Because of the effects of temperature, moisture, and traffic on pavement materials, knowledge of the insitu material properties of pavement layers is essential for evaluating the effective structural capacity of the pavement and selecting an appropriate rehabilitation strategy. Destructive and nondestructive tests are used for field testing and evaluating pavement layers. Although many highway agencies frequently use deflection testing techniques for pavement evaluation, experience has shown that these techniques may not provide an accurate characterization of the insitu material properties of the asphalt concrete pavement layers.
Thus, research is needed to evaluate existing methods and to identify or develop suitable methods for determining the insitu material properties of asphalt concrete pavement layers commonly used in pavement evaluation, i.e., resilient modulus and thickness. These methods will enable engineers to make rational pavement evaluations and to select and design appropriate rehabilitation strategies.
The objective of the research is to identify or develop suitable methods for determining the insitu resilient modulus and thickness of the asphalt concrete pavement layers in flexible pavements and resurfacing of portland cement concrete pavements. These methods are expected to complement and improve the reliability of deflection testing procedures for determining insitu properties. The research will make use of the information developed under Phase I of NCHRP Project 10-44, Nondestructive Testing to Determine Insitu Material Properties of Pavement Layer.
Accomplishment of this project objective will require at least the following tasks.
Phase I: (1) Describe the field test methods that may be suitable for measuring the insitu resilient modulus and thickness of the asphalt concrete layers used in flexible pavements and rigid pavement overlays. (2) Evaluate--with consideration to relevance, accuracy, practicality, repeatability, cost, and other pertinent factors--the insitu test methods identified in Task 1. Discuss the merits and deficiencies of these methods and rate and rank them according to their overall suitability for efficiently and reliably measuring resilient modulus and thickness of the asphalt concrete layers. Identify the most promising methods and propose modifications to improve field test methods currently used for measuring insitu resilient modulus and thickness of the asphalt concrete layers, for further evaluation in Task 5. (3) Develop a detailed work plan for an experimental investigation to evaluate and validate the promising and improved test methods identified in Task 2. The detailed work plan, to be executed in Task 5, should include the rationale; describe the test methods, the evaluation and validation techniques, and the calibration requirements; address repeatability and reproducibility of the tests proposed in this investigation; and provide other pertinent details. (4) Prepare an interim report that documents the research performed in Tasks 1 through 3 and includes a detailed work plan for the Phase II portion of the project. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the NCHRP. Work on Phase II of the project will not begin until approved by NCHRP.
Phase II: (5) Execute the work plan approved in Task 4. Based on the results of this work, recommend test methods for measuring the resilient modulus and thickness of the asphalt concrete layers. (6) Develop protocols, in a format suitable for consideration and adoption by AASHTO, for the methods recommended in Task 5. (7) Submit a final report that documents the entire research effort.
The research has been completed, and the agency final report has been received and distributed to all state departments of transportation.
The final report has been summarized in NCHRP Research Results Digest 271