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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.

PRODUCT STANDARDS

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.

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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.

IMMEDIATE RESPONSE

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.



BIGGEST BANG FOR THE BUCK

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.

WHAT LIES BENEATH

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.”



SUCCESSFUL RESULTS

“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.

AN OUNCE OF PREVENTION IS WORTH A POUND OF CURE

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.

REFLECTIONS IN HINDSIGHT

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.”

GOING GREEN

Visit www.AtlantaWatershed.org/GreenInfrastructure for more information on Atlanta’s green infrastructure initiatives.

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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 icpi@icpi.org.

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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 www.astm.org, 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.

UPDATES TO THE CONCRETE PAVER STANDARD

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.

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2016 HNA Hardscape Project Awards

The HNA Hardscape Project Awards recognize outstanding hardscape projects by contractors building residential walkways, patios, driveways, commercial plazas, parking lots and streets. In its ninth year, the awards program received 114 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. Combination of Hardscape Products – Commercial – More than 20,000 SF

UNIVERSITY OF SAN FRANCISCO

  • LOCATION: San Francisco, CA
  • CONTRACTOR: The Legacy Paver Group
  • MANUFACTURERS: Pavestone Company & Natural Granite Pavers
  • DESIGNER: Interstice Architects

The University of San Francisco campus has undergone major redevelopment over the last eight years, removing asphalt driveways and paths and replacing them with over 50,000 sf of interlocking concrete pavers. The new science building included over 30,000 sf of granite pavers. The campus walk consists of Pavestone Villa pavers, and the science building pavers are custom-cut granite slabs in various sizes and shades of gray. The most challenging aspect of the installation was working with tight deadlines over the summer to get everything in place before students returned for the fall semester.


2. Combination of Hardscape Products – Commercial – Less than 20,000 SF

NURSING HOME COURTYARD

  • LOCATION: Wilmington, MA
  • CONTRACTOR: Monello Landscape Industries
  • MANUFACTURERS: Techo‐Bloc
  • DESIGNER: Joe Monello

The contractor provided the client with a showcase for the ages utilizing outdoor kitchens, pergolas, water fountains, audio, lighting, seat walls, custom pavers, a sensory garden and a variety of beautiful plantings. The outdoor kitchens feature a steel superstructure and have an exterior veneer. A leathered granite was installed for the countertops and was also used for the many bistro tables throughout the courtyard. Half of the tables were lowered to ADA height compliance so wheelchair users can sit and enjoy the space. The main patio uses Techo-Bloc Blu 60 aged pavers while the inner walkways contain Techo-Bloc Blu 60 smooth pavers. Using two different pavers creates a unique identity while instilling a sense of movement throughout the space.


3. Combination of Hardscape Products – Residential – More than 4,000 SF

BALTAZAR RESIDENCE

  • LOCATION: Wilbraham, MA
  • CONTRACTOR: Bahler Brothers
  • MANUFACTURERS: Techo‐Bloc
  • DESIGNER: Jen Kloter, Bahler Brothers

The owners of Baltazar Residence have large families and frequently entertain, so they needed a large space for activities supporting both. A series of retaining walls and patio levels create several outdoor rooms. To preserve the panoramic view from the back of the house, the design kept a low profile. An infinity-edge pool was a crucial focal point of the design. The overall design and curves of each of the 10 walls created niches for intimate spaces as well as more expansive areas. The interaction between landscape bed lines, patio edges and walls flows across the different levels, working together as a whole. The entire area becomes a resort-like oasis for entertaining 100 people, yet has intimate enough spaces to be comfortable for this family of four.


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

BUTLER REAR YARD MAKEOVER

  • LOCATION: Oceanside, CA
  • CONTRACTOR: Landmark Pavers
  • MANUFACTURERS: Belgard
  • DESIGNER: Isaiah Ruczewski

This project’s initial challenge was taking full advantage of the expansive view of a ridgeline and canyon location while maximizing the shallow depth of the backyard space. A family-friendly, conversational fire pit surrounded by freestanding seating walls creates a focal point for the hardscape setting. A Belgard Cambridge Cobble patio accented by raised planter bed walls with soft-curved lines was installed next to an artificial turf yard to complete this outdoor entertaining space. The one unforeseen challenge during construction was the elevation that required drainage well beneath the standard depth while providing adequate fall to the street. Having solved this, the homeowners now enjoy their westward sunset view, surrounded by a colorful softscape of organics that complement this stunning hardscape installation.


5. Concrete Paver – Commercial – More than 15,000 SF

CENTENNIAL MALL

  • LOCATION: Lincoln, NE
  • CONTRACTOR: Dreamscapes, Inc.
  • MANUFACTURERS: Pavestone Company
  • DESIGNER: Clark Enerson

Built in 1967 to commemorate Nebraska’s 100th anniversary, Centennial Mall recently underwent a complete makeover to serve as a community gathering place. The recent renovation effectively connects the state capitol to the University of Nebraska via a pedestrian-friendly environment. Stretching from K Street to R Street, visitors encounter information about Native American tribes, Nebraska’s diverse eco-regions, transportation history, state leaders and community supporters. Pavestone supplied 30,000 sf of pavers instrumental to telling the Nebraska story. Various paver colors depict the different eco-regions of Nebraska. Using special tools and creative talents, the contractor engraved and inlaid pavers to depict Nebraska’s rivers and railroad lines. The design also included a dark, monolithic, square-edged paver to highlight the importance of the state capitol building. Fountains along the way celebrate education, imagination and creativity—supporting Nebraska’s motto, “The Good Life.”


6. Concrete Paver – Commercial – Less than 15,000 SF

TERRITORY SQUARE LIBRARY

  • LOCATION: Florence, AZ
  • CONTRACTOR: Re‐Create Companies, LLC
  • MANUFACTURERS: Belgard
  • DESIGNER: Hidell Associates Architects

This project supports a multi-faceted, multi-owner project in development along the Gila River dedicated to the future of the entire community. The town worked closely with a legendary architect and planner to develop a bold vision linking this historic town with the growing suburbs. Pavers create a warm, beautiful and inviting environment for senior citizens, adults, teenagers and children to join together for the use of the surrounding amenities. Square units dominate the installation, starting with the overall layout, the 12 x 12 in. paver stack bond walkways, and finishing with a field of ashlar pattern pavers. A ground-face soldier course frames each paver area elegantly. Additionally, the differing paver colors helped maintain consistency with the overall design of the building.


7. Concrete Paver – Commercial – More than 3,000 SF

NEVADA WOLFPACK BASKETBALL COURT

  • LOCATION: Reno, NV
  • CONTRACTOR: Hain Enterprises
  • MANUFACTURERS: Basalite Concrete Products
  • DESIGNER: Mark Hain

Always up for a creative challenge, Mark Hain of Hain Enterprises was asked to create a basketball court for a customer that replicated the one at Lawlor Events Center on the University of Nevada, Reno, campus. Mark accepted the challenge, obtaining access to the actual court at the Lawlor Events Center, creating a template over the center court logo and then creating an intricate concrete paver design. Through painstaking scribing and an insistence on precision handmade cuts, Mark’s crews crafted a court that’s now the envy of all Nevada Wolfpack fans and one that will last a lifetime. His use of several different paver colors and shapes to enhance the periphery of the logo completes the artistic canvas, in addition to the logo itself that can be seen and enjoyed by airplane passengers flying south of Reno.


8. Concrete Paver – Commercial – Less than 3,000 SF

ZEPLIN RESIDENCE

  • LOCATION: Omaha, NE
  • CONTRACTOR: Paver Designs, LLC
  • MANUFACTURERS: Belgard/Techniseal
  • DESIGNER: Jim and Justin Hampton

This project design features a paver patio with inlay, seat wall, fire pit and water feature to deliver some height and character to the large flat backyard. The homeowner wanted to make the patio a destination spot that would draw guests and visitors. To access the patio, one first crosses over a stream via a stone bridge. Paver Designs hand-carved two stone pillars and inset stained glass backlit with LED lighting to lead the way. After laying the pavers, Paver Designs hand-drew the inlays for cutting. A band of natural stone included in the wall columns matches those on the house. Forty tons of granite boulders create a waterfall feature, which includes a shallow wading area for the homeowner’s grandchildren. LED lighting throughout the project creates a warm and welcoming effect at night.


9. Concrete Paver – Permeable – Commercial

SEA SCOUT BASE GALVESTON

  • LOCATION: Galveston, TX
  • CONTRACTOR: Gulf Coast Pavers
  • MANUFACTURERS: Pavestone Company
  • DESIGNER: Studio Outside

The Sea Scout Base Galveston is a destination and educational experience for Boy Scouts and Sea Scouts from all over the country. Concrete pavers were used throughout the site to connect multiple outdoor spaces and provide a functional yet beautiful underlying floor with high-end finishes and textures. With a focus on environmental stewardship, the site landscape captures and reuses rainwater. Parking for 50 cars and associated driveways are executed with permeable pavers, allowing rainwater to be collected via below-grade storage. By using locally-manufactured permeable pavers in colors with high solar reflectivity, the project earned sustainable sites and resource conservation credits toward LEED Platinum Certification. The pavers used for this job were 6 x 12 City Stone I and Eco-Priora permeable pavers in charcoal, shot-blast pewter and marble Quartex finishes.


10. Concrete Paver – Permeable – Residential

POST OAK COMMUNITY

  • LOCATION: Atlanta, GA
  • CONTRACTOR: Surfaces Group, LLC
  • MANUFACTURERS: Pavestone Company
  • DESIGNER: Watts & Browning Engineers, Inc.

Post Oak Community is a private subdivision in an upscale Atlanta suburb. The permeable paver design met the impervious cover limitations and water quality requirements. Pavestone’s Eco-Venetian four-piece combo created a striking visual interest to the pavement. The designer managed storm drainage and provided stormwater detention with an aesthetic that matches the design of the new homes while complementing the surrounding existing homes. The warmth of the Chattanooga Sandstone color includes earth tones of buff and charcoal for a subtle blend of natural stone. By using a permeable paver system, all stormwater is out of sight and mind. The result: an inviting neighborhood that draws one in like a Norman Rockwell painting.



HONORABLE MENTIONS

1. Combination of Hardscape Products – Commercial – More than 20,000 SF

Tivoli Auraria Campus

  • LOCATION: Denver, CO
  • CONTRACTOR: Continental Hardscape Systems
  • MANUFACTURER: Pavestone Company
  • DESIGNER: Wenk Landscape Architecture and Planning

The Heights at Sugarloaf

  • LOCATION: Duluth, GA
  • CONTRACTOR: Worthing Southeast Builders
  • MANUFACTURER: Pavestone Company
  • DESIGNER: SGN+A, Brian Nonemaker, Principle

2. Combination of Hardscape Products – Commercial – Less than 20,000 SF

Oak Ridge Country Club

  • LOCATION: Oak Ridge, TN
  • CONTRACTOR: Ladd‐Scapes, Inc.
  • MANUFACTURER: Belgard

3. Combination of Hardscape Products – Residential – More than 4,000 SF

Collo Backyard Retreat

  • LOCATION: Ashburn, VA
  • CONTRACTOR: Holloway Company
  • MANUFACTURER: Travertine
  • DESIGNER: Ted Tidmore

Hot Tub Movie Theater

  • LOCATION: Wayne, NJ
  • CONTRACTOR: Monello Landscape Industries
  • MANUFACTURER: Techo‐Bloc
  • DESIGNER: Joe Monello

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

Beausir Residence

  • LOCATION: Overland Park, KS
  • CONTRACTOR: MW Lawn and Landscape
  • MANUFACTURER: Pavestone Company
  • DESIGNER: Aaron Albertson

5. Concrete Paver – Commercial – More than 15,000 SF

State Farm Regional Office at Cityline

  • LOCATION: Richardson, TX
  • CONTRACTOR: Builders Services Company
  • MANUFACTURER: Pavestone Company
  • DESIGNER: The Office of James Burnett

6. Concrete Paver – Commercial – Less than 15,000 SF

Look Cinemas Prestonwood

  • LOCATION: Dallas, TX
  • CONTRACTOR: Arlington Pavers
  • MANUFACTURER: Pavestone Company
  • DESIGNER: StudioOutside

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

Honeysuckle Lane Residence

  • LOCATION: Appleton, WI
  • CONTRACTOR: CLA Landscaping
  • MANUFACTURER: County Materials Corporation

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

Old Town Oasis

  • LOCATION: Fort Collins, CO
  • CONTRACTOR: Lindgren Landscape
  • MANUFACTURER: Belgard
  • DESIGNER: Tim Lindgren

Hardscape Art

  • LOCATION: Kingsport, TN
  • CONTRACTOR: Jackson Jones Construction
  • MANUFACTURER: Techo‐Bloc
  • DESIGNER: Jackson Jones Construction

9. Concrete Paver – Permeable Commercial

Riviera Beach Marina

  • LOCATION: Riviera Beach, FL
  • CONTRACTOR: Precise Paving
  • MANUFACTURER: Belgard
  • DESIGNER: Calvin, Giordano & Associates Engineers, EDSA Landscape Architects

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Shed the Shovel, Halt the Salt

Winter’s snowfall brings inconvenience and injury risk for many across North America. Slipping on snow or icy surfaces can cause hip dislocations, wrist fractures or even head injuries. From private residences to commercial storefronts, snow and ice removal is a responsibility not to be taken lightly. A snowmelt heating system effectively tackles that responsibility with benefits beyond merely melting snow. By significantly reducing or potentially eliminating the need for deicers and shoveling, a pavement heating system can also help preserve the beauty and longevity of pavers while reducing liability.

While the cost to install a pavement heating system may qualify it as a luxury item, the return on investment comes from saving hours of shoveling and deicer costs. When considering the savings season after season, particularly in heavy snowfall regions, the investment yields valuable returns.



HYDRONIC OR ELECTRIC?

There are two types of pavement heating systems: electric and hydronic. Electric systems conduct heat through wires or cables, whereas hydronic systems pump and recirculate a mix of glycol and water through a loop of flexible polymer or synthetic rubber tubing. Generally, an electric system is cheaper to install but costs more to operate over time because the current draws continuously while the system is on. A hydronic system is more expensive to install due to the additional components required such as a dedicated boiler, pumps and manifolds, often installed by a plumber. Hydronic systems have lower operating costs because they reheat and recirculate the fluid. With more parts, hydronic systems may require more maintenance over time than electric systems.

THE INSULATION FACTOR

Another key factor to determine at the outset is whether or not an insulation layer is required by local building codes. Places like Aspen, CO, or Sun Valley, ID, for example, require an insulation layer for pavement heating systems to maximize energy efficiency. This adds costs and can cause the pavement to fail if not correctly installed.

“I’ve seen a 70-foot driveway where the pavers slid six inches and left a gap at the top,” said Marc Larsen of Mountain West Paver Specialists. The insulation material often used is squishy, like bubble-wrap, explained Larsen, and installers mistakenly place it on top of the base. “You have to remove the flexibility of that insulation material by putting it under the rigid base of a concrete slab.”

If there is no building code requirement to use insulation, it can be presented to the customer as an efficiency option but it’s not necessary for the system to function optimally, according to Larsen. The ICPI construction guidelines in ICPI Tech Spec 12 – Snow Melting Systems for Interlocking Concrete Pavements do not recommend insulation below the bedding sand in residential driveways. However, insulation below the bedding sand is acceptable for pedestrian-only applications such as a patio or sidewalk. For roads or crosswalks, concrete or asphalt bases are recommended.



PERFORMANCE PLANNING

The design and performance of a snowmelt system depends on three environmental factors: the rate of snowfall, the temperature of the snow and wind conditions. Snowmelt rates will vary with the application. For example, melting 1 in. (25 mm) of snow per hour is usually acceptable for a residence but may be unacceptable for a sidewalk in front of a store. Most manufacturers of hydronic and electric snowmelt systems provide design guidelines and/or software to calculate the BTUs per square foot (watts/m2) required to melt a range of snowfalls for a given region.

The design methods work through a series of calculations that consider the snow temperature (density), air temperature, exposure of the pavement to wind, and unusual site conditions. The calculations indicate the size and spacing of cables or tubing required, as well as the temperature of the fluid, its flow rate, or the electricity required. The Radiant Panel Association (radiantpanelassociation.org) provides design guidelines for liquid snow melt systems.

LAYOUT AND CONSTRUCTION

With electric and hydronic systems, the best performance comes from a heat source placed as close to the pavers as possible, nestled into the bedding sand. The recommended depth for bedding sand is normally 1 inch. However, the wires or tubing need a ½ inch of sand over them for protection from abrasion and possible rupture. Therefore, the diameter of the wires or tubing may increase the bedding sand thickness to a maximum of two inches before compaction.

Once the base is installed and compacted to the proper depth and density per ICPI Tech Spec 2 – Construction of Interlocking Concrete Pavements, a galvanized wire mesh is placed over the surface of the base and secured to the base with stakes. The wires or tubing for the heating system are then fastened to the wire mesh with plastic zip ties. Installation of wires or tubing should be done by an electrician or plumbing contractor experienced with these systems. Before placing sand or pavers over the system, it should be tested for leaks.

Some contractors install the wires or tubing into the top inch of the base to forego the wire mesh and facilitate easier sand screeding. In this case, base material is added around the wires or tubing and then compacted to bring the level of the base to its final grade. The wires or tubing are exposed flush with the compacted surface of the base.

While the above guidance is suitable for pedestrian and residential driveway applications, areas subject to constant vehicular traffic such as crosswalks or roads require wires or tubing placed within a concrete slab or asphalt, rather than on top of the base. This protects the heating system from tire damage. Check with the wire or tubing manufacturer to be sure materials can withstand hot asphalt and its compaction. When an asphalt or concrete base is used, 2-inch diameter weep holes should be added at the lowest elevations for drainage, filled with washed pea gravel, and covered with geotextile to prevent bedding sand loss.

For permeable interlocking concrete pavements, wire or tube spacing will most likely be reduced to account for heat loss to the air voids within the permeable aggregate bedding layer. The manufacturer of the heating system should be consulted on durability of the wires or tubing when placed against bedding aggregate and then subjected to vehicular tire loads.

ts12INSTRUCTION AND GUIDANCE

ICPI Tech Spec 12 – Snow Melting Systems for Interlocking Concrete Pavements provides detailed installation guidance and is available for download from the resource library page of ICPI’s website: icpi.org/resource-library. ICPI also offers courses that provide instruction and certification. Visit icpi.org/education-certification to learn more and to register.

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New Product Spotlight

The 2016 Hardscape North America trade show featured many new products on display at exhibitor booths. These are just a few that caught attendees’ attention. ICPI does not endorse these products and welcomes member companies to submit information on new products to icpi@icpi.org.

provenceslabsPROVENCE SLABS

Belgard’s new Provence Slabs are designed with Satura technology, emulating the look and feel of natural stone but with standard dimensions to lower labor costs and shorten project timelines compared to natural stone installations. Available in a three-piece modular set, large square and large rectangle options, Satura’s surface coating also enhances color saturation and provides improved protection against stains and efflorescence. The availability of natural stone is often limited by region; Provence Slabs offer popular bluestone and ledgerock hues to a broader market and open new possibilities for project designs and color selection.

ADJUSTABLE HEIGHT PEDESTALS

buzonbcpedestalsystemOn display at the Techo-Bloc booth, Buzon BC Series pedestals for slab applications feature a screw-jack design for quick and easy installation. The pedestals can be extended to a height of 44 in. (1,100 mm) using couplers. Slope corrector components of the system allow for a 5% pitch adjustment or compensation for uneven subbases up to the same amount. Made from 78% recycled and 100% recyclable polypropylene, each pedestal can support loads of more than 1 ton (1,000 kg).

starlitesSOLAR-POWERED LED STARLITES

No wires, no trenching, no timer, no electrician needed. Kerr Lighting by SEK’s self-contained, solar-powered LED lights come in a range of sizes and shapes, including standard rectangular paver dimensions, and can be placed into an installation as easily as setting a paver. Unlike lithium ion batteries, the double-layer capacitor used in these lights will not need replacement. Under full sunlight, charging time is 3-5 hours to provide 12 hours of working time. The stainless steel light fixture with UV-resistant polycarbonate lens is engineered to withstand light vehicular traffic, is waterproof and has a slip-resistant surface. In addition to standard warm white, special order alternatives of red, green, blue, yellow and cool white colors are also available.

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The Best of the Best

Oak Leaf Landscaping of Danville, OH, won the 4th Annual HNA Installer Championship at the 2016 Hardscape North America trade show, an Interlocking Concrete Pavement Institute (ICPI) event.

Twenty-four segmental concrete pavement installation teams from throughout the United States and Canada competed in the two-day event. Each installation project was judged on safety, craftsmanship and compliance with industry best practices.

 

In the preliminary round, the teams were given 60 minutes to construct an 8 ft x 10 ft interlocking concrete patio with a seat wall as specified in drawings provided by the competition committee. Teams with the top four scores qualified for the championship round where they were given 90 minutes to construct their own creative design.

In the championship round, Oak Leaf Landscaping scored 402 out of a possible 450 points for its original design and construction of a square patio area with an ornate checkerboard table and two bench seats. The team consisted of Tobias Yoder, Daniel Nisley and Owen Nisley. They received the championship prize package that included a $1,000 award, an iQ Powertools 360 14” dustless masonry table saw with accessories, and a Weber MT CF3 Pro forward-plate compactor.

Second place was awarded to the Cheeseheads Team, Zillges Materials of Oshkosh, WI. Team members were Emmanuel Oesterreich and Jourdain Oesterreich. In the championship round, they scored 393 points and were awarded $400 and an iQ Powertools 360 dustless masonry table saw.

“It’s an adrenaline rush,” said Emmanuel Oesterreich. “It not only tests someone’s skill level, but really tests their composure and how they react under pressure.”

Third place went to Epic Pavers of Evless, TX, with team members Luis Garcia, Jose Garcia and Samuel Guijarro. The team scored 388 points in the championship round. For their efforts, the team received a $100 award. Fourth place was awarded to LR Landscaping of Lincoln, CA, with team members Lee Reveles, Daniel Preciado and Elmer Casasola. In the championship round, they scored 378 points.

All four finalist teams also received a hand tool package provided by Ox Tools and a plaque.

The judges for the Championship were Fred Adams of Fred Adams Paving Co., Inc.; Frank Gandora of Creative Hardscape Company; Tim Huinker of Anchor Wall Systems; and Chuck Taylor of Belgard Hardscapes by Oldcastle.

The Championship was sponsored by Alliance Designer, Anchor Wall, Belgard, iQ Power Tools, Ox Tools, Pavestone and Weber MT.

Watch this video from last year’s HNA Installer Championship.

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What If?

Many cities maintain a database describing the condition of their road pavements. The database includes the pavement structure, condition information listed as various ‘distresses,’ as well as their extent and severity. The database is used to calculate a pavement condition index (PCI) based on these combined factors. A PCI can rate a single pavement or a network from 1 to 100 with 100 being a brand new, perfect pavement while 1 suggests a surface like the Ho Chi Minh Trail after a B-52 bombing raid.

Two ASTM standards describe the index calculation process. For asphalt and concrete pavements, there is ASTM D6433 Standard Practice for Roads and Parking Lots Pavement Condition Index Surveys. For segmental concrete pavement, there is ASTM E2840 Standard Practice for Pavement Condition Index Surveys for Interlocking Concrete Roads and Parking Lots. (Both standards can be purchased at www.astm.org.)

Pavement condition surveys for asphalt and concrete streets have been in existence for decades. Municipal and state road agencies refine their models characterizing wear over time to accurately predict required maintenance, types, costs and budgets. For interlocking concrete pavements, such surveys exist in The Netherlands due to extensive segmental pavement use there. For the U.S. and Canada, there are millions of square feet of municipal interlocking concrete pavements. However, most are installed as specialty applications to highlight downtown or neighborhood business district improvements. There are only a handful covering an entire neighborhood, larger residential or commercial districts, or entire city centers.

Most municipalities struggle financially to maintain existing asphalt and concrete pavements. These pavements are institutionalized over the past 100 years through design, construction and maintenance requirements, plus equipment and crew investments. Considering wider use of interlocking concrete pavements by municipal road agencies is simply out of the question unless the industry presents compelling evidence for substantial reductions in material, equipment and personnel costs.

Such reductions from interlocking concrete pavement beg exploring in the context of a road network in a neighborhood or district. Experience has demonstrated that when properly designed and installed, interlocking concrete pavements last 30 to 40 years. The absence of damage and reduced pavement life from utility cuts, almost all-season repairs, no resurfacing, possible lane and parking space striping with colored pavers, lower capital expenses from using less and simpler maintenance equipment, and paver re-use all appear to present lower life-cycle costs for a municipal street system. ASTM E2840 provides tools to calculate PCIs from databases as a prerequisite to measuring costs and benefits.

ICPI would like to take this to the next level. Here’s the pitch: The industry seeks a willing municipal road agency (and possible supporting pavement consultant) with a pavement management system who would like to model the what-if life-cycle costs of interlocking concrete pavements to better understand and reduce agency costs, plus operational and institutional changes that would yield taxpayer benefits. Together, we might be surprised after examining the what-ifs that the next question turns out to be why not?

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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.

Table_1

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.

Table_2

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.