Accelerated pavement tests including full-scale Accelerated Pavement Testing (APT) and laboratory-scale tests (torture tests such as: Hamburg Test, Asphalt Pavement Analyzer (APA) test, etc.) aim at simulating the actual pavement test conditions using full/scaled wheel sizes and load magnitude to evaluate the material performance. APTs especially those of laboratory scale tests have been widely used in pavement material evaluation. They usually give ¿go¿ or ¿no go¿ to mixes by established criteria. However, no fundamental material properties such as dynamic modulus, yielding stress and internal structure parameters can be obtained from APTs due mainly to the lack of an analytical method and a rational constitutive model for asphalt concrete. Therefore, test results of APTs are not well utilized; the test results of APTs at a smaller scale cannot be conveniently interpreted to permit the evaluation of the material performance under other testing configurations such as full-scale. The proposed study will apply advanced numerical techniques such as Finite Element Method (FEM), Inverse Technique (IT), the measured deformed transverse profile and rutting accumulation process, and creep tests to calibrate a reliable constitutive model using laboratory-scale, routine, and simple APTs (such as Hamburg, APA, and Model Mobile Load Simulator, MMLS) to calculate the dynamic modulus, yielding stress and internal parameters representing the relative stiffness between binder and aggregates. A successful conclusion of this research will add tremendous extra values to APTs including torture tests and the full-scale APT, enabling pavement engineers to design mixes of better performance and therefore reducing rehabilitation cost. The end product of this research is a test procedure and a computer program that will calculate the fundamental engineering properties from simple and route APT tests (torture tests and MMLS test), saving efforts of some other, more complex, tests. The method to be developed can be applied to any laboratory-scale APT tests, the ALF (Accelerated Load Facility) machine, the MMLS and the HVS (Heavy Vehicle Simulator).

The main objective of this pooled-fund study is to develop, verify and implement methods to compute the fundamental and performance related engineering properties including dynamic modulus, yielding stress and a parameter representing the binder-aggregate skeleton interaction using simple and routine APT tests for material performance evaluation and MEPDG implementation. A correlation between these three parameters and other parameters will be developed for convenient use in practice.

The scope of the study includes three stages related to development, verification and implementation. In the development stage, a user friendly computer program will be developed to compute the fundamental properties real time using the measured rutted profile, the rutting accumulation process and /or deflections from simple and routine APT tests. In the verification stage, three to five mixes from each participating state will be studied. A factorial design will be developed so that the mixes from different states will cover dominating factors such as gradation, binder type, asphalt content, and air void content etc. Efforts will be made to select those mixes with known field performance so that potential criteria may be established for the yield stress and the internal parameter for evaluating the performance of a mix through statistical analysis of the experimental results and the calculated results. The fundamental materials properties of these mixes will be measured using the conventional methods and computed through the method developed in stage one for comparison, verification and correlation. In the implementation stage, a workshop will be conducted for materials engineers and technicians on how to use the program and procedure to compute the fundamental engineering properties. Detailed description of the method will be attached when submitting to interested states for review.

The three-stage project will last for three years. The first two stages will roughly take about 30 months and the last stage will need 6 months. Each participating state and/or FHWA is suggested to contribute $30,000/year with the leading state (Virginia) contributing $40,000/year for three years. As many State DOTs use simulative tests to evaluate asphalt mixes, the proposed method will add significantly additional values for these existing tests.