region is predominantly experimental and application-oriented, focusing on compressive strength, density, water absorption, and durability of bricks, paving blocks, and interlocking blocks incorporating HDPE, LDPE, and PET. Africa contributes 7 papers, mainly from Nigeria, Ghana, Burkina Faso, and South Africa, with a strong emphasis on plastic-bonded sand bricks, interlocking blocks, and low-cost masonry units aimed at addressing housing shortages and plastic waste challenges. Latin America is represented by 3 papers, mostly from Brazil, focusing on PET-modified soil-cement bricks and pavers with attention to mechanical performance and practical applicability. The remaining 3 papers originate from Europe and other developed regions, consisting mainly of foundational reviews and methodological contributions on plastic recycling, polyethylene properties, and systematic review frameworks, which provide the theoretical and scientific basis for experimental studies elsewhere. Across all regions, PET is the most widely investigated plastic type, reflecting its global availability, while HDPE and LDPE studies are more regionally concentrated, shaped by local waste streams and processing practices. Overall, the literature indicates that developing regions dominate applied experimental research, targeting sustainable construction and material performance, whereas developed regions contribute critical conceptual, recycling, and methodological foundations that support the plastic waste management challenge.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2 Temporal Distribution and Research Evolution\u003c/h2\u003e \u003cp\u003eThe temporal distribution of the 26 references indicates a clear and progressive evolution of research on plastic-modified building materials from foundational knowledge to applied engineering solutions. Early studies (2000\u0026ndash;2006) are limited in number and largely theoretical, focusing on the fundamental properties of polyethylene and plastic recycling technologies [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], providing the material-science and concrete-technology baseline. Between 2014 and 2016, research activity began to shift toward construction applications, with early experimental investigations and predictive models examining PET, HDPE, and LDPE as partial aggregate replacements in concrete and bricks [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. From 2017 to 2019, a noticeable expansion occurred, marked by increased experimental validation and global contextualization of plastic waste issues, including performance testing of plastic-containing masonry units and global plastic flow assessments [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The period from 2020 to 2022 represents a consolidation phase, with a growing number of comparatives, durability-focused, and review studies evaluating different plastic types and mix proportions, often framed within sustainability and circular economy narratives [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The most recent phase (2023\u0026ndash;2025) shows a mature and sophisticated research direction, characterised by advanced experimental designs, optimisation techniques, microstructural analysis, thermal performance assessment, and region-specific construction solutions such as interlocking blocks and lightweight systems [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Overall, the temporal trend reflects a transition from material characterisation to performance-driven, sustainability-oriented construction applications, with increasing methodological consistency and contextual relevance in recent years.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Plastic Types and Replacement Ratios\u003c/h2\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1 Distribution of Plastic Types Studied\u003c/h2\u003e \u003cp\u003eThe analysis of the 26 included studies shows that polyethylene terephthalate (PET) is the most commonly investigated plastic, either individually or in combination with other plastics, appearing in 13 studies. This is due to its availability from beverage containers [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], used as fibres, shredded aggregates, or molten binders in concrete, bricks, paving blocks, and interlocking units. High-density polyethylene (HDPE) was examined in 7 studies, typically collected from water sachets, especially in West African cases, milk jugs, and detergent bottles [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e], used as a partial replacement for fine or coarse aggregates in cement-based materials, with research focusing on compressive strength, density variation, and water absorption characteristics, while low-density polyethylene (LDPE) appeared in 6 studies, usually sourced from plastic bags and flexible packaging [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], mainly used in plastic-sand composites, lightweight bricks, and paving applications, taking advantage of its low melting temperature and binding capability\u003c/p\u003e \u003cp\u003eSome investigations also used mixed plastics, including a blend of either PET, HDPE, and LDPE or combinations incorporating polypropylene, in about 8 studies, reflecting a variety of mixed waste streams and possible advantages from polymer blending [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Different comparative studies evaluating performance between different plastic types provided particularly useful evidence for selecting a suitable plastic material for construction applications [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e3.3.2 Material Ratio Ranges\u003c/h2\u003e \u003cp\u003eSome studies tried different amounts of plastic to see how it could affect the strength of a construction material. While other studies tried very large amounts to test how far plastic could be used as the main binder, especially in sand-plastic bricks. For high-density polyethylene the majority of studies concentrate in the 10% to 40% range for sand-plastic brick and as low as 2.5% by weight for partial cement substitution, where the balance between mechanical performance and waste utilisation becomes optimum [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. For polyethylene terephthalate, replacement ratios ranged from 3% by volume to 70% in PET-sand binder systems, with many studies focused on 10% to 30% for concrete applications and 40% to 60% for sand-plastic brick applications [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. For low-density polyethylene, replacement ratios ranged from very small additions of 0.5% by weight in cement-based systems to 60% by volume in pavement block applications [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], and 30% to 50% for sand-plastic bricks [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.3.3 Manufacturing Method Categories\u003c/h2\u003e \u003cp\u003eThe most commonly used method is the melt and bind approach, which involves melting or softening thermoplastics and combining them with sand or other aggregates so that the plastic itself becomes the binder. This produces lightweight bricks and can incorporate relatively high plastic contents (around 25\u0026ndash;75%), [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e], [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Second, the shredding and dry-mixing approach whereby plastic waste are grinded into flakes and mixed with cement using standard concrete equipment so the plastic replaces part of the aggregate [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Third, the binder-addition approach, the method combines shredded plastic with additional polymer binders such as polyurethane to form composite bricks [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Fourth, the foundry-sand substitution approach, incorporating the shredded plastic with waste foundry sand, as a partial substitute for fine aggregate [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. The last is the small-percentage incorporation approach, which adds only 0.5 to 5 percent plastic into cementitious mixtures, where the plastic mainly acts as a filler rather than a replacement aggregate [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Mechanical Properties\u003c/h2\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e3.4.1 Compressive Strength pattern of different plastic materials\u003c/h2\u003e \u003cp\u003eHigh-density polyethylene (HDPE) shows good compressive strength, especially when the amount of plastic used is at an optimum level. Studies show that strength can be improved further by using construction additives. For example, one study found that a sand-HDPE mix attained very high strength when kaolin clay was added, whereby a sand to HDPE ratio of 75:25 produced baseline compressive strength of 21.4 MPa and 52.76 MPa with the addition of 5% kaolin clay, mainly because the clay improved bonding between the sand and plastic [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Other researchers also found that small or moderate amounts of HDPE can sometimes increase strength compared with normal concrete or bricks, due to better particle packing and the filler effect [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Even when higher HDPE percentages are used, strength generally decreases gradually rather than suddenly, which means HDPE can be used at optimum levels while still meeting desirable building strength requirements [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e], where it can maintain a compressive strength of at least 13.8 MPa for the addition of up to 35% HDPE content [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePolyethylene terephthalate (PET) shows a wide variation of results. In many different sand-plastic or cement-plastic ratios, PET gives lower compressive strength than HDPE at the same percent of material used [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. For example, interlocking PET-sand bricks show lower compressive strength with a 70:30 PET to sand ratio, achieving compressive strength of 7.86 MPa, lower than HDPE strength; however, showed a very good bending strength [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Some designs, such as sand-filled PET bottle bricks, achieved compressive strength similar to or even higher than normal concrete, where by it give a compressive strength ranging from 17.44 to 35 MPa [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Moderate PET replacement inside cement mixes can also increase strength in some cases, while very small additions in soil-based bricks reduce strength slightly but still remain acceptable for non-structural uses [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. According to [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e] increasing PET content to a ratio of 72:25 resulted in improved compressive strength.\u003c/p\u003e \u003cp\u003eLow-density polyethylene (LDPE) shows a broad range of results. In some mixes, a very small amount leads to the highest strength, but slightly higher amounts cause a large drop. This means LDPE is very sensitive to how much is added, example 0.5% LDPE by weight of sand produced a maximum compressive strength of 24.83 MPa, while 1.5% LDPE produced only 12.32 MPa, representing a 50% reduction [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. When LDPE replaces sand at higher levels, studies show a steady fall in strength, example range from 10% to 60%, reporting compressive strengths ranging from 14.70 to 47.29 MPa [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Overall, LDPE perform good for very small additions that are carefully controlled, or for construction products where lower strength is acceptable in exchange for other benefits such as lighter weight or lower cost [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e3.4.2 Tensile and Flexural Strength Patterns\u003c/h2\u003e \u003cp\u003eTensile and flexural properties are important because they determine how the recycled plastic materials respond to cracking, bending, and different failure modes [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. From the studies, the results of the two properties obtained deviate from compressive results [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The analysis from different studies showed that incorporating plastics, especially PET or mixed plastic blends, can significantly improve tensile and flexural performance even when compressive strength does not increase. For example, PET-sand bricks have shown a higher flexural strength due to PET\u0026rsquo;s ability to bond microcracks and enhance ductility, while mixed plastic bricks have demonstrated higher tensile and flexural values than clay bricks despite having almost similar compressive strength [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], example, a 70:30 ratio achieved exceptional flexural strength of 21.94 MPa, [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. These results indicate a shift from brittle compression failure toward more ductile behaviour, which may offer advantages in applications exposed to seismic loads or impact conditions [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSome studies have also shown the improvements in cement-based systems at low replacement levels, they found that PET particles can enhance the bond at the microscale and improve crack control, leading to higher flexural strength in both plain and reinforced concrete mixes example; 10% PET granule replacement in concrete demonstrated positive impacts on flexural and cracking performance [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. The pattern has also been observed for HDPE when additives such as kaolin are used, leading to higher impact and shear resistance [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Overall, while compressive strength may decrease in some cases, tensile and flexural behaviours often remain stable or improve, suggesting that plastic incorporation could be advantageous in applications where bending, ductility and crack resistance are critical [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Physical Properties\u003c/h2\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003e3.5.1 Recycled Plastic Material Density Properties\u003c/h2\u003e \u003cp\u003eIncorporating plastics into construction materials consistently reduces the density of a construction material, with the extent of reduction being highly influenced by the type of plastic, replacement ratio, and composition. This is because plastic material has a lower specific gravity than building materials like sand (\u0026asymp;\u0026thinsp;2.65 g/cm\u003csup\u003e3\u003c/sup\u003e) and cement (\u0026asymp;\u0026thinsp;3.15 g/cm\u003csup\u003e3\u003c/sup\u003e). Whereby, LDPE (0.91\u0026ndash;0.93 g/cm\u003csup\u003e3\u003c/sup\u003e), HDPE (0.93\u0026ndash;0.97 g/cm\u003csup\u003e3\u003c/sup\u003e), and PET (1.38\u0026ndash;1.40 g/cm\u003csup\u003e3\u003c/sup\u003e) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eStudies have quantified the density reduction effect, where Tamboura et al. reported that adding PET at 3\u0026ndash;7% by volume in cement-stabilised laterite bricks reduced bulk density from 1.67 g/cm\u003csup\u003e3\u003c/sup\u003e to 1.58 g/cm\u003csup\u003e3\u003c/sup\u003e, representing a 5.4% reduction [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Mydin et al. found that 25% PET replacement in foamed mortar led to a 15% decrease in density, demonstrating substantial benefits for lightweight construction applications [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Similarly, increasing HDPE content in concrete lowered density, affecting both structural loading and thermal performance [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Nursyamsi et al. observed that 20% LDPE replacement produced lighter bricks compared to the original product [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. These results indicate that recycled plastic materials are particularly good for lightweight construction, such as high-rise buildings, where reductions in dead load provide structural and economic advantages [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section3\"\u003e \u003ch2\u003e3.5.2 Water Absorption Behaviour\u003c/h2\u003e \u003cp\u003eWater absorption in recycled plastic construction materials shows varying trends, which are influenced by plastic type, composition, interfacial bonding quality, porosity and the production method [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. For polyethylene terephthalate (PET), several studies report reduced water absorption with increasing plastic content. For example, Mydin et al. found that replacing 0\u0026ndash;25% of foamed mortar with PET reduced water absorption by 20%, due to PET\u0026rsquo;s hydrophobic surface nature that blocks the connected pore networks [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Similarly, PET-sand bricks showed nearly negligible water absorption (0-0.35%), offering excellent moisture resistance [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e], [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. Nnorom et al. reported that interlocking PET-sand bricks with a 3:1 sand-to-plastic ratio absorbed only 0.5% water, making it lower than other common masonry building materials [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe trend is different for low-density polyethylene (LDPE), which shows more variable results. Some studies report increased absorption with plastic addition due to poor interfacial bonding, while others find non-monotonic trends depending on formulation. Ohemeng et al. observed higher water absorption in concrete pavement blocks with increasing LDPE content, which is caused by interfacial voids that allowed water penetration [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Aryasatiani \u0026amp; Alfiah reported a non-linear pattern, with water absorption lowest to 4.65% at 1% LDPE but increasing to 6.45% at 2%, showing the complex relationship between packing density and bonding quality [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFor HDPE, a small addition of a material shows good results on the performance of a recycled construction material, for example, using 1% of HDPE can significantly reduce water absorption [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. By comparison, when different types of plastics are combined, the results are usually positive. Jajere, Nwufo and Subhani et al. showed that plastic-foundry sand bricks absorbed water at a rate lower than conventional clay bricks, due to hydrophobic plastic coating eliminating connected porosity [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Rajan et al. reported water absorption below 7% for optimised plastic-sand paver blocks, meeting standard performance criteria [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Similarly, Yadav found 3.7% absorption for concrete pavers with 7.5% plastic replacement, indicating suitability for exterior applications [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Ali et al. found that bricks with HDPE show competitive moisture resistance characteristics, with absorbency influenced by voids [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eWater Absorption Trends for Different Plastic Materials\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlastic Type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMaterial / Application\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePlastic Content\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWater Absorption\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePET\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFoamed mortar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u0026ndash;25% replacement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026darr; 20%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePET\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSand bricks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e----\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0-0.35%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePET\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInterlocking sand bricks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3:1 sand: plastic\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLDPE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eConcrete pavement blocks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIncreasing replacement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026uarr;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLDPE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eConcrete blocks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.5-2%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.65\u0026ndash;6.45%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMixed plastics\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFoundry sand bricks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e----\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026asymp;\u0026thinsp;1/10 of clay bricks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMixed plastics\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePaver blocks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOptimized\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMixed plastics\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eConcrete pavers\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.5% replacement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e4.1 HDPE exhibits superior mechanical performance\u003c/h2\u003e \u003cp\u003eConstruction material made up of HDPE generally has the highest mechanical strength compared to PET or LDPE at similar mixing ratios. HDPE-based bricks and blocks maintain high compressive strength across moderate replacement levels, making them suitable for structural applications. The material also supports improved workability and durability without excessively increasing density, providing a reliable option for sustainable construction materials. Its consistent performance across different production methods and mix designs highlights its practical potential for wider adoption in construction projects. HDPE also performs very well when combined with other construction materials. Even small amounts of additives can significantly enhance bonding and increase compressive and flexural strength. This demonstrates HDPE\u0026rsquo;s versatility for producing stronger and more durable construction materials. HDPE-based construction materials are suitable for applications such as paving blocks, lightweight masonry, partition walls, and outdoor structures due to their high compressive strength, durability, and workability; however, they have limitations including lower fire resistance, potential thermal deformation at high temperatures, and variable long-term bonding with mineral aggregates, which require careful design and testing before structural use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e4.2 PET is strong in bending, has good insulation, and is widely available\u003c/h2\u003e \u003cp\u003ePET generally shows lower compressive strength than HDPE but offers advantages that make it suitable for non-structural construction applications. PET-based composites exhibit strong flexural performance and improved crack resistance, providing good bending capacity and dimensional stability. These properties make PET appropriate for interior partitions, fa\u0026ccedil;ade panels, cladding systems, and other lightweight building elements. PET performs particularly well in plastic-sand composites at higher plastic contents, where its flexibility enhances material behavior. In cement-based mixes, lower PET replacement levels are more effective in maintaining adequate strength. The hydrophobic nature of PET improves moisture resistance, supporting durability in humid or wet environments. Its wide availability supports large-scale plastic waste utilisation. Overall, PET is best applied where bending resistance, insulation, and durability are prioritised over compressive strength.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section2\"\u003e \u003ch2\u003e4.3 LDPE most variable behaviour and a more limited use\u003c/h2\u003e \u003cp\u003eLDPE exhibits highly variable mechanical performance, with compressive strength strongly dependent on its dosage and processing conditions. Small LDPE additions can occasionally improve strength by filling voids and enhancing particle packing, but higher replacement levels typically lead to significant strength reductions. This sensitivity is mainly due to LDPE\u0026rsquo;s low density, softness, smooth surface texture, and weak bonding with cementitious and mineral materials. Its low melting temperature further influences performance, making processing conditions critical. As a result, LDPE strength outcomes vary widely across mixture designs and manufacturing methods. LDPE is most suitable at very low replacement levels under controlled production conditions. Alternatively, it can be applied in non-structural or low-load elements where compressive strength is not a primary design requirement. Overall, LDPE functions better as a secondary modifier rather than a structural material in construction applications.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eFindings from this review suggest that recycled plastics can be used effectively in construction materials only when they are carefully selected and designed to meet specific performance requirements, it also reveals that the effectiveness of recycled plastics in construction materials is determined mainly by plastic type, processing method, and mix design, rather than the amount of plastic used alone. Treating all plastic waste as the same material during production leads to inconsistent performance and unsafe use of plastic material; instead, material selection should be guided by performance needs such as load bearing and water resistance, production method, and availability of plastic waste materials. HDPE is the best choice when high compressive strength and consistent performance are required, especially for structural or load-bearing uses and when melt-and-bind processing is available. PET is more suitable when flexibility, bending resistance, and moisture resistance are important, making it ideal for lightweight, non-structural applications, particularly where bottle waste is readily available. LDPE is most suitable for simple, lightweight applications where performance demands are low. It is a practical choice when low processing temperatures for melt-and-bind processing and reduced costs are important, but it is limited to non-structural uses.\u003c/p\u003e \u003cp\u003eTo move this technology into practical use and beyond laboratory-scale experiments, future research needs to focus on standardisation and practical validation, which includes improving production methods to reduce product failures. Key priorities include understanding long-term durability of a material, evaluating fire performance, assessing environmental and economic impacts, and developing clear testing and design guidelines. Closing these gaps will be essential for regulatory approval, consistent quality, and large-scale adoption.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGeyer R, Jambeck JR, Law KL (2017) Production, use, and fate of all plastics ever made. 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J Sustainable Dev 7(5):169\u0026ndash;179. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5539/jsd.v7n5p169\u003c/span\u003e\u003cspan address=\"10.5539/jsd.v7n5p169\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Ardhi University","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Thermoplastics (HDPE, LDPE, PET), Sustainable Building Materials, Tensile strength, Flexural Strength, Compressive Strength","lastPublishedDoi":"10.21203/rs.3.rs-9091978/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9091978/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis systematic review examines the use of three common recycled plastics, which are: high-density polyethylene (HDPE), polyethylene terephthalate (PET), and low-density polyethylene (LDPE), for the manufacturing of bricks and blocks, focusing on their mechanical and physical properties. The study addresses two major industry challenges: managing increasing plastic waste and developing sustainable alternatives to conventional building materials. Following PRISMA 2020 guidelines, a comprehensive search was conducted across five academic databases for peer-reviewed studies published between 2014 and 2025. After careful screening and quality assessment, 26 studies were included in the analysis, covering plastic type, replacement ratios, mechanical and physical properties, and manufacturing methods.\u003c/p\u003e \u003cp\u003eThe common manufacturing methods used are melt and bind, dry mixing, binder addition, aggregate substitution and small percent incorporation. The results show that HDPE consistently provides the highest compressive strength, often exceeding 20 MPa at optimal replacement of around 7.5% and 75:25 for the melt and bind method. Polyethylene terephthalate showed moderate strength but excellent flexural performance, with optimal ratios from 15% to 30%. Low-density polyethylene produced highly variable results, with peak compressive strength of 24.83 MPa at only 0.5% replacement, and reduced strength at higher levels. For all plastic types, density decreased by about 5% to 15%, such as from 1.67 to 1.58 grams per cubic centimetre in bricks containing polyethylene terephthalate. Water absorption trends were varying, such as polyethylene terephthalate often lowering absorption by up to 20%, while higher low-density polyethylene contents tended to increase it.\u003c/p\u003e","manuscriptTitle":"Performance Comparison of Recycled HDPE, PET, and LDPE in Construction Materials: A Systematic Review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-12 11:55:15","doi":"10.21203/rs.3.rs-9091978/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"31a0d2dd-6c28-45e1-a25c-193987c049ef","owner":[],"postedDate":"March 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":64302235,"name":"Civil Engineering"},{"id":64302236,"name":"Environmental Engineering"}],"tags":[],"updatedAt":"2026-03-12T11:55:19+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-12 11:55:15","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9091978","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9091978","identity":"rs-9091978","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}