Pervious Concrete Pavement Systems

What is Pervious Concrete? Pervious concrete is a (non-proprietary) mixture of pea-sized aggregate, portland-cement and water. There is generally no sand in the mix. Pervious concrete can be manufactured in most facilities that produce conventional concrete. Pervious concrete can be used as a pavement material in a dual-use application to meet the demands of the EPA - Clean Water Act and to act in concert with the new EPA - Green Infrastructure - Statement of Intent. To learn more about pervious concrete, and how it can be used, visit the General Information page. Note: The design and construction details for the dual-use system have been derived from the NIBS - Federal Green Construction Guide for Specifiers and the EPA Web Site "Porous Pavement".

How do I find a good Pervious Concrete Contractor? It is very important that a qualified contractor be selected to construct any pervious concrete pavement. However, not all Concrete Contractors have equal experience with the material properties and field requirements for constructing pervious concrete pavements. The National Ready-Mixed Concrete Association (NRMCA), in conjunction with ACI and ASTM, has created a program to train and certify individuals in the construction of Pervious Concrete Pavements. NRMCA recognizes the individuals within the U.S. that have demonstrated the knowledge and experience to qualify for Certification.

It may be in the best interest for the Owner/Developer to select a Sole Source Contractor for their project. (See the Sole Source Justification page.)

In selecting a qualified contractor, the best choice is to select a Contractor that has Employees that are NRMCA Certified Craftsmen. Only Certified Craftsmen have the verifiable knowledge and experience (3,000-hours) necessary to make field adjustments that may be required to construct pervious concrete pavements. (See the section on Testing on the Details & Specifications Page.)

Important: Because of the lack of standardized test for quality control, more of the demand for quality control goes to the Concrete Contractor. It is critical that whoever is making the decisions for acceptance of both the fresh concrete, and the finished pavement, that they are qualified to do so. The decision-maker must have adequate knowledge and experience to recognize the essential properties of Pervious Concrete, and know how to make field-adjustments. (Note: Both the NRMCA, and the National Institute of Building Sciences, recognize that only NRMCA Certified "Craftsmen" have the 1500-3000 hours of experience necessary as a basis of qualification.)

Because of the verifiable knowledge and experience of NRMCA Certified Craftsmen, it is suggested that a NRMCA Craftsman be engaged for every multi-load project (more than one-load of pervious concrete).

One Contractor, Magruder Construction has more NRMCA Certified Craftsmen Employees than any other Concrete Contractor in the U.S.

Are Special Tools required to Finish Pervious Concrete Pavements? Pervious Concrete construction does require special tools. Finishing-tools generally used with conventional concrete construction are not used with Pervious Concrete. Generally, these specialized tools, such as Glaspey-Rollers, are not available on the open market, and must be copied, and built, by new Contractors wishing to become certifiable as Pervious Concrete Contractors.

Many of the specialized tools, such as the various roller-compactors, were developed by Bruce Glaspey, currently Division Manager of Magruder Construction. These tools have been adopted by the Industry as the best finishing tools for constructing Pervious Concrete Pavements, and are specified for most projects across the Nation. See pictures of these special tools, developed by Mr. Glaspey, on the Pictures Page.

How much does it cost? Material and labor costs to construct pervious concrete pavements may vary depending on many factors, and are not generally given as a standard square-foot price. A Concrete Contractor should know the full scope of work before quoting a price to a prospective customer. However, budget-quotes can sometimes be given to a customer to qualify a range for which the pavements may be constructed. More on costs of pervious concrete pavements can be found on the Engineer's Page.

Site Development costs, using the Dual-Use System, are generally reduced to less than half of the costs of asphalt pavements and associated stormwater infrastructures and retention-pond (land costs) for commercial developments.

Generally, there is no charge for receiving an estimate on a project. If you are looking for a budget-quote, or would like to receive a qualified bid-for-construction, on any project, contact Don Wade with Magruder Construction.

A quick reference-guide for figuring costs would be to take the local price for pervious concrete - per cubic yard delivered, and divide that price by 54 (number of square-feet one cubic yard of material will cover at 6-inches deep). Take that figure and double it - to cover the cost of other items - (such as forms), tools & equipment, labor and profit. The final figure should give an approximate cost of the six-inches of pervious concrete pavement. (Additional conditions may raise the cost to three times, or more, of the material costs.) That is why each project requires a full knowledge of "the scope of work" before a qualified bid-for-construction can be submitted.

Costs that should be considered; the cost of the pervious concrete pavement, and base, should be compared to the cost of conventional pavements - plus the cost of the required stormwater inlets, storm-sewer pipes, and the cost of the retention/detention ponds - (to include the cost of the land where the ponds are constructed). When all the costs are compared, the Dual-Use system is generally much less than the cost of conventional systems. The reason; the pavement and base of the dual-use system takes the place of all the other conventional systems and infrastructure, thereby reducing the overall cost of development. Generally, for commercial parking lots, the Dual-Use system costs are less than half of non-permeable pavements (asphalt) and their associated stormwater systems and land costs.

How Can I get LEED Credits? LEED Credits are a part of the "Sustainable Building Program" and the U.S. Green Building Council. Several levels of awards can be achieved by accumulating "points" based on a specific rating system. Many new government projects are being designed to comply with the initiatives of the program. Pervious concrete can be used, and can collect multiple points depending on the application. See the section on LEED. Also, contact Don Wade for additional information on the design of pervious concrete systems for LEED Credits. Mr. Wade should be included as a part of the early Design Team to insure the maximum credits allowed for LEED Certification by using pervious concrete systems.

How long will it last? Pervious Concrete Pavements are based on the properties of portland cement, which typically gets harder as it ages. Many of the pervious concrete projects completed over 20-years ago in Florida are still functioning the same as when constructed - with no overlays. (Pictures of these pavements are available upon request, or site-visits can be arranged.) Contact Don Wade with requests. Unlike asphalt, portland-cement based concretes can last over a thousand years. How long a pavement will last is often a function of how well it was constructed. To choose a qualified construction Contractor, see: How do I find a good Pervious Concrete Contractor?

What about Stormwater Runoff? Pervious Concrete pavements allow the stormwater to pass directly through the pavement, not run off as a source of pollution. (See the NRMCA Video.) Also, each state will have different requirements on how to deal with stormwater runoffs. (See: What are the Stormwater Requirements in my State? listed directly below.) The Dual-Use System deals directly with how to save much of the construction and development cost of a project by storing stormwater directly beneath the pavement - inside the infiltration basin (on-site pond). Pervious concrete pavements can probably be used on most commercial projects throughout the U.S.

What are the Stormwater Requirements in my State? Every State has different requirements for dealing with Stormwater Maintenance. A good start for information is on the Stormwater Page. (Click on any state on the map to get stormwater compliance information on that state.)

What about Freeze/Thaw? Magruder Construction has installed many Pervious Concrete Pavements in northern states where freeze/thaw is an issue such as Ohio, Missouri and Nevada. These pavements have gone through many freeze/thaw cycles and are still functioning. The NRMCA has also published a guide on using pervious concrete pavements in freeze/thaw environments. The Iowa State University has also published a document on their research on Pervious Concrete in Cold Weather Climates. In conclusion, there are enough completed projects in almost every northern state to qualify that pervious concrete works as well in the northern states as it does in the southern states.

What do I do if my Property is sloped? Many properties will not be flat. However, for the Dual-Use system to function properly as an infiltration system the gravel base should have a flat bottom. If the site cannot be cut-and-filled to facilitate a flat system, then the site should be divided into separate cells with each cell being a separate flat system, and each cell connected by a sloped ramp similar to a parking-garage design. More on the design of pavements can be found on the Engineer's Page.

What happens if the soil doesn't perk well? Many soils within the U.S. do not perk well, but will usually have some measurable perk rate. The perk rate of the insitu soils, compacted to 95%, should be tested, and become part of the design criteria. The perk rate should be known to determine the storage-capacity required for the design of the thickness of the layer of gravel/crushed-stone directly below the pavement. A higher perk rate can reduce the thickness requirements, and lower the cost of materials. In a few areas the perk rate may be high enough that a layer of gravel for storage would not be required. The volume of storage required may vary from site to site depending on local conditions. It is generally up to the Project Civil Engineer, or Engineer of Record to determine the conditions for the design for each site. Contact Don Wade for additional requirements-of-design for the Dual-Use systems.

Is a High Water-Table a Problem? Many properties now being developed have a water-table near the surface. This can create a problem for developers where local ordinances require a specific distance from the bottom of the stormwater treatment train to the mean high-water table. Many States require a minimum of 2-4 feet. If open-ponds are being considered as the stormwater BMP, then imported fill may be required to bring the site to an elevation, such that, when the pond is constructed, the bottom of the pond is still above the mean high-water table. The imported-fill requirement can result in a very high cost for developers.

The Dual-Use system can substantially reduce the cost of development in areas of high water tables. The entire stormwater storage/treatment train can be constructed on, or near the surface, thereby eliminating the need for imported fill. The entire pavement/storage/treatment train is typically only one-foot thick.

Are there any Maintenance Requirements? Pervious Concrete Pavements are by nature, infiltration systems. Therefore, a regular maintenance program should be required to keep the pavements clean. (See the Federal Highway Administration (FWA) page on Stormwater BMPs.) The FWA page also gives some information on maintenance costs.

A typical maintenance program should include periodic inspections for debris (see: EPA - TMDL), resulting in a hard-vacuum cleaning as required. Representatives from the Elgin (Street-Sweeper) Company recommend a straight-vacuum process rather than a vacuum/sweeper combination. The City of Olympia, Washington also recommends a straight-vacuum cleaning system for their pervious concrete sidewalks. These vacuum-cleaning procedures generally restore up to 200% of the perk-rate of the system comparable to no maintenance. (See the Executive Summaries produced by the RMC Research Foundation and UCF.)

The perk rate of new pervious concrete pavements are typically higher than required by design - see the NRMCA Video. Therefore, even if the pavements no longer function as shown in the video, they are probably still functioning at a higher perk rate than required. Generally, it is the Owner's responsibility to provide maintenance of their parking lots. The Owner/Developer should include a whole-building commissioning program and schedule during the design, construction and operation of the project.

All pervious concrete pavement projects should include a maintenance-schedule and commissioning-program in the project design and specifications.

The Design Engineer should also consider the vacuum-cleaning maintenance requirements in their initial design. Pervious concrete placed directly on compacted soil limits the quantity of air that can be drawn through the bottom of the pavement. However, pervious concrete placed on a layer of clean gravel (as in the dual-use system) allows air to flow freely through the bottom of the pavement - thereby increasing the cleaning efficiency.

Where Can I get Samples? Samples can generally be acquired from a local ready-mix concrete supplier at no charge. However, some facilities may not be aware of the nature of pervious concrete and would not be able to provide samples. If samples are not available from a local supplier contact Don Wade with the contact information of the ready-mix facility. If a project is involved, where the sample is needed for product knowledge, then contact can be made to secure a sample. Everyone involved in a project where the material is to be used should be familiar with the properties. Samples can provide a good knowledge-base for an understanding of the material, and how it functions.

Where can I find Specifications? The Project Engineer is generally responsible for creating the specifications for the construction of pervious concrete pavements, especially where stormwater maintenance is an integral part. The Engineer should consider the specification guidelines listed on this website specifically for the (non-proprietary) dual-use systems. It is important that the person in charge of creating specifications for pervious concrete systems be familiar with the material properties and field-requirements, such as, how the material is tested for quality control and acceptance. See the section on Testing on the Details and Specifications Page. The design and construction details for the dual-use system have been derived from the NIBS - Federal Green Construction Guide for Specifiers and the EPA Web Site "Porous Pavement".

How is Pervious Concrete Tested? The material properties of Pervious Concrete are different than those of conventional concrete. (See the General Information Page.) As a consequence, testing requirements for Pervious Concrete is considerably different than the testing requirements for conventional concrete. Because of the physical properties of Pervious Concrete, many of the tests generally associated with conventional concrete do not work with Pervious Concrete, or do not apply. More on the Testing of Pervious Concrete can be found on the Details and Specifications Page of this website.

Even though tests generally used for conventional concrete do not apply for Pervious Concrete, there are general Industry-accepted, Quality Control, testing guidelines for the fresh material when it arrives on the jobsite. Most of the testing of the fresh materials is the responsibility of the Concrete Contractor. The Concrete Contractor must have the ability, based on experience, to make judgments of the material based on a visual inspection. The Concrete Contractor must also be able to make the field-adjustments, to compensate for variables in the mixes from load to load. Only a NRMCA Certified Craftsman has the required, verifiable-experience to be able to make the required field adjustments. As a consequence, only an NRMCA Certified Craftsman should have the authority to reject the load(s) if the mix is unacceptable. See the section on Criteria for Acceptance on the Details & Specifications Page.

Important: Because of the lack of standardized test for quality control and acceptance of Pervious Concrete, it is critical that whoever is making the decisions for acceptance of both the fresh concrete, and the finished pavement, that they are qualified to do so. The decision-maker must have adequate knowledge and experience to recognize the essential properties of Pervious Concrete, and know how to make field-adjustments. (Note: Both the NRMCA, and the National Institute of Building Sciences, recognize that only NRMCA Certified "Craftsmen" have the 1500-3000 hours of experience necessary as a basis of qualification.)

Because of the verifiable knowledge and experience of NRMCA Certified Craftsmen, it is suggested that a "Craftsman" be engaged for every multi-load project.

Magruder Construction is a Concrete Contractor that has the personnel with the NRMCA Craftsman Certifications necessary to perform the required field-adjustments. Contact Don Wade for additional information regarding the testing of Pervious Concrete.

What are the Strength Requirements? There are no compressive, or flexural, strength requirements for Pervious Concrete Pavements. The reason for this is because there have been no proposed strength requirements for parking lot loadings as they might relate to the design of pervious concrete pavements. As a consequence, there are no related design standards for the thickness requirements based on strengths (as with conventional concrete). Pavement thicknesses for Pervious Concrete are based on generally accepted Industry guidelines that have proven to be effective for parking lot loadings. Five to six-inches of (non-reinforced) pervious concrete is generally accepted as a thickness requirement for slow-moving automobile and light-truck loadings. Eight-inches is generally recommended for heavier truck-traffic lanes. Because there are no acceptable standards for strength requirements, there are also no reasons to create cylinders or beams at the jobsite for corresponding strength tests. (See also the NIBS - Federal Green Construction Guide.)

What about Wire-mesh or Steel Reinforcements? Any type of steel reinforcements, or imbedded items, are not recommended for Pervious Concrete pavements. Steel reinforcements, such as wire-mesh, would rust in pervious concrete, and is not required for parking lot pavements. ACI does not recommend wire-mesh for conventional concrete parking lots, and there is no reason to include it in pervious concrete pavements. Also, embedded-items such as steel key-cold joints are not recommended. Experience has shown that pervious concrete pavements that have been constructed with key-cold joints have failed at the joints. No reinforcements are required in Pervious Concrete pavements. Experience has shown that typical parking lot loadings do not require pavement reinforcements, and the generally accepted Industry Standards do not recommend their use.

How soon can I drive on the Pavement? Industry Standards recommend that fresh Pervious Concrete Pavements remain covered with a plastic-sheeting (visqueen) for a minimum of seven-days to moist-cure. Generally, if the pavements have been constructed properly, the pavements can be opened to traffic after the moisture-barrier has been removed. In some cases, the pavements can be opened to foot-traffic after only one day. However, the plastic-sheeting should still remain in place for the full seven days.

Can Color be added to Pervious Concrete? A variety of coloring agents can be used effectively with Pervious Concrete, similar to conventional concrete. However, some types of color-materials work better than others. The Concrete Contractor should have verifiable experience with different types of color to be able to know which applications would be better in different circumstances. Note: The Owner, or Owner's Representative should realize that in all types of concrete work there will generally be a color differential between different loads of material. Also, in Pervious Concrete Pavements, there may also be surface discolorations due to the plastic-sheeting cover used during the curing process. The discoloration generally bleaches-out over time.

Magruder Construction has worked with many different types of coloring agents and recognize which are best. Contact Don Wade for more information on using color in Pervious Concrete, and to obtain a quote for a specific project.

If I'm an Engineer, do I need to be Certified by the NRMCA? In the best interest of the Owner, and as the Owner's Representative, the Engineer should know as much as possible about the properties of the material, and how to design around it. Reading the Manual, and sitting for the class and exam, is one way of obtaining a background knowledge of Pervious Concrete. More about the NRMCA Certification process can be found on the Contractor's Page. It is also important for the Engineer to recognize that not all people are going to have the adequate knowledge and experience to be able to make the necessary decisions about the design and construction of Pervious Concrete Systems. This makes it even more important to involve the experience of a competent Concrete Contractor. See the section on Testing on the Details and Specifications Page.

How can I become a Certified Technician? NRMCA Certification is generally administered at the state-level. Many state ready-mixed concrete associations, or local ACI Groups, may have the authority to administer the tests. More about what to do, and where to find additional information can be found on the Contractor's Page of this website.

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Last updated: 2/23/08