# Research on Grooved Concrete pavement Based on the Durability of Its Anti-Skid Performance
## 2 Materials and Methods
### Anti-Skid Tests  
The dynamic rotating friction coefficient tester developed by the research team, which has been patented (Patent no.: CN20082022395.X), was used to measure the anti-skid performance of the samples (shown in Figures 3 and 4). It was operated by installing a test slide sample under a certain load on the test disc, then placing the test disc onto the pavement. When the disc is rotated at a given speed, the torque required to drive the disc is obtained from the driving engine. The friction coefficient of the pavement surface is calculated according to Equation (1):  
Figure 1: Sketch of the longitudinally-transversely grooved (LT) form.  
Figure 2: These images show the preparation of the test samples. (**a**) The grooving technology and process; (**b**,**c**) the grooved test samples.  
\[\mu=\frac{N}{dG} \tag{1}\]  
where \(\mu\) is the friction coefficient of the pavement surface, \(N\) is the torque required to drive the disc, \(d\) is the friction arm (10 cm), and \(G\) is the vertical load (21.56 N).  
The texture depth (TD), the British Pendulum Number (BPN), and the friction coefficient (\(\mu\)) methods are all commonly used to evaluate the anti-skid performance of pavement. Table 6 shows the Chinese code performance requirements [20]. Of these methods, the TD method is the most suitable for evaluating concrete pavement. Hence, the \(\mu\), adopted to evaluate the anti-skid performance in this paper, needed to be converted to TD in the laboratory tests.  
Table 6 shows the anti-skid requirements for concrete pavement, where special road section refers to interchanges, grade crossings, and speed change lanes of expressways and first-class highways.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Road Section**} & \multicolumn{2}{c}{**Acceptance Value of TD**} & \multicolumn{1}{c}{**Unit**} \\ \hline Expressway, First-Class & General Road Section & 0.7–1.10 & mm \\ Highway & Special Road Section & 0.8–1.20 & mm \\ \hline \hline \end{tabular}
\end{table}
Table 6: Anti-skid requirements for concrete pavement 1.  
Figure 4: Image of the test disc of the dynamic rotating friction coefficient tester.  
Figure 3: Sketch of the dynamic rotating friction coefficient tester. The tester includes the following: (1) speed control device, (2) engine, (3) axis of rotation, (4) shell, (5) torque sensor, (6) digital display instrument, (7) weighing plate, (8) bearing, (9) test disc, and (10) rubber slider.  
Contrast tests, using nine samples, were implemented between the dynamic rotating friction coefficient tester method and the sand-laying method [27]. The test results are shown in Table 7.  
The regression equation was obtained by the data in Table 7, as shown in Equation (2).  
\[\mu=\frac{TD-0.8904}{3.7599 TD^{2}-2.9579}+0.5427 TD(R=0.8863) \tag{2}\]  
As seen in Equation (2), \(\mu\) and \(TD\) are positively correlated. By using the conversion relation of \(\mu\) and \(TD\), the results of \(\mu\) should meet the specified requirements shown in Table 8.  
In order to compare and analyze the effects of different grooved forms on skid resistance, two types (T and LT) of grooved samples were prepared to implement comparative anti-skid tests.