1. Introduction
Snow and ice on road pavements are common in most regions of China during winter. These conditions significantly reduce the road surface’s adhesion coefficient and skid resistance, leading to decreased vehicle speed, extended travel times, increased fuel consumption, and even traffic accidents [
1]. Furthermore, traffic issues caused by icy road conditions are a global concern [
2]. Consequently, snow and ice melting have become integral components of winter road maintenance, carrying substantial economic and societal benefits [
3]. Consequently, many nations prioritize the treatment of road snow and ice and have conducted extensive research. The literature has explored various solutions, including manual and mechanical removal, snow melting agent application, heated pavement systems, conductive concrete, freezing inhibition pavement technology, and ice-suppressing and coating technologies [
4,
5].
Ice-suppressing materials, which can lower the freezing point through embedded melting agents or isolate the ice layer from the road surface using hydrophobic materials, have emerged as effective solutions. These materials are applied to asphalt pavements through manual brushing or mechanical spraying [
6]. When rain or snow falls, the ice-melting- and snow-removing materials on the carrier are released to melt snow and ice. Simultaneously, hydrophobic materials within the ice-suppressing material isolate the ice layer from the pavement, effectively reducing adhesion and facilitating easy removal. Compared to traditional deicing methods, ice-suppressing and coating technologies offer several advantages, including active ice and snow melting, excellent environmental performance, efficient and long-lasting deicing, and preventive capabilities [
7].
Hydrophobic ice-suppressing technology originally found its application in the treatment of icing on high-voltage transmission lines [
1]. This involved the application of a superhydrophobic nano-deicing coating material on the conductors, effectively reducing ice formation on the transmission lines. In the field of road science and technology, efforts have been made to develop anti-icing and thin-ice removal coatings using hydrophobic deicing technology for high-voltage transmission lines [
8].
Ma et al. conducted a study on the anti-icing performance of asphalt pavement using hydrophobic surface and thin-ice removal pavement coating technology. They developed a coating technology with hydrophobic properties, inspired by the deicing mechanism employed for high-voltage conductors [
9,
10]. This technology involves the creation of a hydrophobic film on the asphalt pavement surface, which isolates the ice layer. However, this approach does not rely on self-melting capabilities. While some preliminary test sections were conducted, there is a lack of comprehensive documentation of the construction process, technology, and specialized construction machinery and equipment.
The concept of an environmentally friendly asphalt pavement snow and ice-melting coating technology was initially proposed by Yang [
11]. This eco-friendly technology offers hydrophobic properties that reduce adhesion between the ice layer and the pavement. It also provides slow-release snow melting and deicing capabilities. Although the coating’s performance has been studied, there is a lack of construction technical indicators, requirements, and specific construction tools and machinery tailored to the coating’s features [
12].
Several scholars have examined ice-suppressing materials and explored construction technologies based on the principles of ice and snow melting and ice suppression [
4,
13]. An anti-freeze ice-suppressing material for asphalt pavement was developed by adding a suitable amount of slow-release anti-icing agent (Mafilon) to emulsified asphalt. Tests were conducted to evaluate deicing effectiveness and conductivity at various Mafilon contents, including an experiment to determine the optimal spraying thickness of the ice-suppressing material. Siegmund Werner et al. used porous adsorption materials to absorb self-melting snow additives, achieving long-term snow melting through slow-release mechanisms [
14]. Kaemereit Wilhelm et al. successfully prepared 0.5~1 mm granular self-melting snow additive material by utilizing cement as a carrier material through cement solidification [
15]. The V-260 snow melting agent developed by Verglimit Company in Switzerland consists of calcium chloride-coated hydrophobic material and is widely used today [
16].
In Japanese self-snow melting technology, porous zeolite is used as an absorbent to adsorb salt, which is then added to asphalt mixtures in powder form to replace fine aggregate or mineral powder. This approach achieves snow melting and ice removal through salt release [
17,
18,
19]. China first introduced imported self-snow melting technology and materials around 2000. In recent years, many domestic road researchers have embarked on the study of self-snow melting technology [
20]. Zhou et al. adopted Japanese snow melting technology to research and develop self-snow melting additives [
21].
Ma et al. have researched and developed the granular snow melting admixture Iceguard, known for its slow-release- and non-corrosive properties. It is considered safe and environmentally friendly for the metal components of bridges and road structures [
5]. Shan et al. conducted studies measuring pavement wettability after applying a hydrophobic coating, changes in stone absorption rates, and the length and density of cracks in the ice layer following the impact of a steel ball [
22]. Zheng et al. conducted an analysis and evaluation of the deicing coating’s performance from various perspectives, including anti-ice and snow performance, durability of the coating materials, and impact on pavement skid resistance [
23]. Wu et al. developed a regression model for long-term snow melting performance and provided a calculation formula for determining the precipitation amount of additives on self-melting asphalt pavement in different regions of the country [
24]. The long-term snow melting performance of asphalt mixtures with Iceguard was evaluated through comparisons with foreign products and testing roads, complemented by rapid dissolution tests to determine Iceguard’s service life [
25,
26].
Through research and the application of ice-suppressing materials both in China and abroad, it becomes evident that current ice-suppressing material technologies are in their initial and exploratory stages. A comprehensive set of technical evaluation indicators and quality control standards for ice-suppressing materials has yet to be established, and ongoing project applications remain in the testing phase [
27,
28].
The ice-suppressing material developed in this study exhibits several key characteristics: active deicing, no adverse impact on roads, bridges, ancillary facilities, and vegetation, preventive pavement maintenance, and continuous winter deicing. This presents a novel approach to road deicing. The composition design method for the ice-suppressing material is proposed, and considering the material’s unique characteristics, a performance evaluation methodology is introduced. This evaluation serves as a theoretical foundation for the widespread adoption of asphalt pavement ice-suppressing materials.
3. Results and Discussion
3.1. Analysis of Anti-Icing Test Results
Two sets of Marshall specimens and rutting plate specimens were prepared using AC-13 grade asphalt mixture with an asphalt-aggregate ratio of 5.0%. One set of Marshall specimens and rutting plate specimens were subjected to a spraying treatment with an ice-suppressing material at a rate of 0.5 kg/m
2, while the other set of Marshall specimens and rutting plate specimens were left untreated. The testing procedures followed the anti-icing test protocol, including the falling ball impact test.
Figure 4 and
Figure 5 illustrate the Marshall specimens after the falling ball impact test and the gravity knockdown test, respectively.
Figure 6 depicts the rutting plate specimens following the falling ball test.
From
Figure 4, it can be deduced that the surface of the Marshall specimen in the contrast group (left) displays only steel ball impact marks and pits. In contrast, the surface of the Marshall specimen in the spraying group (right) exhibits clear fracture boundaries, and there is no residual ice adhesion in the fractured areas. This qualitative assessment suggests that the ice-suppressing substance has a superior anti-icing effect. The calculated ice broken area is 12.72 cm
2, determined through indoor measurements of the Marshall specimen in the spraying group, resulting in a calculated breakage rate of 16.2%.
Figure 5 demonstrates that the ice layer on the surface of the sprayed Marshall specimen can be completely removed by gravity, leaving no residual dark ice on the specimen’s surface. Conversely, the Marshall specimen in the contrast group (unsprayed) exhibits substantial dark ice, indicating a higher adhesion between the ice layer and the specimen in the contrast group compared to the spraying group.
Regarding the falling ball impact test of the rutting plate specimen shown in
Figure 6, it can be inferred that the ice layer on the rutting plate specimen in the contrast group partially detaches in a small area after impact, with most of the ice layer remaining attached to the specimen. In contrast, the rutting plate specimen sprayed with the ice-suppressing material experiences a significant detachment of the ice layer over a large area, with no dark ice remaining on the rutting plate after the fall. This suggests that the ice-suppressing material effectively isolates the ice layer from the specimen, and the ice layer on the specimen treated with the ice-suppressing material is easily removed.
3.2. Analysis of Hydrophobic Performance Test Results
In accordance with the test procedure of the droplet image analysis method, water droplets were placed on the surfaces of both uncoated glass slides and glass slides coated with the ice-suppressing material. Photographs were taken at various time intervals (5 s, 30 s, 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min). The comparison of static contact angles from the test results is presented in
Figure 7. In each image, the droplets on the left side are on regular glass slides (contrast group), and those on the right side are on slides coated with the ice-suppressing material (spraying group). The change in droplet contact angles over time is illustrated in
Figure 8.
Figure 8 demonstrates the temporal evolution of droplet contact angles. The contact angle gradually decreases as time progresses, primarily due to water droplet evaporation and the gradual spreading of droplets on the slide’s surface. To minimize errors and obtain more accurate contact angle measurements, it is advisable to measure the contact angle as quickly as possible.
For droplets on slides coated with the ice-suppressing material, the contact angle was 99.5° at 5 s and gradually decreased to 83.3° at 20 min. In contrast, the contact angle for droplets on clean slides ranged from 39.2° to 29° over the same time period. A comparison of the data leads to the conclusion that the ice-suppressing material exhibits excellent hydrophobic properties and significantly reduces the adhesion between the ice layer and the road surface.
3.3. Analysis of Adhesion Performance Test Results
In accordance with the test methods and procedures for assessing adhesion performance, asphalt mixture specimens that were sprayed with ice-suppressing material and contrast asphalt mixture specimens that remained unsprayed were subjected to both tensile and shear tests. The interfaces between the ice layer and the specimens after the tensile and shear tests are visually depicted in
Figure 9 and
Figure 10, while the results of these tests are presented in
Figure 11.
The tensile test results presented in
Figure 11 indicate that, in the case of the sprayed group specimen, the ice layer becomes detached from the specimen when the tensile force reaches 1084 N. Additionally, there is virtually no dark ice remaining on the specimen’s surface, and the cross-section appears flat. This phenomenon is attributed to the chemical action of the freezing point inhibitor, which results in the interface’s strength becoming weaker than that of the ice, leading to fracture at the interface.
In contrast, for the unsprayed contrast group specimen, the ice layer becomes detached from the specimen when the tensile force reaches 1755 N. In this case, the two specimens break from the middle of the ice layer, leaving a substantial amount of dark ice on the specimen’s surface. The cross-section between the test piece and the ice layer exhibits a conical shape. The tensile force between the ice layer and the surface of the test piece, after being treated with the ice-suppressing material, is reduced by 38.2% compared to the untreated specimen. This lower tensile force indicates a weaker adhesive force between the ice-suppressing material test piece and the ice layer, making it easier to remove the ice layer.
The shear test results reveal that, when subjected to shear force, the sprayed group specimens detach from the ice layer when the shear force reaches 4000 N. Similar to the tensile test, there is minimal dark ice remaining on the specimen’s surface, and the cross-section appears flat. In contrast, the unsprayed contrast group specimens detach from the ice layer under shear force reaching 11,000 N. In this case, the two specimens break from the middle of the ice layer, leaving a substantial amount of dark ice on the specimen’s surface. The cross-section between the test piece and the ice layer exhibits a conical shape, similar to the results of the tensile test. After applying the ice-suppressing material, the shear force between the ice layer and the specimen’s surface is reduced by 63.6%. A lower shear force is advantageous for crushing the ice layer under the wheel’s pressure.
3.4. Ice-Melting Performance Test and Result Analysis
The effectiveness of the ice-suppressing material in melting ice is a crucial factor that influences the separation of the ice layer from the asphalt pavement. The ice-suppressing material works by melting the lower surface of the ice layer, leading to the separation of the ice layer from the asphalt pavement. To simulate the ice-melting performance of the ice-suppressing material on the ice layer, the following test method and procedure were employed.
Marshall test specimens were prepared for both the spraying group and the unsprayed contrast group. Each group had a total ice mass of 60 g, and the test was conducted at −30 °C, with the temperature increasing by 2 °C every hour. To minimize the temperature-induced changes in ice mass, the maximum temperature was limited to 0 °C. The results of the ice-melting performance test are presented in
Table 9 and
Figure 12.
Figure 12 illustrates the relationship between temperature and the mass reduction in ice cubes. As the temperature increases, the mass of the ice cubes gradually decreases, and the rate of mass reduction steadily increases. Notably, at the same temperature, the mass reduction rate of the unsprayed group’s ice cubes is significantly lower than that of the sprayed group’s ice cubes. This observation, after accounting for the influence of temperature rise on the change in ice cube mass, suggests that the ice-suppressing material exhibits excellent ice-melting performance.