# Field Trial and Performance Evaluation of Soybean-Based Bio-Fog Seals for Asphalt Rejuvenation
## 2 Materials and Methods
### Experimental Plan
#### 2.4.1. Pavement Friction  
Pavement surface texture plays a critical role in maintaining friction between the tire and the road surface, which affects vehicle stopping distance and stability. Two primary factors influencing pavement texture are macrotexture and microtexture. Macrotexture (Figure 6a), with irregularities with wavelength ranging from 0.5 to 50 mm, is assessed through measurements of texture depth or profile depth and is crucial for preventing hydroplaning at high speeds. Microtexture (Figure 6b), on the other hand, refers to the roughness of the aggregate particles and is essential for providing skid resistance at lower speeds. To assess the influence of the fog seals on the pavement's skid resistance, the Sand Patch Volumetric Method, British Pendulum Test (BPT), and Dynamic Friction Test (DFT) were used.  
Figure 4: Application truck.  
Figure 5: Experimental Plan.  
The Sand Patch Volumetric Method assesses macrotexture by measuring the mean texture depth (MTD) (Figure 6a). The test was conducted following the ASTM E965 [30], spreading a known volume of sand on the pavement surface. The sand fills the voids, and the area of the resulting circular patch is measured. MTD reflects the average depth below the surface peaks.  
The British Pendulum Test (BPT) is a dynamic pendulum impact-type test that simulates the contact between a tire and the pavement surface using a rubber slider (Figure 6c). The test measures the energy loss when the slider impacts the pavement, which is indicative of the surface's frictional properties and an indirect evaluation of skid resistance. The results are expressed as the British Pendulum Number (BPN), in which a higher number signifies greater skid resistance. This test is conducted following ASTM E303 [31], and it requires a minimum BPN of 55 for high-traffic roads, like motorways, trunk roads, class 1 roads, and heavily trafficked urban areas (over 2000 vehicles per day) [32].  
The Dynamic Friction Tester (DFT) measures surface friction using a horizontally spinning disk with three spring-loaded rubber sliders, according to ASTM E1911 [33] (Figure 6d). The tester applies a controlled load and rotates the disk at varying speeds. The decrease in the disk's speed upon contact with the pavement reflects the friction between the sliders and the surface, thus allowing an indirect evaluation of microtexture. In this study, DFT was conducted before and after one month of treatment on the middle lane and outer wheel path under wet conditions. Additionally, in the St. Michael section, DFT was used to assess the immediate change in friction at 30-min, 60-min, and 90-min intervals following fog seal application.  
It is important to note that DFT provides valuable information about pavement microtexture; however, it is not typically used as the sole criterion for pavement friction by Departments of Transportation (DOTs). In this study, due to its strong correlation with Skid Number at 40 mph (65 km/h) with Ribbed Tire (SN40R) [34], a minimum DFT threshold of 0.35 at 40 mph (DFT40) was chosen based on recommendations for skid resistance intervention on motorways [35].