Pavement surface characteristics are important to both the safety of the pavement surface and the comfort of the drivers. As of yet, texture and friction measurements have not been incorporated into the design of pavement surfaces. Seven different wearing surface mixtures, placed at the Virginia Smart Road pavement facility, were studied over a one year time period for both friction and texture properties. A locked wheel skid trailer and a laser profilometer were used to assess the pavement surface characteristics. Laboratory testing of the pavement wearing surface mixtures was performed to determine volumetric and mixture specific characteristics. Testing included gyratory compaction, specific gravity, maximum theoretical specific gravity, ignition testing, and gradation analysis. These material properties were used to study the impact of material properties on pavement surface characteristics. The pavement surface characteristics were analyzed using regression analysis with some measured and calculated parameters relevant to the pavement wearing surface properties. Analysis variables included the skid number at 64 kilometers per hour measured using the ASTM E501 (smooth) and ASTM E524 (ribbed) tires, the mean profile depth, the slope of a linear SN-speed model, the skid number at zero speed from the Pennsylvania State University (1) model, and the International Friction Index parameters. Analysis determined that testing particulars such as the grade of the test did not significantly affect the measured skid number. However, there is a significant difference between the skid numbers measured using the two tires. Additionally, the relationship between speed and skid resistance is assessed differently between the two test tires. Regression analysis concluded that there is a relationship between surface characteristics and HMA design properties such as the VMA, VTM, Percent Passing #200 sieve, and Binder Type. The influence of these variables on each of the analysis parameters varied. / Master of Science

Wet-pavement friction is a public concern because of its direct relation to highway safety. Both short- and long-term seasonal variations have been observed in friction measurements. These variations have been attributed to different factors, such as traffic, rainfall, and temperature. Since both the tire rubber and the HMA pavement surface are viscoelastic materials, which are physically sensitive to temperature changes, temperature should affect the measured frictional properties. Although several researchers have attempted to explain and quantify the effect of temperature on pavement friction, it remains to be fully understood. The objective of this research was to quantify the effect of pavement surface temperature on the frictional properties of the pavement-tire interface. To accomplish this, tests conducted on seven different wearing surfaces at the Virginia Smart Road under different climatic conditions were analyzed. Due to the short duration of this study and the low traffic at the facility, only short-term effects of temperature on pavement friction were investigated. To accomplish the predefined objective, skid test data from both ribbed and smooth tires were collected over two and a half years (from January 2000 to August 2002) and then analyzed. Six sets of tests were conducted under different environmental conditions. The pavement and air temperatures during each test were obtained using thermocouples located directly under the wearing course (38mm below the surface) and close to the pavement surface, respectively. Regression analyses were conducted to determine the effect of pavement temperature on the measured skid number at different speeds, as well as on friction model parameters. The main conclusion of this investigation is that pavement temperature has a significant effect on pavement frictional measurements and on the sensitivity of the measurements to the test speed. Both the skid number at zero speed (SN0) and the percent normalized gradient (PNG) tend to decrease with increased pavement temperature. This results in the pavement temperature on the measured skid number being dependent on the testing speed. For the standard wearing surface mixes studied at low speed (lower than 32 km/hr), pavement friction tends to decrease with increased pavement temperature. At high speed, the effect is reverted and pavement friction tends to increase with increased pavement temperature. Temperature-dependent friction versus speed models were established for one of the mixes studied. These models can be used to define temperature correction factors. / Master of Science