Specification for Use of Nonnuclear Technology
Earthwork and unbound aggregates, collectively called compacted geomaterials, are a noteworthy portion of the development of pavements. The source of much of the distress observed in pavements, especially in flexible pavements, can be traced to characteristics or construction deficiencies in those materials. Adequate pavement performance can only be guaranteed with appropriate process control to ensure the geomaterials used are similar to the one chosen, appropriate processing of the material to ensure that the material is uniformly mixed and contains an appropriate amount of moisture before compaction, and adequate compaction equipment to ensure proper density and stiffness. The primary tool for quality management currently utilized by FAA are the sand cone and the Nuclear Density Gage (NDG) to ensure that appropriate density is achieved. Measurement of moisture content and dry density, even though viable and straightforward, does not directly tie the construction quality with the mechanistic-empirical design processes where stress and modulus are utilized. The use of in-situ nondestructive testing (NDT) devices that estimate the stiffness parameters of a built pavement structure have been considered by transportation agencies. Such stiffness parameters are more representative of the pavement performance predicted during the mechanistic-empirical based design process. A transformation from density-based to modulus-based quality assurance (QA) approach involves technical and organizational challenges that must be recognized and addressed in order to create an efficient and practical modulus-based specification.
Project Objectives:
- Explore alternative ways of characterizing unbound pavement materials (subgrade, subbase and base) based on modulus, density or other material properties.
- Develop draft specifications for acceptance of constructed layers based on alternate methods/devices.
PSPA Performance Testing (Click to Zoom)
PSPA Performance Testing (Click to Zoom)
For more information on the devices shown on this page, follow the links to the detailed FAA webpages.
HWD
BAKFAA
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