# Evaluation of the Functional Performance of Paving Materials Based on the Driving Wheel
## 1 Introduction  
Transportation is a fundamental and evolving national industry, which provides important support for economic and social development. By the end of 2018, China's total highway mileage had exceeded 4.856 million km [1, 2]. With the continuous growth of highway mileage and service time, the new concept of \"equal emphasis on construction and maintenance\" has gradually been accepted for highway development. Pavement maintenance has become a key task for the Department of Transportation in China. Although there have been many studies performed on pavement maintenance and preservation [3, 4], new types of maintenance measures and materials are still needed to cope with new demands, such as rapid maintenance under heavy traffic conditions. Traditionally, engineering research focused on the bearing capacity of pavement structures [5, 6, 7, 8]. However, the functional damage of the road surface is receiving more attention than before. The functional performance of pavement refers to the performance not related to the road structure, such as the anti-sliding, anti-stripping, noise reduction, and water permeability performance provided by the functional layer of the pavement surface. Although there are methodologies used to evaluate the functional performance of pavements [9; 10; 11], such as the sideways force coefficient routine investigation machine (SCRIM) test, the grip tester, and on-board sound intensity (OBSI). These methods are used on the constructed pavement surface. Therefore, it is difficult to obtain data in a controlled environment through these on-site methods. Due to limitations related to the test conditions (e.g., environment, materials, and technology), it is necessary to find an indoor test method that could control and quantitatively evaluate the factors influencing a pavement's functional performance. Some contractors have proposed control indicators from the perspective of commercial interests [12; 13]. However, these indicators are not enough for guiding actual construction or for quality evaluation purposes. Pavement surfaces with good functional performance offer safer driving conditions for vehicles, provide good anti-sliding performance, anti-stripping performance, and reduce the tire-pavement noise. These functional performances directly determine the economic benefits of pavement maintenance measures. At present, tests for pavement functional performance include indoor simulation tests and full-scale track tests [14; 15; 16; 17; 18; 19; 20]. Full-scale track tests could directly reflect pavement performance but require a huge amount of investment and a long test cycle. Therefore, such tests are not suitable for routine use. Furthermore, as the wheels of a circular track testing machine moved in a circle, the road surface was subjected to centrifugal forces. However, in addition to the vertical force and shearing force of the wheel, the road surface was also subjected to radial shear forces [21], which was not entirely consistent with the actual tire-pavement interaction mechanism. Therefore, the variation of pavement function performance under complex environmental conditions should be simulated by an indoor pavement accelerating test to overcome this problem. Various experts and engineers have promoted pavement acceleration devices for pavement surface function tests (Table 1), such as the Michigan Indoor Wear Track developed by the Michigan Department of Transportation (MDOT) [22], which uses a circular pavement track and simulates the rolling process of a car with two wheels. By applying a vertical load on the wheel, the wheel was towed to achieve rapid wear on the road surface. The three-wheel accelerated wear tester (ASTM E660-1990 2015) was developed by the American Asphalt Technology Centre [23]. The friction coefficients of specimens were then measured using a friction coefficient tester.