The Microstructure and Thermochemical Evaluation Properties of Polypropylene-Modified Asphalt Concrete for Enhanced Performance

The Microstructure and Thermochemical Evaluation Properties of Polypropylene-Modified Asphalt Concrete for Enhanced Performance | 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 Research Article The Microstructure and Thermochemical Evaluation Properties of Polypropylene-Modified Asphalt Concrete for Enhanced Performance Charles Gbenga Williams, Chukwuka Stanley Ezemenike, Remilekun Ikumawoyi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6809139/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract In the road construction industry, efforts are being made to incorporate polypropylene with polymer properties into asphalt mixtures to improve the mechanical performance of the pavement layers and address the environmental demands caused by the significant accumulation of plastic waste. The impact of recycled polypropylene on the chemical, thermal, rheological, and microstructural characteristics of the specified asphalt mixture is the main emphasis of this study, which also identifies how each attribute enhances performance. The polypropylene and modified bitumen were characterised using thermogravimetric, dynamic shear rheometer, rotational viscosity, penetration, softening point, flash and fire point, ductility, water-in-bitumen, viscosity, x-ray diffraction, and x-ray fluorescence. The asphalt concrete was produced with varying proportions of polypropylene at 5%, 10%, 15%, and 20%, respectively. Moreover, the polypropylene-modified asphalt concrete was analysed to determine its microstructures. It has been observed that polypropylene enhances the physical, chemical, thermal, and rheological properties of bitumen. The Marshall stability result showed that the values obtained complied with Nigeria's general road and bridge specifications 1997 and Asphalt Institute 1997 standards. These results concluded that polypropylene could improve and strengthen flexible pavement and reduce environmental hazards. polypropylene plastic modified bitumen polypropylene-modified asphalt concrete (PMAC) rheology plastic pollution performance Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 1 Introduction The primary causes of road issues in developing countries like Nigeria, especially concerning asphalt concrete roads, are an interaction of low-quality materials for construction, substandard design principles, difficult environmental conditions, and inadequate maintenance. First, roads constructed using asphalt and aggregate materials of inferior quality are prone to cracking, ravelling, and other types of distress since these materials frequently fall short of international requirements. When procurement processes have been compromised or mismanaged and cost-cutting methods jeopardise the integrity of infrastructure, inferior materials are often used. In addition, many roads are constructed without considering the unique traffic loads and the prevailing weather conditions under which the road will operate. Because heavy vehicles consistently travel Nigerian highways, the designs are frequently unable to withstand the stress and pressure placed on them, leading to rapid deterioration, particularly in high-traffic locations. Moreover, Nigeria's weather, characterised by a lot of rain, makes asphalt pavements even more vulnerable. Inadequate drainage systems result in water buildup, which weakens the pavement's structure and creates surface defects like potholes. The unpredictable weather patterns in the nation add to these environmental concerns, making the situation even more unstable. Furthermore, one major problem is the absence of regular maintenance. Lack of proper planning for maintenance schedules and inadequate funding allocations cause many roads to fall into deterioration. As a result, little concerns like surface wear or tiny cracks are frequently disregarded until they become bigger difficulties that call for expensive repairs or a whole replacement. In addition to harming road safety, this disregard raises travel times and vehicle running expenses for drivers. Moreover, Nigeria's fast urbanization has raised traffic levels, which frequently overwhelm the country's already inadequate road infrastructure. The combined effect of these components results in an endless process of deterioration, whereby insufficient solutions to issues worsen the situation and make managing road networks even more challenging. One of the worst effects of these problems is the high frequency of traffic accidents, which frequently occur due to the bad road conditions. Unpredictable surface features, such as potholes and uneven surfaces, are prevalent for drivers and raise the possibility of collisions. These road issues have major economic ramifications that impact trade, transportation, and overall economic productivity. Road damage raises transportation costs for businesses, discouraging investment and slowing economic growth. Considering these challenges, Asphalt concrete's exceptional binding characteristics, flexibility, and durability can greatly improve the performance of flexible pavements. Aggregates and asphalt binders work together to provide a durable surface that evenly distributes traffic loads and lowers the risk of structural problems like cracking and rutting. Compared to rigid pavements, asphalt concrete is less likely to experience thermal cracking because of its flexibility, which enables it to adjust to changing temperatures and stresses. Furthermore, the waterproofing properties of the binder aid in preventing moisture intrusion, which might erode the pavement's structural integrity. The resistance of the material to ageing and deformation can be further increased by adding additives, such as fibres or polymers, which will increase its overall lifespan. Furthermore, resurfacing is a simple way to renew asphalt concrete, extending its lifespan without requiring total replacement. Asphalt concrete is a great option for flexible pavements because of its elasticity and capacity to provide a smooth, skid-resistant surface, which enhances road infrastructure safety, comfort, and affordability. All things considered, the use of asphalt concrete helps to create flexible pavements that are more durable and sustainable and are better equipped to endure the demands of contemporary traffic and environmental conditions. Over the last few years, the enhanced mechanical and thermal qualities of polypropylene-modified asphalt concrete (PMAC) have become more widely acknowledged, indicating that it is a viable material for use in pavement applications. According to [ 1 ], Nigeria is positioned ninth globally in terms of plastic pollution, generating approximately 2.5 million tons of plastic waste annually, with fewer than 12% of these materials being recycled. The right disposal techniques are a major challenge to most countries, as the two most common methods (landfill and incinerator) are not eco-friendly in the long run [ 2 ]. Incorporating polypropylene waste plastic to modify asphaltic concrete for improved engineering properties/performance of flexible pavement could be a better technique for handling this industrial waste in our environment. Consequently, the cost of overall construction is reduced. Polypropylene fibres are incorporated into the asphalt matrix to create PMAC's microstructure, which is essential to enhancing the material's overall performance. A review of the literature has revealed that: adding polypropylene improves aggregate dispersion and results in a combination that is more homogeneous [ 3 ]; Kumar and Ghosh [ 4 ] noted that, this enhanced dispersion results in increased tensile strength and decreased susceptibility to breaking under heat stress; the load-bearing capacity of the pavement is improved by the efficient interaction of polypropylene fibres with the asphalt binder, which creates a network-like structure [ 5 ]; adding polypropylene has been associated with a rise in the viscosity of the asphalt, which enhances its ability to withstand rutting and deformation from strong traffic loads [ 6 ]. All things considered, polypropylene-induced microstructural changes result in asphalt concrete that is tougher and long-lasting. PMAC's outstanding thermal stability is shown by thermal characterisation, which makes it especially appropriate for areas with wide temperature swings. Polypropylene alters the thermal transition behaviours of asphalt, increasing its resilience to high temperatures and softening point, according to differential scanning calorimetry (DSC) studies [ 7 ]. This feature reduces the possibility of long-term deformation, like rutting, in hot weather [ 8 ]. PMAC was also observed to have better viscoelastic qualities, which are essential for sustaining performance under a range of stress circumstances, according to dynamic mechanical analysis (DMA) [ 9 ]. Based on the literature, polypropylene helps to improve the durability and serviceability of asphalt mixtures by lowering their heat susceptibility [ 10 ]. In regions where asphalt can become brittle in the winter and unduly soft in the summer, the thermal stability provided by polypropylene modification is particularly advantageous [ 5 , 11 ]. Overall, adding polypropylene to asphalt concrete improves both its heat resilience and microstructural integrity, making it a feasible alternative for contemporary pavement engineering [ 3 , 6 , 8 ]. By strengthening their mechanical characteristics and thermal stability, PMAC ‘s microstructure and thermal characterization greatly improve flexible pavement performance. As reported by [ 3 , 4 ], the addition of polypropylene fibres to the asphalt matrix promotes a more even dispersion of aggregates, which increases tensile strength and improves crack resistance under heat stress. Particularly in situations of high traffic, this fibrous network enhances load distribution and lowers the possibility of rutting and permanent deformation [ 5 , 6 ]. The result of a thermal investigation carried out using differential scanning calorimetry (DSC) revealed PMAC to have higher softening points, which is important for reducing the effects of high temperatures [ 7 , 8 ]. Moreover, enhanced viscoelastic characteristics are indicated by dynamic mechanical analysis (DMA), enabling the asphalt to endure temperature swings and dynamic loading more effectively [ 9 , 10 ]. The microstructural alterations in PMAC promote enhanced adhesion between the asphalt binder and aggregates, improving durability and resistance to moisture damage [ 5 , 6 ]. PMAC offers a novel approach to contemporary pavement engineering, maximising performance under various environmental circumstances and traffic volumes [ 8 , 9 ]. All things considered, the addition of polypropylene fibres to asphalt mixes has advanced the creation of flexible pavements by improving their resilience and structural integrity [ 4 , 7 , 10 ]. In this study, the polypropylene-based waste chairs were evaluated to determine the microstructural, rheological and thermal properties to enhance the performance of asphalt concrete pavement. 2 Methodology 2.1 Materials In this study, bitumen, aggregates, and discarded polypropylene plastic chairs were used as research materials. Aggregates and 60/70 penetration grade bitumen were purchased from KK Hassan Nigeria Limited in Akure, Nigeria. Waste polypropylene plastic chairs were obtained from Elizade University, Ilara-Mokin and the surrounding area of Akure City. 2.2 Methods The aggregates utilised were sun-dried before being subjected to a series of tests using the relevant ASTM procedures to ascertain their physical characteristics. These tests include the moisture content [ 12 ], aggregate sieve analysis [ 13 ], aggregate impact test [ 14 ], aggregate crushing values [ 15 ], specific gravity [ 16 ], flakiness, and elongation index tests [ 17 , 18 ], thermogravimetric analysis (TGA) [ 19 ], X-ray diffraction [ 20 ], and X-ray fluorescence test [ 21 ] were used to ascertain the chemical characteristics of polypropylene plastic. The shredded white polypropylene plastic chairs (Fig. 1 ) were pulverised to produce the polypropylene plastic powder that could pass through a 0.015 µmm filter (Fig. 2). The modified bitumen was prepared by partially replacing bitumen with 5%, 10%, 15%, and 20% powdered polypropylene plastic. The modified bitumen was thoroughly blended. To ascertain the physical and rheological properties of the bitumen and modified bitumen, the samples were subjected to penetration test [ 22 ], softening point test [ 23 ], flash and fire point test [ 24 ], ductility [ 25 ], viscosity [ 26 ], water in bitumen [ 27 ], dynamic shear rheometer [ 28 ], and rotational viscosity [ 29 ]. The mixture of modified bitumen and aggregates produced cylindrical samples of asphalt concrete; Marshal Stability and Flow tests [ 30 ] were conducted on the asphalt concrete and the modified asphalt concrete produced. The cracked surfaces of modified asphalt concrete were examined using a scanning electron microscope SEM [ 31 ] to assess the microstructural characteristics of the material. 3 Results and Discussions 3.1 Sieve Analysis The sieve analysis results of the aggregates, when compared to the design envelope for hot asphalt mix (Fig. 3 ), indicated that the aggregate used meets both the upper and lower specification limits, confirming its appropriateness for asphalt concrete production. 3.2 Physical Properties of Aggregates The results from the different physical characteristics of the aggregates analysed in this research are presented in Table 1 . The results indicate that the aggregates conform to the quality standards for aggregates as defined by FMWHM, 2013. 3.3 Characterisation of Bitumen and Modified Bitumen The results of penetration tests, softening point, flash and fire point, viscosity, water in bitumen, and ductility are used to ascertain the physical characteristics of bitumen and polypropylene-modified bitumen Table 1 Summary of physical properties of Aggregates S/N Test Obtained value Specification as per FMWHM, 2013. 1 Moisture Content 0.75% Max 5% 2 Aggregate Impact Value 23.80% 20–30% 3 Aggregate Crushing Value 33.18% 27–35% 4 Specific gravity 3.0g - 5 Flakiness and Elongation Index Test 25.64% Max 35% 3.3.1 Penetration for Bitumen and Polypropylene-Modified Bitumen The results of penetration tests conducted on bitumen and bitumen modified with different percentages of polypropylene by weight of bitumen are presented in Fig. 4 . The results indicated that the penetration grade steadily decreased with increased polypropylene content in the bitumen. The penetration trend decreases in order of their viscosity. This suggests that the polypropylene addition hardens and standardises the modified bitumen, which is beneficial in that it might increase the mix's resistance to rutting; however, it might also reduce the bitumen's flexibility by making the asphalt much stiffer, which could positively impact the resistance to fatigue cracking. 3.3.2 Softening Point for Bitumen and Polypropylene Modified Bitumen Figure 5 presents the results of the ring and ball softening point test, which identifies the temperature at which asphalt reaches a particular level of softness. The results indicate that the softening point values for modified bitumen at 5, 10, 15, and 20% polypropylene contents are 48, 52, 56, and 66°C, respectively. These results clearly illustrate that the softening point value rises in correlation with the amount of polypropylene. This observation implies that the binder exhibits greater heat resistance, thus diminishing its tendency to soften in elevated temperatures. Consequently, the adverse impacts of temperature on bituminous materials will be lessened with the addition of polypropylene. The rise in the softening point also suggests a reduction in bleeding during the summer, which will enhance vehicle traction and reduce the slippery conditions in wet weather. 3.3.3 Flash and Fire Point As illustrated in Fig. 6 , the outcome of the flash and fire point test establishes the safe temperature at which bitumen can be heated in the presence of an open flame before it ignites. The fire point and flash values increased proportionately to the amount of polypropylene added to the bitumen. By adding 5% of the bitumen's weight in polypropylene, the bitumen's flash point increased from 207°C to 216°C. When the bitumen's polypropylene content was raised from 10–20%, a similar increase was seen, with the greatest value being attained at 20%, or 247°C. The modified bitumen's fire point results grow from 5–20%, reaching its maximum value of 285°C at 20%. Waste plastic ignites at high temperatures, which explains why the modified bitumen has a higher flash and fire point. This suggests that adding polypropylene to bituminous materials will probably reduce the material's associated fire risk and regulate its safety. 3.3.4 Ductility The unmodified bitumen has a ductility value of 97cm (Fig. 7 ) which decreases as the polypropylene content in the bitumen increases. According to the American Standard for testing material, the maximum ductility value for bitumen should not exceed 100cm. The results obtained revealed a lower value for modified bitumen. As may be observed, polypropylene maintains its ductility value of less than 100cm. The outcomes demonstrate a significant reliance on the polymer's chemical makeup and base bitumen polymer compatibility. 3.3.5 Viscosity The Viscosity test results determined how long it takes the modified samples to flow at a given temperature between the tube timing markers. The amount of polypropylene in the bitumen increases, so does its viscosity (Fig. 8 ). It was found that the value achieved was more than the standard value. The viscosity increases from 135.50 seconds for 5% polypropylene content to 159.95 seconds at 20%. Up to a 20% polypropylene content, there was an increasing trend in the viscosity of bitumen containing polypropylene. This increase indicates that bituminous materials made with polypropylene will adhere to the aggregates when utilized in asphalt preparation. 3.3.6 Water in Bitumen (Dean and Stark Method) Figure 9 illustrates the level of water in bitumen and polypropylene-modified bitumen as a result of the water-in-bitumen test. The percentages of water content obtained in bitumen and polypropylene-modified bitumen as presented in Fig. 9 complied with the required specification (Table 2 ). The percentages of water content in all the samples tested are significantly lower than the 5% ASTM D95-20 acceptable limit. Compared with conventional bitumen, bitumen made from polypropylene has the lowest moisture content. According to ASTM-D95-20, the physical characteristics of bitumen and bitumen modified with polypropylene that were examined in this satisfied the standard limit (Table 2 ). 3.4 Rheological Properties of Bitumen and Modified Bitumen The dynamic shear rheometer test results and rotational viscosity were utilised to ascertain the rheological characteristics of bitumen and modified bitumen: Table 2 Standard Specification of Bitumen Properties Test Unit Limit Test Method (ASTM) Penetration @25 \(\:\varvec{℃}\) Dmm 60–70 D5/D5M-19 Softening Point O C 49–56 D36-19 Ductility @ 25 \(\:\varvec{℃}\) cm 100Min D113-19 Flash Point O C 280 Min D92-20 Fire Point O C 320 Max D92-20 Viscosity cSt 300Min D2171-20 Water in Bitumen % 5 Max D95-20 3.4.1 Dynamic Shear Rheometer Using a dynamic shear rheometer (DSR), the viscoelastic behaviour of asphalt binders was investigated at 60 ºC, 70 ºC, 80 ºC, and 90 ºC. The test results are displayed in Figs. 10 and 11 , which show the complex modulus and phase angle, respectively, against various binder temperatures. The best values of complex modulus obtained at 0% (452.9) Kpa; 5% (441.8) Kpa; 10% (435.8) Kpa, 15% (415) Kpa, 20% (408) Kpa and the values of phase angle at 0% (75) δ, 5% (72.5) δ, 10% (70) δ, 15% (60.4) δ, 20% (52.6) δ. As the temperature increased, all samples exhibited a decrease in complex modulus values and an increase in phase angle, as revealed in Figs. 10 and 11 , respectively. Higher complex shear moduli are needed to guarantee bituminous pavement's continued strong resistance to deformation at elevated temperatures. Greater complex shear modulus is advantageous since it reduces asphalt deformation and rutting issues. Asphalt binder with a lower phase angle is more elastic than viscosity and will return to its initial state without releasing energy. A lower phase angle is preferable at higher temperatures because it decreases irreversible deformation. 3.4.2 Rotational Viscosity Adding Polypropylene significantly changed the asphalt's rotational viscosity (RV). The RV of the asphalt increased quickly when the polypropylene content was added. The results of the laboratory tests show that the RV values of polypropylene at 135 o C and 165 o C are high and low respectively (Fig. 12 ), because polypropylene reduces the molecular weight of the modified asphalt binder when a higher temperature is applied. High-stiff asphalt binders are ideal for preventing rutting, however, to prevent cracking, the rotational viscosity shouldn't go over a certain threshold (3000 MPa). 3.5 Chemical and Mineralogical Properties Polypropylene To examine the mineralogical characteristics of polypropylene plastic, X-ray fluorescence (XRF), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) tests were used. The XRD diffractogram correlates with that of a structure that is semi-crystalline or partially crystalline (Fig. 13 ). Based on elemental composition data from XRF analysis, it has been determined that the major constituents of polypropylene are carbon and hydrogen. Polypropylene syndiotactic (C 3 H 6 ) n and polypropylene isotactic (C 3 H 6 ) n are the patterns that were identified. Figure 14 depicts the thermal degradation of polypropylene at 480°C, which resulted in a total weight loss of 18.75%. A second thermal degradation with 1.2% of inert residue occurs at 700°C. This could be caused by the bonding phases, morphology, and composition of the constituent polypropylene in the material composite. 3.6 Marshal Stability Result of Polypropylene Modified Asphalt Figure 15 displays the variation of the stability values. When polypropylene was added in percentages, it was seen to increase initially before declining at 7.0 bitumen content. This could be explained by increased internal friction and binder cohesiveness, which improve the strength and functionality of asphalt concrete [ 32 ]. The ideal stability of 10.50 KN, 12.40 KN, 12.20 KN, and 15.80 KN was attained for polypropylene contents of 5%, 10%, 15%, and 20%. Additionally, the result suggested that the percentage for light, medium, and high traffic falls within the minimal value stated in Table 3 . The Asphalt Institute Criteria for the Marshall Mixture Design Method, 1997 specification was satisfied by Marshall stability values, as may be concluded from the results Table 3 Asphalt Institute Criteria for the Marshall Mixture Design Method, 1997 Mix Specification Heavy traffic (greater than 10 6 ESAL) Light traffic (less than 10 4 ESAL) Medium traffic (10 4 -10 6 ESAL) Min Max Min Max Min Max Stability (Minimum) 6672N - 2224N - 3336 - Flow (0.25mm) 8 16 8 20 18 - Air Void (%) 3 5 3 5 3 5 Compaction (50 blows each side of specimen) 35 50 - 75 Note : ESAL is the Equivalent Single Axle Load. Source: Asphalt Institute 3.7 SEM/EDS Analysis of Polypropylene Modified Asphalt Concrete Figures 16 and 17 show the SEM images of the polypropylene-modified asphalt and the unmodified asphalt, respectively. A higher porosity is noted in the unmodified asphalt concrete (Fig. 17 ) compared to the sample with polypropylene content. Furthermore, polypropylene-modified asphalt exhibits agglomeration of the polypropylene particles in the asphalt, unlike Fig. 17 with zero polypropylene content. Surface tension and the presence of contaminants in the polypropylene particles could be the cause. According to the Energy Dispersive Spectroscopy (EDS) analysis, the principal elements found are O 2 , Al, and Ca, utilised as components of the Ziegler-Natta catalyst for polypropylene synthesis. Both Al(OH) 3 and fire-retardant Mg (OH) 2 may contain magnesium. TiO 2 contains titanium, which can be used as a pigment. Si most likely originates from catalytic constituents or soil contaminants. The catalyst for the Olefin polymerization reaction or a component of PVC called Cl. 4 Conclusion This study primarily focused on assessing the influence of recycled polypropylene on the chemical, thermal, rheological, and microstructural properties of a specified asphalt mixture, highlighting the contributions of each attribute to performance enhancement. Experimental results demonstrated that the addition of polypropylene significantly improved the physical, chemical, thermal, and rheological properties of bitumen. The Marshall stability tests confirmed compliance with the 1997 Nigerian General Specification for Roads and Bridges and the Asphalt Institute standards. Furthermore, the microstructural analysis revealed that polypropylene-modified asphalt exhibits homogeneous behaviour. These findings suggest that incorporating polypropylene enhances the performance and durability of flexible pavements while offering a sustainable approach to mitigating plastic pollution, addressing a critical global environmental challenge. Declarations Authors Contributions Charles Gbenga wrote the main manuscript and prepared and organised all figures and tables. Chukwuka Stanley developed the conceptualisation and methodology. Remilekun Ikumawoyi, Charles Gbenga, and Chukwuka Stanley reviewed the manuscript collaboratively. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Research involving human and animal participants. This article does not contain any studies involving animals human participants performed by any of the authors. Funding Statement: No funding was received for conducting this study. Conflict of Interest: The authors have no conflicts of interest to declare that are relevant to the content of this article. Acknowledgement The Authors acknowledge Professor Oyedepo's support throughout the research process. His expertise and insights were invaluable in shaping our research and helping us overcome challenges. References Yalwaji, B., H. O. John-Nwagwu, & T. O. Sogbanmu. (2022). Plastic pollution in the environment in Nigeria: A rapid systematic review of the sources, distribution, research gaps and policy needs. Scientific African , 16 , e01220. Ezemenike, C., O. Oyedepo, and O. Aderinlewo, I. Oladele & O. Olukanni. 2022. Rheological characterization of industrial waste modified bitumen. Journal of Engineering Sciences , (3), 126-135. Zhang, Y., X. Wang, and J. Liu. 2020. Effect of polypropylene fibres on the performance of asphalt mixtures. Journal of Materials in Civil Engineering , 32(6), 04020139. Kumar, A. and A. Ghosh. 2019. Mechanical properties of polypropylene-modified asphalt concrete. Construction and Building Materials , 207, 180-189. Li, S., Y. Wang & R. Zhang. 2021. 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Department of Civil Engineering, Ahmadu Bello University, Zaria, Nigeria. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 17 Jul, 2025 Reviews received at journal 16 Jul, 2025 Reviewers agreed at journal 13 Jul, 2025 Reviewers agreed at journal 07 Jul, 2025 Reviews received at journal 28 Jun, 2025 Reviewers agreed at journal 22 Jun, 2025 Reviewers invited by journal 12 Jun, 2025 Editor assigned by journal 11 Jun, 2025 Editor invited by journal 11 Jun, 2025 Submission checks completed at journal 10 Jun, 2025 First submitted to journal 10 Jun, 2025 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. 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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-6809139","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":470141076,"identity":"269df3aa-ac8b-4840-a513-22ba35f1e0df","order_by":0,"name":"Charles Gbenga Williams","email":"data:image/png;base64,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","orcid":"","institution":"Elizade University","correspondingAuthor":true,"prefix":"","firstName":"Charles","middleName":"Gbenga","lastName":"Williams","suffix":""},{"id":470141078,"identity":"859dfff0-0688-4be1-b46d-35570730b8a4","order_by":1,"name":"Chukwuka Stanley Ezemenike","email":"","orcid":"","institution":"Elizade University","correspondingAuthor":false,"prefix":"","firstName":"Chukwuka","middleName":"Stanley","lastName":"Ezemenike","suffix":""},{"id":470141082,"identity":"1827f619-ca93-46bc-abb9-247c2efb6091","order_by":2,"name":"Remilekun Ikumawoyi","email":"","orcid":"","institution":"Elizade University","correspondingAuthor":false,"prefix":"","firstName":"Remilekun","middleName":"","lastName":"Ikumawoyi","suffix":""}],"badges":[],"createdAt":"2025-06-03 08:53:30","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6809139/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6809139/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84555363,"identity":"cb9816d2-b603-4a95-8a97-3878c8ff7a3f","added_by":"auto","created_at":"2025-06-13 11:23:34","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":250460,"visible":true,"origin":"","legend":"\u003cp\u003eShredded white polypropylene waste plastic\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/fd826a8c54d8956f7152794b.png"},{"id":84555345,"identity":"78b529d4-777b-4747-b6ee-ce8e2c0ba241","added_by":"auto","created_at":"2025-06-13 11:23:34","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":267816,"visible":true,"origin":"","legend":"\u003cp\u003eGrounded white polypropylene waste plastic\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/47718e0a47e039732d0d6858.png"},{"id":84555424,"identity":"a9755f2e-8704-4f9e-88e3-926b71ad695a","added_by":"auto","created_at":"2025-06-13 11:23:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":96817,"visible":true,"origin":"","legend":"\u003cp\u003eAggregates’ gradation curve\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/d49f93b9a4245b93c2f43943.png"},{"id":84555327,"identity":"3fa40fa5-e735-46a5-912a-5448daae256f","added_by":"auto","created_at":"2025-06-13 11:23:33","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":8873,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of Penetration with Polypropylene Content\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/dfe0f108a13d432a6f089734.png"},{"id":84555331,"identity":"40a539da-5a79-4807-9c1b-071092ce7e1e","added_by":"auto","created_at":"2025-06-13 11:23:33","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":8826,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of Softening Point Polypropylene Content\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/ba58ad1ab75102c1688b4fa0.png"},{"id":84555396,"identity":"9f9d4211-1332-46c6-85a5-b7605d8035dd","added_by":"auto","created_at":"2025-06-13 11:23:36","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":13707,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of Flash and Fire Point with Polypropylene Content\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/4256e4f44f7031bb38f13ab4.png"},{"id":84555395,"identity":"5ac2c4d6-4433-4059-a2ca-db66d5effcf1","added_by":"auto","created_at":"2025-06-13 11:23:35","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":7939,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of Ductility with Polypropylene Content\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/a6e9cce08286e4d527a8ddac.png"},{"id":84555399,"identity":"590f882b-c82b-46d4-9e85-cb1cd41da022","added_by":"auto","created_at":"2025-06-13 11:23:36","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":10420,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of Viscosity with Polypropylene Content\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/b5e29b5621817605e219f495.png"},{"id":84555765,"identity":"8fac17ff-0e91-4f6c-81a2-cb16bb6901af","added_by":"auto","created_at":"2025-06-13 11:31:35","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":10744,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of Water in Bitumen with Polypropylene Content\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/99a1fe529e4a4b3735944f8c.png"},{"id":84555360,"identity":"739f8bce-e2a5-4b19-9611-b79b09165254","added_by":"auto","created_at":"2025-06-13 11:23:34","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":14880,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of Complex Modulus against Temperature\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/d18e6912c9bb0d021bbd0502.png"},{"id":84555354,"identity":"4bf45ec9-0b15-490d-8afa-e1429a8cff1c","added_by":"auto","created_at":"2025-06-13 11:23:34","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":13706,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of Phase Angle against Temperature\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/498dc09e8696c5077378877b.png"},{"id":84555414,"identity":"3e988be6-a056-4db6-9455-c152dd23ae79","added_by":"auto","created_at":"2025-06-13 11:23:37","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":10825,"visible":true,"origin":"","legend":"\u003cp\u003eRotational Viscosity against varying Proportions of Polypropylene.\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/98ac650dbb1e634d2cb358ff.png"},{"id":84555764,"identity":"5f1f4493-af4a-4b0f-a99b-dd2c4666f6db","added_by":"auto","created_at":"2025-06-13 11:31:35","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":42893,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray diffractogram of Polypropylene\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/24c2915c1c0f438ddbabb03f.png"},{"id":84555757,"identity":"10261147-b363-4888-9c9b-6a801403a5fc","added_by":"auto","created_at":"2025-06-13 11:31:34","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":44158,"visible":true,"origin":"","legend":"\u003cp\u003eThermo gravimetric–Differential Scanning Calorimeter pattern of polypropylene\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/ed6012937fc3505e8b41c88e.png"},{"id":84555411,"identity":"49ae4de1-34a6-4c76-b3e7-ab90329e364c","added_by":"auto","created_at":"2025-06-13 11:23:36","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":16543,"visible":true,"origin":"","legend":"\u003cp\u003eMarshal Stability of Polypropylene Modified Asphalt against Bitumen Content\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/92b9728ac27fade374d39a00.png"},{"id":84555763,"identity":"a28d3d13-7d16-4ad9-ab94-6db9f2820012","added_by":"auto","created_at":"2025-06-13 11:31:35","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":253928,"visible":true,"origin":"","legend":"\u003cp\u003eSEM with EDS Analysis of Polypropylene-Modified Asphalt Concrete\u003c/p\u003e","description":"","filename":"16.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/c542c80444ca3fbbd5c1420a.png"},{"id":84555338,"identity":"9f5bff36-57b2-4fcf-a598-ed4df757952a","added_by":"auto","created_at":"2025-06-13 11:23:34","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":240485,"visible":true,"origin":"","legend":"\u003cp\u003eSEM with EDS Analysis of Asphalt Concrete (zero polypropylene)\u003c/p\u003e","description":"","filename":"17.png","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/30c3e5041b1169847b5450e4.png"},{"id":84556300,"identity":"1e32f1ec-83d6-4e06-ac64-f457e93933f7","added_by":"auto","created_at":"2025-06-13 11:39:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2396724,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6809139/v1/fbb961cc-4b3c-4053-87a3-d8c59c658677.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eThe Microstructure and Thermochemical Evaluation Properties of Polypropylene-Modified Asphalt Concrete for Enhanced Performance\u003c/p\u003e","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe primary causes of road issues in developing countries like Nigeria, especially concerning asphalt concrete roads, are an interaction of low-quality materials for construction, substandard design principles, difficult environmental conditions, and inadequate maintenance. First, roads constructed using asphalt and aggregate materials of inferior quality are prone to cracking, ravelling, and other types of distress since these materials frequently fall short of international requirements. When procurement processes have been compromised or mismanaged and cost-cutting methods jeopardise the integrity of infrastructure, inferior materials are often used. In addition, many roads are constructed without considering the unique traffic loads and the prevailing weather conditions under which the road will operate. Because heavy vehicles consistently travel Nigerian highways, the designs are frequently unable to withstand the stress and pressure placed on them, leading to rapid deterioration, particularly in high-traffic locations. Moreover, Nigeria's weather, characterised by a lot of rain, makes asphalt pavements even more vulnerable. Inadequate drainage systems result in water buildup, which weakens the pavement's structure and creates surface defects like potholes. The unpredictable weather patterns in the nation add to these environmental concerns, making the situation even more unstable. Furthermore, one major problem is the absence of regular maintenance. Lack of proper planning for maintenance schedules and inadequate funding allocations cause many roads to fall into deterioration. As a result, little concerns like surface wear or tiny cracks are frequently disregarded until they become bigger difficulties that call for expensive repairs or a whole replacement. In addition to harming road safety, this disregard raises travel times and vehicle running expenses for drivers. Moreover, Nigeria's fast urbanization has raised traffic levels, which frequently overwhelm the country's already inadequate road infrastructure. The combined effect of these components results in an endless process of deterioration, whereby insufficient solutions to issues worsen the situation and make managing road networks even more challenging. One of the worst effects of these problems is the high frequency of traffic accidents, which frequently occur due to the bad road conditions. Unpredictable surface features, such as potholes and uneven surfaces, are prevalent for drivers and raise the possibility of collisions. These road issues have major economic ramifications that impact trade, transportation, and overall economic productivity. Road damage raises transportation costs for businesses, discouraging investment and slowing economic growth.\u003c/p\u003e \u003cp\u003eConsidering these challenges, Asphalt concrete's exceptional binding characteristics, flexibility, and durability can greatly improve the performance of flexible pavements. Aggregates and asphalt binders work together to provide a durable surface that evenly distributes traffic loads and lowers the risk of structural problems like cracking and rutting. Compared to rigid pavements, asphalt concrete is less likely to experience thermal cracking because of its flexibility, which enables it to adjust to changing temperatures and stresses. Furthermore, the waterproofing properties of the binder aid in preventing moisture intrusion, which might erode the pavement's structural integrity. The resistance of the material to ageing and deformation can be further increased by adding additives, such as fibres or polymers, which will increase its overall lifespan. Furthermore, resurfacing is a simple way to renew asphalt concrete, extending its lifespan without requiring total replacement. Asphalt concrete is a great option for flexible pavements because of its elasticity and capacity to provide a smooth, skid-resistant surface, which enhances road infrastructure safety, comfort, and affordability. All things considered, the use of asphalt concrete helps to create flexible pavements that are more durable and sustainable and are better equipped to endure the demands of contemporary traffic and environmental conditions.\u003c/p\u003e \u003cp\u003eOver the last few years, the enhanced mechanical and thermal qualities of polypropylene-modified asphalt concrete (PMAC) have become more widely acknowledged, indicating that it is a viable material for use in pavement applications. According to [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], Nigeria is positioned ninth globally in terms of plastic pollution, generating approximately 2.5\u0026nbsp;million tons of plastic waste annually, with fewer than 12% of these materials being recycled. The right disposal techniques are a major challenge to most countries, as the two most common methods (landfill and incinerator) are not eco-friendly in the long run [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Incorporating polypropylene waste plastic to modify asphaltic concrete for improved engineering properties/performance of flexible pavement could be a better technique for handling this industrial waste in our environment. Consequently, the cost of overall construction is reduced.\u003c/p\u003e \u003cp\u003ePolypropylene fibres are incorporated into the asphalt matrix to create PMAC's microstructure, which is essential to enhancing the material's overall performance. A review of the literature has revealed that: adding polypropylene improves aggregate dispersion and results in a combination that is more homogeneous [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]; Kumar and Ghosh [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] noted that, this enhanced dispersion results in increased tensile strength and decreased susceptibility to breaking under heat stress; the load-bearing capacity of the pavement is improved by the efficient interaction of polypropylene fibres with the asphalt binder, which creates a network-like structure [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]; adding polypropylene has been associated with a rise in the viscosity of the asphalt, which enhances its ability to withstand rutting and deformation from strong traffic loads [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. All things considered, polypropylene-induced microstructural changes result in asphalt concrete that is tougher and long-lasting.\u003c/p\u003e \u003cp\u003ePMAC's outstanding thermal stability is shown by thermal characterisation, which makes it especially appropriate for areas with wide temperature swings. Polypropylene alters the thermal transition behaviours of asphalt, increasing its resilience to high temperatures and softening point, according to differential scanning calorimetry (DSC) studies [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. This feature reduces the possibility of long-term deformation, like rutting, in hot weather [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. PMAC was also observed to have better viscoelastic qualities, which are essential for sustaining performance under a range of stress circumstances, according to dynamic mechanical analysis (DMA) [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Based on the literature, polypropylene helps to improve the durability and serviceability of asphalt mixtures by lowering their heat susceptibility [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In regions where asphalt can become brittle in the winter and unduly soft in the summer, the thermal stability provided by polypropylene modification is particularly advantageous [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Overall, adding polypropylene to asphalt concrete improves both its heat resilience and microstructural integrity, making it a feasible alternative for contemporary pavement engineering [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. By strengthening their mechanical characteristics and thermal stability, PMAC \u0026lsquo;s microstructure and thermal characterization greatly improve flexible pavement performance. As reported by [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], the addition of polypropylene fibres to the asphalt matrix promotes a more even dispersion of aggregates, which increases tensile strength and improves crack resistance under heat stress. Particularly in situations of high traffic, this fibrous network enhances load distribution and lowers the possibility of rutting and permanent deformation [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The result of a thermal investigation carried out using differential scanning calorimetry (DSC) revealed PMAC to have higher softening points, which is important for reducing the effects of high temperatures [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Moreover, enhanced viscoelastic characteristics are indicated by dynamic mechanical analysis (DMA), enabling the asphalt to endure temperature swings and dynamic loading more effectively [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The microstructural alterations in PMAC promote enhanced adhesion between the asphalt binder and aggregates, improving durability and resistance to moisture damage [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePMAC offers a novel approach to contemporary pavement engineering, maximising performance under various environmental circumstances and traffic volumes [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. All things considered, the addition of polypropylene fibres to asphalt mixes has advanced the creation of flexible pavements by improving their resilience and structural integrity [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In this study, the polypropylene-based waste chairs were evaluated to determine the microstructural, rheological and thermal properties to enhance the performance of asphalt concrete pavement.\u003c/p\u003e"},{"header":"2 Methodology","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eIn this study, bitumen, aggregates, and discarded polypropylene plastic chairs were used as research materials. Aggregates and 60/70 penetration grade bitumen were purchased from KK Hassan Nigeria Limited in Akure, Nigeria. Waste polypropylene plastic chairs were obtained from Elizade University, Ilara-Mokin and the surrounding area of Akure City.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Methods\u003c/h2\u003e \u003cp\u003eThe aggregates utilised were sun-dried before being subjected to a series of tests using the relevant ASTM procedures to ascertain their physical characteristics. These tests include the moisture content [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], aggregate sieve analysis [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], aggregate impact test [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], aggregate crushing values [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], specific gravity [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], flakiness, and elongation index tests [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], thermogravimetric analysis (TGA) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], X-ray diffraction [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], and X-ray fluorescence test [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] were used to ascertain the chemical characteristics of polypropylene plastic. The shredded white polypropylene plastic chairs (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) were pulverised to produce the polypropylene plastic powder that could pass through a 0.015 \u0026micro;mm filter (Fig.\u0026nbsp;2).\u003c/p\u003e \u003cp\u003eThe modified bitumen was prepared by partially replacing bitumen with 5%, 10%, 15%, and 20% powdered polypropylene plastic. The modified bitumen was thoroughly blended. To ascertain the physical and rheological properties of the bitumen and modified bitumen, the samples were subjected to penetration test [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], softening point test [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], flash and fire point test [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], ductility [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], viscosity [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], water in bitumen [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], dynamic shear rheometer [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], and rotational viscosity [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The mixture of modified bitumen and aggregates produced cylindrical samples of asphalt concrete; Marshal Stability and Flow tests [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] were conducted on the asphalt concrete and the modified asphalt concrete produced. The cracked surfaces of modified asphalt concrete were examined using a scanning electron microscope SEM [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] to assess the microstructural characteristics of the material.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and Discussions","content":"\u003cdiv class=\"Heading\"\u003e\u003cb\u003e\u003c/b\u003e\u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Sieve Analysis\u003c/h2\u003e \u003cp\u003eThe sieve analysis results of the aggregates, when compared to the design envelope for hot asphalt mix (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e), indicated that the aggregate used meets both the upper and lower specification limits, confirming its appropriateness for asphalt concrete production.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Physical Properties of Aggregates\u003c/h2\u003e \u003cp\u003eThe results from the different physical characteristics of the aggregates analysed in this research are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The results indicate that the aggregates conform to the quality standards for aggregates as defined by FMWHM, 2013.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Characterisation of Bitumen and Modified Bitumen\u003c/h2\u003e \u003cp\u003eThe results of penetration tests, softening point, flash and fire point, viscosity, water in bitumen, and ductility are used to ascertain the physical characteristics of bitumen and polypropylene-modified bitumen\u003c/p\u003e \u003cp\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\u003eSummary of physical properties of Aggregates\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS/N\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTest\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eObtained value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSpecification as per FMWHM, 2013.\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMoisture Content\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.75%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMax 5%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAggregate Impact Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23.80%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20\u0026ndash;30%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAggregate Crushing Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.18%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27\u0026ndash;35%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecific gravity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.0g\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFlakiness and Elongation Index Test\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25.64%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMax 35%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1 Penetration for Bitumen and Polypropylene-Modified Bitumen\u003c/h2\u003e \u003cp\u003eThe results of penetration tests conducted on bitumen and bitumen modified with different percentages of polypropylene by weight of bitumen are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The results indicated that the penetration grade steadily decreased with increased polypropylene content in the bitumen. The penetration trend decreases in order of their viscosity. This suggests that the polypropylene addition hardens and standardises the modified bitumen, which is beneficial in that it might increase the mix's resistance to rutting; however, it might also reduce the bitumen's flexibility by making the asphalt much stiffer, which could positively impact the resistance to fatigue cracking.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e3.3.2 Softening Point for Bitumen and Polypropylene Modified Bitumen\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e presents the results of the ring and ball softening point test, which identifies the temperature at which asphalt reaches a particular level of softness. The results indicate that the softening point values for modified bitumen at 5, 10, 15, and 20% polypropylene contents are 48, 52, 56, and 66\u0026deg;C, respectively. These results clearly illustrate that the softening point value rises in correlation with the amount of polypropylene. This observation implies that the binder exhibits greater heat resistance, thus diminishing its tendency to soften in elevated temperatures. Consequently, the adverse impacts of temperature on bituminous materials will be lessened with the addition of polypropylene. The rise in the softening point also suggests a reduction in bleeding during the summer, which will enhance vehicle traction and reduce the slippery conditions in wet weather.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e3.3.3 Flash and Fire Point\u003c/h2\u003e \u003cp\u003eAs illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the outcome of the flash and fire point test establishes the safe temperature at which bitumen can be heated in the presence of an open flame before it ignites. The fire point and flash values increased proportionately to the amount of polypropylene added to the bitumen. By adding 5% of the bitumen's weight in polypropylene, the bitumen's flash point increased from 207\u0026deg;C to 216\u0026deg;C. When the bitumen's polypropylene content was raised from 10\u0026ndash;20%, a similar increase was seen, with the greatest value being attained at 20%, or 247\u0026deg;C. The modified bitumen's fire point results grow from 5\u0026ndash;20%, reaching its maximum value of 285\u0026deg;C at 20%. Waste plastic ignites at high temperatures, which explains why the modified bitumen has a higher flash and fire point. This suggests that adding polypropylene to bituminous materials will probably reduce the material's associated fire risk and regulate its safety.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e3.3.4 Ductility\u003c/h2\u003e \u003cp\u003eThe unmodified bitumen has a ductility value of 97cm (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e) which decreases as the polypropylene content in the bitumen increases. According to the American Standard for testing material, the maximum ductility value for bitumen should not exceed 100cm. The results obtained revealed a lower value for modified bitumen. As may be observed, polypropylene maintains its ductility value of less than 100cm. The outcomes demonstrate a significant reliance on the polymer's chemical makeup and base bitumen polymer compatibility.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e3.3.5 Viscosity\u003c/h2\u003e \u003cp\u003eThe Viscosity test results determined how long it takes the modified samples to flow at a given temperature between the tube timing markers. The amount of polypropylene in the bitumen increases, so does its viscosity (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e). It was found that the value achieved was more than the standard value. The viscosity increases from 135.50 seconds for 5% polypropylene content to 159.95 seconds at 20%. Up to a 20% polypropylene content, there was an increasing trend in the viscosity of bitumen containing polypropylene. This increase indicates that bituminous materials made with polypropylene will adhere to the aggregates when utilized in asphalt preparation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e3.3.6 Water in Bitumen (Dean and Stark Method)\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e illustrates the level of water in bitumen and polypropylene-modified bitumen as a result of the water-in-bitumen test. The percentages of water content obtained in bitumen and polypropylene-modified bitumen as presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e complied with the required specification (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The percentages of water content in all the samples tested are significantly lower than the 5% ASTM D95-20 acceptable limit. Compared with conventional bitumen, bitumen made from polypropylene has the lowest moisture content. According to ASTM-D95-20, the physical characteristics of bitumen and bitumen modified with polypropylene that were examined in this satisfied the standard limit (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Rheological Properties of Bitumen and Modified Bitumen\u003c/h2\u003e \u003cp\u003eThe dynamic shear rheometer test results and rotational viscosity were utilised to ascertain the rheological characteristics of bitumen and modified bitumen:\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eStandard Specification of Bitumen Properties\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTest\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLimit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTest Method (ASTM)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePenetration @25\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varvec{℃}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDmm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60\u0026ndash;70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD5/D5M-19\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoftening Point\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003csup\u003eO\u003c/sup\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e49\u0026ndash;56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD36-19\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuctility @ 25\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varvec{℃}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003ecm\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100Min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD113-19\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlash Point\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003csup\u003eO\u003c/sup\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e280 Min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD92-20\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFire Point\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003csup\u003eO\u003c/sup\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e320 Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD92-20\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eViscosity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ecSt\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e300Min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD2171-20\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWater in Bitumen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD95-20\u003c/em\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 \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e3.4.1 Dynamic Shear Rheometer\u003c/h2\u003e \u003cp\u003eUsing a dynamic shear rheometer (DSR), the viscoelastic behaviour of asphalt binders was investigated at 60 \u0026ordm;C, 70 \u0026ordm;C, 80 \u0026ordm;C, and 90 \u0026ordm;C. The test results are displayed in Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003e, which show the complex modulus and phase angle, respectively, against various binder temperatures. The best values of complex modulus obtained at 0% (452.9) Kpa; 5% (441.8) Kpa; 10% (435.8) Kpa, 15% (415) Kpa, 20% (408) Kpa and the values of phase angle at 0% (75) δ, 5% (72.5) δ, 10% (70) δ, 15% (60.4) δ, 20% (52.6) δ. As the temperature increased, all samples exhibited a decrease in complex modulus values and an increase in phase angle, as revealed in Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003e, respectively. Higher complex shear moduli are needed to guarantee bituminous pavement's continued strong resistance to deformation at elevated temperatures. Greater complex shear modulus is advantageous since it reduces asphalt deformation and rutting issues. Asphalt binder with a lower phase angle is more elastic than viscosity and will return to its initial state without releasing energy. A lower phase angle is preferable at higher temperatures because it decreases irreversible deformation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e\u003cb\u003e3.4.2 Rotational Viscosity\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eAdding Polypropylene significantly changed the asphalt's rotational viscosity (RV). The RV of the asphalt increased quickly when the polypropylene content was added. The results of the laboratory tests show that the RV values of polypropylene at 135 \u003csup\u003eo\u003c/sup\u003eC and 165 \u003csup\u003eo\u003c/sup\u003eC are high and low respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e12\u003c/span\u003e), because polypropylene reduces the molecular weight of the modified asphalt binder when a higher temperature is applied. High-stiff asphalt binders are ideal for preventing rutting, however, to prevent cracking, the rotational viscosity shouldn't go over a certain threshold (3000 MPa).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Chemical and Mineralogical Properties Polypropylene\u003c/h2\u003e \u003cp\u003eTo examine the mineralogical characteristics of polypropylene plastic, X-ray fluorescence (XRF), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) tests were used. The XRD diffractogram correlates with that of a structure that is semi-crystalline or partially crystalline (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e13\u003c/span\u003e). Based on elemental composition data from XRF analysis, it has been determined that the major constituents of polypropylene are carbon and hydrogen. Polypropylene syndiotactic (C\u003csub\u003e3\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003e)\u003csub\u003en\u003c/sub\u003e and polypropylene isotactic (C\u003csub\u003e3\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003e)\u003csub\u003en\u003c/sub\u003e are the patterns that were identified. Figure\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e14\u003c/span\u003e depicts the thermal degradation of polypropylene at 480\u0026deg;C, which resulted in a total weight loss of 18.75%. A second thermal degradation with 1.2% of inert residue occurs at 700\u0026deg;C. This could be caused by the bonding phases, morphology, and composition of the constituent polypropylene in the material composite.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Marshal Stability Result of Polypropylene Modified Asphalt\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e15\u003c/span\u003e displays the variation of the stability values. When polypropylene was added in percentages, it was seen to increase initially before declining at 7.0 bitumen content. This could be explained by increased internal friction and binder cohesiveness, which improve the strength and functionality of asphalt concrete [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The ideal stability of 10.50 KN, 12.40 KN, 12.20 KN, and 15.80 KN was attained for polypropylene contents of 5%, 10%, 15%, and 20%. Additionally, the result suggested that the percentage for light, medium, and high traffic falls within the minimal value stated in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The Asphalt Institute Criteria for the Marshall Mixture Design Method, 1997 specification was satisfied by Marshall stability values, as may be concluded from the results\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAsphalt Institute Criteria for the Marshall Mixture Design Method, 1997\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMix Specification\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eHeavy traffic (greater than 10\u003csup\u003e6\u003c/sup\u003e ESAL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eLight traffic (less than 10\u003csup\u003e4\u003c/sup\u003e ESAL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eMedium traffic (10\u003csup\u003e4\u003c/sup\u003e-10\u003csup\u003e6\u003c/sup\u003e ESAL)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMax\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMax\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMax\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStability (Minimum)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6672N\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\u003e2224N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3336\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlow (0.25mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAir Void (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCompaction (50 blows each side of specimen)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003cb\u003eNote\u003c/b\u003e: ESAL is the Equivalent Single Axle Load. Source: Asphalt Institute\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.7 SEM/EDS Analysis of Polypropylene Modified Asphalt Concrete\u003c/h2\u003e \u003cp\u003eFigures \u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e16\u003c/span\u003e and \u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e17\u003c/span\u003e show the SEM images of the polypropylene-modified asphalt and the unmodified asphalt, respectively. A higher porosity is noted in the unmodified asphalt concrete (Fig.\u0026nbsp;\u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e17\u003c/span\u003e) compared to the sample with polypropylene content. Furthermore, polypropylene-modified asphalt exhibits agglomeration of the polypropylene particles in the asphalt, unlike Fig.\u0026nbsp;\u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e17\u003c/span\u003e with zero polypropylene content. Surface tension and the presence of contaminants in the polypropylene particles could be the cause. According to the Energy Dispersive Spectroscopy (EDS) analysis, the principal elements found are O\u003csub\u003e2\u003c/sub\u003e, Al, and Ca, utilised as components of the Ziegler-Natta catalyst for polypropylene synthesis. Both Al(OH)\u003csub\u003e3\u003c/sub\u003e and fire-retardant Mg (OH)\u003csub\u003e2\u003c/sub\u003e may contain magnesium. TiO\u003csub\u003e2\u003c/sub\u003e contains titanium, which can be used as a pigment. Si most likely originates from catalytic constituents or soil contaminants. The catalyst for the Olefin polymerization reaction or a component of PVC called Cl.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eThis study primarily focused on assessing the influence of recycled polypropylene on the chemical, thermal, rheological, and microstructural properties of a specified asphalt mixture, highlighting the contributions of each attribute to performance enhancement. Experimental results demonstrated that the addition of polypropylene significantly improved the physical, chemical, thermal, and rheological properties of bitumen. The Marshall stability tests confirmed compliance with the 1997 Nigerian General Specification for Roads and Bridges and the Asphalt Institute standards. Furthermore, the microstructural analysis revealed that polypropylene-modified asphalt exhibits homogeneous behaviour. These findings suggest that incorporating polypropylene enhances the performance and durability of flexible pavements while offering a sustainable approach to mitigating plastic pollution, addressing a critical global environmental challenge.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthors Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCharles Gbenga wrote the main manuscript and prepared and organised all figures and tables. Chukwuka Stanley developed the conceptualisation and methodology. Remilekun Ikumawoyi, Charles Gbenga, and Chukwuka Stanley reviewed the manuscript collaboratively.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResearch involving human and animal participants.\u003c/strong\u003e This article does not contain any studies involving animals human participants performed by any of the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Statement:\u0026nbsp;\u003c/strong\u003eNo funding was received for conducting this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest:\u0026nbsp;\u003c/strong\u003eThe authors have no conflicts of interest to declare that are relevant to the content of this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Authors acknowledge Professor Oyedepo\u0026apos;s support throughout the research process. His expertise and insights were invaluable in shaping our research and helping us overcome challenges.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eYalwaji, B., H. O. John-Nwagwu, \u0026amp; T. O. Sogbanmu. (2022). Plastic pollution in the environment in Nigeria: A rapid systematic review of the sources, distribution, research gaps and policy needs. \u003cem\u003eScientific African\u003c/em\u003e, \u003cem\u003e16\u003c/em\u003e, e01220.\u003c/li\u003e\n\u003cli\u003eEzemenike, C., O. Oyedepo, and O. Aderinlewo, I. Oladele \u0026amp; O. Olukanni. 2022. Rheological characterization of industrial waste modified bitumen. \u003cem\u003eJournal of Engineering Sciences\u003c/em\u003e, (3), 126-135.\u003c/li\u003e\n\u003cli\u003eZhang, Y., X. Wang, and J. Liu. 2020. 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(2020). \u003cem\u003eASTM D2171-20\u003c/em\u003e\u003cem\u003e: Standard test method for viscosity of asphalts by vacuum capillary viscometer\u003c/em\u003e. ASTM International.\u003c/li\u003e\n\u003cli\u003eAmerican Society for Testing and Materials (ASTM). (2020). \u003cem\u003eASTM D95-20: Standard test method for water in petroleum products and bituminous materials by distillation\u003c/em\u003e\u003c/li\u003e\n\u003cli\u003eAmerican Society for Testing and Materials (ASTM). (2019). \u003cem\u003eASTM D7175-19: Standard test method for determining the rheological properties of asphalt binder using a dynamic shear rheometer\u003c/em\u003e. ASTM International. \u003c/li\u003e\n\u003cli\u003eAmerican Society for Testing and Materials (ASTM). (2018). \u003cem\u003eASTM D4402-18: Standard test method for viscosity determination of asphalts by rotational viscometer\u003c/em\u003e. ASTM International\u003c/li\u003e\n\u003cli\u003eAmerican Society for Testing and Materials (ASTM). (2006). \u003cem\u003eASTM D6927-06: Standard test method for Marshall stability and flow of asphalt mixtures\u003c/em\u003e. ASTM International.\u003c/li\u003e\n\u003cli\u003eAmerican Society for Testing and Materials (ASTM). (2020). \u003cem\u003eASTM E1508-20: Standard guide for scanning electron microscopy (SEM) of materials\u003c/em\u003e. ASTM International.\u003c/li\u003e\n\u003cli\u003eAliyu, I., A. Usman, J. Kaura, M. Ashiru, I. Kingsley. (2015). Polyethylene from water sachet as a modifier in hot asphalt mixture. \u003cem\u003eDepartment of Civil Engineering, Ahmadu Bello University, Zaria, Nigeria.\u003c/em\u003e\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-civil-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Civil Engineering](https://www.springer.com/journal/44290)","snPcode":"44290","submissionUrl":"https://submission.nature.com/new-submission/44290","title":"Discover Civil Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"polypropylene plastic, modified bitumen, polypropylene-modified asphalt concrete (PMAC), rheology, plastic pollution, performance","lastPublishedDoi":"10.21203/rs.3.rs-6809139/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6809139/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn the road construction industry, efforts are being made to incorporate polypropylene with polymer properties into asphalt mixtures to improve the mechanical performance of the pavement layers and address the environmental demands caused by the significant accumulation of plastic waste. The impact of recycled polypropylene on the chemical, thermal, rheological, and microstructural characteristics of the specified asphalt mixture is the main emphasis of this study, which also identifies how each attribute enhances performance. The polypropylene and modified bitumen were characterised using thermogravimetric, dynamic shear rheometer, rotational viscosity, penetration, softening point, flash and fire point, ductility, water-in-bitumen, viscosity, x-ray diffraction, and x-ray fluorescence. The asphalt concrete was produced with varying proportions of polypropylene at 5%, 10%, 15%, and 20%, respectively. Moreover, the polypropylene-modified asphalt concrete was analysed to determine its microstructures. It has been observed that polypropylene enhances the physical, chemical, thermal, and rheological properties of bitumen. The Marshall stability result showed that the values obtained complied with Nigeria's general road and bridge specifications 1997 and Asphalt Institute 1997 standards. These results concluded that polypropylene could improve and strengthen flexible pavement and reduce environmental hazards.\u003c/p\u003e","manuscriptTitle":"The Microstructure and Thermochemical Evaluation Properties of Polypropylene-Modified Asphalt Concrete for Enhanced Performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-13 11:23:16","doi":"10.21203/rs.3.rs-6809139/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-17T07:20:46+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-16T21:36:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"296953368272464162244706046104500158763","date":"2025-07-14T03:54:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"82439061642594229029489330745400283312","date":"2025-07-07T20:08:29+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-29T03:41:40+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"193076333042832144986952820161135024119","date":"2025-06-23T01:41:04+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-12T05:14:19+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-12T02:00:40+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-06-11T14:22:13+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-10T11:45:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Civil Engineering","date":"2025-06-10T11:42:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-civil-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Civil Engineering](https://www.springer.com/journal/44290)","snPcode":"44290","submissionUrl":"https://submission.nature.com/new-submission/44290","title":"Discover Civil Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"efbd3a89-b076-493f-bccf-97660b221b8d","owner":[],"postedDate":"June 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-10-21T05:38:14+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-13 11:23:16","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6809139","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6809139","identity":"rs-6809139","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}