Ten Tremendous Tales of Pervious Concrete - Map Your … · Ten Tremendous Tales of Pervious...

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Ten Tremendous Tales of Pervious

Concrete

Matt Offenberg, PE

W.R. Grace & Co.

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 filters and treats rainfall

• Rainfall is spread over entire parking area

(instead of detention pond)

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

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

Overview: Ten Tremendous Tales

• Design

• Construction

• Decorative

• Maintenance

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

Design

Stormwater Codes: Good

Stormwater Codes: Bad

Permitting Rules

• Stormwater Management– Quality/quantity credit

– Aquatic Resource Protection

– Flood Protection

• Credit for pervious area (ISR)

• ‘Big Box’ ordinances

• Wetland rules

• Tree ordinances

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

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.

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…”

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.

CSS Permeable Pavement “Credits”

Specifications: Good - Water

Harvesting

Specifications: Bad

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

Specification Aid

Includes

– Submittals

– Quality Control

– Products

– Execution

• Batching

• Placing

• Finishing

• Jointing

• Curing

• Tolerances

What it is missing

– Slump

– Strength

– Mixture Proportions

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

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

The Missing Test Methods

• Paste Consistency (Workability)

• Air Entrainment

• Field Strength (Sawed Beams, Cores)

Design: Good – Improve Profit

Photo Courtesy of Dan Huffman

Design: Bad – Increase Maintenance

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

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

• Flat system offers the maximum

storage

Base Thickness

• Typically 150 mm +

• Greater than 150 mm to increase

storage

• Greater than 150 mm for freeze-

• Not required in some cases

– Minimize root damage

– Native soils highly permeable

Freeze-thaw Resistance

• Store water in

aggregate base

• Dry Freeze– 100-200 mm of aggregate

• 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

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

Construction

Compatible Mix and Equipment:

Photo Courtesy of Spin Screed

Compatible Mix and Equipment:

Mix Design: Good

Photo Courtesy of Magruder Construction

Mix Design: Bad

Process Efficiency: Good

Photo Courtesy of Z-Con

Process Efficiency: Bad

Curing & Protection: Good

Curing & Protection: Bad

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,

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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

Decorative

Decorative: Good

Photo Courtesy of Envirocrete

Decorative: Bad

Keys to Success in Decorative

• 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,

Maintenance and Repair

Maintenance: Good

Maintenance: Bad

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,

Repair: Good

Repair: Bad

Photos Courtesy of Google

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,

For Further Reading…

• www.perviousblog.com

• ACI 522R

• ACI 522.1

• NRMCA

Thank You!

Any Questions?

Matt Offenberg

Grace Construction Products

matthew.offenberg@grace.com