Minnesota Department of Transportation
This report presents results of the research that examined various asphalt pavement surfaces in the MnROAD facility. It covers the fundamentals of surface profilometry, describes the construction of the textures and elucidates the performance trends of the various surface parameters. The variables examined include friction, measured with the lock wheel skid truck, smoothness, measured with the light weight profiler, mean profile depth measured by the circular track meter, sound absorption measured by the acoustic impedance tube and Tire- Pavement-Interaction-Noise measured by the on board sound intensity device. Traffic difference was found to be a significant variable in the friction trend of the asphalt surfaces when the low-volume road inside lane of the cells were compared to the corresponding outside lane and when the mainline driving and passing lanes were compared. Based on the Wilcoxon Rank sum, Wilcoxon Sign Rank, and the T-test, traffic levels affected skid resistance. Additionally, the frictional-time series appeared to follow the half-life equation typical of disintegrating materials. A similar test on tire-pavement-noise difference found traffic to be insignificant within the five years of monitored performance of the same test tracks. This study found that certain surface characteristics change with time regardless of traffic while others change with time and traffic. As the study found friction to be related to traffic, periodic measurements of friction can be performed when practicable, otherwise the half-life model developed in this study may be a rough predictor. In the deduced model, friction degradation appeared to be a function of the initial friction number and traffic-induced decay factor. In the low-volume road, there was hardly any evidence of effect of traffic on friction from a comparison of the traffic and environmental lanes. However, at higher traffic levels, (mainline driving versus passing lanes) traffic appeared to affect noise and friction. The study also proposes a temperature-based correction algorithm for Tire-Pavement-Interaction-Noise. From distress mapping, IRI, and permeability measurements, there were no noticeable trends within the five years of study. Additionally, this research performed advanced data analysis, identified significant variables and accentuated intrinsic relationships between them. Additionally, the "on board sound intensity" (OBSI)-Temperature correlation exhibited a negative polynomial relationship indicating the higher importance of temperature to OBSI relationship in asphalt than published characteristics of concrete pavements. It ascertained that texture mean profile depth was not as significant as texture skewness in predicting surface properties. Smoothness measurements indicated that most asphalt surfaces are not associated with laser-induced anomalous IRI reading errors. The major properties affecting ride in most asphalt surfaces were evidently extraneous to the surface texture features..
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