360338 - The Lightweight Deflectometer (LWD) as an Acceptance Tool for Compacted, Open-graded Aggregates in Permeable Pavements

Tuesday, June 5
2:00 PM - 3:30 PM
Location: Skyway Room
Co-Authors: Garry Aicken, Leesburg, VA – Kessler Soils Engineering, Inc.; Robert Bowers, Uxbridge, Ontario – Interlocking Concrete Pavement Institute

Permeable pavements use open-graded aggregates for water storage and infiltration. Most compaction guidelines to specifications to help achieve structural stability state a specific number of passes with a roller compactor or a plate compactor exerting a certain force. The basis of acceptance is no visible movement of the compacted aggregate. Other compaction guidelines specify attaining a minimum 95% Proctor density. The former guideline has no means to measure and verify the quality of the compacted aggregates and the latter guideline is generally not measurable with a nuclear density gauge used in backscatter mode.

With ASTM standards and emerging AASHTO guidelines, lightweight deflectometers (LWDs) are becoming established and accepted by state departments of transportation to replace density measurements of compacted soils and dense-graded bases by measuring deflection and elastic modulus. While not articulated in technical literature to date, LWDs also offer an alternative means to quickly measure the extent and variation in compaction of open-graded bases used in the construction of permeable pavements. This paper provides data from three construction sites where ASTM No. 2 aggregate subbases and ASTM No. 57 bases were compacted and deflections measured using an LWD. The data suggests deflection ranges and potential criteria for acceptance of bases used in permeable interlocking concrete pavements and likely in bases used in porous asphalt, pervious concrete and in other permeable pavements.

David R. Smith

Interlocking Concrete Pavement Institute

David R. Smith has been working with permeable pavements since 1977. Early work began with laboratory and in-situ testing of concrete grid pavements to determine runoff coefficients. Since the advent of permeable interlocking concrete pavements (PICP) in the early 1990s, he authored many technical papers, articles and a best-selling 100-page design manual on PICP for the Interlocking Concrete Pavement Institute (ICPI). Mr. Smith also developed an ICPI student manual and training program for permeable interlocking concrete pavement contractors. Besides communicating best practices, he emphasizes integration of permeable pavements into broader green infrastructure site and urban design goals.

Mr. Smith has developed guidance documents Caltrans and for state stormwater agencies. These include the Minnesota Pollution Control Agency and an update to Chapter 18, permeable pavement guidelines for the North Carolina Department of Environment and Natural Resources. He also provided comments on permeable pavement guidelines for state stormwater agencies in Virginia, West Virginia, Wisconsin, Washington (state), Washington, DC, Maryland, Pennsylvania, New Jersey, and Colorado. He regularly supports civil engineers in consulting and public agency roles on PICP project design, construction and maintenance. Projects include parking lots, green alleys and roads.

Mr. Smith serves on the ASCE Permeable Pavements Technical Committee and is one of three editors of a book of the same name published in 2015 by ASCE covering all permeable pavements. He is on another ASCE committee developing a national standard on design, construction and maintenance of PICP. He has contributed to a monograph developed by a third ASCE Committee on Cold Climate Practices for Permeable Pavements. In other standards-making activities, he developed various ASTM standards and test methods for segmental paving products including C1781 for surface infiltration rates of segmental permeable pavements. Mr. Smith’s background includes stormwater management modeling and a graduate degree in environmental planning from Virginia Tech.


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360338 - The Lightweight Deflectometer (LWD) as an Acceptance Tool for Compacted, Open-graded Aggregates in Permeable Pavements

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