Advanced Asphalt Overlay Thickness Design and Analysis System

The placement of an asphalt overlay is the most common method used by many state Departments of Transportation (DOT) to rehabilitate existing flexible and rigid pavements. To perform well, an asphalt overlay must have a good balance of rutting and reflective cracking performance. The main objective of this paper is to present a comprehensive mechanistic-empirical (M-E) asphalt overlay thickness design system to assist pavement engineers to design a balanced asphalt overlay based on traffic loadings, climate, the existing pavement conditions, and the engineering properties of the asphalt overlay mix. The design system developed incorporates models for both reflective cracking and rutting of the proposed asphalt overlay. The Paris’ law-based reflective cracking model was chosen and further developed for predicting reflective cracking development. The required fracture properties of an asphalt overlay can be easily determined using the Overlay Tester. The proposed reflective cracking model was calibrated using a variety of overlay test sections including the LTPP-SPS5 sections on US175 near Dallas, Texas, and then verified using the California Heavy Vehicle Simulator test results. To predict asphalt overlay rutting, the well-known VESYS layer rutting model was adopted and later calibrated using the field rutting data from the National Center for Asphalt Technology ( NCAT) test track 2006 and LTPP-SPS5 on US175. The material properties required for this model were obtained from repeated load tests. The reliability and accuracy of the calibrated rutting model was further validated using one set of independent rutting data from NCAT test track 2000. The calibrated reflective cracking and rutting models were then integrated into an asphalt overlay thickness design and analysis program. A sensitivity analysis was conducted to identify the significant parameters influencing the predicted levels of reflective cracking and rutting. It was found that the six most important input parameters are 1) traffic loading level, 2) climate, 3) asphalt overlay thickness, 4) overlay mix type, 5) asphalt binder type, 6) load transfer efficiency (LTE). Furthermore, it was also noticed that asphalt overlay life in terms of reflective cracking is not linearly proportional to overlay thickness. A four in. asphalt overlay can have more than twice the life of a 3 in. overlay. The proposed asphalt overlay thickness design and analysis program provides the designer with a tool to compute pavement life in terms of rutting and reflective cracking. The system permits the designer to use up to two different overlay mixes such as a crack relief layer and a wearing surface. The system is fully operational and undergoing implementation within the Texas Department of Transportation (TxDOT).

Language

  • English

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  • Accession Number: 01328025
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 20 2011 11:22AM