Technical Note – Permeable Paver Systems
Posted by Mike Munn on Mar 18, 2015
Permeable pavers are becoming increasingly popular as people and agencies strive to protect our environment. Permeable pavers help prevent water runoff and charge aquifers. Permeable pavers can only achieve designed drainage when specific aggregates are installed to create a totally permeable “system.” This system is comprised of a top layer of concrete pavers that have small joints filled with small stones. Water then enters the joints penetrating various layers of larger crushed washed stones to allow the water to either be stored, or infiltrate the soil subgrade and help filter pollutants.
The Interlocking Concrete Paver Institute (ICPI) worked with several agencies, architects and manufacturers to develop recommendations for aggregates which are shown below. Graniterock fully supports the “Green” movement so that end users can earn LEED points by using locally produced aggregates and minimizing water runoff that achieve desired results. The specifications listed below are from Section 02795 Interlocking Concrete Pavers. ICPI recommends most permeable paver installations as follows:
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Joint Fill: ASTM No. 8 or 9 Crushed Stone (Graniterock ¼” Premium Drain Rock is preferred over 3/8” Drain rock because it fits better between the paver joints)
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Typical coverage is 2 lbs/sq.ft.
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Bedding: ASTM No. 8 Crushed Stone (Graniterock 3/8” Drain Rock)
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Typical depth is 1-1/2” - 2”
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Base: ASTM No. 57 Crushed Stone (Graniterock 1”x4” Concrete Rock)
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Typical depth is 4”
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Sub-Base: ASTM No. 2 Crushed Stone (Graniterock 1-1/2” Ballast)
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Typical depth is 6” - 8”
Photo diagram courtesy of ICPI
ICPI adopted the gradation and stone sizes designed by the American Society for Testing and Materials (ASTM) in their D 448 Specifications for Road and Bridge Construction. ICPI recommends larger washed crushed stone rock on the bottom layer to provide a stable base and high water-storage capacity. Finer crushed stone is used directly under the pavers to act as a leveling course and enhancing the system’s permeability. Graniterock is committed to providing high quality crushed washed stone for these applications. Quality is carefully controlled through all phases of the production process at our own quarry. These products are readily available at most Graniterock facilities from South San Francisco to Monterey. Please contact your Graniterock Account Manager to learn more about the specific Graniterock materials that are compatible with your permeable paver systems.
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