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Ten Tremendous Tales of Pervious
Concrete
Matt Offenberg, PE
W.R. Grace & Co.
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Stormwater Pollution Treatment
• About 90% of the surface pollutants are
carried off by the first 12 to 25 mm of
rainfall (first flush)
• First flush passes through pavement into
soil
• Soil filters and treats rainfall
• Rainfall is spread over entire parking area
(instead of detention pond)
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Pervious Concrete Environmental
Advantages
• Recharges Groundwater→ Increases River Base Flow
• Water Resources are Conserved
• Less Need for Irrigation- Allows More Rainwater to
Trees and Vegetation
• Runoff to Streams and Lakes is Reduced, Cooler and
Cleaner
• Cooler Surface Has Less Impact on Air
• Temperature – Mitigates Urban Heat Island
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Property Owner Benefits
• EPA best management practice
• Pervious concrete is eligible for one or more LEED credit
points for the USGBC Green Building Rating System. Other
credits can be earned by using concrete.
• Impervious area zoning restrictions
• Decrease stormwater utility fees
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Overview: Ten Tremendous Tales
• Design
• Construction
• Decorative
• Maintenance
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Assumptions
• You Know a Little About Pervious Site Design
• You Understand Pervious Construction
• You’ve Been Exposed to Pervious Mixture
Proportioning
• This Isn’t the First You’ve Heard of Pervious
Concrete
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Design
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Stormwater Codes: Good
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Stormwater Codes: Bad
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Permitting Rules
• Stormwater Management– Quality/quantity credit
– Aquatic Resource Protection
– Flood Protection
• Credit for pervious area (ISR)
• ‘Big Box’ ordinances
• Wetland rules
• Tree ordinances
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South Carolina DHEC BMP Manual
Porous PavingPorous pavement is a permeable pavement surface with an underlying
stone reservoir to temporarily store surface runoff before it infiltrates
into the subsoil. This porous surface replaces traditional pavement,
allowing parking lot storm water to infiltrate directly and receive water
quality treatment, and also reducing runoff from the sit
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South Carolina DHEC BMP Manual
When and Where to Use ItPorous pavement options include porous asphalt, pervious concrete,
and grass pavers. The ideal application for porous pavement is to treat
low-traffic or overflow parking areas. Porous pavement also has
highway applications where it is used as a surface material to reduce
hydroplaning.
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Coastal Stormwater Supplement to the
GSMM - Recommendations
• 7.7.2 “In these situations, site planning and
design teams may also want to consider
the use of alternative paving surfaces, such
as pervious concrete…”
• 7.7.4 “If parking lot footprints cannot be
minimized using any of the techniques
described above, planning and design
teams should consider the use of
alternative paving surfaces, such as
pervious concrete…”
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Coastal Stormwater Supplement to the
GSMM - Credits
• Stormwater Management “Credits”
The Center for Watershed Protection
(Hirschman et al., 2008) recently documented
the ability of permeable pavement systems to
reduce annual stormwater runoff volumes and
pollutant loads on development sites.
Consequently, this low impact development
practice has been assigned quantifiable
stormwater management “credits” that can be
used to help satisfy the SWM Criteria presented
in this CSS.
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CSS Permeable Pavement “Credits”
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Specifications: Good - Water
Harvesting
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Specifications: Bad
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Do’s and Don’t Specifying Pervious
Concrete
• Review Good Pervious
Specs (UFGS, ACI 522.1)
• Talk to Local Concrete
Supplier
• Talk to Local Contractor
• Understand Current Test
Methods and Field
Practices
• Use Specs for Plain
Concrete
• Specify Compressive
Strength, Flexural Strength,
Slump…
• Ignore Contractor
Certification
• Make It Up As You Go…
DO DON’T
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Specification Aid
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Includes
– Submittals
– Quality Control
– Products
– Execution
• Batching
• Placing
• Finishing
• Jointing
• Curing
• Tolerances
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What it is missing
– Slump
– Strength
– Mixture Proportions
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ACI 522.1 Specification Checklist
• Specify nominal maximum aggregate size
• Specify subgrade preparation and permeability requirements
in appropriate section of Contract Documents.
• Specify final surface elevations and pavement thicknesses in
Contract Documents.
• Specify joint locations, depths, and dimensions on Project
Drawings.
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Current Test Methods
• ASTM C 1688 Standard Test Method for
Density and Void Content of Freshly Mixed
Pervious Concrete
• Hardened Density by ASTM C 1754
• Thickness by ASTM C 42, C 174
• Raveling Potential: ASTM C 1747
• Infiltration Rate: ASTM C1701
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The Coming Test Methods
•ASTM C09.49 Tests in Development:
Compressive Strength
Flexural Strength
•Other Tests in R&D
Field Raveling Resistance
Embedded Ring Infiltration
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The Missing Test Methods
• Paste Consistency (Workability)
• Air Entrainment
• Field Strength (Sawed Beams, Cores)
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Design: Good – Improve Profit
Photo Courtesy of Dan Huffman
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Design: Bad – Increase Maintenance
Cost
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Do’s and Don’t Designing Pervious
Concrete
• Drain Landscaping Down
and Away from PrvsC
• Design for Freeze-Thaw
Protection Drainage
• Use Curbs to Protect
Edges and Control
Subgrade Erosion
• Design PrvsC with Steep
Slopes without Erosion
Protection
• Drain Impervious
Pavements onto PrvsC
• Use PrvsC for Commercial
Driveways and Heavy
Traffic Areas
DO DON’T
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Ideal Pervious Concrete Pavement
• Pavement System
– Supports traffic
– Allows water to pass
• Water should flow vertically
• Minimize horizontal flow
• Storage in stone base
• Can use pavement and ponding
zone
• Flat system offers the maximum
storage
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Base Thickness
• Typically 150 mm +
• Greater than 150 mm to increase
storage
• Greater than 150 mm for freeze-
thaw
• Not required in some cases
– Minimize root damage
– Native soils highly permeable
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Freeze-thaw Resistance
• Store water in
aggregate base
• Dry Freeze– 100-200 mm of aggregate
base
• Wet Freeze– 100-200 mm of
aggregate base
– Air-entraining admixture
• Hard Wet Freeze– 200-600 mm of crushed
rock drainage base
– Air-entraining admixture
– Perforated drainage pipe
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Pavement Thickness
• Minimums– 150 mm Parking lots
– 150 mm Residential
Driveways
– 200 mm Streets
• Consider
Conventional
Concrete
Pavement– Heavy truck traffic
– High volume traffic
– Commercial Driveways
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Construction
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Compatible Mix and Equipment:
Good
Photo Courtesy of Spin Screed
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Compatible Mix and Equipment:
Bad
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Mix Design: Good
Photo Courtesy of Magruder Construction
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Mix Design: Bad
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Process Efficiency: Good
Photo Courtesy of Z-Con
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Process Efficiency: Bad
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Curing & Protection: Good
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Curing & Protection: Bad
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Keys to Success in Construction
• Knowledgeable Concrete Supplier
• Equipment/Mixture Compactibility
• Trained, Skilled, Experienced Crew
• Proper Mixture and Batching
• Efficient Placement
• Robust Curing and Protection
• GC Scheduling
January 20,
2014
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2014
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Production - At the Batch Plant
• Newer trucks
• Short Loads:
– 5 m3 loads
– Good mixing
– Less balling
– Saves wear
• Extra Mixing Time
• Maintained Plant
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Batching
– Wet Aggregate -- Know Your Moistures
– Don’t Hold Back too Much Water
– Never Batch with Hot Water
– Slow Load Rate
– 90% of Mix Water In First with Admixture
– Rock Starts
– Cement Ribbons In
– 10% of Mix Water Last
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Decorative
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Decorative: Good
Photo Courtesy of Envirocrete
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Decorative: Bad
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Keys to Success in Decorative
PrvsC
• Sound Architectural Design
• Extreme Water Control (Robust Admix)
• Skilled, Trained, Experienced Crew
• Well-Tuned Equipment
• Efficient Production
• Extreme Attention to Detail
• Robust Curing and Protection
January 20,
2014
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Maintenance and Repair
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Maintenance: Good
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Maintenance: Bad
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Maintenance Notes
• Good Design Significantly Reduces
Maintenance Demands
• Protect Pavement During Construction
• Remove Raveled Material Regularly
• Heavy Cleaning with Combination of Pressure
Washing and Power Vacuuming
• Worst Surface Contamination can be Ground Off
January 20,
2014
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Repair: Good
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Repair: Bad
Photos Courtesy of Google
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Repair
• Remember 20-Year Design Life
• Surface Repairs Have not Proven Durable in
Service
• Full-Depth Repairs: Remove Entire Panel for
Structural Integrity
• Use Pervious Materials for Repair to Maintain
Stormwater Design
January 20,
2014
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For Further Reading…
• www.perviousblog.com
• ACI 522R
• ACI 522.1
• NRMCA
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Thank You!
Any Questions?
Matt Offenberg
Grace Construction Products
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