Recipient: Concrete Masonry & Hardscapes Association
Grant: $10,000
Completion: 2022
Project Summary: 33
Lightweight deflectometers (LWDs) have been around since the 1980s. They are seeing increased use by state DOTs (e.g., Indiana, Minnesota, Nebraska, Florida, etc.) and by municipal road agencies to measure the stiffness of compacted soil subgrades and aggregate bases. ASTM test methods govern their calibration and use. LWD use is becoming the preferred test method because measured deflection relates directly to pavement base and subgrade stiffness whereas the current standard of practice is to use a nuclear density gauge to measure density, to indicate stiffness and the potential for deflection. Open-graded aggregates (OGA) used in permeable pavements present additional problems for the use of a nuclear density gauge. It is almost impossible to insert the radiation source rod into OGA. This requires the operator to use the gauge in backscatter mode, which provides highly variable readings caused by irregular voids, odd angled faces, and particle shapes in the aggregate.
For these reasons, the Foundation funded research (~$150,000) by Oklahoma State University (OSU) for developing an LWD test protocol and a draft ASTM test method for open-graded bases for permeable pavements. See Fact Sheet 30 for more information on the Developing Deflection Acceptance Criteria for Compacted Open-graded Aggregate (OGA) Bases for Permeable Pavements Using LWD research project.