Thermo-Rheological Characterization and Performance Evaluation of Sustainable TiO2-Modified Hot Mix Asphalt (HMA) Formulations for Urban Pavement Infrastructure

Thermo-Rheological Characterization and Performance Evaluation of Sustainable TiO2-Modified Hot Mix Asphalt (HMA) Formulations for Urban Pavement Infrastructure | 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 Thermo-Rheological Characterization and Performance Evaluation of Sustainable TiO 2 -Modified Hot Mix Asphalt (HMA) Formulations for Urban Pavement Infrastructure Pablo Cabrera, Ignacio Zapata Ferrero, Gerardo Botasso, Ana M. Castro Luna This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7457711/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Urban heat islands (UHIs), exacerbated by conventional asphalt pavements that absorb up to 95% of solar radiation, elevate urban temperatures, energy demands, and air pollution. To mitigate UHI effects, this study investigates the thermal and mechanical performance of asphalt pavements modified with titanium dioxide (TiO 2 ), a photocatalytic pigment that enhances solar reflectance and promotes surface cooling. The physicochemical properties of reference and TiO 2 modified asphalt mastics were evaluated, including penetration, softening point, and rheo-logical behavior (rutting resistance via G*/sinδ and fatigue performance via G*·sinδ). Aging effects were assessed through controlled UV and oxidative exposure. Results demonstrate that TiO 2 incorporation increased solar reflectance by 45,5% in 12 months, reducing surface temperatures by up to 8°C compared to conventional asphalt pavement. This cooling effect, attributed to TiO 2 ’s dual role as a photon-reflective and photocatalytic material, was maintained even after aging, with the solar reflectance increasing under outdoors environmental degradation. Mechanically, the modified mastic exhibited comparable rutting resistance and enhanced fatigue performance to reference mastic. Furthermore, TiO 2 modified specimens demonstrated enhanced moisture resistance (modified Lottman test) and retained deformation resistance comparable to conventional asphalt mixture in wheel tracking tests. These findings position TiO 2 modified asphalt mastic as a multifunctional solution for UHI mitigation, combining passive radiative cooling, photocatalytic pollution reduction, and robust pavement performance. Future work should optimize TiO 2 dispersion protocols and evaluate long-term cost-benefit ratios for scalable urban implementation. Environmental Engineering Materials Engineering Civil Engineering Cool Pavements TiO2 Albedo Urban Heat Island Asphalt Mastic Aging Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction Fighting against climate change is one of the most urgent challenges facing the community in the 21st century, as climate change shows a serious threat to life. Natural disasters are becoming more frequent, leading to a loss of biodiversity and an increase in ambient temperatures; crops are destroyed, ecosystem diversity is reduced, and the spread of diseases is accelerated. According to statistical projections, by 2050, more than half of the world's population will live in megacities. Currently, modern cities face a continuous increase in population density, which requires meeting the demand for increased housing and transportation infrastructure. To address road traffic problems, natural soil is usually replaced with impermeable surfaces such as asphalt pavements. This modification of the native terrain reduces groundwater infiltration, increases surface runoff, and flood risks. Sustainable and adaptable pavement infrastructure is essential to address current economic and environmental challenges [ 1 ]. An asphalt pavement is composed of asphalt, a mixture of organic compounds mainly hydrocarbons, aggregates of different sizes, and filling material (fillers) to fill voids and improve cohesion. Asphalt acts as a binder to glue both the loose aggregates with an appropriate particle size distribution and the fillers. It is the asphalt that gives the pavement the mechanical properties that allow it to achieve load-bearing capacity and adequate road safety. In summer, high surface temperature of the pavements is one of the contributors to explain the urban heat island effect (UHI), that accounts for a higher ambient temperature in the city than in the surrounding rural areas [ 2 ]. Consequently, fossil energy consumption is necessary to cool buildings and homes. A conventional asphalt pavement has moderate thermal conductivity and can transfer heat to its interior, storing it during daylight hours and releasing it into the air during dusk and night [ 3 ]. Most of the solar absorption is returned to the environment by convection transference and longwave emission [ 4 ]. In addition, as asphalt is viscous, its resistance to load decreases with increasing temperature, which causes irreversible deformations or rutting in the pavement, thus reducing its useful life. Initially in service, dark-colored asphalt pavements have low albedo 1 values of approximately 0,05. Pavements surfaces lighten over time and slightly increase their albedo, heating up a little less. Various strategies have been proposed to mitigate heat emissions from pavements. These include incorporating light-reflective pigments such as titanium dioxide (TiO 2 ) or zinc oxide (ZnO) into asphalt mixtures or applying surface coatings containing these materials through spraying techniques. A lighter colored pavement increases its solar reflectance, which reduces heat absorption and lowers surface temperature, thereby addressing thermal accumulation in urban environments [ 5 ]. A cold pavement is defined as one that, compared to a conventional pavement, reaches lower surface temperature values when exposed to the same solar irradiation. If the pavement is not heated, energy savings are achieved, and the quality of the urban microclimate is improved. There is a link between the albedo of pavements and its effect on air temperature in large cities. Higher albedo reduces solar energy absorption in pavements. Due to its lighter surface color, TiO 2 modified asphalt exhibits lower heat absorption than the reference material, both when newly installed and after one year outdoors, demonstrating its potential to mitigate urban heat island effects [ 6 ]. The fading color of asphalt pavement surfaces is influenced by multiple factors, with aging emerging as a primary contributing factor. The complex molecular structure of asphalt and its chemical components are modified because asphalt exposure to sunlight and atmospheric conditions alter its properties. Given the complex molecular mixture comprising asphalt, chromatographic separation has been proposed as a method to reduce this complexity by fractionating the material into the SARA components (saturates, aromatics, resins, asphaltenes) according to their increasing polarity [ 7 – 9 ]. Asphalt aging entails complex physicochemical changes in the binder induced by heat and ultraviolet (UV) radiation. The latter initiates a photochemical oxidation chain reaction, breaking down molecules, generating oxygen-rich functional groups (e.g., carbonyls, sulfoxides), and increasing asphaltene content. There is an increase in binder stiffness and brittleness and adhesion reduction, causing pavement distress [ 10 – 17 ]. The process synergizes with heat and oxygen, accelerating markedly at higher temperatures. Though UV degradation initiates at the surface, its effects propagate deeper into the pavement via cracking pathways. To understand the evolution of asphalt's internal composition during thermal-oxidative aging, changes in polarity and molecular weight were tracked over time, revealing component degradation and interconversion. Thermal oxidation, an irreversible oxidative aging process, occurs mainly during manufacturing, transport, and placement of asphalt mixtures. It involves volatilization of light components (saturates, aromatics) and microstructural reorganization [ 18 ]. UV oxidation (photo-oxidative aging), however, is the main mechanism for long-term deterioration during service life. Facilitated by ultraviolet radiation and oxygen, it drives the predominant form of long-term asphalt aging. Once asphalt aging occurs in the mixture, cracking is more easily initiated under traffic loads due to the increased stiffness and reduced adhesion of aged asphalt binder. It is possible to delay the UV aging of asphalt by investigating effective proposals to improve the resistance of asphalt to aging. Thus, UV absorbers, light-blocking agents, and antioxidants have been analyzed with the intention of generating a complete and reliable system of resistance to UV aging [ 13 ]. The incorporation of anti-aging agents represents a simple and effective strategy to mitigate asphalt aging. Inorganic anti-aging agents have also garnered extensive attention in asphalt aging resistance research, such as TiO 2 , that can absorb and shield UV radiation [ 15 ]. This study evaluates the rheological behavior of AM-3 asphalt mastic 2 without and with TiO 2 incorporation and before and after accelerate aging in laboratory. The mechanical resistance and opto thermal properties of pavement specimens formulated without and with TiO 2 incorporation were also determined, at the beginning and after one year of outdoor exposure. The specimen key parameters including albedo, emissivity, and surface temperature were determined. Moreover, in specimens without and with TiO 2 addition, the mass loss percentage after aging protocols have been tested according to the requirements of ANRC to evaluate the quality of the modified asphalt pavement. 2. Materials and methods 2.1. Design and dosage of asphalt mixtures Following the technical specifications of the Argentine National Road Commission, ANRC [ 19 ], two asphalt mixtures designed according to the Marshall method were used. Both are a type of discontinuous mix called hot-mix asphalt micro agglomerate, the purpose of which is to provide the road surface of a street or route with the necessary mechanical strength, macrotexture, slip resistance, and acoustic properties. The first mixture, named reference mixture is composed by modified asphalt binder AM-3, coarse and fine aggregates with commercial designations 6–12 and 0–6, respectively, and as combined fillers lime plus the dust coming from the coarse and fine aggregates passing the #200 sieve (75 µm). The second mixture named TiO 2 modified mixture contains the same percentages of coarse and fine aggregates, and in the fillers 2% of lime are replaced with 2% of TiO 2 a powdered pigment compliant with ASTM C979 specifications [ 20 ]. The dosage used in the reference mixture is composed of 57% coarse aggregate, 35,2% fine aggregate, 2,9% lime, and 5% AM-3 asphalt binder. Whereas the dosage of the TiO 2 modified mixture is composed of 57,1% coarse aggregate, 35,2% fine aggregate, 1% lime, 2% TiO 2 , and 4,8% AM-3 asphalt binder. Quadrangular prism (300 mm × 300 mm × 50 mm) and cylindrical (Ø 102 mm × 64 mm) specimens were prepared using both reference and TiO 2 modified asphalt mixtures for subsequent experimental testing. 2.2. Conditioning of the mastic prior to analysis Three accelerated aging protocols were implemented to evaluate the effect of TiO 2 addition on the physical and rheological properties of the reference mastics: i) short-term thermal oxidative aging via the Rolling Thin Film Oven Test (RTFOT) [ 21 ]; ii) long-term thermal oxidative aging through sequential RTFOT and Pressure Aging Vessel (PAV) [ 22 ]; and iii) RTFOT and UV, photo-oxidative aging in a chamber equipped with lamps that emit UV-A radiation at a wavelength of 368 nm [ 23 ]. 2.2.1. Determination of physical and rheological properties of mastics The performance of asphalt mastics was evaluated by measuring the softening point (via ring-and-ball technique) [ 24 ] and the penetration (via needle penetrometer method) [ 25 ]. These measurements used mastics with compositions identical to those in the reference mixture and the TiO 2 modified mixture before and after short-term thermal aging RTOFT. The penetration test measures the hardness and consistency of asphalt mastics, and the softening point test determines the temperature at which the material reaches a specific degree of softening under controlled conditions. Using a dynamic shear rheometer (DSR), the complex shear modulus (G*) and phase angle (δ) were measured to determine rheological parameters related to short-term failure, rutting parameter G*/sinδ, and long-term failure, fatigue parameter, G*.sinδ [ 26 – 27 ]. G*/sinδ is determined on both mastics, without and with short-term thermal aging, and G*.sinδ is determined on both mastics with long-term thermal aging, the latter comprising a short-term thermal aging followed by a second conditioning using PAV. 2.3. Analysis of the mechanical behavior of both specimens The impact on the mechanical behavior of the asphalt mixtures used is analyzed. To this end, moisture-induced damage is evaluated using the modified Lottman test [ 28 ], which shows the loss of mastic-aggregate adhesion that the mixture will experience. Resistance to rutting damage is also evaluated using the wheel tracking test [ 29 ]. Furthermore, the mixtures resistance to disintegration under the abrasive and suction effects caused by traffic was determined through the Cantabro wear loss test [ 30 ]. The test analyzes the behavior of reference and TiO 2 modified specimens under different conditioning: i) virgin, ii) with short and long-term thermal aging [ 31 ] and iii) with short-term thermal aging + UV-A photo-oxidative aging. 2.4. Measurements of opto-thermal properties The albedo value of each specimen was evaluated according to the ASTM E1918 standard [ 32 ], modified by Akbari et al. [ 33 ], a clear day in April 2024, and April 2025 in an area adjacent to the parking lot of the Regional Faculty of the National Technological University of La Plata. The instrumentation used was a Kipp&Zonen CMP-3 pyranometer (sensitivity: 25,7 µV.m 2 .W − 1 ; uncertainty: 0,67 µV.m 2 .W − 1 ) associated with a Campbell Scientific CR300 data logger. Each specimen’s albedo was measured through six experimental repetitions, with a standard deviation of ± 0,3%. To determine the ε emissivity 3 of each specimen, a Testo 865 thermal imaging camera with an infrared resolution of 320 x 240 pixels and a temperature difference display of ± 0,1°C was used, in accordance with [ 34 ]. The surface temperatures of the Sun-exposed specimens were recorded using K-type thermocouples connected to data loggers. The values have been taken over four days in April 2024 and April 2025. 3. Results and discussion In this work, the testing methods used to characterize asphalt binders are adopted for the evaluation of the mastic in both the reference asphalt mixture and the TiO 2 modified asphalt mixture. 3.1. Physical characterization of mastics Table 1 shows the penetration and the softening point values of reference and TiO 2 modified mastics without and with short-term thermal aging. Table 1 Physical properties of reference and TiO 2 modified mastics without and with short-term thermal aging. Mastic Virgin Short-term thermal aging Penetration (mm -1 ) Softening Point (°C) Penetration (mm -1 ) Softening Point (°C) Reference 22 111 12 114 TiO 2 modified 22 112 21 114 In virgin mastics, both the reference and the TiO 2 modified mastics show identical penetration values and only a minor difference in their softening point values. However, after short-term thermal aging, there is a notable decrease in the penetration value of the reference mastic, while there is practically no variation in that of the TiO 2 modified mastic. Consequently, 2% TiO 2 significantly improves the aging resistance of the modified mastic. 3.2. Rheological parameters of mastics 3.2.1. Determination of High Temperatures Performance Grade (HTPG) The temperature sweep test was run on both mastics to determine from the G*/sinδ vs temperature values the maximum temperature at which each mastic resists rutting failure. Both mastics exhibit identical HTPG values of 118°C. This behavior indicates that replacing 2% of lime content with TiO 2 in the mixture formulation causes no significant changes in rutting resistance. 3.2.2. Determination of fatigue parameter The fatigue parameter of mastics was evaluated at an intermediate service temperature of 30°C and at a frequency of 10 rad.s − 1 . The corresponding G*·sinδ fatigue parameter values for both mixtures are summarized in Table 2 . Table 2 Physical and chemical properties of crumb rubber. Mastic Fatigue Parameter (kPa) Tolerated Limit (kPa) Reference 2751 5000 TiO 2 modified 1672 The fatigue parameter quantifies an asphalt binder’s resistance to cracking under repeated pavement loading, at intermediate temperature. While values below 5000 kPa indicate acceptable fatigue performance, lower fatigue parameters values correspond to higher resistance to repetitive loading. The results at intermediate temperatures shown in Table 2 indicate that replacing 2% of lime by 2% TiO 2 significantly improves the mastic’s resistance to fatigue failure. 3.3. Mastics analysis by Fourier Transform Infrared Spectroscopy (FTIR) Photo-oxidative aging driven by UV radiation and oxygen exposure has been identified as the predominant mechanism underlying long-term asphalt pavement deterioration. When applied to transport infrastructure surfaces, asphalt materials undergo UV radiation within a specific solar frequency band. This exposure initiates free-radical reactions and progressively increases specific functional groups, especially carbonyl and sulfoxide groups [ 13 ]. FTIR spectra of the unmodified and TiO 2 modified mastics which were treated in a laboratory UV-A chamber during a time equivalent to 5 years of outdoor exposure, are shown in Fig. 1 . Upon photon irradiation, photocatalytic materials facilitate electron transitions from the valence band to the con-duction band, generating electron-hole pairs through photoexcitation. These charge carriers can either directly oxidize organic pollutants or react with dissolved oxygen or OH⁻ ions to produce reactive oxygen species for indirect pollutant oxidation [ 35 ]. Thus, TiO 2 competes with asphalt for UV radiation, acting as a UV shield that reduces degradation of asphalt's organic components. Spectroscopic analysis revealed notably stronger C = O, S = O and C = C bond signals in the reference mastic than in the TiO 2 modified mastic after UV-A photooxidation, indicating a TiO 2 mitigating effect on oxidative aging. The signal of TiO 2 stretching at 450 cm − 1 diminishes after UV-A radiation exposure as found in [ 36 ]. 3.4. Analysis of thermal and UV aging of cylindrical specimens Asphalt aging induces premature and severe pavement deterioration. To simulate in-service climatic degradation mechanisms, cylindrical specimens underwent accelerated aging protocols (both short- and long-term) involving exposure to elevated temperatures and UV-A radiation for controlled durations. It is confirmed that pavement surface color-fading caused by UV-A radiation is much more intense than darkening caused by thermal aging. Long-term thermal aging increases asphalt's asphaltene fraction by degrading saturates, aromatics, and resins. This compositional shift demonstrates oxidative aging accelerates conversion to asphaltenes, the dark-colored asphalt constituents that make pavement darkening. UV-A radiation induces significantly more intense color-fading in pavement surfaces. Unmodified asphalt pavements typically exhibit progressive graying over time. In contrast, TiO 2 modified specimens undergo a distinct color transition sequence: initial brown, dark brown (after thermal oxidative aging), light grey (after photooxidative UV-A aging). 3.4.1. Laboratory testing of specimen’s behavior through simulated in-service pavement conditions Different tests were done to validate the resistance of asphalt mixtures to variable climatic factors and to traffic load. Inducing moisture damage in reference and TiO 2 containing specimens were measured by the modified Lottman test. It was observed that the TiO 2 modified specimen has a higher preserved resistance, showing better adhesion of the mastic to the aggregates. Besides, the specimens were subjected to repeated passes of a loaded wheel, and the rutting depth is measured. After wheel tracking testing, it was not found significant variations in the rutting depth, and both reference and TiO 2 modified specimens performing below the established tolerable limit. The Cantabro test was adopted to evaluate the cohesion of the asphalt mastic in the studied mixture and used as a bearing layer, both reference and TiO 2 modified specimen. This test was also accomplished with specimens after thermal or UV-A radiation treatment. In Table 3 the percentage mass loss of all specimens analyzed are shown. Table 3 Percentage mass loss after aging protocols in reference vs TiO 2 modified pavement specimens. Specimen Reference TiO 2 modified Percentage Mass Loss Percentage Mass Loss Virgin 9 8 Short-Term Thermal Aging 10 10 Long-Term Thermal Aging 11 8 UV-A Aging 10 9 According to European specifications the maximum mass loss percentage tolerable is 20%. The results shown in Table 3 attest that replacing 2% of lime with 2% TiO 2 reduces disintegration maintaining cohesion in virgin specimens. Similar resistance is observed in specimens under thermal aging. The photooxidative UV aging on TiO 2 modified specimens exhibit a close behavior to that of specimens subjected to long-term thermal aging what means that the cohesion was always preserved. 3.5. Images of color changes on the specimens analyzed over time outdoor Figure 3 shows images of the color change in the reference and TiO 2 modified asphalt samples after one month and twelve months of open-air exposure. At month one, the reference specimen exhibits a characteristic black color, whereas the TiO 2 modified specimen displays a brown coloration [ 37 ]. After 12 months of outdoor exposure, the reference specimen developed a dark gray coloration, while the TiO 2 modified specimen exhibited a light gray tone. It can be concluded that prolonged outdoor exposure has caused surface color variations in both analyzed specimens, validating the color change observed in the laboratory. Table 4 displays the measured albedo values in pavement specimens at month one and month twelve of outdoor exposure. Table 4 Albedo measurements for reference and TiO 2 modified specimens under outdoor exposure conditions. Specimen April 2024 April 2025 Reference 0,05 0,07 TiO 2 modified 0,11 0,16 It is verified that the incorporation of TiO 2 into the asphalt mixture increases the albedo from the start of the experiment. After 12 months of outdoor exposure, compared to its initial value, there was a ca 45,5% increase in the albedo of TiO 2 modified specimen. This sustained enhancement in albedo highlights TiO 2 effectiveness in maintaining radiative properties under environmental stress. The time-dependent improvement suggests that TiO 2 contributes to long-term urban heat mitigation capabilities of asphalt surfaces. 3.6. Changes in surface temperature with the solar day of specimens exposed to outdoor conditions In April 2024, the TiO 2 modified specimen exhibited, at solar zenith, a surface temperature 3,1°C lower than that shown by the reference specimen. Twelve months later, April 2025, the TiO 2 modified specimen exhibited, at solar zenith, a ca. 8°C reduction in its surface temperature compared to that of the reference specimen. The observed temperature decreases correlates with higher albedo values in specimens after twelve months of outdoor exposure. Notably, the TiO 2 modified specimen demonstrates persistently lower surface temperatures than the reference specimen, starting from initial measurement and maintaining this thermal advantage throughout one year of outdoor. 4. Conclusions and comments This study evaluates thermal aging, UV radiation aging, and natural weathering effects on two asphalt mixtures: a reference mixture and a TiO 2 modified mixture. The impact of replacing 2% lime with 2% TiO 2 in the reference asphalt mixture was assessed by measuring: (1) formulated mastics' physical and rheological properties; (2) specimens' resistance to moisture-induced damage, rutting, and wear-induced mass loss; and (3) specimens' albedo and surface temperature value changes. The most relevant conclusions are: 1. Initial Albedo: The TiO 2 modified specimen exhibits a higher initial albedo compared to the reference specimen. 2. Albedo Increase Over Time: Both specimens showed increased albedo after aging, but the TiO 2 modified specimen exhibited a more pronounced enhancement (0,11 to 0,16), compared to the reference (0,05 to 0,07). 3. Thermal Impact Reduction: The addition of TiO 2 into the asphalt mixture improved the albedo and made the pavement surface cooler, helping to reduce the heat transference from the pavement surface to the surrounding air. 4. Fatigue Damage Tolerance: At intermediate temperatures, the TiO 2 modified mastic exhibits higher fatigue damage tolerance. 5. TiO 2 acts as a UV shield, reducing oxidation (evidenced by FTIR) and surface fouling, as demonstrated by the albedo and low wear-induced mass loss under UV aging. 6. The TiO 2 modified specimen showed good cohesion across aging conditions, evidenced by reduced wear-induced mass loss, meeting specifications (≤ 20%) (Table 3 ). 7. These findings rank TiO 2 as a dual-functional modifier, merging enhanced urban heat island (UHI) mitigation with mechanical durability, thereby advancing climate-resilient pavement design. Declarations Conflicts of interest The authors declare that there is no conflict of interest regarding the publication of this paper. Funding Universidad Tecnológica Nacional, Facultad Regional La Plata. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Author’s contributions The authors confirm contribution to the paper as follows: Study conception and design: P. Cabrera, A. M. Castro Luna, G. Botasso. Data collection and experimental execution: P. Cabrera, I. Zapata Ferrero. Analysis and interpretation of results: P. Cabrera, I. Zapata Ferrero, A. M. Castro Luna. Draft manuscript preparation: A. M. Castro Luna; P. Cabrera. Technical guidance and validation of asphalt mixtures: G. Botasso; A. M. Castro Luna. Critical revision and final manuscript approval: All authors. All authors reviewed the results, contributed to editorial corrections, and approved the final version of the manuscript. Acknowledgments The authors gratefully acknowledge the financial support provided by the Universidad Tecnológica Nacional - Facultad Regional La Plata (UTN-FRLP). We extend our sincere gratitude to Dr. M.E. Hormaiztegui for performing the FTIR spectroscopic analyses. P. Cabrera acknowledges the doctoral fellowship granted by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). References Akbari H, Cartalis C, Kolokotsa D, Muscio A, Pisello AL, Rossi F, Santamouris M, Synnefa A, Wong NH, Zinzi M (2016) Local climate change and urban heat island mitigation techniques–the state of the art. J Civil Eng Manage 22(1):1–16. http://dx.doi.org/10.3846/13923730.2015.1111934 Beltrán Hernández R, Martínez Ortíz J, Lucho Constantino C, Lizárraga Mendiola L, Alzati B (2020) C. Alternatives to counteract the effects of anthropogenic soil sealing. Padi Boletín Científico de Ciencias Básicas e Ingenierías del ICBI, 15(8). 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Ringand-Ball Apparatus ASTM D5/D5M (2020) Standard Test Method for Penetration of Bituminous Materials AASHTO M 320 (2023) Standard Specification for Performance-Grade Asphalt Binder AASHTO T 315 (2024) Determining the Rheological Properties of Asphalt Binder Using. a Dynamic Shear Rheometer (DSR) AASHTO T 283 (2022) Resistance of Compacted Asphalt Mixtures to Moisture-Induced Damage UNE-EN 12697-22 -, Procedimiento B (2022) Wheel Tracking Test NLT-352 (2000) Caracterización de mezclas bituminosas abiertas por medio del ensayo cántabro por pérdida por desgaste ASTM E1918 (2006) Standard Test Method for Measuring Solar Reflectance of Horizontal and Low-Sloped Surfaces in the Field AASHTO R 30 (2002) Mixture Conditioning of Hot-Mix Asphalt (HMA) Akbari H, Levinson R, Stern S (2008) Procedure for measuring the solar reflectance of flat or curved roofing assemblies. Sol Energy 82(7):648–655. http://dx.doi.org/10.1016/j.solener.2008.01.001 ASTM E1933 (2006) Standard Test Methods for Measuring and Compensating for Emissivity Using Infrared Imaging Radiometers Wang X, Li S, Chen P, Li F, Hu X, Hua T (2022) Photocatalytic and antifouling properties of TiO 2 -based photocatalytic membranes. Mater today Chem 23:100650. https://doi.org/10.1016/j.mtchem.2021.100650 Cortés C, Cadenas J, Pérez A, Costa A, Garcia J, Fermoso J, Esquenal J, Potti J (2011) Envejecimiento foto-oxidativo de betunes asfálticos. XXIV Congre-so Mundial de la Carretera, México Huang M, Wen X (2019) Experimental Study on Photocatalytic Effect of Nano TiO 2 Epoxy Emulsified Asphalt Mixture. Appl Sci 9. http://dx.doi.org/10.3390/app9122464 Footnotes Albedo is the ratio of solar radiation reflected by a surface to the total incident radiation; its value varies from 0 (ab-solute absorber) to 1 (absolute reflector). In this paper specimen denotes asphalt mixture, and mastic denotes asphalt binder + fillers. Emissivity represents the infrared energy released by the hot sample over its entire surface, compared to that emitted by a black body at the same temperature. Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7457711","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":505524339,"identity":"9f972118-fb6a-4858-aae2-46bed94b2357","order_by":0,"name":"Pablo Cabrera","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+klEQVRIiWNgGAWjYHACNjDJz3yA8QBMSIIoLZJtCQwHYKqJ02JwjFgt5uyHnz2uqLgnb3yM98HhAobDdeYMzAdv8zDY5ePSYtmTZm545kyx4bZj7AaHZzAclrBsYEu25mFItmzAocXgBoOZZGNbAuO2+20Mh3mAWgwO8JhJ8zAwG+CyxeAG+zfJxn8J9pvb2GBa+L8BtdTj0cIDtKUhIXEDG1wLDxtQy2GcWix7csoNG44lJM84BtQywyBdcsNhNmPLOQbHcWoxZz++7WFDTYJtfxsb4+OCCmt+g+PND2+8qajG7TBkDjOYy4whjlfLKBgFo2AUjAIsAAAhn03hI2WN9QAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0009-0005-7053-9276","institution":"Universidad Tecnológica Nacional, Facultad Regional La Plata, LEMaC Centro de Investigaciones Viales UTN FRLP – CIC PBA, La Plata, Buenos Aires, Argentina","correspondingAuthor":true,"prefix":"","firstName":"Pablo","middleName":"","lastName":"Cabrera","suffix":""},{"id":505524340,"identity":"35540ff1-b388-4e9e-a407-ab090f7d8cf2","order_by":1,"name":"Ignacio Zapata Ferrero","email":"","orcid":"https://orcid.org/0000-0002-8779-4645","institution":"Universidad Tecnológica Nacional, Facultad Regional La Plata, LEMaC Centro de Investigaciones Viales UTN FRLP – CIC PBA, La Plata, Buenos Aires, Argentina","correspondingAuthor":false,"prefix":"","firstName":"Ignacio","middleName":"Zapata","lastName":"Ferrero","suffix":""},{"id":505524341,"identity":"69d7627d-83a3-4a30-99cf-6c41e83f0bee","order_by":2,"name":"Gerardo Botasso","email":"","orcid":"https://orcid.org/0000-0002-8859-7256","institution":"Universidad Tecnológica Nacional, Facultad Regional La Plata, LEMaC Centro de Investigaciones Viales UTN FRLP – CIC PBA, La Plata, Buenos Aires, Argentina","correspondingAuthor":false,"prefix":"","firstName":"Gerardo","middleName":"","lastName":"Botasso","suffix":""},{"id":505524342,"identity":"13b366e8-0b3c-42b7-aafe-9b3375e66e95","order_by":3,"name":"Ana M. Castro Luna","email":"","orcid":"https://orcid.org/0000-0003-0799-1313","institution":"Comisión de Investigaciones Científicas CIC PBA, La Plata, Buenos Aires, Argentina","correspondingAuthor":false,"prefix":"","firstName":"Ana","middleName":"M. Castro","lastName":"Luna","suffix":""}],"badges":[],"createdAt":"2025-08-26 02:03:20","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-7457711/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7457711/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90014663,"identity":"3a64f644-f6de-4025-8864-f8019352e1e9","added_by":"auto","created_at":"2025-08-27 11:34:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":63408,"visible":true,"origin":"","legend":"\u003cp\u003eIR spectrum of UV treated mastics, reference mastic (red) and TiO\u003csub\u003e2\u003c/sub\u003e modified mastic (blue).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7457711/v1/e30d016b6842ad65c5995e2a.png"},{"id":90014669,"identity":"b69a994a-245d-4e1c-8413-fb5425ec7be0","added_by":"auto","created_at":"2025-08-27 11:34:46","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":679858,"visible":true,"origin":"","legend":"\u003cp\u003eCylindrical specimens: reference (A1–A3) and TiO\u003csub\u003e2\u003c/sub\u003e modified (B1–B3) virgin; reference (A4–A6) and TiO\u003csub\u003e2\u003c/sub\u003e modified (B4–B6) after long-term thermal aging; reference (A7–A9) and TiO\u003csub\u003e2\u003c/sub\u003e modified (B7–B9) after UV-A radiation-induced aging.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7457711/v1/a05cf728cd95d2e24af6ed73.png"},{"id":90014666,"identity":"18d1ec77-e2e9-4225-9c3b-654b74a10d88","added_by":"auto","created_at":"2025-08-27 11:34:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":944518,"visible":true,"origin":"","legend":"\u003cp\u003eReference (A) and TiO\u003csub\u003e2\u003c/sub\u003e modified (C) specimens after one month outdoor and reference (B) and TiO\u003csub\u003e2\u003c/sub\u003e modified (D) specimens after twelve months outdoor.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7457711/v1/851301ff566a72d2cf46bb66.png"},{"id":90015536,"identity":"2620c0c6-ea86-4df6-b1b7-b7fe9a4ec12d","added_by":"auto","created_at":"2025-08-27 11:42:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":20879,"visible":true,"origin":"","legend":"\u003cp\u003eReference (A) and TiO\u003csub\u003e2\u003c/sub\u003e modified (C) specimens after one month outdoor and reference (B) and TiO\u003csub\u003e2\u003c/sub\u003e modified (D) specimens after twelve months outdoor.\u003c/p\u003e","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7457711/v1/ab2329e304f8a3853ad76252.png"},{"id":90015753,"identity":"b3cbfacf-fc5b-419b-a312-62b346fd94cd","added_by":"auto","created_at":"2025-08-27 11:50:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2921699,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7457711/v1/3e4ff0af-4d68-4a12-a0f3-3f39174f7073.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eThermo-Rheological Characterization and Performance Evaluation of Sustainable TiO\u003csub\u003e2\u003c/sub\u003e-Modified Hot Mix Asphalt (HMA) Formulations for Urban Pavement Infrastructure\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eFighting against climate change is one of the most urgent challenges facing the community in the 21st century, as climate change shows a serious threat to life. Natural disasters are becoming more frequent, leading to a loss of biodiversity and an increase in ambient temperatures; crops are destroyed, ecosystem diversity is reduced, and the spread of diseases is accelerated. According to statistical projections, by 2050, more than half of the world's population will live in megacities.\u003c/p\u003e\u003cp\u003eCurrently, modern cities face a continuous increase in population density, which requires meeting the demand for increased housing and transportation infrastructure. To address road traffic problems, natural soil is usually replaced with impermeable surfaces such as asphalt pavements. This modification of the native terrain reduces groundwater infiltration, increases surface runoff, and flood risks. Sustainable and adaptable pavement infrastructure is essential to address current economic and environmental challenges [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAn asphalt pavement is composed of asphalt, a mixture of organic compounds mainly hydrocarbons, aggregates of different sizes, and filling material (fillers) to fill voids and improve cohesion. Asphalt acts as a binder to glue both the loose aggregates with an appropriate particle size distribution and the fillers. It is the asphalt that gives the pavement the mechanical properties that allow it to achieve load-bearing capacity and adequate road safety.\u003c/p\u003e\u003cp\u003eIn summer, high surface temperature of the pavements is one of the contributors to explain the urban heat island effect (UHI), that accounts for a higher ambient temperature in the city than in the surrounding rural areas [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Consequently, fossil energy consumption is necessary to cool buildings and homes.\u003c/p\u003e\u003cp\u003eA conventional asphalt pavement has moderate thermal conductivity and can transfer heat to its interior, storing it during daylight hours and releasing it into the air during dusk and night [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Most of the solar absorption is returned to the environment by convection transference and longwave emission [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In addition, as asphalt is viscous, its resistance to load decreases with increasing temperature, which causes irreversible deformations or rutting in the pavement, thus reducing its useful life. Initially in service, dark-colored asphalt pavements have low albedo\u003csup\u003e1\u003c/sup\u003e values of approximately 0,05. Pavements surfaces lighten over time and slightly increase their albedo, heating up a little less.\u003c/p\u003e\u003cp\u003eVarious strategies have been proposed to mitigate heat emissions from pavements. These include incorporating light-reflective pigments such as titanium dioxide (TiO\u003csub\u003e2\u003c/sub\u003e) or zinc oxide (ZnO) into asphalt mixtures or applying surface coatings containing these materials through spraying techniques. A lighter colored pavement increases its solar reflectance, which reduces heat absorption and lowers surface temperature, thereby addressing thermal accumulation in urban environments [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. A cold pavement is defined as one that, compared to a conventional pavement, reaches lower surface temperature values when exposed to the same solar irradiation. If the pavement is not heated, energy savings are achieved, and the quality of the urban microclimate is improved. There is a link between the albedo of pavements and its effect on air temperature in large cities. Higher albedo reduces solar energy absorption in pavements. Due to its lighter surface color, TiO\u003csub\u003e2\u003c/sub\u003e modified asphalt exhibits lower heat absorption than the reference material, both when newly installed and after one year outdoors, demonstrating its potential to mitigate urban heat island effects [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The fading color of asphalt pavement surfaces is influenced by multiple factors, with aging emerging as a primary contributing factor. The complex molecular structure of asphalt and its chemical components are modified because asphalt exposure to sunlight and atmospheric conditions alter its properties.\u003c/p\u003e\u003cp\u003eGiven the complex molecular mixture comprising asphalt, chromatographic separation has been proposed as a method to reduce this complexity by fractionating the material into the SARA components (saturates, aromatics, resins, asphaltenes) according to their increasing polarity [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAsphalt aging entails complex physicochemical changes in the binder induced by heat and ultraviolet (UV) radiation. The latter initiates a photochemical oxidation chain reaction, breaking down molecules, generating oxygen-rich functional groups (e.g., carbonyls, sulfoxides), and increasing asphaltene content. There is an increase in binder stiffness and brittleness and adhesion reduction, causing pavement distress [\u003cspan additionalcitationids=\"CR11 CR12 CR13 CR14 CR15 CR16\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The process synergizes with heat and oxygen, accelerating markedly at higher temperatures. Though UV degradation initiates at the surface, its effects propagate deeper into the pavement via cracking pathways.\u003c/p\u003e\u003cp\u003eTo understand the evolution of asphalt's internal composition during thermal-oxidative aging, changes in polarity and molecular weight were tracked over time, revealing component degradation and interconversion. Thermal oxidation, an irreversible oxidative aging process, occurs mainly during manufacturing, transport, and placement of asphalt mixtures. It involves volatilization of light components (saturates, aromatics) and microstructural reorganization [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. UV oxidation (photo-oxidative aging), however, is the main mechanism for long-term deterioration during service life. Facilitated by ultraviolet radiation and oxygen, it drives the predominant form of long-term asphalt aging.\u003c/p\u003e\u003cp\u003eOnce asphalt aging occurs in the mixture, cracking is more easily initiated under traffic loads due to the increased stiffness and reduced adhesion of aged asphalt binder.\u003c/p\u003e\u003cp\u003eIt is possible to delay the UV aging of asphalt by investigating effective proposals to improve the resistance of asphalt to aging. Thus, UV absorbers, light-blocking agents, and antioxidants have been analyzed with the intention of generating a complete and reliable system of resistance to UV aging [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The incorporation of anti-aging agents represents a simple and effective strategy to mitigate asphalt aging. Inorganic anti-aging agents have also garnered extensive attention in asphalt aging resistance research, such as TiO\u003csub\u003e2\u003c/sub\u003e, that can absorb and shield UV radiation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis study evaluates the rheological behavior of AM-3 asphalt mastic\u003csup\u003e2\u003c/sup\u003e without and with TiO\u003csub\u003e2\u003c/sub\u003e incorporation and before and after accelerate aging in laboratory. The mechanical resistance and opto thermal properties of pavement specimens formulated without and with TiO\u003csub\u003e2\u003c/sub\u003e incorporation were also determined, at the beginning and after one year of outdoor exposure. The specimen key parameters including albedo, emissivity, and surface temperature were determined. Moreover, in specimens without and with TiO\u003csub\u003e2\u003c/sub\u003e addition, the mass loss percentage after aging protocols have been tested according to the requirements of ANRC to evaluate the quality of the modified asphalt pavement.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Design and dosage of asphalt mixtures\u003c/h2\u003e\u003cp\u003eFollowing the technical specifications of the Argentine National Road Commission, ANRC [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], two asphalt mixtures designed according to the Marshall method were used. Both are a type of discontinuous mix called hot-mix asphalt micro agglomerate, the purpose of which is to provide the road surface of a street or route with the necessary mechanical strength, macrotexture, slip resistance, and acoustic properties. The first mixture, named reference mixture is composed by modified asphalt binder AM-3, coarse and fine aggregates with commercial designations 6\u0026ndash;12 and 0\u0026ndash;6, respectively, and as combined fillers lime plus the dust coming from the coarse and fine aggregates passing the #200 sieve (75 \u0026micro;m). The second mixture named TiO\u003csub\u003e2\u003c/sub\u003e modified mixture contains the same percentages of coarse and fine aggregates, and in the fillers 2% of lime are replaced with 2% of TiO\u003csub\u003e2\u003c/sub\u003e a powdered pigment compliant with ASTM C979 specifications [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The dosage used in the reference mixture is composed of 57% coarse aggregate, 35,2% fine aggregate, 2,9% lime, and 5% AM-3 asphalt binder. Whereas the dosage of the TiO\u003csub\u003e2\u003c/sub\u003e modified mixture is composed of 57,1% coarse aggregate, 35,2% fine aggregate, 1% lime, 2% TiO\u003csub\u003e2\u003c/sub\u003e, and 4,8% AM-3 asphalt binder.\u003c/p\u003e\u003cp\u003eQuadrangular prism (300 mm \u0026times; 300 mm \u0026times; 50 mm) and cylindrical (\u0026Oslash; 102 mm \u0026times; 64 mm) specimens were prepared using both reference and TiO\u003csub\u003e2\u003c/sub\u003e modified asphalt mixtures for subsequent experimental testing.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Conditioning of the mastic prior to analysis\u003c/h2\u003e\u003cp\u003eThree accelerated aging protocols were implemented to evaluate the effect of TiO\u003csub\u003e2\u003c/sub\u003e addition on the physical and rheological properties of the reference mastics: i) short-term thermal oxidative aging via the Rolling Thin Film Oven Test (RTFOT) [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]; ii) long-term thermal oxidative aging through sequential RTFOT and Pressure Aging Vessel (PAV) [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]; and iii) RTFOT and UV, photo-oxidative aging in a chamber equipped with lamps that emit UV-A radiation at a wavelength of 368 nm [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e2.2.1. Determination of physical and rheological properties of mastics\u003c/h2\u003e\u003cp\u003eThe performance of asphalt mastics was evaluated by measuring the softening point (via ring-and-ball technique) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] and the penetration (via needle penetrometer method) [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. These measurements used mastics with compositions identical to those in the reference mixture and the TiO\u003csub\u003e2\u003c/sub\u003e modified mixture before and after short-term thermal aging RTOFT. The penetration test measures the hardness and consistency of asphalt mastics, and the softening point test determines the temperature at which the material reaches a specific degree of softening under controlled conditions. Using a dynamic shear rheometer (DSR), the complex shear modulus (G*) and phase angle (δ) were measured to determine rheological parameters related to short-term failure, rutting parameter G*/sinδ, and long-term failure, fatigue parameter, G*.sinδ [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eG*/sinδ is determined on both mastics, without and with short-term thermal aging, and G*.sinδ is determined on both mastics with long-term thermal aging, the latter comprising a short-term thermal aging followed by a second conditioning using PAV.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Analysis of the mechanical behavior of both specimens\u003c/h2\u003e\u003cp\u003eThe impact on the mechanical behavior of the asphalt mixtures used is analyzed. To this end, moisture-induced damage is evaluated using the modified Lottman test [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], which shows the loss of mastic-aggregate adhesion that the mixture will experience. Resistance to rutting damage is also evaluated using the wheel tracking test [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Furthermore, the mixtures resistance to disintegration under the abrasive and suction effects caused by traffic was determined through the Cantabro wear loss test [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. The test analyzes the behavior of reference and TiO\u003csub\u003e2\u003c/sub\u003e modified specimens under different conditioning: i) virgin, ii) with short and long-term thermal aging [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] and iii) with short-term thermal aging\u0026thinsp;+\u0026thinsp;UV-A photo-oxidative aging.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Measurements of opto-thermal properties\u003c/h2\u003e\u003cp\u003eThe albedo value of each specimen was evaluated according to the ASTM E1918 standard [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], modified by Akbari et al. [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], a clear day in April 2024, and April 2025 in an area adjacent to the parking lot of the Regional Faculty of the National Technological University of La Plata. The instrumentation used was a Kipp\u0026amp;Zonen CMP-3 pyranometer (sensitivity: 25,7 \u0026micro;V.m\u003csup\u003e2\u003c/sup\u003e.W\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; uncertainty: 0,67 \u0026micro;V.m\u003csup\u003e2\u003c/sup\u003e.W\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) associated with a Campbell Scientific CR300 data logger. Each specimen\u0026rsquo;s albedo was measured through six experimental repetitions, with a standard deviation of \u0026plusmn;\u0026thinsp;0,3%.\u003c/p\u003e\u003cp\u003eTo determine the ε emissivity\u003csup\u003e3\u003c/sup\u003e of each specimen, a Testo 865 thermal imaging camera with an infrared resolution of 320 x 240 pixels and a temperature difference display of \u0026plusmn;\u0026thinsp;0,1\u0026deg;C was used, in accordance with [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe surface temperatures of the Sun-exposed specimens were recorded using K-type thermocouples connected to data loggers. The values have been taken over four days in April 2024 and April 2025.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eIn this work, the testing methods used to characterize asphalt binders are adopted for the evaluation of the mastic in both the reference asphalt mixture and the TiO\u003csub\u003e2\u003c/sub\u003e modified asphalt mixture.\u003c/p\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Physical characterization of mastics\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the penetration and the softening point values of reference and TiO\u003csub\u003e2\u003c/sub\u003e modified mastics without and with short-term thermal aging.\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\u003ePhysical properties of reference and TiO\u003csub\u003e2\u003c/sub\u003e modified mastics without and with short-term thermal aging.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eMastic\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eVirgin\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eShort-term thermal aging\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePenetration (mm\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSoftening Point (\u0026deg;C)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePenetration (mm\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eSoftening Point (\u0026deg;C)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e111\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e114\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e modified\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e112\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e114\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIn virgin mastics, both the reference and the TiO\u003csub\u003e2\u003c/sub\u003e modified mastics show identical penetration values and only a minor difference in their softening point values. However, after short-term thermal aging, there is a notable decrease in the penetration value of the reference mastic, while there is practically no variation in that of the TiO\u003csub\u003e2\u003c/sub\u003e modified mastic. Consequently, 2% TiO\u003csub\u003e2\u003c/sub\u003e significantly improves the aging resistance of the modified mastic.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Rheological parameters of mastics\u003c/h2\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e3.2.1. Determination of High Temperatures Performance Grade (HTPG)\u003c/h2\u003e\u003cp\u003eThe temperature sweep test was run on both mastics to determine from the G*/sinδ vs temperature values the maximum temperature at which each mastic resists rutting failure. Both mastics exhibit identical HTPG values of 118\u0026deg;C. This behavior indicates that replacing 2% of lime content with TiO\u003csub\u003e2\u003c/sub\u003e in the mixture formulation causes no significant changes in rutting resistance.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e3.2.2. Determination of fatigue parameter\u003c/h2\u003e\u003cp\u003eThe fatigue parameter of mastics was evaluated at an intermediate service temperature of 30\u0026deg;C and at a frequency of 10 rad.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The corresponding G*\u0026middot;sinδ fatigue parameter values for both mixtures are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\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\u003ePhysical and chemical properties of crumb rubber.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMastic\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFatigue Parameter (kPa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTolerated Limit (kPa)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2751\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e5000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e modified\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1672\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe fatigue parameter quantifies an asphalt binder\u0026rsquo;s resistance to cracking under repeated pavement loading, at intermediate temperature. While values below 5000 kPa indicate acceptable fatigue performance, lower fatigue parameters values correspond to higher resistance to repetitive loading. The results at intermediate temperatures shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e indicate that replacing 2% of lime by 2% TiO\u003csub\u003e2\u003c/sub\u003e significantly improves the mastic\u0026rsquo;s resistance to fatigue failure.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Mastics analysis by Fourier Transform Infrared Spectroscopy (FTIR)\u003c/h2\u003e\u003cp\u003ePhoto-oxidative aging driven by UV radiation and oxygen exposure has been identified as the predominant mechanism underlying long-term asphalt pavement deterioration. When applied to transport infrastructure surfaces, asphalt materials undergo UV radiation within a specific solar frequency band. This exposure initiates free-radical reactions and progressively increases specific functional groups, especially carbonyl and sulfoxide groups [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFTIR spectra of the unmodified and TiO\u003csub\u003e2\u003c/sub\u003e modified mastics which were treated in a laboratory UV-A chamber during a time equivalent to 5 years of outdoor exposure, are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eUpon photon irradiation, photocatalytic materials facilitate electron transitions from the valence band to the con-duction band, generating electron-hole pairs through photoexcitation. These charge carriers can either directly oxidize organic pollutants or react with dissolved oxygen or OH⁻ ions to produce reactive oxygen species for indirect pollutant oxidation [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Thus, TiO\u003csub\u003e2\u003c/sub\u003e competes with asphalt for UV radiation, acting as a UV shield that reduces degradation of asphalt's organic components.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eSpectroscopic analysis revealed notably stronger C\u0026thinsp;=\u0026thinsp;O, S\u0026thinsp;=\u0026thinsp;O and C\u0026thinsp;=\u0026thinsp;C bond signals in the reference mastic than in the TiO\u003csub\u003e2\u003c/sub\u003e modified mastic after UV-A photooxidation, indicating a TiO\u003csub\u003e2\u003c/sub\u003e mitigating effect on oxidative aging. The signal of TiO\u003csub\u003e2\u003c/sub\u003e stretching at 450 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e diminishes after UV-A radiation exposure as found in [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Analysis of thermal and UV aging of cylindrical specimens\u003c/h2\u003e\u003cp\u003eAsphalt aging induces premature and severe pavement deterioration. To simulate in-service climatic degradation mechanisms, cylindrical specimens underwent accelerated aging protocols (both short- and long-term) involving exposure to elevated temperatures and UV-A radiation for controlled durations.\u003c/p\u003e\u003cp\u003eIt is confirmed that pavement surface color-fading caused by UV-A radiation is much more intense than darkening caused by thermal aging. Long-term thermal aging increases asphalt's asphaltene fraction by degrading saturates, aromatics, and resins. This compositional shift demonstrates oxidative aging accelerates conversion to asphaltenes, the dark-colored asphalt constituents that make pavement darkening. UV-A radiation induces significantly more intense color-fading in pavement surfaces. Unmodified asphalt pavements typically exhibit progressive graying over time. In contrast, TiO\u003csub\u003e2\u003c/sub\u003e modified specimens undergo a distinct color transition sequence: initial brown, dark brown (after thermal oxidative aging), light grey (after photooxidative UV-A aging).\u003c/p\u003e\u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\u003ch2\u003e3.4.1. Laboratory testing of specimen\u0026rsquo;s behavior through simulated in-service pavement conditions\u003c/h2\u003e\u003cp\u003eDifferent tests were done to validate the resistance of asphalt mixtures to variable climatic factors and to traffic load. Inducing moisture damage in reference and TiO\u003csub\u003e2\u003c/sub\u003e containing specimens were measured by the modified Lottman test. It was observed that the TiO\u003csub\u003e2\u003c/sub\u003e modified specimen has a higher preserved resistance, showing better adhesion of the mastic to the aggregates. Besides, the specimens were subjected to repeated passes of a loaded wheel, and the rutting depth is measured. After wheel tracking testing, it was not found significant variations in the rutting depth, and both reference and TiO\u003csub\u003e2\u003c/sub\u003e modified specimens performing below the established tolerable limit.\u003c/p\u003e\u003cp\u003eThe Cantabro test was adopted to evaluate the cohesion of the asphalt mastic in the studied mixture and used as a bearing layer, both reference and TiO\u003csub\u003e2\u003c/sub\u003e modified specimen. This test was also accomplished with specimens after thermal or UV-A radiation treatment. In Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e the percentage mass loss of all specimens analyzed are shown.\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\u003ePercentage mass loss after aging protocols in reference vs TiO\u003csub\u003e2\u003c/sub\u003e modified pavement specimens.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSpecimen\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e modified\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePercentage Mass Loss\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePercentage Mass Loss\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVirgin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eShort-Term Thermal Aging\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLong-Term Thermal Aging\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUV-A Aging\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAccording to European specifications the maximum mass loss percentage tolerable is 20%.\u003c/p\u003e\u003cp\u003eThe results shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e attest that replacing 2% of lime with 2% TiO\u003csub\u003e2\u003c/sub\u003e reduces disintegration maintaining cohesion in virgin specimens. Similar resistance is observed in specimens under thermal aging. The photooxidative UV aging on TiO\u003csub\u003e2\u003c/sub\u003e modified specimens exhibit a close behavior to that of specimens subjected to long-term thermal aging what means that the cohesion was always preserved.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.5. Images of color changes on the specimens analyzed over time outdoor\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows images of the color change in the reference and TiO\u003csub\u003e2\u003c/sub\u003e modified asphalt samples after one month and twelve months of open-air exposure.\u003c/p\u003e\u003cp\u003eAt month one, the reference specimen exhibits a characteristic black color, whereas the TiO\u003csub\u003e2\u003c/sub\u003e modified specimen displays a brown coloration [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. After 12 months of outdoor exposure, the reference specimen developed a dark gray coloration, while the TiO\u003csub\u003e2\u003c/sub\u003e modified specimen exhibited a light gray tone. It can be concluded that prolonged outdoor exposure has caused surface color variations in both analyzed specimens, validating the color change observed in the laboratory.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e displays the measured albedo values in pavement specimens at month one and month twelve of outdoor exposure.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAlbedo measurements for reference and TiO\u003csub\u003e2\u003c/sub\u003e modified specimens under outdoor exposure conditions.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpecimen\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eApril 2024\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eApril 2025\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0,05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0,07\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e modified\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0,11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0,16\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIt is verified that the incorporation of TiO\u003csub\u003e2\u003c/sub\u003e into the asphalt mixture increases the albedo from the start of the experiment. After 12 months of outdoor exposure, compared to its initial value, there was a ca 45,5% increase in the albedo of TiO\u003csub\u003e2\u003c/sub\u003e modified specimen. This sustained enhancement in albedo highlights TiO\u003csub\u003e2\u003c/sub\u003e effectiveness in maintaining radiative properties under environmental stress. The time-dependent improvement suggests that TiO\u003csub\u003e2\u003c/sub\u003e contributes to long-term urban heat mitigation capabilities of asphalt surfaces.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e3.6. Changes in surface temperature with the solar day of specimens exposed to outdoor conditions\u003c/h2\u003e\u003cp\u003eIn April 2024, the TiO\u003csub\u003e2\u003c/sub\u003e modified specimen exhibited, at solar zenith, a surface temperature 3,1\u0026deg;C lower than that shown by the reference specimen. Twelve months later, April 2025, the TiO\u003csub\u003e2\u003c/sub\u003e modified specimen exhibited, at solar zenith, a ca. 8\u0026deg;C reduction in its surface temperature compared to that of the reference specimen.\u003c/p\u003e\u003cp\u003eThe observed temperature decreases correlates with higher albedo values in specimens after twelve months of outdoor exposure. Notably, the TiO\u003csub\u003e2\u003c/sub\u003e modified specimen demonstrates persistently lower surface temperatures than the reference specimen, starting from initial measurement and maintaining this thermal advantage throughout one year of outdoor.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusions and comments","content":"\u003cp\u003eThis study evaluates thermal aging, UV radiation aging, and natural weathering effects on two asphalt mixtures: a reference mixture and a TiO\u003csub\u003e2\u003c/sub\u003e modified mixture. The impact of replacing 2% lime with 2% TiO\u003csub\u003e2\u003c/sub\u003e in the reference asphalt mixture was assessed by measuring: (1) formulated mastics' physical and rheological properties; (2) specimens' resistance to moisture-induced damage, rutting, and wear-induced mass loss; and (3) specimens' albedo and surface temperature value changes.\u003c/p\u003e\u003cp\u003eThe most relevant conclusions are:\u003c/p\u003e\u003cp\u003e1. Initial Albedo: The TiO\u003csub\u003e2\u003c/sub\u003e modified specimen exhibits a higher initial albedo compared to the reference specimen.\u003c/p\u003e\u003cp\u003e2. Albedo Increase Over Time: Both specimens showed increased albedo after aging, but the TiO\u003csub\u003e2\u003c/sub\u003e modified specimen exhibited a more pronounced enhancement (0,11 to 0,16), compared to the reference (0,05 to 0,07).\u003c/p\u003e\u003cp\u003e3. Thermal Impact Reduction: The addition of TiO\u003csub\u003e2\u003c/sub\u003e into the asphalt mixture improved the albedo and made the pavement surface cooler, helping to reduce the heat transference from the pavement surface to the surrounding air.\u003c/p\u003e\u003cp\u003e4. Fatigue Damage Tolerance: At intermediate temperatures, the TiO\u003csub\u003e2\u003c/sub\u003e modified mastic exhibits higher fatigue damage tolerance.\u003c/p\u003e\u003cp\u003e5. TiO\u003csub\u003e2\u003c/sub\u003e acts as a UV shield, reducing oxidation (evidenced by FTIR) and surface fouling, as demonstrated by the albedo and low wear-induced mass loss under UV aging.\u003c/p\u003e\u003cp\u003e6. The TiO\u003csub\u003e2\u003c/sub\u003e modified specimen showed good cohesion across aging conditions, evidenced by reduced wear-induced mass loss, meeting specifications (\u0026le;\u0026thinsp;20%) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e7. These findings rank TiO\u003csub\u003e2\u003c/sub\u003e as a dual-functional modifier, merging enhanced urban heat island (UHI) mitigation with mechanical durability, thereby advancing climate-resilient pavement design.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eConflicts of interest\u003c/h2\u003e\u003cp\u003eThe authors declare that there is no conflict of interest regarding the publication of this paper.\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eUniversidad Tecnol\u0026oacute;gica Nacional, Facultad Regional La Plata. Consejo Nacional de Investigaciones Cient\u0026iacute;ficas y T\u0026eacute;cnicas (CONICET).\u003c/p\u003e\u003ch2\u003eAuthor\u0026rsquo;s contributions\u003c/h2\u003e\u003cp\u003eThe authors confirm contribution to the paper as follows:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eStudy conception and design: P. Cabrera, A. M. Castro Luna, G. Botasso.\u003c/li\u003e\n \u003cli\u003eData collection and experimental execution: P. Cabrera, I. Zapata Ferrero.\u003c/li\u003e\n \u003cli\u003eAnalysis and interpretation of results: P. Cabrera, I. Zapata Ferrero, A. M. Castro Luna.\u003c/li\u003e\n \u003cli\u003eDraft manuscript preparation: A. M. Castro Luna; P. Cabrera.\u003c/li\u003e\n \u003cli\u003eTechnical guidance and validation of asphalt mixtures: G. Botasso; A. M. Castro Luna.\u003c/li\u003e\n \u003cli\u003eCritical revision and final manuscript approval: All authors.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eAll authors reviewed the results, contributed to editorial corrections, and approved the final version of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e\u003cp\u003eThe authors gratefully acknowledge the financial support provided by the Universidad Tecnol\u0026oacute;gica Nacional - Facultad Regional La Plata (UTN-FRLP). We extend our sincere gratitude to Dr. M.E. Hormaiztegui for performing the FTIR spectroscopic analyses. P. Cabrera acknowledges the doctoral fellowship granted by the Consejo Nacional de Investigaciones Cient\u0026iacute;ficas y T\u0026eacute;cnicas (CONICET).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAkbari H, Cartalis C, Kolokotsa D, Muscio A, Pisello AL, Rossi F, Santamouris M, Synnefa A, Wong NH, Zinzi M (2016) Local climate change and urban heat island mitigation techniques\u0026ndash;the state of the art. J Civil Eng Manage 22(1):1\u0026ndash;16. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.3846/13923730.2015.1111934\u003c/span\u003e\u003cspan address=\"10.3846/13923730.2015.1111934\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBeltr\u0026aacute;n Hern\u0026aacute;ndez R, Mart\u0026iacute;nez Ort\u0026iacute;z J, Lucho Constantino C, Liz\u0026aacute;rraga Mendiola L, Alzati B (2020) C. 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Mater today Chem 23:100650. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.mtchem.2021.100650\u003c/span\u003e\u003cspan address=\"10.1016/j.mtchem.2021.100650\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCort\u0026eacute;s C, Cadenas J, P\u0026eacute;rez A, Costa A, Garcia J, Fermoso J, Esquenal J, Potti J (2011) Envejecimiento foto-oxidativo de betunes asf\u0026aacute;lticos. XXIV Congre-so Mundial de la Carretera, M\u0026eacute;xico\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHuang M, Wen X (2019) Experimental Study on Photocatalytic Effect of Nano TiO\u003csub\u003e2\u003c/sub\u003e Epoxy Emulsified Asphalt Mixture. Appl Sci 9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.3390/app9122464\u003c/span\u003e\u003cspan address=\"10.3390/app9122464\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Footnotes","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003e Albedo is the ratio of solar radiation reflected by a surface to the total incident radiation; its value varies from 0 (ab-solute absorber) to 1 (absolute reflector).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e In this paper specimen denotes asphalt mixture, and mastic denotes asphalt binder\u0026thinsp;+\u0026thinsp;fillers.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e Emissivity represents the infrared energy released by the hot sample over its entire surface, compared to that emitted by a black body at the same temperature.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Universidad Tecnológica Nacional, Facultad Regional La Plata, LEMaC Centro de Investigaciones Viales UTN FRLP - CIC PBA, La Plata, Buenos Aires, Argentina","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Cool Pavements, TiO2, Albedo, Urban Heat Island, Asphalt Mastic Aging","lastPublishedDoi":"10.21203/rs.3.rs-7457711/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7457711/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUrban heat islands (UHIs), exacerbated by conventional asphalt pavements that absorb up to 95% of solar radiation, elevate urban temperatures, energy demands, and air pollution. To mitigate UHI effects, this study investigates the thermal and mechanical performance of asphalt pavements modified with titanium dioxide (TiO\u003csub\u003e2\u003c/sub\u003e), a photocatalytic pigment that enhances solar reflectance and promotes surface cooling. The physicochemical properties of reference and TiO\u003csub\u003e2\u003c/sub\u003e modified asphalt mastics were evaluated, including penetration, softening point, and rheo-logical behavior (rutting resistance via G*/sinδ and fatigue performance via G*\u0026middot;sinδ). Aging effects were assessed through controlled UV and oxidative exposure. Results demonstrate that TiO\u003csub\u003e2\u003c/sub\u003e incorporation increased solar reflectance by 45,5% in 12 months, reducing surface temperatures by up to 8\u0026deg;C compared to conventional asphalt pavement. This cooling effect, attributed to TiO\u003csub\u003e2\u003c/sub\u003e\u0026rsquo;s dual role as a photon-reflective and photocatalytic material, was maintained even after aging, with the solar reflectance increasing under outdoors environmental degradation. Mechanically, the modified mastic exhibited comparable rutting resistance and enhanced fatigue performance to reference mastic. Furthermore, TiO\u003csub\u003e2\u003c/sub\u003e modified specimens demonstrated enhanced moisture resistance (modified Lottman test) and retained deformation resistance comparable to conventional asphalt mixture in wheel tracking tests. These findings position TiO\u003csub\u003e2\u003c/sub\u003e modified asphalt mastic as a multifunctional solution for UHI mitigation, combining passive radiative cooling, photocatalytic pollution reduction, and robust pavement performance. Future work should optimize TiO\u003csub\u003e2\u003c/sub\u003e dispersion protocols and evaluate long-term cost-benefit ratios for scalable urban implementation.\u003c/p\u003e","manuscriptTitle":"Thermo-Rheological Characterization and Performance Evaluation of Sustainable TiO2-Modified Hot Mix Asphalt (HMA) Formulations for Urban Pavement Infrastructure","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-27 11:34:41","doi":"10.21203/rs.3.rs-7457711/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"77abb66f-1179-4504-b2dc-e7590b7c7a1c","owner":[],"postedDate":"August 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":53691517,"name":"Environmental Engineering"},{"id":53691518,"name":"Materials Engineering"},{"id":53691519,"name":"Civil Engineering"}],"tags":[],"updatedAt":"2025-08-27T11:34:41+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-27 11:34:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7457711","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7457711","identity":"rs-7457711","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}