Transforming Rice Husk Ash into Road Safety: A Sustainable Approach to Glass Microsphere Production

Abstract

Glass microspheres are essential components in horizontal road markings due to their retroreflective properties, enhancing visibility and safety under low-light conditions. Traditionally produced from soda-lime glass made with high-purity silica from sand, their manufacturing raises environmental concerns amid growing global sand scarcity. This study explores the viability of rice husk ash (RHA)—a high-silica byproduct of rice processing—as a sustainable raw material for microsphere fabrication. A glass composition containing 70 wt% SiO₂ was formulated using RHA and melted at 1500 °C. Microspheres were produced through flame spheroidization and characterized following the Brazilian standard NBR 16184:2021 for Type IB beads. The RHA-derived microspheres exhibited high sphericity, appropriate size distribution (63–300 μm), density of 2.42 g/cm³, and the required acid resistance. UV-Vis analysis confirmed their optical transparency, and the refractive index was measured as 1.55 ± 0.03. Retroreflectivity tests under standardized conditions revealed performance comparable to commercial counterparts. These results demonstrate the technical feasibility of replacing conventional silica with RHA in glass microsphere production, aligning with circular economy principles and promoting sustainable infrastructure. Given Brazil’s significant rice production and corresponding RHA availability, this approach offers both environmental and socio-economic benefits for road safety and material innovation.

1. Introduction

Horizontal road markings play a critical role in modern transportation systems, serving as visual guides that regulate traffic flow, delineate lanes, and enhance road safety, especially under low-visibility conditions [1,2]. However, the lack of adequate road markings or their premature deterioration is a persistent issue worldwide, contributing to a significant number of road traffic accidents. According to estimates from the World Health Organization (WHO) [3], over 1.1 million people die annually in road traffic crashes, and many of these incidents are exacerbated by insufficient or ineffective road signage and demarcation.

To enhance the visibility and durability of road markings, glass microspheres are incorporated into paints and thermoplastic materials. These microspheres function as retroreflective elements, reflecting the incident light from vehicle headlights directly back to drivers, thereby improving nighttime and low-light visibility driving [4,5,6]. The optical performance of these microspheres depends largely on their physical and chemical properties, including morphology, refractive index, and composition [6,7,8,9].

Soda-lime glass is the predominant material used in their production due to its favorable optical properties and ease of processing [10,11,12]. However, traditional glass manufacturing relies heavily on high-purity silica sourced from natural sand deposits, a resource under increasing scarcity. Recent studies predict that by 2060, the world may face a significant shortage of suitable sand for use in glass production and construction, due to rapid urbanization and unsustainable extraction practices [13,14,15]. This scenario underscores the urgent need to identify alternative and renewable sources of silica.

Rice husk, a byproduct of the rice milling industry, represents approximately 20% of the total weight of rice grains [16,17]. When properly treated and burned under controlled conditions, it produces rice husk ashes (RHAs), a residue that can contain up to 99.6 wt% of amorphous silica (SiO₂), which is comparable to high-purity quartz sand (95–99.9 wt% SiO₂) used in glass production [16,17,18,19]. Unlike sand, the silica in RHA is mostly amorphous, offering higher reactivity and lower melting temperatures, which are advantageous in glassmaking [18]. On the other hand, it was already demonstrated that RHA industrially calcinated without any further purification treatments was employed successfully in the production of conventional glass [20,21]. Furthermore, RHA is a renewable and low-cost by-product, presenting a sustainable alternative to sand mining and consequently offers itself as a promising raw material for glass synthesis, aligning with the principles of waste valorization and circular economy [18]. Brazil, as one of the largest producers globally—with a harvest of over 10 million metric tons annually—generates a substantial quantity of rice husk and, consequently, RHA [22,23]. Utilizing this abundant biomass residue for high-value applications such as glass microsphere production could place Brazil as a strategic player in the transition towards more sustainable infrastructure materials. Moreover, this approach supports the objectives of the United Nations 2030 Agenda for Sustainable Development, particularly Goals 9 (Industry, Innovation, and Infrastructure), 11 (Sustainable Cities and Communities), and 12 (Responsible Consumption and Production) [24].

In the Brazilian context, the classification and technical standards for glass microspheres are defined by NBR 16184:2021 [11], which includes the specification of Type IB microspheres. This nomenclature is specific to Brazilian regulatory frameworks and may differ from international classifications. Type IB microspheres are typically applied as “premix” materials, incorporated into road marking compounds prior to application, and are required to meet stringent criteria regarding size distribution, morphology, density, chemical resistance, and retroreflective performance. Unlike drop-on microspheres, which provide immediate retroreflectivity, Type IB microspheres become optically active only after partial wear of the paint layer, gradually emerging to maintain reflectivity as the surface coating degrades. This delayed-action mechanism ensures sustained visibility of horizontal road markings throughout their lifecycle, contributing to improved long-term road safety.

In this study, we propose the first study, to the best of our knowledge, to report the synthesis and characterization of Type IB glass microspheres produced in accordance with a technical standard, using glass derived from rice husk ash, an agricultural residue. The goal is to evaluate the technical viability of this novel and alternative silica source by comparing the physical, chemical, and optical properties of the resulting microspheres with those of commercially available products and the standard NBR 16184:2021. Thus, this work contributes to both road safety innovation and the sustainable management of agricultural residues, offering a circular economy solution with positive environmental and socio-economic implications for Brazil and beyond.

2. Materials and Methods

2.1. Glass Fabrication

For the production of glass samples, rice husk ash (RHA) was sourced from a local supplier. The glass batch composition, in weight percentages (wt%), was defined as follows: (70.00) SiO₂:(13.00) Na₂O:(7.00) CaO:(10.00) B₂O₃. Sodium and calcium carbonate, together with Borax (sodium tetraborate decahydrate), were used as raw materials. To achieve the target composition, the oxide content of the RHA—previously characterized by X-ray Fluorescence (XRF) Spectroscopy (Malvern Panalytical, Epsilon 1, São Paulo, Brazil) and CHN analysis—was also taken into account. The raw materials were weighed individually and homogenized using a mortar and pestle. The homogenized mixture was transferred to a platinum–gold crucible and subjected to a melting procedure in a muffle furnace using three heating ramps:

(1)

Heating at 10 °C/min to 900 °C, with a 1 h dwell time;

(2)

Heating at 7 °C/min to 1200 °C, with a 1 h dwell time;

(3)

Heating at 5 °C/min to 1500 °C, held for 3 h.

The dwell times were chosen in order to fully remove bubbles from carbonates and allow for a more homogenized matrix. After melting, the molten glass was poured onto a stainless-steel plate preheated to 480 °C and immediately transferred to an annealing furnace at the same temperature for 1 h to relieve internal stresses. A total of 200 g of RHA-derived glass was produced.

2.2. Glass Characterization

The fabricated glass samples were optically characterized using two distinct techniques. First, their transmittance properties were evaluated by UV-Visible spectrophotometry in the wavelength range of 300 to 750 nm. Prior to this analysis, the glass surfaces were sanded and polished using a metallographic polisher (Fortel, PLF model, São Paulo, Brazil) to ensure suitable optical quality. The refractive index was subsequently determined using the Brewster’s angle method [25], which identifies the incidence angle at which reflectance of p-polarized light reaches a minimum. This measurement was carried out using a custom-built experimental setup consisting of a 650 nm TM-polarized laser and a goniometer (Thorlabs, XRNR1, São Carlos, Brazil), also used as a sample holder, with a 0.1° angular resolution.

2.3. Microsphere Production

In order to produce the Type IB microspheres, the glass was crushed with a mortar and pestle, and the resulting fragments were sieved using mesh sizes of 63 μm, 150 μm, 212 μm, and 300 μm to obtain the desired particle size distribution. Fragments retained in the coarser sieves were re-ground and re-sieved until they fell within the specified size range. Particles smaller than 63 µm were stored for the production of new glass. Different manufacturing methods can be implemented for microsphere production [12]: in this work, a lab-made horizontal flame spheroidization method was applied. The apparatus consisted of a horizontal stainless-steel pipe (1485 mm length, 84 mm inner diameter) connected to a vertical stainless-steel tube (1000 mm height, 162 mm inner diameter) via a 90° elbow. Crushed glass fragments were fed through a funnel positioned above the flame. The particles were heated by two atmospheric burners made of galvanized steel, positioned in parallel to increase the particle residence time within the flame. The burners were supplied by a 13 kg LPG cylinder, operating at an outlet pressure of 1 atm. Air intake regulation was achieved through a vertical slit located at the rear of each burner, equipped with an adjustable screw mechanism. This configuration allowed for fine control of the air-to-gas ratio by modifying the slit opening, enabling efficient aspiration of ambient air by the LPG flow and ensuring proper gas mixing. As a result, the flame characteristics could be effectively adjusted to optimize the heating conditions. Upon exposure to the flame (approx. 1000 °C), the fragments softened and spheroidized due to surface tension while flying, and they were collected at the bottom of the vertical tube in an aluminum tray. Figure 1 presents a photograph and a schematic diagram illustrating the details of the manufacturing process employed. The used method proved suitable for the fabrication of microspheres with diameters up to 300 µm.

2.4. Microsphere Characterization

2.4.1. Chemical Composition and Density

The chemical composition of the microspheres produced from RHA-based glass was analyzed and compared with commercial Type IB (Premix) microspheres, using the Brazilian standard NBR 16184:2021 as reference [11]. Elemental composition was analyzed by XRF spectroscopy. Three replicates of each sample type were analyzed, and the average values were reported. The primary goal of this analysis was to quantify analysis mainly aimed at determining the silica content and the potential toxic elements in the glass composition. The density of the microspheres was measured via the liquid displacement method using isopropyl alcohol as the immersion medium. For each measurement, 5.0 g of microspheres were submerged in 20.0 mL of alcohol, and density was calculated as the ratio of mass to the displaced alcohol volume.

2.4.2. Morphology and Particle Size Distribution

Morphological features and particle size distribution of the microspheres were assessed using Scanning Electron Microscopy (SEM). To evaluate the particle size distribution as well as the morphology of the elements generated, the concept of statistical sample size (n) was applied [26]. Sample size provides the number of observations that must be evaluated in a given population. Here, the population corresponds to the total quantity of microspheres, which can be considered infinite, while the sample size represents the minimum number of microspheres that should be evaluated for statistical significance. To determine a statistically significant sample sizes for the microsphere morphological analysis, a confidence level of 95%, population proportion π = 0.5, and a 5% margin of error were considered, resulting in a required sample size of at least 385 elements. Consequently, 400 elements were analyzed for each sample type in triplicate, totaling 1200 particles per sample. Microspheres were classified as spherical, ovoid, twin-shaped, or shards. This classification enabled the quantification of production quality and the identification of defects or irregularities associated with the manufacturing process.

2.4.3. Retroreflectivity Measurements

Retroreflectivity measurements were conducted using an Easylux Classic horizontal retroreflectometer (Easylux GmbH, Bocholt, Germany), compliant with national road marking standards [27,28,29]. Retroreflectivity data were collected for the 15 m geometry, where the vehicle is set to be 15 m away from the road sign observation point. Two test conditions were employed:

(1)

Black Dry Surface: Medium-density fiberboard (MDF) panels (34 cm × 10 cm) were painted with matte black acrylic paint to represent a low-reflectivity background; in this case, the microspheres were not anchored in the black paint surface, allowing the determination of the intrinsic retroreflectivity.

(2)

White Painted Surface: Water-based white acrylic road marking paint was applied to MDF panels using a polyester foam roller. A uniform thickness (~0.6 mm) was ensured using a metal depth gauge. A fixed quantity of 1.7 g of microspheres (equivalent to 50 g/m²) was manually deposited onto both test surfaces: (1) matte black (dry) and (2) white painted. To ensure consistent coverage, the application was performed inside a closed chamber, which allowed any loose microspheres to be collected and uniformly reapplied. For the black dry surface, where the microspheres remained unanchored, ten retroreflectivity measurements were taken per sample (RHA-based and commercial microspheres), moving the panel among measurements to account for different configurations for the bead positions. In contrast, for the white painted surface, where the microspheres adhered to the substrate, three retroreflectivity measurements were conducted for each sample. The average and standard deviation of the retroreflectivity measurements values were reported as the final result.

2.4.4. Hydrochloric Acid and Calcium Chloride Corrosion Resistance

The Brazilian standard NBR 16184:2021 recommends a visual inspection of the microsphere surface after hydrochloric acid and calcium chloride exposure, specifically to assess whether the surface has become dull or cloudy, which may indicate surface degradation. Acid resistance was evaluated by immersing 10.0 g of microspheres in hydrochloric acid (pH 5.0–5.3) for 90 h. Calcium chloride (CaCl₂) resistance was assessed by submerging the microsphere in a CaCl₂ solution (1 N) for 3 h, following the standard [11]. In both cases, after immersion, the microspheres were rinsed with distilled water and air-dried. Optical microscopy at (100× and 200× magnification) was used to examine changes in surface shine brightness and integrity. These results were qualitatively compared with untreated control samples to assess chemical durability. In order to quantify any surface degradation, ten retroreflectivity measurements were made for the samples before and after treatment. Measurements were also carried out using the 15 m geometry and the unpainted matte black surface to assess the intrinsic retroreflection of the microspheres. The microsphere density was again chosen to be 1.7 g per test area (50 g/m²). The granulometry range was chosen to be between 150 and 180 µm to guarantee less dispersion between the retroreflectivity measurements.

3. Results

3.1. Rice Husk Ash Composition and Bulk Glass Measurements

Table 1. RHA composition in weight percentage.

RHA Composition (wt%)
SiO2	Al2O3	MgO	CaO	P2O5	C *	Others < 0.1
88.3	1.4	3.1	0.3	0.5	6.3	0.1

* quantified by CHN.

presents the chemical composition of the rice husk ash used for glass production. Initially, the carbon content was quantified through CHN elemental analysis. The oxide composition of the ash was determined by XRF, with the total percentage normalized to 100%, considering the carbon content. As shown, the ash contains a high percentage of silicon dioxide, similar to results presented in other works [30], which enabled its use as a silica source in glass fabrication. To achieve the target glass composition, the silica content was adjusted by increasing the mass of the ashes relative to pure silica.

Once the glass samples were fabricated, they were characterized using UV-Vis spectrophotometry, and the refractive index was determined based on the Brewster angle method. Figure 2 presents the UV-Vis spectrum of a sample with 3 mm thickness, highlighting the visible region of the electromagnetic spectrum (400–700 nm), with the inset of a typical sample obtained under the selected fabrication conditions. As observed, from 400 nm to 700 nm, the glass exhibits very high and nearly constant transmittance, which characterizes it as colorless. The measured refractive index, accounting for the goniometer uncertainty, was 1.55 ± 0.03, a typical value for silica-based glasses [25].

3.2. Microspheres Measurements

Table 2. XRF results for RHA-based and commercial microspheres.

Microspheres Composition (wt%)
	SiO2	Na2O	CaO	Toxic Oxides (As2O3, PbO, Sb2O3)	Others
From RHA	72.8	2.8	20.5	ND	3.9
Commercial	72.7	4.7	21. 0	ND	1.6

ND = Not detected.

presents the XRF results for both rice husk ash (RHA-based) and commercial microspheres. Overall, it is observed that both samples exhibit a high percentage of silicon dioxide and do not contain toxic oxides such as As₂O₃ (arsenic oxide), PbO (lead oxide), or Sb₂O₃ (antimony oxide).

Figure 3 shows scanning electron microscopy images of the microspheres. Figure 3a displays a representative image of commercial microspheres, where different geometrical outcomes resulting from the production process can be identified, such as spherical microspheres (predominant), shards, ovoids, and twin-shaped particles. Figure 3b, in turn, presents a representative image of RHA-based microspheres. In this image, the particles exhibit a predominantly spherical morphology, with diameters ranging from approximately 50 to 180 µm.

The morphology and size distribution of glass microspheres are critical parameters for their use in horizontal road markings. Morphological analysis determines whether the particles exhibit a spherical geometry, as deviations from sphericity can diminish the retroreflective efficiency [31]. Meanwhile, particle size distribution enables the categorization of microspheres within specific dimensional ranges, directly influencing their suitability for different application methods [11].

Table 3. Morphology of RHA-derived and commercial microspheres.

Sample	Total Counts	Spheres (%)	Ovoids/Twinned (%)	Shards (%)
RHA Glass	1200	91 ± 3	7 ± 2	1.5 ± 0.2
Commercial Glass	1200	86 ± 3	11 ± 3	2.1 ± 0.4

presents the morphological analysis results for both RHA-derived and commercial microspheres. In both cases, the evaluation was performed in triplicate, totaling 1200 particles. As observed, particles with a perfect spherical shape predominate in both samples when compared to other morphological types. Notably, the high proportion of spherical RHA microspheres indicates that the chosen glass composition is well suited for producing glass beads intended for road marking applications.

During the morphological analysis that resulted in Table 3, it was also possible to assess the diameter of the produced microspheres. In this case, only particles with a spherical shape were considered. Figure 4 displays the percentage distribution of microspheres retained by different sieves as a function of the sieve aperture. The dashed black lines indicate the size limits defined by the Brazilian standard for Premix-type (Type IB) microspheres. As shown, the particle size distributions of both the commercial and RHA-derived samples fall within the specified range, confirming their compliance with national regulations and classifying the manufactured microspheres as suitable for Premix-type applications.

Regarding mass density, the results indicate that both types of glass exhibit values consistent with typical soda-lime glasses, with 2.42 ± 0.01 g/cm³ for the rice husk ash (RHA) microspheres and 2.43 ± 0.01 g/cm³ for the commercial microspheres [32].

After validating the production process with respect to the physical characteristics and chemical composition, the retroreflectivity performance of both RHA and commercial microspheres was evaluated on matte black (unpainted) and white (painted) surfaces. The measurements were carried out using the 15 m geometry, which is the standard configuration adopted by most road authorities in Brazil [29]. Typically, Type IB glass beads are premixed into the road marking paint at a concentration of 250 g/L [33]. Here, a lower density of 1.7 g per test area (equivalent to 85 g/L) was selected for both samples. This reduced amount was intentionally chosen to prevent bead overlap, which could affect the consistency of the measurements. The primary objective of these measurements was not to achieve the highest possible retroreflectivity [34], but rather to compare the retroreflective performance of the RHA-based microspheres with that of their commercial counterparts of the same type. For the unpainted configuration test case, a matte black board served as the reference surface, whereas for the painted configuration case, the reference consisted of the white paint film, both without microspheres. Figure 5 presents the retroreflectivity results obtained for both samples, considering the particle size distribution described in Figure 4. As expected, both sample types showed substantial increases in retroreflectivity compared to their respective controls. More importantly, the results revealed that RHA-based microspheres exhibited retroreflectivity values comparable to those of commercial glass beads, supporting their potential implementation in road marking applications.

Moreover, the evaluation of glass microspheres under chemical attack from hydrochloric acid and calcium chloride resistance test is essential to assess the microspheres durability against chemical agents commonly found in the environment, such as acid rain or cleaning products used in traffic areas [11,12]. These agents can degrade the microsphere surface over time, potentially altering key properties such as surface integrity, adhesion to paint, and their retroreflective performance, reducing road marking visibility and thereby increasing the risk of traffic accidents. Figure 6a,b and Figure 6c,d shows representative images of the RHA microspheres before and after immersion in hydrochloric acid and calcium chloride, respectively. No visible alterations in the surface appearance (shine or hue) were observed for either sample, indicating resistance to hydrochloric acid and CaCl₂-induced surface degradation. To complement this analysis, retroreflectivity measurements were also carried out before and after each chemical exposure to verify whether the optical performance was compromised. The results, as reported in Figure 6e, also showed no significant change, confirming the chemical stability and performance reliability of the RHA glass microspheres under both hydrochloric acid and CaCl₂ exposure.

4. Discussion

The physical, chemical, and optical properties of the microspheres produced using rice husk ash as a raw material were evaluated with reference to the NBR 16184:2021 standard, as well as in comparison with commercial microspheres of the same type.

Table 4. Requirements of the Brazilian standard NBR 16184:2021 for Type IB glass beads.

Type IB Microspheres (Premix)
SiO2 content	≥65%
Toxic elements (As, Pb, Sb)	Maximum 200 mg/kg
Color	Colorless
Refractive index	≥1.5
Granulometry (φ)	63 µm ≤ φ ≤ 250 µm
Morphology	Ovoid/twin	Shards	Spherical
	Maximum 20%	Maximum 3%	≥77%
Density (g/cm3)	2.4 ≤ d ≤ 2.6
Resistance to hydrochloric acid	Surface without fogging

and

Table 5. Compiled results obtained for RHA-based and commercial microspheres.

Sample Properties	RHA Microspheres	Commercial Microspheres
SiO2 Content (%)	72.8	72.7
Toxic Elements (As, Pb, Sb)	ND	ND
Color	Colorless	Colorless
Refractive Index	1.55 ± 0.03	–
Granulometry (φ)	Categorized as Type IB	Categorized as Type IB
Morphology
— Ovoid/Twin (%)	7 ± 2	11 ± 3
— Shards (%)	1.5 ± 0.2	2.1 ± 0.4
— Spherical (%)	91 ± 3	86 ± 3
Density (g/cm3)	2.42 ± 0.01	2.43 ± 0.01
Resistance to Hydrochloric Acid	Surface without fogging	Surface without fogging

ND = Not detected.

summarize the requirements of the Brazilian standard NBR 16184:2021 for Type IB glass beads, along with the results obtained for both RHA-based and commercial microspheres presented in this work, respectively.

As can be observed, regarding the silica content and the presence of toxic elements, the XRF results revealed SiO₂ contents above 72%, which exceeds the minimum threshold established by the standard. Additionally, no toxic elements such as As, Pb, or Sb were detected in either sample. Regarding color, UV-Vis spectrophotometry demonstrated high transmittance throughout the visible spectrum, indicating that the produced glass can be classified as colorless. Moreover, visual inspection of the RHA and commercial microspheres revealed a similar appearance in terms of coloration. The refractive index of the produced glass was measured as 1.55 ± 0.03 at a wavelength of 650 nm (the upper boundary of the visible spectrum). Although this measurement was performed at a single wavelength, physical models for homogeneous materials such as glass indicate that the refractive index typically increases for shorter wavelengths [25,35]. Therefore, it can be stated that the refractive index across the entire visible range is at least 1.55 ± 0.03, which meets the requirements of NBR 16184:2021. Although it has not been possible to measure the refractive index of the commercial microspheres, considering that the base glass of these microspheres is soda-lime, its bulk refractive index is <1.52 in the visible spectrum [25]. The higher refractive index observed in the glass derived from rice husk ash (RHA), when compared to commercial soda-lime glass, is likely attributed to the presence of boron in its composition: borossilicate glass can present higher refractive indexes [36]. This can also explain the slightly higher retroreflectivity values measured for the RHA-based microspheres compared to the commercial ones, as reported by other authors [37].

In terms of particle size, both the RHA and commercial microspheres fall within the 63–300 μm range, classifying them as Type IB microspheres according to the standard. This makes them suitable for incorporation into road marking paint prior to application. Moreover, the RHA-based glass formulation employed in this study resulted in a high percentage of spherical particles when compared to other outcomes (shards, ovoids, twin-shaped), fulfilling the morphology criteria established by NBR 16184:2021, and demonstrating the thermochemical feasibility to use this agricultural waste as a source material. Furthermore, both the measured density and resistance to chemical attack (hydrochloric acid and calcium chloride) were within the acceptable limits set by the standard. These results collectively demonstrate that the microspheres produced from rice husk ash exhibit comparable properties to those of commercial glass beads and comply fully with all specifications outlined in the Brazilian regulation. Although the comparison in this work is based on a Brazilian standard, minor formulation adjustments could be made to ensure compliance with international standards as well. Overall, the RHA presents itself as a valuable alternative for glass retroreflective microspheres production.

5. Conclusions

This study demonstrates the technical feasibility of producing Type IB glass microspheres for road marking applications using soda-lime glass derived from rice husk ash (RHA). All physical, chemical, morphological, and optical characterizations confirmed that the microspheres fabricated from this renewable silica source meet the specifications outlined in the Brazilian standard NBR 16184:2021. Key parameters—such as the silica content (72.8 wt%), the absence of toxic element, refractive index (1.55 ± 0.03), density (2.42 ± 0.01 g/cm³), particle size distribution (63 µm–250 µm), spherical morphology (91 ± 3%), chemical resistance (no fogging), and retroreflectivity (138 ± 2 mcd/lux/m²)—were found to be comparable, equivalent, or superior to those of commercial products and in accordance with the standard. Beyond meeting technical criteria, the process offers a sustainable and scalable route for converting agricultural waste into high-value materials for infrastructure. The successful transformation of RHA into glass microspheres supports the principles of circular economy and waste valorization, while reducing reliance on finite natural resources such as high-purity sand. Given the abundance of rice production in countries like Brazil, this approach presents an environmentally responsible and economically viable alternative for large-scale implementation in the road marking industry. Overall, this work highlights a promising pathway for enhancing road safety through sustainable materials innovation, contributing to the broader goals of responsible production, sustainable cities, and infrastructure resilience.