Great Expectations

Building systems and pavement systems must become institutionalized before they are fully embraced by designers, owners, and users. We’re not talking about the institutionalization of people into wards of the state, but rather, how building technologies become normal and expected in a society. In order for building systems to achieve that level of expectation in a culture, the institutionalization process begins with the manufacturing industry of that particular building or pavement system.

Components of the Process:

  • Standard product specifications (i.e., ASTM/CSA), design and construction criteria
  • Research to expand applications and define limits—this can be materials testing or testing the performance of systems and assemblies
  • Construction training for qualified labor
  • University education for young and emerging design professionals
  • Manufacturing quality control and quality assurance certification
  • Marketing via advertising, public relations, brochures, trade shows, continuing education presentations, and websites to communicate system features, advantages and benefits


Most of the pavement owned by public agencies and private corporations is asphalt or concrete. Institutionalization of these pavements began about a century ago and continues today. We expect these pavements in our culture. They are in our mental as well as our physical landscape. We’d like to see similar expectations develop for segmental concrete pavement here in North America. Segmental concrete pavement is already expected and used extensively in many other countries, such as the Netherlands and Germany.

As pavement owners, federal, provincial, state and local governments annually invest billions of dollars in construction, ownership, and maintenance. Industry and academia conduct research and train young designers as investment momentum builds. This process is a key characteristic of a mature and fully institutionalized pavement technology, where pavement owners take over the reigns from industry to see through the final stage of institutionalization.

Permeable pavement is experiencing this transition now, thanks to tougher stormwater runoff regulations. Since the late 1990s, pervious concrete, porous asphalt, and permeable interlocking concrete pavement (PICP) have seen millions invested in university research, construction, and performance evaluations. The industries representing these pavements started the process, and some stormwater agencies are continuing it.

Though much polluted runoff comes directly from roads, transportation agencies have been slower to accept permeable pavement as the norm for low-speed pavements. That’s because permeable pavement must follow the same institutionalization path as conventional pavement types, and transportation agency gatekeepers demand it. Their path is more technically demanding than that required for acceptance by stormwater management agencies because of concerns about structural support, safety, and durability, among others.

The additional research required to address these concerns leads to transportation agency ownership of the institutionalization process.

When a sufficient number of transportation agencies embrace permeable pavement, their energy and funding will accelerate the institutionalization process. We are already seeing small signs of this in the works. Federal and state regulatory forces gathering behind the scenes are pushing transportation agencies from vague interest into needing permeable pavements. When that happens, agency ownership of the institutionalization advances. This eventually leads to our society expecting permeable pavement—and that is a great expectation.


Kortright Centre Study

The Toronto and Region Conservation Authority (TRCA) released a two-year study on the performance of a permeable pavement parking lot built at their Kortright Centre in Vaughn, Ontario, in metropolitan Toronto. The pavements consisted of two types of permeable interlocking concrete pavement (PICP), pervious concrete and an impervious (conventional) asphalt pavement as a control surface. The contiguous parking areas each are about 3,400 sf (320 m2).

kortright1The permeable pavements did not produce surface runoff throughout the 22-month monitoring period of this study. The permeable systems reduced the outflow volume via underdrains by 43 percent, and completely captured rainfall events up to 1/4 in. (7 mm) deep. Not surprisingly, the permeable pavements delayed and reduced peak flows existing underdrains throughout all seasons by an average of 91 percent, compared to surface runoff from the conventional asphalt pavement. The slower, controlled outflow closely mimics nature, and reduces the flooding risks and downstream erosion in receiving waters.

Cold, hard facts

During freezing temperatures, the permeable pavements functioned well and did not exhibit significant surface heaving or settlement. A substantial spring thaw occurred in March 2011 and the permeable pavements delayed the outflow of snowmelt by three days, greatly reducing peak flows. Increases in outflow volume happened occasionally during the winter and spring due to delayed release of stormwater stored within the aggregate reservoir.

Monitored median and mean concentrations of several pollutants in the permeable pavement outflows were significantly lower than those from the asphalt, including suspended solids, extractable solvents (oil and grease), ammonia-ammonium nitrogen (NH3, NH4+), nitrite, total Kjeldahl nitrogen (TKN), total phosphorus, copper, iron, manganese and zinc.  The permeable pavements also generated a net reduction in total pollutant mass for all of these constituents, in addition to dissolved solids, chloride, sodium, phosphate, and nitrates.

In the winter, deicing salt-related pollutants were considerably higher from the asphalt runoff than in the permeable pavement outflows. The reduction in concentration is from detention and diluting winter stormwater. Water quality data collected below native soils indicated that sodium and chloride migrated into them. Further investigation is needed to determine how the presence of these constituents may affect the mobility of other stormwater contaminants, such as metals, as well as impacts on groundwater.


Surface infiltration measurements indicated substantial reductions in permeability over the monitoring period. However, reduced surface permeability still provided sufficient infiltration rates to rapidly infiltrate all rainfall from the storms. Between June 2010 and May 2012, permeability reductions of a narrow-jointed PICP, a wide-jointed PICP, and the pervious concrete were 87, 70 and 43 percent, respectively. The pervious concrete was installed about 6 months after the PICP systems, so the comparison in reductions is a bit uneven.

kortright2The pervious concrete maintained high surface infiltration capacity even after two years, with a median rate of 422 in./hr (1,072 cm/hr) at the end of the study in 2012. The infiltration rate of the narrow jointed PICP was 8 in./hr (20 cm/hr) after two years. Vacuum sweeping provided partial restoration of surface permeability for the PICP surfaces. Interestingly, no benefit from increased infiltration rates was observed from vacuuming the pervious concrete. The researchers found that vacuuming all of the permeable pavements produced highly variable surface infiltration results, and did not provide consistent removal of embedded fines within them.

As part of the study’s recommendations, the researchers suggested that further tests using different techniques for loosening or dislodging compacted material should be conducted in permeable pavements prior to cleaning.  Further experimentation could likely improve the effectiveness of regenerative air and vacuum sweeping trucks. Based on maintenance practices evaluated in this study, annual vacuum cleaning of PICP is recommended to increase their operational life.


The two PICP cross sections consisted of 3 1/8 in. (80 mm thick) concrete pavers, 2 in. (50 mm) bedding (similar to ASTM No. 8 stone), 4 to 5 in. (100 to 125 mm) of material similar to No. 57 stone, and about 8 in. (200 mm) of material similar to No. 3 subbase stone. The pervious concrete was 6 in. (150 mm) thick, placed over 2 in. (50 mm) of No. 57 stone and about 14 in. (350 mm) of No. 3 subbase stone. The asphalt pavement was 3 in. (75 mm) thick over almost 15 in. (370 mm) of dense-graded aggregate base. The silt to silty-clay soil subgrade was covered with geotextile prior to placing subbase aggregates. The soil’s clay content ranged from 7 percent to 30 percent.

The study is among several over the past three decades that underscore the ability of permeable pavements to reduce runoff and stormwater pollutants. In addition, the maintenance study confirmed the ability of highly clogged PICP surfaces to be rehabilitated by using vacuum equipment, whereas highly clogged pervious concrete presents additional challenges regarding restoration of surface infiltration. 



The Oklahoma City National Memorial, which honors the victims, survivors, and rescuers of the bombing that occurred in 1995, is one of the city’s most visited landmarks.

Located on the former site of the Alfred P. Murrah Federal Building, the memorial consists of a field filled with empty chairs to honor the 168 people killed in the bombing, a reflecting pool and a wall inscribed with
the names of survivors.

Since city planners wanted to connect the memorial to the city’s waterfront, pavers were used to bring the urban development effort together with this significant landmark.

The copper architectural panels on the memorial “gates,” flanking the ends of the memorial grounds, provided inspiration for a pattern that bridged the urban space with the existing walkways.

Rather than use the predominantly charcoal-colored finish of the Project 180 pavers, lighter colors were selected to match the reflecting pool’s border. The effect, says Jereck Boss of the Office of James Burnett, was an alignment of the memorial with the rest of the city. “It’s amazingly beautiful to see,” he says. “It follows the city’s plan to connect the memorial to the waterfront, while still designating the memorial as its own unique space.”


A Contractor’s Project Perspective

This was a difficult project for a number of reasons, recounts the ICPI member contractor whose company laid the plaza pavers.

bridge4The wet-cast, hand-molded pavers selected for this project made it difficult to get the lines just right because of the variance from one paver to the next. Some of the lines were 200 feet (60 m) or longer, which would present a challenge even with straight-edged pavers, the contractor says. Another challenge was working with long, narrow pavers, 12 to 18 in. (300 to 450 mm) in length by 3 in. (75 mm) across. If such pavers are not set just right, they tend to cant to one side or the other. One way to avoid this, the contractor explains, is by using step boards so that the installer doesn’t roll the previous paver as he lays the next one down.

No complaints though, says the contractor. The job is to get it done, satisfy the contract, and make everyone happy.


Remaking a City

Cities are constantly renovating—fixing potholes, freshening sidewalks, adding landscaping—but Oklahoma City was ready for a bigger change. Rather than continue with the usual pace of urban tweaks, landscape architects and planners decided on an ambitious, large-scale project that would remake 180 acres of land, effectively transforming the downtown into a whole new city.

feature1“To my knowledge, there’s never been another city that took on a renovation of this scale,” says Jereck Boss, a principal in The Office of James Burnett, the landscape architecture firm that developed the project’s master plan. “You just don’t see cities willing to tear everything out and replace it. Many cities do a block or two, but this is the whole downtown.”

As part of the larger aesthetic and functional vision, the firm opted for pavers to be used in “amenity zones” between streets and sidewalks. These zones, with abundant trees and benches, create a unified look to the project that likely wouldn’t have been possible
without the pavers. “Pavers have been a key piece to this transformation,” says Boss.

Seeing the Vision

The impetus for Project 180 was twofold: walkability and business retention.

According to Shannon Cox, project coordinator for Oklahoma City, a 2008 ranking of walkable cities by Prevention magazine was a harsh wake-up call. Out of 500 cities, Oklahoma City came in last place, she says. Similar surveys also gave the city low marks, and one website called it “the land of no sidewalks.” The city commissioned its own survey about traffic patterns and found that a lack of amenities was very problematic for pedestrians, Cox notes.

About the same time, a major boost for renovation came in the form of corporate interest. Devon Energy, one of the city’s largest employers with 5,400 employees, began considering a headquarters move to Houston. The company’s CEO, Larry Nichols, wanted to stay in Oklahoma City, where he’d spent most of his life, but was hesitant to construct an expensive new building in the midst of a city in disrepair.

Devon proposed construction of a 50-story, $750 million skyscraper in the center of the city, but issued a challenge: It would only get built if the city could embark on a major revamp. “They wanted the area surrounding their building to be just as nice as what they had planned,” says Scott Howard, principal at Howard Site Design, which did the landscape architecture for Project 180.

To pay for such a large-scale change, Devon agreed to put up about 10 years’ worth of tax monies. With that tax increment financing, the planning began in 2010, and the city laid out a $128 million, two-phase plan that would take four years to complete, resulting in a whole new cityscape.

Creating Momentum

The Office of James Burnett was chosen to lead the city through a steering committee process that included design development. In all, it took 16 architectural, engineering, and landscape architecture firms to handle all of the revamp components.

“The level of teamwork and coordination was pretty impressive,” says Howard. “Everybody had to work together or this wasn’t going to happen.”

feature2Devon Energy set the bar high when it came to design. The company had not only embarked on a new headquarters building, but also planned a lush corporate campus directly adjacent to the city’s 16-acre (6.5 ha) Myriad Botanical Gardens.

In conjunction with that effort, Project 180 focused on creating a city that would land at the top of walkability surveys through new landscaping, public art, decorative street and pedestrian lighting, and renovation of the lawn in front of City Hall.

Myriad Botanical Gardens also received significant improvements, including construction of an outdoor amphitheater, ice skating rink, grand entrance, and children’s play area.

Role of Pavers

One of the most significant aspects of Project 180 has been the use of concrete pavers, an important part of giving the city a walkable feel that it had been missing. Planners chose pavers that were 6 x 12 in. (150 x 300 mm), for a surface that flowed with the urban feel of the project.

The majority of the pavers are a modified charcoal color, of which three-quarters were shotblasted and the rest have a standard finish. The second color selected was tan, one-quarter of which were shotblasted. Using the two different colors and textures created visual interest, Howard says.

The entire project called for 430,000 pavers. As a subbase, concrete was used, with bedding sand above that.

The amenity zones, where pavers are used, feature trees, benches, bike racks, multi-space parking meters, and waste and recycling receptacles. Cox notes that pavers were chosen over concrete for their aesthetic potential, given their unique patterning, color, and finish variance. Also, she believes that pavers will have greater longevity and sustainability.

Another top reason for using pavers was flexibility. Because city services like water mains and sewer lines run underground next to roads, the city needed to be able to dig up parts of amenity zones occasionally and then put them back together without ruining the pleasant look of the area.

The sheer breadth of the project meant that challenges were likely to crop up, and they did, initially. Howard notes that it took time to settle on a pattern for pavers that didn’t result in “slivers of pavers” used in certain areas. “We didn’t want odd pieces just kind of stuck in there to fill the space,” he says.

Fortunately, the uniformity of the zones helped. Trees are spaced 22 ft (6.7 m) apart, lining up with parallel parking spaces. Even with the mixture of pavers, that consistency allowed landscape architects to create an aesthetically pleasing pattern for zones that are as functional as they are eye-catching.

Big Project, Big Future

Now in phase two of its development, Project 180 is scheduled for completion at the end of 2014, according to Cox. That’s about six months later than anticipated, but delays occurred when crews ran into inaccurately mapped utility lines and unexpected basement spaces when they dug up older downtown streets.

feature4Over the next year and a half, planners and construction teams will focus on revamping more streets, sidewalks, parks, and plazas. New bicycle lanes encourage more bicycle commuting, and the changes have created additional on-street parking spaces, helping to draw more people into the city.

Devon Tower, the new skyscraper that helped to kick off the project, was completed in October 2012, and includes a top-floor restaurant named Vast, which will give visitors a view of the area from 52 stories up.

When Project 180 is complete, it will be an impressive achievement, believes Boss, and pavers certainly play a big part of that. “They’re such a nice enhancement, and really go with the project,” he says. “With those, and with all other aspects of the project, Oklahoma City seems brand new.”


A Titan Passes

Dr. Brian Shackel, professor, consultant, and friend to many in the interlocking concrete pavement industry, lost his battle with cancer on November 18, 2012, at age 71.

shackel4Dr. Shackel graduated from the University of Sheffield, England, in 1962 and joined the Department of Main Roads, New South Wales, Australia. He was appointed Shire Engineer to Central Darling Shire in New South Wales, Australia, in 1964. In 1966, he accepted a teaching fellowship at the University of New South Wales where he earned a masters and a doctorate in civil engineering.

He later moved to South Africa and joined the National Institute for Transport and Road Research as the Senior Research Officer from 1978 to 1981. Dr. Shackel returned to the University of New South Wales Department of Geotechnical Engineering from 1989 to 1993, and subsequently served as Director of the Munro Centre for Civil & Environmental Engineering.

Dr. Shackel held the position of visiting professor at numerous acclaimed universities around the world, including the School of Civil Engineering at Tokyo University and the Technical Universities of Delft, Vienna, Copenhagen, and Nihon University, Japan. He published over 100 research papers on mechanics and pavement engineering, of which more than 60 are on interlocking concrete pavement. His 1990 book, The Design and Construction of Interlocking Concrete Block Pavements, was translated into several languages and remains one of the most acknowledged resources on the subject.

He is also the author of the Lockpave software program for design and specification of interlocking concrete pavement used by several industry associations worldwide, including the Interlocking Concrete Pavement Institute. He was a member of the Small Element Pavement Technologists since its inception in 1988.

Dr. Shackel taught pavement engineering at the University of New South Wales, Sydney, Australia, at the undergraduate and postgraduate level for more than 35 years. He travelled extensively and lectured in 24 countries worldwide. In addition to his theoretical work, Dr. Shackel conducted leading-edge experimental studies in pavement engineering, including accelerated trafficking tests of more than 200 full-scale pavements.

Having consulted on numerous projects around the world, Dr. Shackel is remembered for his work on heavy-duty pavements, such as ports, industrial pavements, and airport pavements. Above all, he was passionate and dedicated to communicating new technologies and designs.

Dr. Brian Shackel’s work influenced industry associations around the world, including the Interlocking Concrete Pavement Institute.

His contributions have been great. He will be sorely missed as a friend to, and advocate for the industry.


ICP for 75th Anniversary

The Golden Gate Bridge at the entrance of San Francisco Bay has been an American icon since its completion in 1937. For its 75th anniversary, as “gifts to the bridge,” the Golden Gate National Parks Conservancy, in partnership with the Golden Gate Bridge District and the U.S. National Park Service, commissioned the Golden Gate Bridge Plaza and Pavilion.

bridge2The pavilion visitor center and surrounding plaza, with 17,700 sf (1,770 m2) of concrete pavers, now greet and inform 10 million annual visitors who photograph, walk and bike the iconic bridge.

The central plaza’s slender proportions echo those of the bridge towers. Narrow, modular pavers create an alternating pattern of light and dark for an optical effect similar to the moiré pattern of the bridge cables, as seen while driving across the bridge. Long, transverse bands composed of thin pavers are reminiscent of the massive cables supporting the bridge, each comprised of many thinner cables.

The project’s designers, Surfacedesign Inc. of San Francisco, chose narrow modular pavers to express these visual themes through subtle paver coloring and their distinctive shapes. The paving supports constant pedestrian use and occasional vehicle access. The designers also wanted a pavement that could be seamlessly repaired after the inevitability of the Bridge District requiring access to aging utility lines that cross beneath the site.

The plaza and pavilion were built concurrently in winter 2011-12 by an ICPI member contractor and supplied by an ICPI manufacturing member. The project required completion for the citywide bridge anniversary celebration in May 2012. With pavers, the general contractor was able to use them as a platform for building walls and curb construction. Moreover, the sand-set concrete pavers enabled installation in wet weather, which could not have been done with poured concrete paving. Given the tight schedule, the pavement was finished on time, yet allows for partial removal for future exhibits and furnishings.


Eastern Thought Permeates

The China Construction Units Association (CCUA) hosted the 10th International Conference on Concrete Block Paving (ICCBP) in Shanghai, People’s Republic of China, November 24-26, 2012.

Home to about 22 million inhabitants, the conference setting of Shanghai represents China’s door to the west, a place where ideas meet and become industries.

The triennial conference consisted of 163 delegates: 44 from foreign countries and the rest from China, mostly paver manufacturers and suppliers. Twenty-five papers were presented, and several more were provided during the conference proceedings.

Conference papers focused on sustainable aspects of segmental concrete pavements, including permeable interlocking concrete pavement, and the use of recycled materials in concrete paving units. Among the recycled materials examined were foundry sand, flyash, and waste from building demolition. A discussion about how to reduce worker fatigue and accidents on construction sites expanded the meaning of sustainable construction.

Permeable pavement for heavy load applications received a boost from the full-scale load testing and design guidelines published by the UK industry association, Interpave. Design methods were examined using a perforated asphalt layer under the bedding layer, as well as cement-stabilized aggregates not unlike pervious concrete. North American design guidelines and best practices for permeable pavement construction and maintenance were also presented.

New products presented included new paver shapes from Spain and China. Two papers from Japan examined the reuse of pavers after earthquakes and the recent tsunami, something other paving materials don’t offer. Pictures of the striking damage and fast repair provided an impressive lesson in pavement resilience for any region subject to earthquakes or tsunamis.

A significant discovery of the conference was that 2.6 billion sf (260 million m2) of concrete pavers were sold in 2011 and that about 2.4 billion sf (240 million m2) are expected in 2012, due to a slight downturn in the Chinese economy. (A slight downturn means a national economy growing at 7 percent annually instead of 9 percent.) These production figures equate to about 2 sf (0.2 m2) per capita. While municipal governments embrace segmental paving for sidewalks and plazas, their use appears restricted from roads. This raises the question of what might be required from transportation authorities to accept interlocking concrete pavements for roads.

Supply Chain Optimization

The conference included a technical tour of a paver plant about 75 miles (120 km) from Shanghai, equipped with Japanese automated manufacturing equipment similar to that in North America.

The plant had the benefit of being located next to a river so that aggregates and cement could be delivered economically, and likewise, the pavers could then be easily loaded back onto the barges.

Pavers, slabs, permeable and pervious (no fines) pavers were the norm for this manufacturer.

China exploring additional uses

In China, interlocking concrete pavements are used mostly for pedestrian sites. One paper explored using interlocking concrete pavements for the shoulder lane of highways as a means to expand the industry.

The Chinese have significant experience with supplying pavers to Hong Kong International Airport (about 5 million sf or 500,000 m2) in commercial heavy aircraft parking, as well as many hec-tares in container handling areas in the ports of Hong Kong and Yantian. The paver supplier told the stories behind these projects and why concrete pavers were the preferred choice, i.e., cost and performance.

Permeable interlocking concrete pavements are now seeing expanded use under rubber-tracked military vehicles in the U.S., thereby demonstrating their ability to remain stable under significant lateral loads.