# A Review of Long-Term Skid Resistance of Asphalt Pavement
## 3 Skid Resistance Mechanism and Influencing Factors of
### Effect of Aggregate Properties on Skid Resistance of Asphalt Pavement
Fine aggregates are usually used to fill the voids in the pavement structure to provide a properly stabilized aggregate structure, which has a potential impact on the internal friction angle and flow deformation resistance of the mix, and the morphological characteristics of the fine aggregates also have a direct impact on the skidding texture of the pavement, which in turn affects the skidding resistance of the pavement [97; 98; 99]. Fine aggregate has a significant effect on the skid resistance at the macroscopic texture level, and the correlation between fine aggregate and construction depth is the highest; the more complex the angularity of fine aggregate, the greater the construction depth of the AP and the better the skid resistance [7]. In addition, fine aggregate has the role of interacting with coarse aggregate to jointly form the macroscopic structure of the pavement and then improve the skid resistance of the pavement [97]. From the results of the existing research, it can be seen that the fine aggregate has a greater influence on the road performance of AP, especially the high-temperature stability, water stability, and shear resistance performance [100]. The friction coefficient during the process of vehicles traveling on the road surface is mainly provided by the friction coefficient of the aggregate surface texture and the hysteresis friction coefficient. Figure 6: Schematic diagram of pavement abrasion [73]. (1) Friction coefficient component of aggregate surface texture: The aggregate surface texture has a significant impact on the skid resistance of AP. The friction coefficient component of aggregate surface texture is  
\[\mu_{a2}=\frac{\pi\sqrt{1-k^{2}}}{2k}\text{PSV} \tag{17}\]  
where \(\mu_{a1}\) is the friction coefficient component of aggregate surface texture;  
PSV is the aggregate abrasion value. The component of the coefficient of friction provided by the surface texture at standard temperature is  
\[\mu_{a2}=0.01144a_{s}PSV \tag{18}\]  
\(a_{s}\) is the area ratio of surface-exposed coarse aggregate, calculated by the following formula:  
\[a_{s}=(1-n_{s})P_{s} \tag{19}\]  
\(P_{s}\) is the volume percentage of coarse aggregate to AP mineral material (%);  
\(n_{s}\) is the surface void area ratio (%). (2) Hysteresis friction coefficient component: the depth of the particles embedded in the tire is  
\[d_{i}=\frac{1}{4}\pi^{4}(K_{1}+K_{2})^{2}q_{i}^{2}r_{i} \tag{20}\]  
Then, the hysteresis friction coefficient component is  
\[\mu_{pi}=\frac{1}{3}\pi(K_{1}+K_{2})q_{i}\sqrt{8-\pi^{4}(K_{1}+K_{2})^{2}q_{i }^{2}} \tag{21}\]  
The modulus of elasticity of rubber is taken as 225 MPa, and the hardness and modulus of elasticity of aggregate are much greater than those of rubber, which taken as \(K_{1}=0\) and \(K_{2}=\frac{1}{K_{2}}\), then  
\[\mu_{pi}=0.00465q_{i}\sqrt{8-0.001924q_{i}^{2}} \tag{22}\]  
The wheel load is P, the particle radius is \(r_{i}\), the radius of the equivalent circle of the wheel track is \(\delta\), and the number of particles involved in the contact with an equal-sized sphere is N\({}_{i}\); then, the particle contact pressure is  
\[q_{i}=\frac{3}{2\pi}\left[\frac{4}{3}\frac{\left(\frac{p}{N_{i}}\right)^{\frac {1}{2}}}{\pi(K_{1}+K_{2})r_{i}}\right]^{\frac{2}{3}} \tag{23}\]  
\[N_{i}=\left\{(1-\varnothing)\delta^{2}\left[\frac{4}{3\pi Pr_{i}(K_{1}+K_{2}) }\right]^{\frac{2}{3}}\right\}^{\frac{3}{5}} \tag{24}\]  
where \(q_{i}\) is the contact pressure of individual particles (MPa);  
\(\varnothing\) is the porosity of dense accumulation of single-grained aggregate.