Creating Elegance from In-between Spaces

The 2017 Hardscape North America Project Awards witnessed a record 146 submissions. The breadth and depth of attention to detail rose to new levels. A large number of entries often equates to tougher choices for the contest judges. Selecting one excellent project winner over another excellent one can mean some worthy projects don’t win. For this reason, there is this Editor’s Choice column.

Hardscape and landscape merge to create a linear backyard space with a mix of singular and group places.

A case in point is a backyard project submitted by Shawn Kelly with Mirror Lake Designs in Spring, Texas. The project is about elegant landscaping that redeems a tiny backyard as much as the hardscaping, and vice versa. Mr. Kelly aptly described the backyard’s narrow geometry as a bowling alley quieted with a landscape/hardscape transformation into a meditation space. Even with a shallow depth yard, the designer created secluded, intimate areas while supporting foot traffic that certainly arrives with backyard gatherings.

The Awards contest is in part one requiring excellent photography that communicates the designer’s intent. Successful photographic representations enhance the reader’s perception, and especially the contest judges’ perceptions. When combined with superb, uncluttered design, such photography makes it easy for the reader to vicariously enter and enjoy the place. This project merges both to land you there.


Excellence Exemplified

The HNA Hardscape Project Awards recognize outstanding hardscape projects by contractors building residential walkways, patios, driveways, commercial plazas, parking lots and streets. In its tenth year, the awards program received a record 149 entries. Projects were judged on intent, design, quality of construction and craftsmanship, compatibility with related construction materials and systems, construction innovation, detailing and overall design excellence.

1. Concrete Paver – Residential – More than 3,000 SF

Pasqualoni Pool Project

  • Location: South Windsor, CT
  • Contractor: Bahler Brothers
  • Manufacturer: Techo-Bloc
  • Designer: Ryan King, Bahler Brothers

The main design intent for this backyard resort was to ensure there would be enough space for entertaining large crowds. There needed to be multiple gathering spaces serving different purposes for the guests and homeowners.

The main focal point of the project is the pool, with a large patio space to connect all the different spaces and functions of the backyard. Some of the design features include a large outdoor kitchen, a seating area to watch the sunsets each night, an over-sized sunken fire pit area and a bocce ball court.

Honorable Mention: Family Entryway Location: Tomball, TX Contractor: Mirror Lake Designs Manufacturer: Belgard Designer: Michael Shawn Kelly, Mirror Lake Designs

2. Concrete Paver – Residential – Less than 3,000 SF

Foutch Residence

  • Location: Logan, IA
  • Contractor: Paver Designs, LLC
  • Manufacturer: Belgard and Techniseal
  • Designer: Justin Hampton, Paver Designs LLC

The homeowners wanted to create a one-of-a-kind outdoor living space for large groups of guests and family to congregate and relax. A grilling area/bar and a fire feature were must-haves. Paver Designs’ signature custom inlays were another must-have. A multi-level design was created, cutting into a hillside that sloped toward the house, providing for more usable space. Circular planters finish off the seat walls for more green space. A large fire boulder and pebble mosaic reflective wall accent the fire feature. The outdoor kitchen includes a grill and refrigerator for cooking needs. LED lighting was installed throughout to create a warm, inviting space at night.

Honorable Mention: Oak Brook Outdoor Transformation Location: Oak Brook, IL Contractor: Premier Outdoor Environments, Inc. Manufacturer: Unilock Designers: Kevin Barnes & Nathan Flipp

3. Concrete Paver—Commercial, More than 15,000 SF

Local Government Federal Credit Union

  • Location: Raleigh, NC
  • Contractor: Fred Adams Paving Co.
  • Manufacturer: Hanover Architectural Products
  • Designer: Stewart Landscape

The reinvigorated space at 3600 Wake Forest Road is designed to LEED Silver specifications and represents the workplace of the future—a facility that is both energy efficient and a healthy, inspiring place to work. With a fully integrated transit shelter, employees will be able to access the workplace through public transportation, eliminating the need for expansive surface parking. Rather, the facility features an integrated parking garage, which reduces the need for surface parking and provides space for an outdoor courtyard. The outdoor courtyard, which seamlessly brings together the building space, landscape and hardscape, serves multiple purposes, including space for employee lunches, a zone for private calls and an outdoor venue for informal meetings and large catered events.

Honorable Mention: Denver International Airport–Westin Hotel Location: Denver, CO Contractor: Rocky Mountain Hardscape Manufacturer: Hanover Architectural Products Designer: Stewart Landscape

4. Concrete Paver—Commercial, Less than 15,000 SF

Blue Bell Country Club Fire Pit Lounge

  • Location: Blue Bell, PA
  • Contractor: FS Landscaping Contractors, Inc.
  • Manufacturer: Belgard
  • Designer: Brian Stover, FS Landscaping Contractors, Inc.

The construction of the fire pit was excavated into a hillside along the edge of the 18th hole and clubhouse pond. To maximize the area, a custom curved Trex deck was cantilevered over the edge of the pond, and a flush patio and fire pit lounge to complement the curved deck was built. The fire pit is a wirelessly controlled gas unit custom built using antique wall stone. A retaining/sitting wall, pillars and boulders complete the retention of the hillside. Plant material softens the hardscape project and provides spring and summer color. TruScapes Landscape & Hardscape Lighting was installed to complete this outdoor living space for guests to enjoy into the evening hours.

Honorable Mention: Market Plaza & Exchange Plaza Location: Raleigh, NC Contractor: Fred Adams Paving Co. Manufacturer: Belgard Designer: Surface 678

Honorable Mention: Steak & Shake: University of Kentucky Campus Location: Lexington, KY Contractor: Decorative Paving Manufacturer: Pavestone Designers: Sherman Carter Barnhart Architects

5. Concrete Paver—Permeable, Residential

Emile Court Residence

  • Location: Gillett, WI
  • Contractor: Shawano Lawn and Stone
  • Manufacturer: County Materials Corporation
  • Designer: Shawano Lawn and Stone

Local and county zoning requirements mandated there could not be any impermeable surfaces within 100 feet of the shoreline. After exploring several options, the homeowners learned about the possibilities of a permeable paver system. They wanted the new patio to have a clean, modern look to match the feel of the home’s recently remodeled interior. They selected a solid white Holland paver with a solid gray paver for a border. Properly integrating the system with the site was a major, yet important challenge to effectively prevent runoff and protect the lake’s water quality. Special design consideration was given to the selection and installation of base materials to ensure the system would properly capture and filter storm water.

Honorable Mention: Belgard Aqualine 3pc Dominion Pavers Cypress Creek Job Location: Smithfield, VA Contractor: Dominion Pavers Manufacturer: Belgard Designer: Sasser Construction

6. Concrete Paver—Permeable, Commercial

University of Tennessee—University Center Bridge

  • Location: Knoxville, TN
  • Contractor: Hickory Hardscapes
  • Manufacturer: Belgard

The University of Tennessee wanted to create a masterpiece with a well-designed permeable walkway that would connect the classrooms on “The Hill” to the library. Hickory Hardscapes constructed the design using four different colors of Belgard Aqua-Roc II in a basket weave. The University of Tennessee loved this permeable walkway so much they have used it for numerous events. Local news teams often set up on the walkway to cover stories on campus. Every time ESPN’s GameDay is at UT for a football game, they set up their broadcast booth on the area—great exposure for permeable pavers!

Honorable Mention: Firstenburg Community Center Location: Vancouver, WA Contractor: Eastern States Paving Manufacturer: Williamette Graystone Designer: Robertson Engineering, PC

Honorable Mention: Southeast Atlanta Green Infrastructure Initiative Location: Atlanta, GA Contractor: Four Seasons Landscape

Management, Inc. Manufacturer: Belgard Designer: AMEC

7. Combination of Hardscape Products—Residential, More than 4,000 SF


  • Location: Mullica Hill, NJ
  • Contractor: Darlington Designs
  • Manufacturer: EP Henry
  • Designer: Simon Darlington

This project, a multi-phase installation with components still to come to complete the master plan, fulfilled the client’s dream of a beautiful outdoor living space. Components of this multi-level design plan include an outdoor kitchen complete with grill and side burner, refrigerator, storage drawers and trash bin. Adjacent to the kitchen is a dining area and an open, luxurious living space for comfortable relaxation. The custom pool, with waterfall and spa, make for resort-style living at home and feature lights and laminars for day-to-night pool use. A pool heater extends the season for swimming.

Honorable Mention: Backyard Oasis Location: Canton, GA Contractor: Miller Landscape, Inc. Manufacturer: Pavestone and FireMagic Designers: John Whittingslow & Bruce Miller

Honorable Mention: DiPonio Residence Location: Rochester Hill, MI Contractor: Decra-Scape, Inc. Manufacturer: Techo-Bloc

Honorable Mention: Focht Location: Robesonia, PA Contractor: Anewalt’s Landscape Contracting Manufacturer: EP Henry Designer: John Shandra, ELA

8. Combination of Hardscape Products—Residential, Less than 4,000 SF

Strosin Outdoor Retreat

  • Location: Waukesha, WI
  • Contractor: Extreme Exteriors (Big Bend, WI)
  • Manufacturer: Unilock
  • Designer: Jamon Peterson, Extreme Exteriors

Along with an in-ground pool, the client had an expansive list of items they wanted to incorporate into the design, including water, fire, cooking, entertaining, etc. With the existing yard at a severe slope, there were limited places to put the pool; it was clear the design would require multiple levels to incorporate all of the client’s wish list items. The construction process took over four months to complete.

The final result: a beautiful open, flowing design with plenty of space to entertain hundreds of people, with over 3,000 sf of paver patio, 1,200 sf of wall stone, six fire features, four water features, a brick pizza oven, full outdoor kitchen, a 20-foot-long bar and 140 low-voltage light fixtures that are completely automated with a phone or tablet.

Honorable Mention: Houston Residence Location: Knoxville, TN Contractor: Precision Landscapes Manufacturer: Belgard Designer: Jeremy Rose, Precision Landscapes

9. Combination of Hardscape Products—Commercial, More than 20,000 SF

Westlake Shopping Center 

  • Location: Peoria, IL
  • Contractor: Interlock Brick Paving
  • Manufacturers: Belgard, Unilock, Solistone, Milestone Imports 
  • Designer: Cohen Development Company with Bruce Brown, AIA, and Zumwalt and Associates, PE

As part of this $25 million award-winning redevelopment, all asphalt was removed from main parking fields, entrance driveways, Main Street, and approaches, and rebuilt entirely of interlocking concrete pavers. Approximately 300,000 sf of asphalt was removed. The project also came with an industry-first 30-year commercial warranty against defects from Belgard, guaranteed by Northfield Bend/Oldcastle. The high solar reflectivity finish on the ICP makes the parking lot 20 degrees cooler than the old asphalt lot. During rainstorms, wind and snow, adhesion is improved. People love the traffic calming, the cobblestone sound effects and the overall aesthetics of ICP!

10. Combination of Hardscape Products—Commercial, Less than 20,000 SF

Church Mutual

  • Location: Merrill, WI
  • Contractor: PICS Inc.
  • Manufacturer: County Materials Corporation
  • Designer: Carey Owen

Because this building is a rented space, the business owner wanted the option to take anything invested into the building to a new location if they ever moved. The patio project was carefully designed and constructed to integrate on top of an existing concrete slab. The contractor mortared the retaining wall into place on top of the concrete slab. Each wall unit was individually leveled then mortared because of the slab’s uneven surface. Meeting the owner’s need to create a relaxing space for employees was met with the expansive application of pavers surrounded by tall retaining walls to block the sound of passing traffic. An outdoor grill and kitchen area doubles as an ideal spot for work celebrations or to take a lunch break.

Honorable Mention: Courtyard & Curb Appeal Homerun Location: Hamilton, NJ Contractor: Monello Landscape Industries Manufacturer: Techo-Bloc Designer: Joe Monello

Honorable Mention: Semco Outdoor Display Location: Cincinnati, OH Contractor: Outside Insight (Cincinnati, OH) Manufacturer: Belgard and Unilock Designer: Scott Gifford, Outside Insight


Community Catalyst

Located a short boat ride from Peanut Island and the Palm Beach Inlet, the Riviera Beach Marina features 140,000 sf of interlocking concrete pavers, of which 105,000 sf are permeable. Winner of a 2016 Hardscape North America Honorable Mention Award, the $35 million Riviera Beach Marina redevelopment, completed in March 2016, concluded phase one of a multiphase revitalization project planned for the entire 26-acre Riviera Beach Marina District.

To attract the interest of private developers necessary for future phases of the revitalization master plan, the City of Riviera Beach and the Riviera Beach Community Redevelopment Agency (RBCRA) set their sights on the marina and the surrounding public land as the best site for phase one. The project was jointly funded with the City contributing one-third of the cost and RBCRA the rest.

“It was very important to the city council that this infrastructure investment project accomplish two things,” said Scott Evans, interim executive director of RBCRA. “Create a great waterfront public space for residents and visitors and attract future development from the private market.”

Photos courtesy of Coastal, an Oldcastle Company and Precise Paving, Inc.


Given the scope and scale of the Riviera Beach Marina District revitalization master plan, RBCRA had to apply for an Environmental Resource Permit (ERP) from the South Florida Water Management District. An ERP is required for development or construction activities to prevent flooding, protect the water quality of lakes and streams from stormwater pollution, and protect wetlands and other surface waters.

“Permeable [interlocking concrete] pavers were presented to us by the engineering design team as an environmentally positive method of construction,” said Mr. Evans. In addition to satisfying the ERP requirements for onsite stormwater capture and treatment, the permeable pavement was chosen for aesthetics, sustainability and lower cost.

“Using permeable concrete pavers in the parking lots and on the upper promenade was more cost effective than a traditional underground drainage system,” said Jill Lanigan, Director of Business Development at Song + Associates, the architectural design firm for the Riviera Beach Marina project.

“The soils in coastal municipalities are well suited for the use of permeable pavers,” said Patrick Figurella, P.E., Director of Engineering at Calvin, Giordano, and Associates. Based on the success his firm has had with other permeable paver projects in the region, Mr. Figurella said, “We are always looking for opportunities to use permeable pavers in other locations because of the advantages permeable systems afford with regard to reduction of runoff and providing water storage.”

The permeable paver system with standard exfiltration trenches allows the less than 14-acre marina site to provide 75% of the drainage for the entire Marina District, Mr. Figurella said. The Riviera Beach Marina site not only met the ERP’s present requirements, it established a sustainable site for future vertical development and related impervious surfaces.

In the interim, while RBCRA negotiates with a private developer for phase two construction, the public space created during phase one will be utilized for community programs to attract more visitors. Outdoor music festivals, a weekly green market and movies in the park are just a few of the events planned for the new space to serve the community and entice private developers to join the revitalization effort.


Initial ocean-themed design concepts for the paver fields considered curvilinear patterns to emulate waves, but through several variations evolved toward an orthogonal design, explained Ms. Lanigan. The waves became geometric, with the varying widths of the fields and the varying lengths of the bands representing a stylized interpretation of waves rolling in and out from the shore. Ultimately, the final design responded better to the marina layout with an added benefit of streamlining the installation process, she said.

To reduce the heat island, the design team chose for the permeable paver fields lighter, natural colors, SRI>29 labelled Amaretto and Napoli. For the bands, they selected darker, contrasting slate to complement the other colors. With the large area of permeable pavers in the upper promenade and parking lots, the 25,000 sf lower promenade along the waterfront instead used standard 2 3/8 in. thick concrete pavers.

Except for 30,000 sf of roadway that was machine-installed, the majority of the pavers were hand installed, according to Rob Goossens, Vice President of Precise Paving. The standard paver section along the dock was installed first and was completed by December 2015. Construction delays compressed the paving schedule for the remaining portion of the project, but Precise Paving successfully installed 105,000 sf of permeable pavers in three months to meet the deadline.

“It was hectic, we had to double up our crews on this job,” Mr. Goossens said. “One good thing with permeable pavers, when you screed the No. 89 bedding aggregate, you don’t have to worry as much about rain causing bedding displacement as you do with regular sand-set pavers.” This allowed his first crew to be more aggressive, screeding up to 10,000 sf sections at a time while the second crew followed behind laying the pavers.

Video courtesy of Precise Paving, Inc.


The unique design of the upper promenade with variable field widths and darker bands between prevented machine installation and were installed by hand. For the permeable paver cross section, 14 in. of ASTM No. 4 stone was placed first, then 5 in. of No. 57 stone, followed by 2 in. of No. 89 stone for a total water storage depth of 19 in. beneath the 4 x 8 x 3 1/8 in. thick permeable pavers.

For the roadway, the only section of the project that could be machine installed, the paver manufacturer worked with Precise Paving to optimize mold configuration and determine the best way to palletize the product in order to achieve maximum speed and efficiency.

“Most of it went according to plan,” Mr. Goossens said. “The speed tables in the roadway were probably the biggest challenge.” The original design planned for the speed tables to be poured concrete, but Mr. Goossens convinced the design team to use permeable pavers instead, which saved time and cost by eliminating the concrete for these four 20-foot wide sections. This modification also maintained the continuity of the paver roadway from one end to the other. “It saved the project time, money, and at the end of the day, I think it’s a better product,” Mr. Goossens said.

“It’s not too difficult of a task, but you do have to account for the slopes and the elevations you need to hit,” Mr. Goossens said. “That starts of course with the base and also our screeding.” The elevation change of 6 in. brought the speed tables up flush with the curbs and pedestrian walkways from the parking lot to the event center so they could serve the dual purpose of being crosswalks as well. White pavers were used to demarcate the crosswalks and also for arrows on either side of the tables to alert drivers. Red stripes of ADA-compliant pavers were placed on both sides of each crosswalk.

“This was the first time we used permeable pavers in this manner and they worked beautifully,” said Mr. Figurella.


Permeable interlocking concrete pavements (PICP) have become more efficient from a structural and water management perspective. The biggest change agent advancing PICP toward greater use is their cost-effectiveness, especially for redevelopment projects such as the Riviera Beach Marina where every parcel is premium property. Sacrificing land to a detention pond or paying the high cost of installing underground storage vaults can’t compete with the volume and pollutant reduction efficiency, minimal maintenance, longevity, and aesthetic quality of PICP.

Another factor advancing growth is studies by various universities confirming PICP performance. Last but not least, mandates from the U.S. Environmental Protection Agency for onsite stormwater detention, treatment and infiltration make PICP a superior management option. From a life-cycle cost standpoint, the paver surface will last 40 to 50 years without replacement. In contrast, an asphalt surface cracks, requiring routine and unsightly patching, and eventual milling and repaving two or three times over 50 years.


Over a year has passed since phase one completion of the Riviera Beach Marina. “We’ve seen a large boost in the number of visitors, thousands of people,” Mr. Evans said. “And our waterfront businesses have had increased traffic as well.” Feedback from the community has been positive. “People really love the public spaces we’ve created.”

Despite initial trepidation by some, Mr. Evans said, concerns have been laid to rest on using permeable pavers for such a large area. “Performance has been positive and the system is working as designed. We’re extremely happy with it.”

Regarding maintenance, RBCRA has conducted occasional spot cleaning and sweeping, but hasn’t had any major issues, Mr. Evans said. “We’ve installed a few monument signs recently and there was concern that the process would be more challenging, but it went smoothly. We were able to take up the pavers, make some changes for the signs, and then put them back successfully.”

“It really turned out to be a great project,” Mr. Goossens said. “We had a demonstration there in June, brought in a fire truck and doused an area with 200 gallons per minute for 10 minutes. Walking over the area after they shut off the hose, there was no standing water and you could actually hear all the water filtering down through the aggregates. It’s impressive.”

“This marks the first time we’ve used permeable pavers for a city street,” Mr. Figurella said. “Riviera Beach is leading other municipalities to consider the utilization of permeable pavers for public roadways or alleyways.”


Holistic Design

As the car pulls into the driveway at the end of a long workday, worries about schedules, traffic, politics, rising prices and other everyday concerns suddenly begin melting away. Stepping out of the car, the driver immediately is embraced by a stylish, welcoming environment promising joy, relaxation, family warmth and good company.

A rapidly growing number of stressed-out homeowners nationwide experience this transformation daily. Thanks to innovative contractors building imaginative designs with interlocking concrete pavers, dull driveways are transformed and cliché backyard patios become relaxing, resort-caliber environments.

“For both new homes and remodels, people are looking to create beautiful extensions of their homes,” said Joe Raboine, Director of Research and Development at Atlanta-based Belgard Design Studio & Elements. “They’re furnishing and putting in fireplaces, outdoor kitchens, lighting and music. They want to create a cohesive and beautiful space with a uniform look throughout their whole property.”

From Driveway to Patio

For people looking to give their property visually and functionally integrated styling and luxurious amenities of a high-end resort, pavers are the best way to go, said David Park, CEO of Landmark Pavers in Temecula, CA. “When they hear about the benefits, they’ll often contemplate, for the sake of uniformity more than anything else, doing all of their hardscapes at once, including their driveway, walkway and patio, using interlocking pavers for the whole project, front and back.”

Mr. Raboine believes that more homeowners are transforming their exterior home space into a welcoming, engaging environment as a dedicated effort to re-connect with family and friends. “It may sound a little bit sappy, but I think that as we become more connected and electronic, we’re actually becoming more disconnected than ever before in face-to-face interactions,” he said. “These types of spaces help bring people together.”

It’s not only homeowners in warm climates such as Southern California, Arizona and Florida that want to upgrade their homes’ surroundings. “In Colorado, we have four seasons,” observed Tim Lindgren, president of Lindgren Landscape & Irrigation in Fort Collins, CO. “Our winter season is not always warm enough for us to get outside, but the shoulder seasons can be extended when we build these areas and put in fireplaces and fire pits, outdoor heating elements, infrared heaters and fans.”

Mr. Raboine agreed, noting that there’s also a strong demand for visually and functionally integrated home environments in many northern areas. “In the Midwest, Northeast and Eastern Canada, their seasons are so much shorter that people want to spend every possible minute outside when it’s nice.”

Rising home prices also play an important role in motivating people to upgrade their current properties, rather than simply picking up and moving to a larger property. “In some markets, real estate sells at a premium, especially in many major cities,” Mr. Raboine says. “Land is becoming increasingly expensive and harder to find. Our market here in San Diego has really changed within the last 10 years, from pavers as a replacement of concrete, to pavers as part-and-parcel of a large, all encompassing project,” Mr. Park said. “The very successful paver installers in our area have been able to change with the market and offer a full landscape design option for the customer.”

Environmental conditions sometimes make pavers the only logical choice for a major exterior space project. “In Northern Colorado, we have very expansive soils and a freeze/thaw process unlike anywhere else that I’m aware of,” Mr. Lindgren said. In January, it’s not uncommon for daily temperatures to reach 70 degrees or higher. A few days later, lows may bottom out at sub-zero levels. “So the ground freezes, and then it thaws, then it freezes, and thaws, and it expands and it contracts,” Mr. Lindgren said. “That’s devastating on concrete, especially decorative concrete or stamped concrete—the finish doesn’t hold up.”

Designing and Planning

Not surprisingly, major, complex projects, such as a complete exterior space remodeling, require much thought and planning. “We have five designers in house, and we try to find the best designer for the scope of work that we understand the client wants to do,” Mr. Lindgren said. “Some designers have strength in hardscape, some have strength in plant material, some have strength in retrofits and others have strengths in new construction.”

The next step is an onsite consultation. “We sit down with the homeowners and listen to their wish list for the property and their goals,” Mr. Lindgren said. “We walk the site with them, give them a little insight on what we think the site is capable of and by the end of the meeting we have a proposal ready for them.”

Mr. Park said convincing homeowners to use pavers isn’t all that difficult. “People generally love the look of pavers, but when they find out the benefits—the structural integrity and the other benefits of pavers—they really are very happy with that.”

Addressing Challenges

The scope and scale of an integrated home environment project can be intimidating, even for an experienced contractor. Suddenly, the contractor finds itself responsible for an array of tasks extending far beyond paver work, including landscaping, electrical and plumbing installation and, in some cases, even long-term maintenance services. And the client always wants the job completed yesterday—or sooner.

Mr. Lindgren said contractors should be realistic about their capabilities and to outsource work they don’t feel comfortable tackling. “We, as a general contractor, will hire the electrician, framer, plumber and mason—whatever trade we need that we don’t do in house,” he said. “We handle the pavers, we do the landscaping and many other things, but we still have to coordinate with a handful of subcontractors to complete most projects.”

Finishing a project on time and on budget requires a great deal of planning and coordination with subcontractors. “The biggest challenge is trying to make sure that everything is thoroughly thought out from beginning to end,” Mr. Raboine said. “When you start talking about things like adding electrical, plumbing, gas lines, music and lighting, all of those things can take several to perhaps a half-dozen subcontractors to create.” Mr. Raboine noted that it’s important to plan tasks with as much detail as possible and to make sure that subcontractors are meeting all of their work and schedule obligations, including following local codes.

“Lighting and all other fixtures must be decided and planned before a shovel ever touches the ground,” Mr. Lindgren said. “The gas line, its size, who’s doing the installation, electrical switch and outlet locations, model numbers and so on all need to be spelled out before starting work.”

Attracted to the Flame

An increasingly popular patio centerpiece is a fireplace or fire pit, available in either kit form or custom built. “Manufacturers offer really neat kits that can be put together with predesigned segmental units,” Mr. Park said. “They’re much more cost-effective to build.”

Palletized kits can be assembled on-site with very little planning or work, Mr. Lindgren said. “I think they’re great, especially when you have an inexperienced contractor that doesn’t have the industry knowledge necessary to do custom work.” Mr. Lindgren noted that to the untrained eye, a kit is virtually indistinguishable from a conventional installation.

Kits also save a great deal of manpower. “Fire pits go together without any mortar—they’re all free stacking,” Mr. Lindgren explained. “You don’t have to build a foundation, do any mortaring or veneering on the stone or put a masonry cap on top—it’s basically a puzzle that you put together.”

However, fire pit and fireplace kits have their limits. “They have their place, and they work great, but if you have a custom site where the homeowner wants the installation to match the house’s stone or capstones, and everything needs to tie in, then kits don’t work,” Mr. Lindgren said. Fireplaces require concrete foundations due to their weight and these are generally hidden from view by the fireplace.

Another downside to kits is the relatively limited number of design options. “You kind of get what you get with a kit,” Mr. Park said. “Typically, if someone doesn’t like the look of a unit that’s prefabricated, you don’t have any alternative as a contractor other than to build something with a custom design, which, of course, costs more.”

Mr. Lindgren also recommended against mixing fireplace/fire pit kits and paver brands. “It’s nice to stick with a single manufacturer when picking products so that the colors and styles match,” he said. He suggested using the same manufacturer for pavers, fireplaces/fire pit kits, vertical elements, retaining walls, bench seating and most other key project elements.

Kit and custom-built fireplaces/fire pits generally require the same amount of maintenance. “If they’re designed to use gas, there’s very little maintenance,” Mr. Lindgren said. If they’re wood burning, there can be a lot or work.” Park says his San Diego customers rarely ask for wood-burning installations. “They’re worried about casting off embers and starting a fire in an arid climate,” he said.

Moving Forward

The growing demand for visually and functionally integrated home environments is taking paver installers into areas where many have little or no prior experience. “The trend for the traditional paver installer is going to be one of offering more all-inclusive landscape designs,” Mr. Park said. “Not only installing pavers, but also doing landscaping, synthetic turf, patio covers and offering a wide variety of other products.”

As contractors cope with new customer demands, they also face the challenge of rising prices. “The cost of materials is going up,” Mr. Lindgren said. “The cost of labor is also going up, and labor in our industry is so hard to find.” Mr. Park, however, is optimistic that most contractors will be able to adjust to the new challenges and to continue operating profitably in the years ahead. “The bottom line is that as long as the job market in a region is strong, and the housing market is strong, the hardscape market will also be strong,” he said.


Retrospective: Dayton, Ohio

As the birthplace of aviation and key manufacturing industries, Dayton, Ohio (2013 pop. 143,355) is also the birthplace of the first machine-assisted municipal street with interlocking concrete pavement. Built in November 1985, the repaving project likely never generated much cocktail chatter among Dayton’s historical society, but it was part of the city’s multimillion-dollar investment to help revitalize several historic districts. The city supported millions in private investment by urban pioneers during the 1970s and 1980s. Such funding renewed vintage late-1800s homes and brought physical and social stability to old neighborhoods.

After 20 years, this magazine issued an interim report in 2005 on the 11,000 sf Tecumseh Street in Dayton’s Oregon Historic District. When constructed in 1985, it was considered a demonstration project by the City, an expression of support for a rundown neighborhood being revitalized with a consistent infusion of restorative sweat equity by residents. While a lightly trafficked pavement in a residential neighborhood, the editor again visited the 31-year-old street last year to inspect the project. Since the editor was responsible for building the project for the City in 1985, the visit was more like listening to an old friend.

From a functional perspective, there were only a few cracked interlocking concrete pavers. Most pavement cracking occurred within the deteriorated concrete collars set around manholes and shutoff valves. By comparison, the pavers will certainly outlast the cast-in-place collars.

Tecumseh_StreetThe decades-old road base is a 7-inch thick mix of cement and aggregates, a hardened slurry that once supported a macadam surface, a thin layer of asphalt mixed with sand. This base had roughly 20% of it removed and replaced in 1985 due to deteriorated areas. As part of the renovation, the macadam, an early version of today’s asphalt surfacing, and the top of the concrete base were ground out and removed to receive an inch of bedding sand and 3 1/8-inch thick concrete pavers. These were machine-set in a 90-degree herringbone pattern in three days.

The aging base shows in a few areas where the paver surface has settled. Had the surface been asphalt, they would have been potholes. The pavers accommodate such movements while continuing to provide service to passing vehicles.

The pavement structure has at least another decade of remaining life. The pavers will almost certainly outlast the base. The strongest indicator of a need for repairs will happen when the base settles in places that eventually set off neighborhood driver complaints. That is unlikely as vehicle speeds are generally below 20 mph.

From a life-cycle cost analysis (LCCA) perspective, Tecumseh Street asks the question, what’s the long-term expense to Dayton’s taxpayers compared to asphalt or concrete? Would more street pavers ultimately save the City money? Since 1985, asphalt prices have fluctuated while interlocking concrete pavement has not. For residential streets in northern states, resurfacing (shave and pave) can be reasonably set at 17 to 20 years. An LCCA favorable to interlocking concrete pavement would compare costs for periodic asphalt pavement resurfacing. Such resurfacing during higher priced markets could likely register a savings by using concrete pavers.

The larger question asked by the street is institutional in nature. Just about every city has organized design, specifications, construction and maintenance equipment, and labor around asphalt and, to a lesser degree, concrete pavements. From a certain perspective, cities’ street maintenance departments are committed to asphalt because it’s cheap. Rather than a single street in pavers, what if Dayton had an entire neighborhood, district, or city with them? While an investment in a third pavement is an additional expense, would interlocking concrete pavement be less expensive to maintain from a city budget perspective if it was the majority pavement, replacing asphalt?

Cost comparisons could be modeled using pavement management software that most cities use to project maintenance costs. One aspect is for certain, departmental investment in construction and maintenance equipment, as well as labor and materials, would be significantly lower for concrete pavers than that required for asphalt. If deemed a cost savings, a shift by any city street maintenance department to pavers would require phasing out asphalt in low-speed streets. There would likely be a commensurate increase in property values due to enhanced neighborhood character. Whether a historic district or not, such enhancements benefit the City and property owners alike.


Is Bigger Really Better?

Project owners and designers specify segmental concrete paving slabs due to their unique visual appeal and finishes. Their large format often fits a particular dimensional module for the design of the project, complements the architectural character of adjacent buildings, or enhances the landscape architecture of the site. Some designers understate segmental pavement patterns by using paving slabs with fewer joints. In other situations, designers may mix smaller and larger slab units to create strong visual effects. While most applications are for at-grade or roof deck pedestrian uses, paving slabs are seeing increased use in areas with vehicular traffic. ICPI is engaged in field-testing research to assess the performance of slabs under vehicular loads.

When properly designed and constructed, paving slabs can withstand a limited amount of automobile and truck traffic. Unlike interlocking concrete pavements, slabs offer little to no vertical, horizontal or rotational interlock. Each unit bears applied loads and does not transfer applied loads to neighboring ones. Hence, their application to areas with limited vehicular traffic.

The load-carrying capacity of paving slabs and interlocking concrete pavements is put into perspective by reading ICPI Tech Spec 4 Structural Design of Interlocking Concrete Pavements and ASCE 58-16 Structural Design of Interlocking Concrete Pavement for Municipal Streets and Roadways. Both publications provide base thickness tables for pavements receiving up to 10 million 18,000 lb (80 kN) equivalent single axle loads or ESALs. Now underway, an emerging ICPI Tech Spec on structural design of paving slabs provides designs for up to 75,000 ESALs. This suggests that the structural capacity of paving slabs is less than 1% of that offered by interlocking concrete pavement. This further suggests that paving slabs should be exposed to limited vehicular traffic, and very few trucks per day.

Paving slabs are sometimes mistakenly called pavers. This misnomer has led to applying slabs under inappropriate vehicular applications in a few instances. To reduce confusion, the segmental concrete pavement industry is following other countries where product nomenclature and product standards specifically differentiate pavers from slabs. Figure 2 illustrates the difference.

A practical construction-related difference between concrete pavers and paving slabs is the former generally requires one hand to install a unit and the latter requires at least two hands to lift and place. In reality, most slab installations use clamps or vacuum equipment shown in Figure 3. Most commercial slab applications subject to trucks will be installed on a concrete base. Asphalt is generally not used as a base because it can’t be easily formed into an even surface.


In the U.S., ASTM C1782 Standard Specification for Utility Segmental Concrete Paving Slabs defines them as having an exposed face area greater than 101 in.2 (0.065 m2) and a length divided by thickness of greater than four. The minimum thickness is 1.2 in. (30 mm), and maximum length and width dimensions are 48 in. (1,220 mm). C1782 was issued by ASTM in 2016. Units having a length divided by thickness of 4 or smaller with a minimum 2 3/8 in. (60 mm) thickness fall under ASTM C936 Standard Specification for Solid Concrete Interlocking Paving Units.

In Canada, Canadian Standards Association or CSA A231.1 Precast Concrete Paving Slabs defines their dimensional envelope with a face area greater than 139.5 in.2 (0.09 m2) and a length divided by thickness of greater than four. The minimum thickness is 1.2 in. (30 mm), and the maximum length and width dimensions are 39.37 in. (1,000 mm). This product standard was first issued by CSA in 1972. Units having a length divided by thickness of four or smaller with a minimum 2 3/8 in. (60 mm) thickness fall under CSA A231.2 Precast Concrete Pavers.

ASTM C1782 requires an average minimum flexural strength of 725 psi (5 MPa) with no individual unit less than 650 psi (4.5 MPa). The CSA standard requires a minimum average of 650 psi (4.5 MPa) with no individual unit less than 580 psi (4.0 MPa). A noteworthy aspect of the flexural strength is doubling the thickness of a paving slab increases the flexural strength by four times. This suggests that larger units may need to increase their thickness in order to withstand vehicular traffic. Some concrete paving slabs may use fibers to increase their flexural strength as well.

Freeze-thaw durability requirements in ASTM C1782 references ASTM C1645 Standard Test Method for Freeze-thaw and De-icing Salt Durability of Solid Concrete Interlocking Paving Units. This test method involves test specimens with a specified dimensional range from the corner of paving slabs. The specimens are immersed in water or a 3% saline solution and subjected up to 49 freeze-thaw cycles. The mass lost from the coupons are measured at 28 and 49 cycles. If no more than an average of 225 grams per square meter of surface area are lost after 28 cycles, the paving slab from which the specimen was cut passes this requirement. If not, the freeze-thaw cycles continue to a maximum of 49. If no more than an average of 500 grams per square meter of surface is lost after 49 cycles, the paving slabs pass this requirement. The lowest temperature in this test is 23° F or -5° C.

In the CSA test, the top of the paving slab is enclosed with a leak-proof compartment and the interior receives a 3% saline solution. See Figure 4. After completing 28 freeze-thaw cycles, the paving slabs pass the CSA requirement if the surface yields no more than an average loss of 300 grams per square meter of the inundated surface area or 500 grams lost for specimens with an architectural finish.

An architectural finish is wearing surface amended with face mix, ground (polished) or shot blasted treatments, formed (to look like stone per Figure 5), hammered and/or flame-treated to provide a more stone-like appearance. If the architectural paving units do not meet the mass lost requirement at 28 cycles, the freeze-thaw cycles continue until 49 cycles are completed. The paving slabs meet the durability requirements in CSA A231.1 when the average loss after 49 cycles does not exceed 800 grams per square meter or 1,200 grams for units with an architectural finish. The lowest temperature in this test method is more severe than C1782, i.e., 5° F or -15° C. 

Dimensional tolerances are similar in ASTM and CSA paving slab standards. Dimensional tolerances are determined from unit dimensions provided by the manufacturer for specific products. Tolerances for length, width and height and for convex and concave warpage are as follows:

  • Length and width: -0.04 and +0.08 in. (–1.0 and +2.0 mm)
  • For units over 24 in. (610 mm), ASTM C1782 allows -0.06 and +0.12 in. (-1.5 and +3 mm)
  • Height: ±0.12 in (±3.0 mm)
  • Concave/convex warpage for units up to and including 18 in. (450 mm) in length or width: ±2.0 mm; units over 18 in. (450 mm): ±3.0 mm

Paving slabs meeting these dimensional tolerances are loosely laid, or can be installed on a sand setting bed (i.e., sand-set) if tolerances are consistent. However, these tolerances are generally not suitable for precision sand-set, bitumen-set or pedestal-set (typically roof) applications. These installation methods require length, width, thickness and warpage tolerances not exceeding 0.06 in. (1.5 mm) than the specified dimensions. In some cases, paving units may require post-production grinding to achieve these tolerances. This treatment is sometimes called gauging. For additional information of bitumen-set applications, read ICPI Tech Spec 20 – Construction of Bituminous-Sand Set Interlocking Concrete Pavement.

Soon to move through the ASTM balloting process is a second paving slab standard. This one is called Standard Specification for Architectural Segmental Concrete Paving Units. The draft has flexural strength and freeze-thaw de-icer durability requirements identical to C1272. This new standard, however, has much closer dimensional tolerances not exceeding 0.06 in. (1.5 mm), making the units suitable for tightly-fitted sand-set applications, bitumen-set applications, and roof installations supported by pedestals. When this product standard is eventually approved by ASTM, there will be two paving slab product standards; one for mostly residential applications and selected commercial applications, and almost exclusively for high-end commercial applications.


Unconventional Intervention

In July 2012, a series of storms caused combined sanitary and storm sewer overflows in parts of southeast Atlanta, flooding homes and streets. After visiting the flood-prone neighborhoods, Mayor Kasim Reed committed to finding a long-term solution. Thus began the Southeast Atlanta Green Infrastructure Initiative, which led to the largest permeable interlocking concrete roadway project in North America, more than four miles.

The flooding occurred at the nexus of piped natural drainage systems that transfer much of the runoff from downtown Atlanta, a highly impervious area, to Peoplestown, Mechanicsville and Summerhill. Located at a natural drainage point of a 1,500-acre watershed, these downstream neighborhoods finally found relief from the city’s unconventional intervention.


With a mandate from the mayor’s office to solve flooding problems, the Department of Watershed Management rose to the challenge. “We went out into the field with our contractors to do assessments and came back with several projects that could be completed quickly to start providing immediate capacity relief,” said Todd Hill, Director of Environmental Management for the Department of Watershed Management. “We developed a phased approach.”

The bottom line, comprehensive solution meant managing about 24 million gallons of runoff. Phase one, a 30-day immediate response, began with cleaning up all inlets, raising curbs and installing bioswales and rain gardens on city property. These efforts resulted in 350,000 gallons of capacity relief. “Not a lot, but a start,” Mr. Hill said.

Phase two involved constructing a 5.8 million gallon combined sewer storage vault underneath a parking lot at Turner Field during the Atlanta Braves’ four-month offseason. In March 2015, work began on the permeable interlocking concrete roadway renovations that took nearly a year and a half to complete.

Phase three is currently in development and will mitigate eight million gallons through the construction of a combined sewer vault, capacity relief ponds and a community park to be constructed in Peoplestown on the lots that saw some of the worst flooding in 2012. The city is working with homeowners to acquire these properties at fair market value plus an additional percentage to compensate for relocation.


At the outset of planning their roadway renovations, Mr. Hill and his team asked, “What will get us the biggest bang for our buck?” Considering permeable interlocking concrete pavement they agreed, “If we’re going to do a paver project, we want to have the greatest impact possible,’” Mr. Hill said. Looking back, the aggregate capacity relief storage provided by the paver system was less expensive than the water storage vaults.

With a budget of $15.8 million that initially included $1.1 million in allowances for restoring utility lines, the Department of Watershed Management began excavation and installation of permeable interlocking concrete pavers on the first of many streets upstream from the flood-prone areas. The goal was to use permeable pavers and the water storage capacity of deep aggregate reservoirs beneath them to provide downpipe capacity relief. “We picked residential streets that contributed to the flooding of our combined sewer system,” said Mr. Hill. Collectively, the four miles of permeable paver roads provided four million gallons of capacity relief.

Though the original plan had six miles of roadways slated to receive permeable pavers, once crews started peeling back the streets, they unearthed some unforeseen and unfortunate complications. On some of the larger stretches of roads, crews uncovered old streetcar lines alongside utility lines encased in two feet of concrete. “The timeline to even do a few feet at a time was going to be so outrageous that it would blow our schedule, increase cost and make it impossible for residents to access their homes, so we had to make a decision to eliminate that portion,” Mr. Hill said.

According to Mr. Hill, their desire was to place as many concrete pavers as possible and not deplete the budget on extra labor costs. This pragmatic approach was applied throughout the construction phase and brought the project to completion on time and under budget. But there were still many challenges that had to be overcome during the construction phase.


With some street sections nearly 100 years old, the first surprise encountered by construction crews was a layer of old concrete below the asphalt roads that required additional time to remove. Once the roadways were opened up, a new set of challenges emerged. “We had utilities showing up that shouldn’t have been there, and some at depths that weren’t shown on any plans,” Mr. Hill said. Brick manholes were especially difficult to work around and many were replaced. Water mains and old pipes ruptured during excavation and required repair. Of the $1.1 million originally earmarked to address utilities, adjustments brought the total closer to $3 million by project completion.

Another main concern during construction dealt with the close proximity of older homes along some streets. Crews excavated two to four feet for the permeable pavement aggregate subbase layer and installed impermeable liners along the sidewalks to prevent lateral migration of stormwater toward these homes and their basements.

Due to their layout and age, street widths varied as much as a foot from one block to the next, adding a substantial amount of cutting time for the edge pavers. Despite this challenge, machine installation maintained an average rate of about 5,000 sf per day with no time required for concrete to cure.

Managing road closures and rerouting traffic, including public transit buses, also posed a significant challenge. “During the construction phase, there was a bit of inconvenience, to put it mildly,” said Cameo Garrett, External Communications Manager for the Department of Watershed Management. “It was very important that, as things changed during construction, we continuously provided information and updates to the affected communities.”

The original construction time estimates anticipated residents would lose access to their driveways for only a few days. But with all the utility issues encountered, the average road closures stretched to one and a half weeks. “Community outreach and engagement really needs to be taken into account,” said Cory Rayburn, Construction Project Manager for the Department of Watershed Management. “It’s very important for the contractor to have a public information officer onsite at all times during construction. We wrote that into our contract documents, and that’s something we recommend on all future projects.”


“Permeable pavers are a very good solution for stormwater management, especially in highly urban areas with combined sewers that need capacity relief,” Mr. Hill said. “We have been surprised by and pleased with the amount of infiltration into the ground. We were estimating much less.” Many of the sloped streets included check dam systems to encourage infiltration. The paver streets store runoff from a four-hour, 25-year storm yielding 3.68 inches of rainfall.

While achieving capacity relief was the main goal accomplished by this project, the decision to use permeable interlocking concrete pavement also contributed to increased property values for some communities and led to new development investments. “We know the houses that are on the permeable paver streets are more sought after than on other streets in these neighborhoods,” Mr. Hill said. “The residents who live in those areas really love the pavers and think they’re very beautiful,” Ms. Garrett said.

“We have councilmembers pleased, and other councilmembers asking if they can have pavers in their districts,” Mr. Hill said. And the project has drawn not only the attention of some jealous neighbors, but national attention as well. The Department has received calls from other cities including Philadelphia, Washington D.C., San Francisco and Portland, Oregon, and has presented the project at numerous industry conferences throughout the country.


The Atlanta Department of Watershed Management is now focusing efforts on educating contractors who will be working on or around their permeable pavement to prevent damage before it occurs. Nonetheless, some accidents happen from uninformed workers. In one instance, a concrete truck was washed out while parked on a permeable paver street. The runoff clogged the paver joints as well as the aggregate subbase, resulting in a $6,000 repair bill. In other instances, construction sites adjacent to the permeable paver roads needed to carefully manage sediment so it didn’t run into the street.

“It’s going to take education to ensure that anyone digging into these paver roadways has either gone through training or read the maintenance manual,” Mr. Rayburn said. So far, the Department has held an in-depth ‘Train the Trainer’ course for Watershed and Public Works employees based on the maintenance manual that was developed by the contractor, and will follow up with additional guidance and resources. “As of now, the protocol is to call our construction inspectors, the ones who were onsite during the paver installations, to monitor any tie-in construction involving water or sewer lines,” Mr. Rayburn said.

The city has a three-year contract with the project’s design-build contractor to provide service and maintenance for the permeable paver streets. “But after that, we will need a coordinated effort to help ensure the permeable paver streets are maintained,” Mr. Rayburn said.


For any municipality contemplating permeable interlocking concrete pavement streets, Mr. Hill advises, “Spend a lot of time planning the process, thoroughly locate all utilities and determine if they will need rehab in the near future.” Particularly with older urban streets, there may be layers upon layers of unknown mysteries beneath the surface. “Have a full-blown SUE [Subsurface Utility Exploration] performed for every road to identify some of the harder-to-locate utilities before you actually start work,” Mr. Rayburn said. The SUE helps the design-builder come up with a more comprehensive design prior to excavation or construction, saving time and minimizing surprises.

“We are very grateful that our administration was so farsighted with regard to sustainability and making this a very green city,” Mr. Hill said. “They provided the necessary support to make these things happen.”

“Green Infrastructure and Low Impact Development practices are not new. However, the regional application by municipalities to solve flooding and capacity relief is a developing industry,” Mr. Rayburn said. “The social and economic development that can occur when these practices are done right is definitely an added benefit.”

In Atlanta’s case, the green infrastructure initiative has had a direct impact on new investment. “The Historic Fourth Ward stormwater pond adjacent to the Atlanta Beltline created a miniature ecosystem within the heart of Atlanta which reconnected surrounding residents to nature. The main function of the facility is combined sewer capacity relief, but we have seen over $500 million in private redevelopment in the surrounding area,” Mr. Rayburn said.

“We always look for opportunities to utilize green infrastructure where our historical response would have been a bigger pipe or vault,” Mr. Rayburn said. “That way, you can solve the problem while creating a real benefit for the community.”


Visit for more information on Atlanta’s green infrastructure initiatives.


Relaxing Traffic

Just about every urban center in Canada and the U.S. is jammed with traffic, especially during morning and evening rush hour (or rush hours in bigger cities). Regardless of the city size, there consistently seems to be more cars and trucks than pavement to move them. It’s certainly not relaxing traffic for the drivers stuck in it.

Because they are just about the lowest density urban land use, residential areas don’t see many traffic jams. Thanks to spread out land use, residential traffic isn’t quite as hectic. While it’s not relaxing, at least it moves, even during rush hour.

Whether low or high density, residential areas are a rising source of complaints about near misses, car crashes, plus cyclist and pedestrian accidents. Vehicular traffic needs to relax, be calmed and be mindful of non-vehicular users.

There are a variety of tools and designs to calm traffic. They range from the ubiquitous (and cheap) stop sign to more visible designs that extend curbs to narrow intersections and slow traffic. Radical road remedies reduce flows and reclaim space for bus lanes, pedestrian refuge islands, bike lanes, sidewalks, bus shelters, parking or landscaping.

A main motivation for using calming remedies is creating safer streets. The benefits outweigh the costs. According to the National Safety Council, a car accident with an incapacitating injury costs the private and public sectors (medical care, loss of productivity, etc.) about $208,500. The direct and societal costs run over $4 million for each traffic death. In 2013, a motor vehicle injury occurred on average every 14 seconds according to the Rocky Mountain Insurance Information Association. Given these events and costs, an investment in traffic calming can be recovered almost immediately.

When it comes to using pavements to slow drivers, the options are limited: speed humps or the really annoying speed bumps. A forgotten form of relaxation is changing the surface to interlocking concrete pavement. A surface change means a visual and noise change that’s kinesthetically communicated to the driver via the steering wheel. Unfortunately, ICP doesn’t show up regularly in classic traffic-calming references published by the Federal Highway Administration, the American Association of State Highway and Transportation Officials, or the Institute for Traffic Engineers. Why? No experience and no hard before-and-after data.

So let’s start collecting data. The industry seeks a current condition where vehicular and pedestrian traffic conflict is a documented problem as measured by vehicle/pedestrian counts, near-miss reports, accidents and other incidents. For example, we are seeking conditions near schools where traffic calming is essential. We’d like to monitor before and after results via surveys and/or speed/traffic counters. We are seeking a partnership where other stakeholders participate with us financially as well as in the planning, execution and monitoring stages. Potential opportunities include school districts, police/fire/rescue stations, busy residential streets, libraries, parks, business districts and complete street projects. If there is traffic that needs calming, drivers that need to relax and slow down to spare injuries and deaths, we just might have a relaxing solution.

Interested in a partnership to make roads safer? Email


Updates on Paving Product Standards

ASTM’s C1782 Specification for Utility Segmental Concrete Paving Slabs provides a baseline acceptance standard for slab products manufactured with dry-cast, wet-cast and hydraulically pressed processes. Available for purchase on, C1782 determines the minimum average flexural strength (725 psi), dimensional and warpage tolerances, and freeze-thaw durability requirements for paving slabs with dimensions ranging from 12 x 12 to 48 x 48 inches.

Due to their larger size, segmental concrete paving slabs do not conform to ASTM C936 Standard Specification for Solid Concrete Interlocking Paving Units. The only available product standard for slabs prior to C1782 was a CSA (Canadian) paving slab standard in existence since 1972. C1782 now provides requirements with familiar ASTM terms and references that producers can meet. The standard was developed by paving slab manufacturers, testing labs and other experts within the ASTM Subcommittee on Manufactured Masonry Units and Related Units (also known as C15.03).

Architects, civil engineers and landscape architects will benefit most from C1782 by using it in construction specifications. Paving slab manufacturers will use the standard to promote products that meet or exceed its requirements. The standard will also give concrete testing labs the opportunity to provide an additional service in testing paving slabs. Most importantly, C1782 clearly differentiates slabs from the pavers in C936.

ICPI indicated that another segmental concrete paving slab standard will be submitted for balloting by ASTM in the coming months. This one will likely be named Specification for Architectural Segmental Concrete Paving Slabs. The architectural designation means it will cover units with textured architectural finishes such as hammered, polished or molded surfaces. Additionally, the specification will include closer tolerances than C1782 to better accommodate precision installations that use pedestals for roof decks, bitumen-set (sand-asphalt bedding) and some sand-set bedding applications. Such units may require grinding (also known as gauging) to conform to tighter dimensional tolerances.


ASTM C936 Standard Specification for Solid Concrete Interlocking Paving Units received an appendix with a zone map that points to optional use of -15° C (5° F) as the lowest temperature using ASTM C1645 Standard Test Method for Freeze-thaw and De-icing Salt Durability of Solid Concrete Interlocking Paving Units. This test method calls for immersing pavers or coupons cut from paving slabs into a 3% saline solution and then exposing them to a maximum of 49 freeze-thaw cycles (each 24 hours) while inside an automated freezer. The material loss from the paver is weighed and must not exceed 500 grams per square meter of surface area to meet C936. This optional ASTM test method is very similar to that in CSA A231.2 Precast Concrete Pavers. The new optional lower temperature in C936 should increase assurance of winter durability to the purchaser as well as to the manufacturer.


Geosynthetics Part 1: Geotextiles

Geosynthetics can be grouped into several product categories; geotextiles, geogrids, geomembranes, geonets, geosynthetic clay liners, geopipes, geofoam, geocells and geocomposites. This article examines construction with geotextiles and future articles will cover construction using the other geosynthetics. The articles are excerpted from a soon-to-be released ICPI Tech Spec that provides a comprehensive view of geosynthetic materials, selection, and construction in various segmental concrete pavement assemblies.


When placing geotextile avoid wrinkles in the fabric. Follow the overlap recommendations specified in AASHTO M-288 Geotextiles for Highway Applications as noted in Table 1. Make sure the geotextile is placed in full contact with the surrounding soils or aggregates. Voids, hollows or cavities from wrinkles created under or beside the geotextile compromises its intended function.

Figure 1 illustrates a familiar detail, i.e., separating the compacted aggregate base from the soil subgrade with geotextile. This can help maintain consolidation of the base materials over time by preventing intrusion of fines in the bottom and sides. This slows the rate of rutting in the base and on the soil subgrade.

Geotextile placed under the bedding sand next to the curb provides a ‘flashing’ function. This separates the sand from the base and prevents sand loss into joints between the concrete curb and the compacted aggregate base, as they are two structures that can move independently from each other. Table 2 provides guidelines for geotextile selection depending on the soil and fabric functions required.

Figure 2 illustrates geotextile on a concrete base in a crosswalk application. For new sidewalks, crosswalks and streets, 12 in. (300 mm) wide strips of geotextile are recommended over all joints in new concrete bases to prevent loss of bedding sand, as well as over weep holes. New asphalt generally should not require geotextile on it except at curbs, structures and pavement junctions where bedding sand might enter. For existing asphalt and concrete bases, the surface of each should be inspected for cracks, the severity and extent of which determines repairs. If cracks are few and minor (suggesting substantial remaining life in these bases), geotextile should be placed over the cracks to prevent potential future loss of bedding sand. Covering the entire asphalt or concrete surface with a loose-laid sheet of geotextile can present some risk of creating a slip plane for the bedding sand and paving units as a result of repeated vehicular traffic.


Figure 3 illustrates a typical application of geotextile in PICP. Its application against the sides of the subbase and against the excavated soil is essential in all PICP projects that do not use full-depth concrete curbs to completely confine open-graded aggregates at the pavement perimeter. The design and selection of geotextiles for PICP is covered in detail in the ICPI manual, Permeable Interlocking Concrete Pavements – Design, Specification, Construction, and Maintenance.