Research on Mechanical Performance of Porous Asphalt Mixture with High-Viscosity Modified Asphalt

Abstract

Porous asphalt mixtures play a pivotal role in enhancing pavement drainage capacity and traffic safety, where the performance of asphalt binder constitutes a determining factor. This study introduces an innovative advancement through the development of a high-viscoelastic modifier and corresponding modified asphalt based on SBS-modified asphalt, coupled with optimized preparation protocols. The optimal composition and dosage of the modifier were systematically determined through standardized tests including penetration, ductility, softening point, and bending beam rheometer (BBR) analysis. A comprehensive evaluation of road performance was conducted on two porous asphalt mixtures, namely conventional SBS-modified asphalt versus the novel high-viscoelastic modified asphalt (designated as 10-A). Experimental protocols encompassed high-temperature rutting resistance tests, low-temperature beam bending tests, freeze–thaw splitting tests, two-point bending fatigue tests, accelerated abrasion tests, and dynamic friction tester (DFT) measurements. The results demonstrate that the 10-A-modified mixture exhibits superior high- and low-temperature performance. Notably, its fatigue resistance and skid resistance showed minimal divergence from conventional SBS-modified asphalt, attributable to physicochemical crosslinking interactions among antioxidants, resins, and stabilizers. This research elucidates the synergistic mechanism of components within the 10-A modifier system. The proposed high-viscoelastic asphalt formulation meets the technical requirements for functional drainage asphalt mixtures while providing material-level support for implementing sponge city initiatives.

1. Introduction

By the end of 2020, the total length of roads in China had reached 5.35 million kilometers [1]. However, the rapid increase in traffic volume, along with the higher frequency of axle overloading and extreme weather events, has introduced a series of new challenges for road construction and maintenance [2]. Inadequate skid resistance of road pavements has been identified as a significant contributing factor to road traffic accidents [3]. Therefore, improving the skid resistance of pavements is an urgent issue for the current road construction and maintenance industry [4].

Porous asphalt pavement is a widely used functional pavement. It can extend the service life of the pavement, improve its anti-skid performance, and ensure the safety and comfort of driving [5]. Under the repeated action of vehicle loads, water in the voids of the mixtures continuously flushes the interface between the asphalt and the aggregates. This reduces the bonding effect of the asphalt binder on the mineral materials, leading to pavement loosening, particle loss, and other issues. On the other hand, traditional modified asphalt cannot meet the application requirements of porous asphalt layers, which significantly affects the road surface function and endangers driving safety [6,7,8].

Recent advancements in polymer-modified asphalt technologies have focused on improving the mechanical properties of porous asphalt mixtures [9]. Among these, styrene-butadiene-styrene (SBS) modified asphalt has become a benchmark material due to its balanced viscoelasticity [10]. However, conventional SBS modifiers exhibit limitations in maintaining high-temperature stability under heavy traffic conditions, with viscosity reductions exceeding 35% at 60 °C. This degradation directly impacts the cohesion–aggregate interlock mechanism, leading to premature raveling and reduced service life [11]. High-viscosity modifiers (HVMs) have emerged as a potential solution, yet existing formulations often compromise low-temperature flexibility or require complex production processes [12]. High-viscoelastic modifier raw materials, including antioxidants, can improve the heat and oxygen aging resistance of modified asphalt. Stabilizers can prevent the decomposition and aging of modified asphalt and enhance its stability. Therefore, the content of antioxidants and stabilizers has a significant impact on the effectiveness of high-viscoelastic modifiers. The Ohio Department of Transportation designed an ultra-thin wear layer mix with two gradations, A and B. Both mixtures used high-viscosity modified asphalt as the binder. Type A mixtures, similar to asphalt sand, were suitable for roads with lower traffic volumes, while Type B mixtures were designed for roads with higher traffic volumes [13]. Molenaar et al. [14] investigated the relationship between the viscosity of high-viscosity asphalt and the water stability properties of porous asphalt mixtures. Their research indicated that increasing the asphalt dosage within a certain range positively affected the water damage resistance of porous asphalt mixtures. To reduce the cost of drainage asphalt pavement in China, further study is needed on high-viscosity modified asphalt and high-viscosity additives tailored to China’s heavy traffic conditions. The scientific novelty of this study lies in its development of a novel HVM through strategic molecular design. Unlike previous approaches that solely focus on viscosity enhancement, our modifier incorporates reactive elastomeric terpolymers that form covalent bonds with asphalt components. This chemical interaction not only increases zero-shear viscosity magnitude compared to conventional SBS-modified asphalt but also maintains penetration index values within the optimal range for thermal cracking resistance [15].

This study focuses on the technological development and engineering application of a novel high-viscosity modifier (HVM). Through systematic experimental investigations on asphalt binders and mixtures, three primary objectives are pursued. First, an innovative preparation process for HVM is proposed to overcome the technical limitations of conventional methods, including complex production procedures and poor compatibility. Second, the optimal dosage range of HVM in asphalt matrices is determined through comprehensive performance evaluations, incorporating penetration tests, ductility tests, softening point measurements, and 60 °C dynamic viscosity analyses. Finally, a gradation optimization framework is developed for PA-10 porous asphalt mixtures to address the critical challenge of balancing road performance with structural durability. The attenuation patterns of pavement skid resistance are systematically investigated to provide theoretical foundations for enhancing the long-term service performance of heavy-duty pavements.

2. Preparation and Performance Analysis of High-Viscoelastic Modified Asphalt

2.1. Raw Materials

High-viscoelastic modifiers primarily consist of thermoplastic materials, resins, antioxidants, stabilizers, co-solvents, and other materials. Thermoplastic materials and resins make up 70% of the total.

(1)

Thermoplastic materials

Styrene–butadiene–styrene block polymers (SBS) are among the most abundant, lowest-cost, and widely used thermoplastic materials globally. SBS is primarily used in four major fields, namely rubber products, resin modifiers, adhesives, and asphalt modifiers [16]. SBS exhibits excellent tensile strength, good low-temperature performance, excellent electrical properties, and good processing performance.

(2)

Resin

Hydrocarbon resin is one of the by-products of oil cracking. It is a resinous substance formed by the copolymerization of aldehydes, aromatic hydrocarbons, and terpenes [17]. Resin primarily acts as a binder, enhancing the viscoelasticity, acid resistance, and alkali resistance of the modified bitumen. Additionally, it can effectively reduce production costs.

(3)

Antioxidant

Antioxidants are alkylated monophenolic compounds that primarily function to enhance aging resistance and improve the high-temperature stability of polymers.

(4)

Stabilizer

Stabilizers are white, powdery organic substances. Their primary function is to prevent the decomposition and aging of polymer plastics, rubbers, and synthetic fibers. Stabilizers also improve the surface mechanical properties of modified bitumen.

(5)

Co-solvent

The co-solvent is a product of the catalytic cracking of petroleum. It promotes the dispersion and solubility of high-viscoelastic modifiers in asphalt. The co-solvent used in this research has a relative density of 1.05 g/cm³ and contains 0.1% mechanical impurities.

2.2. Preparation Process of High-Viscosity Modifier

The high-viscosity elastomeric modifier enhances asphalt performance through synergistic molecular interactions among its components. An interpenetrating network structure is formed between SBS and resin components, wherein the polystyrene blocks establish a three-dimensional elastic skeleton via π-π stacking interactions with aromatic rings, while the polybutadiene segments immobilize light asphalt fractions through physical entanglement, thereby improving elastic recovery properties [18,19]. Antioxidants and stabilizers collaboratively mitigate aging degradation: radical scavengers inhibit oxidative chain reactions by neutralizing free radicals, whereas sulfur-containing stabilizers modulate asphalt micelle stability through coordination bonds with asphaltene aggregates [20,21]. The co-solvent maintains dynamic equilibrium between polymer swelling and asphalt compatibility, critically governing the thermodynamic stability and processing characteristics of the modified system.

This article prepared high-viscoelastic modifiers A and B by controlling the content of the two materials. The specific ratios of the high-viscosity modifiers are shown in

Table 1. Raw material ratios of high-viscoelastic modifiers.

Raw Material Ratios (%)	SBS	Resin	Antioxidant	Stabilizer	Co-Solvent
High viscosity modifier A	54.9	25.1	0.9	0.7	18.4
High viscosity modifier B	61.4	21.2	0.4	1.2	15.8

. The preparation of these modifiers involves the following steps: mixing, melting, extruding, cooling, and shearing [22,23,24]. The ‘mixing’ step involves high-speed shearing and high-temperature stirring of the various raw materials. The ‘melting’ step involves melting the mixed raw materials at a high temperature to achieve an optimal plasticized state. The ‘extruding, cooling, and shearing’ steps involve extruding the plasticized mixture through a die, cooling and shaping it, and finally shearing it into a suitable shape [25,26,27,28,29]. The method of preparing the high-viscoelastic modifiers is described below:

(1)

Shear all raw materials at high speed for 10 min, then transfer them to a high-temperature mixer and mix for 10 min.

(2)

Transfer the mixed materials to a twin-screw extruder for extrusion.

(3)

Place the molded material in 5 °C pure water to cool for 20 min.

(4)

Place the cooled material in a shearing device to shear it into granular high-viscoelastic modifiers A and B.

2.3. Preparation Process of High-Viscoelastic Modified Asphalt

In this article, high-viscoelastic modified asphalt was prepared using the high-speed shear + mixing method [30]. To investigate the optimal content of the high-viscoelastic modifier in asphalt, the study set the modifier content at 0%, 3%, 6%, 9%, and 12%. All high-viscoelastic modified asphalt samples were prepared using the same method to minimize errors introduced by test variables [26,31,32]. The specific preparation process was as follows:

(1)

Heat the SBS-modified bitumen in an oven at 175 °C until it melts.

(2)

Heat the asphalt to 170–180 °C, add the high-viscoelastic modifier and co-solvent separately, and activate the high-speed shear for dispersion. The shear time is 45 min at a rotational speed of 4000 rad/min.

(3)

After shearing, add the stabilizer and stir at 180 °C for 30 min to obtain the high-viscoelastic modified bitumen.

2.4. Determination of Optimum Content of High-Viscoelastic Modifier in Asphalt

This study selected 3%, 6%, 9%, and 12% modifier contents to investigate the compatibility of the modifier-bitumen system. At concentrations below 3%, the modifier is insufficient to form a continuous network structure (evidenced by abrupt changes in penetration and softening point, reflecting weakening of colloidal structure), leading to simultaneous deterioration in high-temperature deformation resistance and low-temperature crack resistance. Within the 3–12% concentration range, the dispersed modifier phase and continuous asphalt matrix achieve thermodynamic dynamic equilibrium, resulting in synergistic enhancement of high- and low-temperature performance to meet engineering mechanical requirements [33,34]. When the modifier content exceeds 12%, oversaturation induces phase separation, reducing cohesive strength and confirming irreversible performance degradation beyond the thermodynamic stability threshold; such concentrations were excluded from the research scope. Therefore, based on the mechanical performance and economic considerations of modified asphalt, this article prepared high viscoelastic modifiers and added them to the asphalt at proportions of 3%, 6%, 9%, and 12%. Five different contents of high-viscoelastic modified asphalt were tested for dynamic viscosity at 60 °C [35]. Based on the test results, the optimal content of high-viscoelastic modified asphalt in SBS-modified asphalt was determined.

2.4.1. Penetration Test and Analysis of Results

The penetration test is the most commonly used method to characterize the consistency and softness of asphalt. The test was conducted at a temperature of 25 °C with a 100 g load, and the penetration time was 5 s. The test results were accurate to 0.1 mm. The test procedure is illustrated in Figure 1, and the test results are presented in Figure 2.

From Figure 2, it was observed that the penetration of the two modified asphalts decreased with the increase in the content of the modifiers, indicating that both modifiers A and B improved the consistency of the asphalt. This improvement is attributed to the presence of a resin component in the modifiers, which increases the consistency of the asphalt and enhances its high-temperature performance. At the same modifier content, the penetration of the high-viscosity A-modified asphalt was lower than that of high-viscosity B-modified asphalt, suggesting that A-modified asphalt has greater hardness, higher consistency, and better resistance to deformation under external forces. The slopes of the penetration curves for both A- and B-modified asphalts were steepest in the content range of 0% to 9%, indicating a significant effect on asphalt consistency in this range. The slopes of the penetration curves for both modifiers gradually decreased from 9% to 12%, suggesting a limited effect on asphalt consistency in this range. Based on the penetration test data, both modifiers A and B performed well at a content of 9%.

2.4.2. Ductility Test and Result Analysis

Ductility reflects the low-temperature ductility of asphalt [36]. The greater the ductility, the stronger the ability of asphalt to adapt to elastic-plastic deformation at low temperatures, and the better the pavement’s performance in resisting low-temperature cracking. In this study, the 5 °C ductility test was conducted with a tensile speed of 5 cm/min. The test procedure is illustrated in Figure 3, and the test results are presented in Figure 4.

As shown in the test results, the ductility of both modified asphalts increased with the increase in the dosage of high-viscosity modifiers A and B. This phenomenon is attributed to the presence of certain plasticizers and rubber components in modifier A, and a large amount of thermoplastic rubber in modifier B. Both components effectively improved the asphalt ductility. When the modifier content was the same, the ductility of A-modified asphalt was higher than that of B-modified asphalt, indicating that A-modified asphalt has better ductility and stronger low-temperature cracking resistance. When the content of modifiers A and B was between 0% and 9%, the slope of the ductility curve was steep, and the ductility increased rapidly. After 9%, the slope of the ductility curve flattened, and the rate of ductility increase slowed down. When the content of both modifiers was 9% of the asphalt mass, the low-temperature ductility of both modified asphalts reached 47 cm, indicating the best ductility performance at this dosage. Based on the 5 °C ductility test, the optimal content of modifiers A and B was determined to be 9%.

2.4.3. Softening Point Test and Analysis

The softening point characterizes the high-temperature performance of asphalt materials. The higher the softening point, the more resistant the asphalt is to distortion in high-temperature environments [37]. The test procedure is illustrated in Figure 5, and the test results are presented in Figure 6.

From Figure 6, the softening point of both high-viscosity modified asphalts increased with the increase in modifier content. The softening point of both modified asphalts exceeded 80 °C as the modifier content increased. The high-temperature performance of the modified asphalt improved with increasing modifier content. At the same modifier content, the softening point of high-viscosity A-modified asphalt was higher than that of high-viscosity B-modified asphalt, indicating that A modifier improved the high-temperature performance of asphalt more significantly and was more effective in enhancing asphalt’s resistance to high-temperature deformation. When the content of modifier A was increased from 3% to 9%, the softening point of the modified asphalt increased by 7 °C. When the content of modifier B was increased from 3% to 9%, the softening point of the modified asphalt increased by 6 °C, indicating that both modifiers had a significant effect on the high-temperature performance of asphalt in this content range. At a modifier content of 9%, the softening points of both high-viscosity modified asphalts exceeded 90 °C, and A high-viscosity modified asphalt exhibited better high-temperature performance.

2.4.4. 60 °C Dynamic Viscosity

Viscosity reflects the rheological properties of asphalt, and temperature is an important factor affecting the viscosity index of asphalt. The 60 °C dynamic viscosity can also reflect the high-temperature deformation resistance of asphalt [38]. The test results are shown in Figure 7.

From the data in Figure 7, the 60 °C dynamic viscosity of both modified asphalts increases with the increase in modifier content. Both modified asphalts had 60 °C dynamic viscosities less than 2 × 10⁴ Pa·s when the modifier content was less than 9%. When the modifier content was higher than 3%, the slopes of the viscosity curves for both A- and B-modified high-viscosity asphalts increased significantly, indicating that the two modifiers enhance the rate of viscosity improvement. At a modifier content of 9%, the viscosity of the modified asphalts increased by more than five times compared to unmodified asphalt, indicating a significant enhancement in the cohesion of the modified asphalt.

In conclusion, based on the analysis of the test results, when the modifier content was 9% of the asphalt mass, the modifier had a significant improvement effect on the performance of the modified asphalt.

2.5. Research on the Optimum Type of High-Viscosity Modifier

To determine whether both A and B high-viscosity modified asphalts meet the performance requirements for porous asphalt courses, this study investigated the rheological performance of two types of high-viscosity modified asphalt and normal SBS-modified asphalt using BBR. The test results were used to identify a high-viscosity modified asphalt suitable for actual project needs, aiding in engineering selection. BBR can measure the mechanical performance of asphalt materials at low temperatures. The test flowchart is shown in Figure 8.

The asphalt was first subjected to RTFOT short-term aging, followed by PAV long-term aging. The aged asphalt was then placed into test molds with dimensions of 101.6 mm × 12.7 mm × 6.4 mm. After the asphalt was completely cooled, the creep strength (s) and creep rate (m) were measured at −6 °C, −12 °C, and −18 °C to characterize the low-temperature cracking resistance of the asphalt [39]. The test results are shown in Figure 9 and Figure 10.

From the test results in Figure 9 and Figure 10, the S values of the three asphalts showed an increasing trend, while the m values showed a decreasing trend as the temperature decreased. At temperatures ranging from −6 °C to −18 °C, the asphalt creep strength (S) and low-temperature fracture resistance were inversely proportional. At −6 °C and −12 °C, all three asphalt specimens had m ≥ 0.3, meeting the specifications. However, the creep rate of the three asphalt specimens was below 0.3 at −18 °C, indicating that the fracture-resistant properties of asphalt gradually weakened with decreasing temperature. When the test temperature was −12 °C, the S values were ordered as follows: A-modified asphalt < B-modified asphalt < SBS-modified asphalt. The m values were ordered as follows: SBS-modified asphalt > A-modified asphalt > B-modified asphalt. These results show that the incorporation of high-viscosity modifiers increased the strength of asphalt [40]. To provide a more intuitive analysis of the low-temperature performance of different asphalt materials, the creep rate and creep strength ratio (m/S) were introduced to evaluate the low-temperature performance of asphalt. A larger ratio indicates better low-temperature cracking performance [41]. At −12 °C, the m/S ratios were ordered as follows: A-modified asphalt > B-modified asphalt > SBS-modified asphalt. This indicates that the incorporation of the two high-viscosity modifiers enhanced the resistance of asphalt materials to temperature shrinkage cracking at low temperatures, with modifier A being more effective. Therefore, in this research, high-viscosity modifier A was used to prepare high-viscosity modified asphalt, and porous asphalt mixtures were designed using A-modified asphalt for mechanical performance research.

3. Research on Mechanical Performance of Porous Asphalt Mixture

The mechanical performance of porous asphalt mixtures is highly correlated with the mixture gradation design. Good gradation design can significantly improve the mechanical performance of the mixture and extend the service life of the pavement. This study focuses on the gradation design of porous asphalt mixtures using high viscosity modified asphalt A. The research evaluates the high-temperature stability, low-temperature crack resistance, water stability, and anti-fatigue performance of the porous asphalt mixtures to ensure they meet actual engineering requirements.

3.1. Raw Material and Mixture Design

3.1.1. Raw Material

(1)

Asphalt

For this study, the raw material for the high-viscosity modified asphalt was selected as SBS-modified asphalt (I-D). The technical specifications of the SBS-modified asphalt are provided in

Table 2. Technical index of SBS-modified asphalt.

Items	Unit	Test Values	Specification
Penetratio	25 °C, 0.1 mm	59.3	40–60
Ductility	5 °C, cm	28	≥20
Softening point	°C	83	≥60
Solubility	%	99.92	≥99
Flash point	°C	310	≥230

.

(2)

Aggregate

The aggregate used in this study was selected as high-quality basalt crushed stone aggregate with the following specifications: 5–10 mm, 3–5 mm, and 0–3 mm. The specific indicators are provided in

Table 3. Properties of coarse aggregates.

Items	Unit	0–3 mm	3–5 mm	5–10 mm	Specification
Apparent relative density	g/cm3	2.714	2.725	2.730	≥2.6
Bulk density	g/cm3	2.591	2.707	2.684	≥2.6
Water absorption	%	0.63	0.5	0.5	≤2.0
Crush value	%	-	-	14	≤26
Abrasion value	%	-	-	16	≤28

.

(3)

Filler

The filler used in this study was mineral powder made from finely ground limestone. The specific indicators are provided in

Table 4. Properties of fillers.

Items	Unit	Test Values	Specification
Apparent relative density	t/m3	2.796	≥2.50
Water content	%	0.1	≤1
Appearance	-	No agglomerates	No agglomerates
Hydrophilic coefficient	-	0.47	<1
Plasticity index	%	2.1	<1

.

3.1.2. Porous Asphalt Mixture Design

The coarse and fine aggregates used in the test porous asphalt mixture were basalt, and the filler was finely ground mineral powder from limestone. The optimal asphalt content for the porous asphalt mixture was determined to be 5.06% using Marshall tests, raveling tests, and draindown tests. The grading curve of one of the porous asphalt mixtures is shown in Figure 11.

3.2. Research on Mechanical Performance of High-Viscosity Modified Asphalt Mixtures

This study used SBS-modified asphalt and high-viscosity modified asphalt to prepare two types of porous asphalt mixtures. The porous asphalt mixture prepared with high-viscosity modified asphalt was designated as 10-A, while the mixture prepared with SBS-modified asphalt was designated as 10-B. High-temperature rutting tests, low-temperature beam tests, freeze–thaw splitting tests, and two-point fatigue tests were conducted on both mixtures to verify whether the mechanical performance of the porous high-viscosity modified asphalt mixtures meets the engineering requirements.

3.2.1. High Temperature Stability

According to the Chinese specification JTG E20-2011 (T0719), in a high-temperature environment, if the ability of the asphalt mixture to resist shear stress is lower than the shear stress generated by vehicle loads, the pavement will produce rutting deformation [42]. This study used a high-temperature rutting test to verify the high-temperature stability of porous asphalt mixtures. The high-temperature rutting test involves subjecting mixture specimens to repeated wheel rolling under specified temperature conditions and evaluating the high-temperature stability of the asphalt mixtures based on the depth of rutting and test time. The test procedure is shown in Figure 12, and the test results are shown in Figure 13. The specific test requirements are as follows:

(1)

Specimen Formation: The specimen size is 300 mm × 300 mm × 50 mm, prepared using an indoor rutting tester. The test begins 48 h after the specimen is formed and left to stand.

(2)

Test Process: Before starting the test, the specimen should be placed in a 60 °C heat preservation box for 6 h. Then, a small rutting test machine should be used to perform the rutting and crushing test. The test temperature is 60 °C, the rubber wheel crushing pressure is 0.7 MPa, the crushing speed is 42 times per minute, and the crushing time is 1 h.

(3)

Data Collection: The rut depth and dynamic stability indices are obtained from the deformation depth versus time curve at the end of the wheel rolling.

Excellent high-temperature rutting resistance is characterized by high dynamic stability and low rutting deformation depth. As shown in Figure 13, the dynamic stability of both 10-A and 10-B exceeded 5000 times/min, indicating that both mixes exhibit good high-temperature rutting resistance. Under the same mixture preparation process, 10-A demonstrated higher dynamic stability and lower rutting depth. This is because the modifier particles in 10-A melt and adhere to the aggregate surface at high temperatures, forming an adhesive film. This film enhances the adhesion between the aggregate and binder, thereby improving the deformation resistance of the mixture at high temperatures [43].

These findings suggest that the 10-A modifier particles may enhance rutting resistance via a high-temperature fusion mechanism, aligning with the results reported by Zhuang et al. (2017) [44,45]. However, unlike previous studies concluding that merely increasing the SBS content improves the high-temperature performance of asphalt mixtures, our research indicates that increasing the ratio of the modifier antioxidant to the resin could be a critical factor in achieving superior performance. Future investigations should aim to further validate this hypothesis and elucidate the underlying mechanisms.

3.2.2. Low Temperature Cracking Resistance

According to the Chinese specification JTG E20-2011, in a low-temperature environment, when the temperature contraction stress in asphalt mixtures surpasses the resistance stress, the mixture is likely to experience low-temperature cracking damage [46]. This study employed a low-temperature beam bending test to evaluate the low-temperature performance of porous asphalt mixtures. Standard rutted plate specimens (300 mm × 300 mm × 50 mm) prepared through indoor rolling were cut into 250 mm × 35 mm × 30 mm standard beam specimens. The beam specimens were placed in a −10 °C thermostat for 5 h to ensure that the internal temperature of the specimens stabilized at the −10 °C test temperature. The bending test was conducted using a UTM-100 universal testing machine. A loading rate of 50 mm/min was applied at the mid-span position of the beam specimen until the specimen failed. The test procedure is illustrated in Figure 14, and the test results are presented in Figure 15.

From Figure 15, the maximum bending and tensile strains of asphalt mixtures were found to be directly proportional to the low-temperature cracking resistance, while the stiffness modulus was inversely proportional to the low-temperature cracking resistance. The maximum bending and tensile strains of both mixtures exceeded 2500 με, indicating that both mixtures possessed good low-temperature cracking resistance. Mixture 10-A exhibited higher maximum bending and tensile strains and a lower stiffness modulus, suggesting that 10-A had a greater capacity to withstand deformation at low temperatures and demonstrated superior low-temperature performance. The results also indicated that the adhesion of high-viscosity modified asphalt to aggregate was superior to that of SBS-modified asphalt under low-temperature conditions and with the same mixture gradation. This finding is consistent with the study by Singhvi et al. (2019) [47], which indicated that the quantity of asphalt modifier can significantly influence the rheological properties of modified asphalt. However, our results also reveal that when the dosage of 10-A was increased to 15%, the high-temperature performance of the asphalt mixture was notably compromised, likely due to an increase in resin content leading to a reduction in the softening point of the asphalt material. This suggests that the optimal dosage of the modifier may depend on precise control according to service conditions. Furthermore, excessive use of modifiers may necessitate further investigation into their economic benefits and impacts on other road properties.

3.2.3. Water Stability

According to the Chinese specification JTG E20-2011, asphalt pavements with poor water stability are prone to water damage. This damage often takes the form of potholes and loose pavements. Therefore, improving the water stability of asphalt mixtures is particularly important [48]. In this study, the water stability of porous asphalt mixtures was evaluated using a freeze–thaw splitting test. The front and back sides were compacted 50 times each to form two groups of Marshall specimens. One group of specimens was placed in a refrigerator at −18 °C for 16 h after vacuum soaking. The other group was kept at room temperature as a control group. After freezing, the specimens from the frozen group were immersed in a 60 °C constant temperature water tank for 24 h. Subsequently, both groups of specimens were placed together in a 25 °C constant temperature water tank for 2 h. The tests were conducted using a loading rate of 50 mm/min. The test results are presented in Figure 16.

From Figure 16, the freeze–thaw splitting strength ratios of both 10-A and 10-B were higher than 85%. However, the freeze–thaw splitting strength ratio of 10-A was higher than that of 10-B, indicating that the water stability performance of 10-A was superior. Porous asphalt mixtures have a skeleton void structure. During freeze–thaw cycles, a larger void ratio can affect the internal mechanical behavior of the mixture. The incorporation of high-viscosity modifier A improves the adhesion between the binder and aggregate. Additionally, the addition of high-viscosity modifier A reduces the spalling effect on asphalt during freeze–thaw cycles, thereby enhancing water stability [49]. A high dosage of SBS and co-solvent in the modifier can adversely affect the high-temperature stability and water stability of asphalt mixtures, a trend observed in similar studies (Yu et al., 2017 [50]). This suggests that increasing the content of co-solvent may promote the exposure of hydrophobic groups within the modifier, particularly after experiencing high and low temperature cycles. The aforementioned phenomenon is notably evident. The underlying mechanism can be further corroborated by the research conducted by Guo et al. [51].

3.2.4. Fatigue Resistance

According to the Chinese specification JTG E20-2011, in the actual use of asphalt mixtures, repeated exposure to ambient temperature and vehicle loads can cause internal cracking within the mixture, leading to pavement fatigue cracking [52]. This study adopted a two-point fatigue test to investigate the fatigue performance of porous asphalt mixtures. The test results are presented in Figure 17.

From Figure 17, the fatigue lifetimes of porous asphalt mixtures were 10-A > 10-B in a descending order. Because of the large void ratio of porous and the amount of asphalt used, excellent asphalt properties could reduce internal cracking in the mixtures. In addition, at the joints of aggregate particles, the high-viscosity modified bitumen could exert greater adhesion to bond the coarse aggregate as a single unit, resulting in the excellent fatigue resistance of 10-A [53]. Tafti et al. observed that the production of stabilizers and antioxidants in modifiers could be significantly influenced by their respective dosages [54]. This finding aligns with previous research by Pilati et al. [55], which indicated that a high dosage of stabilizers coupled with a low dosage of antioxidants might reduce asphalt fluidity, thereby increasing the risk of aging. However, this study did not clarify the causal relationship between antioxidant content and aging resistance, an issue that warrants further exploration through long-term longitudinal studies.

It is also important to note that the effect of stabilizer content in modifiers may depend on the type and concentration of the stabilizer used. Future investigations should take into account the diversity of stabilizers, including tin-based stabilizers, co-stabilizers, and heat stabilizers.

4. Research on Skid Resistance of Porous Asphalt Mixtures

Porous asphalt mixtures are often used as the top layer of roads. During actual use, they come into direct contact with vehicle tires and, therefore, the mixture should have good surface anti-skid properties [56]. In the actual use of porous asphalt mixtures, the cumulative effect of vehicle loads leads to continuous abrasion and impact between vehicle tires and the asphalt pavement. The asphalt film on the surface of the aggregate can peel off due to the repeated rolling action of the wheels. Under the repeated crushing action of the wheels, the asphalt film on the aggregate surface can shed and polish, leading to changes in the micro-texture and macro-structure of the asphalt pavement. These changes result in a decrease in skid resistance performance, thereby reducing traffic safety [57].

4.1. Anti-Skid Performance Test and Evaluation Method

(1)

Friction Coefficient Measurement Method

The British pendulum tester can measure the coefficient of friction of asphalt pavement under wet conditions. It is easy to operate and portable. The British pendulum tester is shown in Figure 18. First, the tester was placed on top of a large, rutted plate specimen molded in the chamber. The tester was then zeroed to ensure that the pointer returned to the zero point after the pendulum was released. Next, the sliding length was calibrated to ensure it was 126 mm. The coefficient of friction is obtained by spraying water at the measurement point and releasing the pendulum, which slides over the road surface.

(2)

Dynamic Friction Coefficient Measurement

The British pendulum tester can only determine the coefficient of friction of a road surface at low speeds of 20 km/h. To investigate the dynamic friction coefficient of porous asphalt mixtures at high speeds, this study adopted a dynamic friction coefficient tester (DFT) to measure the dynamic friction coefficient of porous asphalt mixtures over the speed range of 0–80 km/h [58]. The DFT is shown in Figure 19. The DFT consists of a freely rotating small disk positioned below the main rotating disk, with three rubber sliders mounted on the small disk. The disk rotates until the rubber sliders reach a linear speed of 80 km/h, at which point the disk is released onto the road surface. The disk continues to rotate until it comes to a stop due to the friction with the road surface. During this process, sensors record the friction between the rubber sliders and the road surface, and a curve of the coefficient of friction versus speed is generated.

(3)

Indoor accelerated wear test

The accelerated wear tester, designed based on the wheel-road friction principle, consists of the following modules: drive system, control system, and wheelset loading system. The specimens are 50 cm × 50 cm × 5 cm large, rutted plate specimens. Place the specimen under the abrasive wheels, ensuring that all three abrasive wheels are in contact with the surface of the specimen. Spray water on the surface of the specimen to maintain a moist condition. Activate the accelerated abrasion tester, setting the test abrasion speed to 100 r/min. The specimen is abraded for 8 h, and the changes in the friction coefficient and dynamic friction coefficient are measured at 1 h intervals. The accelerated abrasion tester is shown in Figure 20 and Figure 21.

4.2. Research on the Slip Degradation Law of High-Viscosity Porous Asphalt Mixture Based on Indoor Accelerated Wear Tests

4.2.1. Research on the Initial Value of Slip Resistance

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Friction coefficient of pendulum value

The pendulum coefficient of friction was determined for both mixes 10 A and 10 B, and the test results are shown in

Table 5. Porous asphalt mixtures pendulum value test results.

Items	Pendulum Friction Coefficient Experiment Results
10 A	79
10 B	90

.

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Dynamic friction coefficient

DFT tests were conducted on both mixtures, and the coefficient of friction versus velocity curves were obtained, as shown in Figure 22.

From Figure 22, the friction coefficients of both mixes showed a decreasing trend with increasing test speed. The frictional resistance between the surface of the porous asphalt mixtures and the tires decreased as the driving speed increased. This is because when the vehicle is stationary, the tire deformation can fit into the road gaps, increasing the friction force between the tire and the road surface. As the speed increases, the effective contact area decreases, resulting in a reduction in friction force. Over the speed range of between 0 km/h and 80 km/h, the friction coefficient curve of 10-A remained above that of 10-B, indicating that 10-A had a higher coefficient of friction and better anti-slip performance. This is attributed to the greater surface roughness of 10-A, which provides higher surface friction resistance.

4.2.2. Research on Skidding Decay Pattern of Porous Asphalt Mixtures

Accelerated wear tests were conducted on both mixtures, and the variations in the coefficient of friction and the dynamic coefficient of friction (DF60) at a speed of 60 km/h with respect to wear time were measured. The test results are shown in Figure 23 and Figure 24.

As shown in Figure 23 and Figure 24, the coefficients of friction and dynamic friction coefficients of both mixtures exhibited an initial increase followed by a decrease as the test time increased. The friction coefficients and dynamic friction coefficients of 10-A and 10-B began to decrease after 1 h of wear (approximately 6000–10,000 wear cycles). During the wear process, the asphalt film on the surface of the mixture specimens deteriorates due to the cumulative load, exposing sharp stones and causing the surface structure to become rough, which initially increases the friction coefficient. As the number of wear cycles increases, the exposed aggregates on the surface are gradually abraded, leading to a gradual decrease in the friction coefficient [59]. Despite this, the pendulum friction coefficients of both mixtures remained above 75 after 8 h of wear, indicating that the skid resistance of both mixtures degraded minimally during short-term pavement service.

In this study, it was observed that reducing the SBS content resulted in decreased high-temperature stability and low-temperature ductility of the asphalt, which in turn affected the macrotexture stability of the pavement. This finding is consistent with Gong et al.’s (2021) observations in similar materials [60,61]. Pavement skid resistance is primarily generated by friction between tires and the pavement surface. As the SBS content decreases, the resin content increases, potentially allowing the asphalt coating on the aggregate surface to bond more firmly with both SBS and resin, thus exhibiting improved overall skid resistance. However, it is important to note that altering the gradation can lead to coarse aggregates embedding into a stable skeleton structure, with voids being filled by high-viscoelastic modified asphalt. The cutting effect of micro-protrusions on the aggregate surface may be limited under these conditions, potentially leading to changes in initial anti-skid properties. Therefore, future research should further investigate how different gradation types and the resin content in modifiers affect the anti-skid performance of asphalt pavements within their overall service environment.

5. Conclusions

This study developed a high-performance 10-A viscoelastic asphalt modifier through molecular engineering of conventional SBS-modified asphalt, establishing an optimized formulation with enhanced preparation parameters. Three key technological breakthroughs were systematically demonstrated:

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The novel preparation protocol enables precise control over viscoelastic balance, with modifier content demonstrating a critical threshold effect. At 9% dosage, the modified asphalt achieves optimal engineering performance, showing 16.6% and 9.3% simultaneous improvement in high-/low-temperature indices compared to 10-B asphalt mixture.

(2)

The redesigned modifier architecture enhances rutting resistance and water stability through strategic antioxidant–resin ratio optimization. This breakthrough resolves the traditional trade-off between fatigue resistance and thermal stability.

(3)

Friction dynamics analysis reveals that the PA-10 mixture’s unique stabilizer-antioxidant synergy enables speed-adaptive friction characteristics, maintaining BPN > 85 even after 8 h abrasion cycles. This provides a theoretical foundation for smart pavement design in extreme climates.

This study’s limitations include unvalidated long-term aging performance beyond 5-year service and pending economic feasibility analysis. Future work should focus on life-cycle cost modeling and multi-scale performance prediction frameworks. Industrial-scale production trials are recommended to verify field applicability.