Determining a temperature-density relationship after completed rolling of HMA

Abstract

During the past few years, the implementation of the nuclear gauge method of testing hot mix asphalt for desired compaction has proven a on-destructive and timesaving option. However, discrepancies between contractors' and WisDOT readings have led to this research which serves to investigate the relationship between the temperature and density of newly placed hot mix asphalt. The theory states that as asphalt cools, it becomes denser. Hence, if a nuclear gauge is used to measure density after the asphalt has been allowed to cool, it should record a higher reading than when the asphalt was measured just after cold rolling the previous day.

This research investigation has found a model that has not reinforced this theory. The research has shown that testing a road for density the morning following paving will not result in a significant difference in density than if it is tested the same day of paving.This research investigates the range of load-carrying capability, in terms of resilient modulus (M sub R), of crushed aggregate base course in Wisconsin and how variables, such as physical characteristics, material type, source lithology and regional factors influence M sub R. Testing was conducted on 37 aggregate sources and the results statistically analyzed to look for correlations between M sub R and these variables and to determine if they could be used to predict M sub R. Results showed that M sub R did not differ between gravel pit and quarry groups and that carbonate quarries generally gave significantly higher M sub R values than Precambrian, felsic-plutonic quarries. Changing gradation of base course from a given source affected M sub R test results, but not consistently or predictably. Certain physical parameters, were found that influence M sub R in some of the geologic subsets. However, none of the correlations were strong enough to predict M sub R with sufficient confidence. The test data will provide a base of information that will be useful when the Wisconsin Department of Transportation adopts a mechanistic-empirical pavement design process.