INCREASING DURABILITY OF HOT MIX ASPHALT PAVEMENTS DESIGNED WITH THE SUPERPAVE SYSTEM
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With the implementation of the Superpave mix design method, state highway agencies have experienced significant problems in durability of Hot Mix Asphalt mixtures due to lower binder content. To get a better understanding of the HMA mix production and the current specifications used by MSHA, the following were examined: i) differences in HMA properties that have been observed between samples taken at the plant (QC) vs. behind the paver (QA), ii)possibility of defining a transfer function between QA and QC data and iii) the potential risk to both the agency and the contractors using simulation analysis and based on the current specifications and pay factor equations. For this purpose a simulation tool was developed. The F and t tests showed that the QA and QC are two different populations and cannot be related. The simulation analysis illustrated that the correlation among mixture parameters doesn't affect the long run average pay factor. In addition it was concluded that the newly adopted pay equations are fairly rewarding and penalizing the contractors for mixtures, but the density pay equation needs modification.