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2017 HNA Awards Entry Open

The HNA Awards recognize outstanding hardscape projects by contractors building residential and commercial walkways, patios, driveways, commercial plazas, parking lots, streets and more.

Award winners and honorable mentions will be recognized during the 2017 Hardscape North America trade show at the HNA Awards Recognition Ceremony in Louisville on October 19.

They also will be announced in a national press release, featured in Interlock Design magazine, and highlighted on the HNA website and in several major industry publications.

A distinguished panel of industry experts will select award winners and honorable mentions.
Entry Rates

Complete your online entry, submit photos and project description by August 14, 2017 for early bird rates ($100 for Members of ICPI, NCMA or BIA/$140 for Non-Members).

Entries will be accepted up to September 11, 2017 at a higher rate ($200 for Members of ICPI, NCMA or BIA/$240 for Non-Members).
2017 HNA Award Categories

Projects for consideration must have been completed between November 1, 2013 and June 30, 2017.
[insert award chart]
*Awards 12-15 can include natural stone, masonry veneer and mortared walls.

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Don’t Be Fooled

Having worked with segmental and monolithic pavements for a few decades, one growing notion popularized in marketing/technical information for competing pavement systems is H-20 loading. Product literature for plastic pipes, chambers, stormwater storage crates, grids, etc., state confidently that their products can receive an H-20 load.

While that may be true, here’s a more complete picture. The H-20 load notion comes from bridge design and not from pavement design. The concept is found in the American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges. Most bridges that receive trucks label such loads as H-20 or HS-20 in the bridge design process. The ‘20’ stands for a 20-ton vehicle, i.e., 4 tons on the steering axle and 16 tons on the drive (rear) axle. Adding an ‘S’ means the truck is a tractor-trailer combination. This adds 16 tons to a third (rear) axle, making a 36-ton vehicle.

The H-20 load is used in bridge structure design, a process that examines how the structure deflects under the weight of the bridge itself (dead load) and the applied truckloads (Iive). Computerized structural design models find the right size beams that limit their movement (deflection) under truckloads. The deflection in the structure is analyzed under H-20 and HS-20 loads, and likely other loading options depending on the anticipated traffic.

H-20 or HS-20 is a single truckload used in the analysis of bridge designs. These designations don’t apply to pavement design. Pavements are not designed to receive a single truck on them. In fact, my grassed front yard could easily receive an H-20 load. Obviously, that lawn is not a suitable pavement structure for repetitive loads from trucks.

Whether grass or something else, pavements do not typically fail from one H-20 or HS-20 load. Their limitations are defined by their ability to receive thousands or even millions of axle loads from trucks. Since axle loads vary with every vehicle, the AASHTO 1993 Guide for Design of Pavement Structures provides a process to equalize them to 18,000 lbs using a pavement concept developed in the 1950s called equivalent single axle loads or ESALs. Applying the ESAL concept, one H-20 load equals about 10 ESALs and one HS-20 load equals 26 ESALs.

Pavement failure (an unserviceable pavement) is typically seen as rutting in asphalt and cracking in rigid concrete pavements. In either case, the pavement surface slowly fatigues from repetitive loads over time due to tension and resulting horizontal strain at the bottom of the pavement surface. This eventually causes the pavement surface to bend or break.

Interlocking concrete pavements have a much higher compressive strength than conventional concrete (8,000 psi versus 4,000 psi). This makes the paving units especially resistant to fatigue from repeated loads compared to conventional asphalt or concrete surfaces. Most interlocking concrete pavements wear out deeper in the pavement, i.e., from repeated compressive strain within the bedding sand, base or at the top of the soil subgrade layer. This suggests that the base thickness needs to be sized and then constructed correctly, as well as testing conducted on soil subgrade compaction.

ICPI provides guidance documents to help with design on www.icpi.org. ICPI Tech Spec 4 Structural Design of Interlocking Concrete Pavements is one such document. Another is ASCE 58-16 Structural Design of Interlocking Concrete Pavement for Municipal Streets and Roadways. Both documents provide structural designs up to 10 million ESALs, a very busy major urban thoroughfare.

In the meantime, don’t be fooled. When the term H-20 appears in product literature, ask what happens when that load is repetitively applied? How long does the pavement last? When does it become unserviceable and fail from rutting or cracking? These are the core pavement design questions that require an answer for designers to create reliable pavements.

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Resetting the Bar

The Transportation & Development Institute (T&DI) of the American Society of Civil Engineers (ASCE) recently updated and released ASCE 58-16 Structural Design of Interlocking Concrete Pavement for Municipal Streets and Roadways. According to the ASCE, “The standard provides preparatory information for design, key design elements, design tables for pavement equivalent (to asphalt) structural design, construction considerations, applicable standards, definitions, and best practices.” This new version, which replaces Standard ASCE/T&DI/ICPI 58-10, includes updated references to quoted ASTM standards, clarification of subgrade type and drainage characteristics, and the addition of new green infrastructure rating systems.

The 42-page design guide provides tables for base thickness using aggregate, asphalt-treated, cement-treated and asphalt bases under interlocking concrete paving units that conform to ASTM C936. The book provides thicknesses for various soil subgrade conditions under traffic up to 45 mph and exerting no more than 10 million lifetime 18,000 lb (80 kN) equivalent single axle loads or ESALs. Transportation engineers, road designers, planners, pavement manufacturers and municipal officials can rely on this comprehensive guide to interlocking concrete pavements.

ASCE Standards_August 2016_new green.inddDave Hein, P. Eng., Vice President of T&DI and chairman of the technical committee that created and updated the standard, notes that, “ASCE 58-16 continues to provide municipal and consulting engineers with this tool to design and implement interlocking concrete pavements in streets, alleys and parking lots. When properly designed and constructed, these pavements can be more cost-effective over their life than conventional asphalt and concrete. And besides, pavers upgrade the appearance of any street.”

Purchase the updated standard at www.asce.org/booksandjournals. The price is $60 for ASCE members and $80 for non-members.

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Clarify and Confirm

Last summer, ASTM approved C1782 Standard Specification for Utility Segmental Concrete Paving Slabs. Needed for decades, the industry now provides a baseline product standard for segmental concrete paving units from 12 x 12 up to 48 x 48 in. (300 x 300 up to 1,200 x 1,200 mm). ASTM C1782, however, was written for paving units that do not require close dimensional tolerances. Such tolerances noted in Table 1 at right are from that standard.

Utility paving slabs often have architectural finishes and are used in residential and some commercial applications for at-grade and roof ballast applications. Architectural finishes include (but are not limited to) blasted, hammered, tumbled, textured and polished surfaces. The Interlocking Concrete Pavement Institute is proposing a second ASTM standard for slabs with closer (tighter) dimensional tolerances. Like products conforming to C1782, products conforming to the proposed standard typically have architectural finishes. However, the main difference between C1782 and the proposed new standard is that the latter has closer dimensional tolerances required for pedestal-set roof applications, as well as for at-grade bitumen-set and some sand-set applications. The new proposed standard formalizes these dimensional tolerances used with architectural paving units for these applications for over 20 years. This proposed new standard below is very similar to ASTM C1782 except for the closer dimensional tolerances shown in Table 2.

Rather than provide optional closer dimensional tolerances within C1782, a new standard is being proposed that differentiates itself from C1782 with higher dimensional tolerances for architectural paving slabs. Also, two distinct paving slab standards (standard and architectural grade) can help reduce confusion between these two groups of paving products among specifiers, contractors, and other users. Freeze-thaw durability and flexural strength requirements are proposed to remain the same as those in C1782. Acceptance of this new standard is anticipated in 2018, but this depends on the outcome of voting by ASTM members.

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Doing the Math

Thanks to a grant from the ICPI Foundation for Education and Research, design tables were developed earlier this year that provide technically conservative base solutions for paving slabs subject to vehicles. The tables were developed using finite element modeling that simulated pressures from truck tires on paving slabs of various sizes and flexural strengths. The modeling included a 1-inch (25 mm) thick sand bed under the slabs, three base materials, and three soil subgrade conditions. This article previews the design approach for pedestrian and vehicular applications derived from that modeling.

For pedestrian applications, 12 x 12 in. (300 x 300 mm) units can be placed on a minimum 6 in. (150 mm) thickness of compacted aggregate base. Thicker bases (generally 8 to 12 in. or 200 to 300 mm thick) should be used in freezing climates and/or on weak clay soils (CBR < 3%). Designers should consider using a lean concrete or concrete base for larger paving units because achieving a very smooth base surface can be difficult with compacted aggregate base.

Design options become a bit more complex for vehicular applications. The first step is determining the maximum number of lifetime 18,000 lb equivalent single axle load or ESAL repetitions. (Caltrans Traffic Indexes are provided in parentheses.) Determining ESALs or TIs can be done using Table 1. It divides them into five categories. Higher ESAL categories generally require thicker units and concrete bases. Applications exceeding 75,000 lifetime ESALs should use interlocking concrete pavers.


Math-Table1


The next step is determining the soil strength. The minimum values for designs is a resilient modulus of 5,100 psi (35 MPa), 3% California Bearing Ratio, or an R-value = 7. The maximum values are 11,600 psi (80 MPa), 10% and 18, respectively. Soils with higher values use the latter set for determining the unit size and thickness. after laboratory tests determine the soil strength, that points to specific slab sizes and bases that will work given the anticipated design ESALs in Table 2. Square paving units are recommended over rectangular ones for vehicular traffic with placement in a running bond pattern.

The ICPI design method offers three base options described below in ascending order of supporting stiffness. Construction should include compacting the soil subgrade and bases/subbases to at least 95% of standard Proctor density per ASTM D698 Standard Test Methods for Laboratory Compaction of Soil Standard Effort.

(a) A 12 in. (300 mm) thick compacted aggregate base with gradation conforming to provincial, state or municipal specifications for road base used under asphalt pavement. If there are no guidelines, use the gradations in ASTM D2940 Standard Specification for Graded Aggregate Material for Bases or Subbases for Highways or Airports and as described in ICPI Tech Spec 2 Construction of Interlocking Concrete Pavements.

Slabs can take a modest amount of trucks but using thicker units. The ICPI guide tells designers and contractors how thick.

Slabs can take a modest amount of trucks but using thicker units. The ICPI guide tells designers and contractors how thick.

(b) A 4 in. (100 mm) thick lean concrete base over a 6 in. (150 mm) thick compacted aggregate base. The lean concrete should have a minimum 725 psi (5 MPa) compressive strength after 7 days per ASTM D1633 Standard Test Methods for Compressive Strength of Molded Soil-Cement Cylinders. Lean concrete is typically a lower strength concrete or a cement-treated base of similar stiffness and strength where an aggregate base is charged with cement (typically 3% to 6% by weight) to bind the aggregates when the cement cures.

(c) A 4 in. (100 mm) thick concrete base over a 6 in. (150 mm) compacted aggregate base. The concrete should have a minimum compressive strength is 3,000 psi (20 MPa) per ASTM C39 Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens.

Table 2 presents a sample of the design tables using a concrete base. The designer finds the paving slab length and width and thickness that corresponds to the soil subgrade strength and slab flexural strength. Paving slab length and widths start at 12 x 12 in. and go up to 48 x 48 in. As an illustrative example, Table 2 only goes to 24 in. slabs and not up to 48 in. due to space limitations. Slab thicknesses are 2, 3, 4 and 5 in. If the exact paving slab length and width are not on the table, the designer finds the closest size paving slab, using a smaller and/or thicker unit as a conservative design measure. The design tables cover square and rectangular slabs only.


Math-Table2


An example follows on how a design table works. The highlighted 24 x 24 x 3 in. thick slab is selected by the designer. This will be a concrete base and aggregate subbase over a 5% CBR subgrade with a minimum 750 psi flexural strength for the slabs. The intersection of the highlighted horizontal and vertical columns is marked OHV which means the maximum lifetime load is 75,000 ESALs per Table 1. If the designer wants to use a 24 x 24 x 3 in. slab on a weaker soil subgrade, then the maximum allowed ESALs would be 30,000. 

Designs using a concrete base include a 1 in. (25 mm) thick sand setting bed under the slabs. This design solution also applies to paving slabs in a bitumen-sand bed (typically 1 in. or 25 mm thick) since bitumen-set applications require a concrete base. This introduces an additional measure of conservative design since bitumen-sand materials provide a modest increase in stiffness and increased stability resisting repeated turning, accelerating, and braking tire lateral loads.

This article was intended to sample how structural design is done with paving slabs. Similar, additional design tables have been developed for planks and an ICPI Tech Spec is expected later in 2017. As partial validation, the ICPI Foundation for Education and Research is funding the construction of a full-scale load testing area at a paver manufacturing facility in Maryland. The area will receive trucks loaded with paving products where each truck pass will exert several ESALs. The condition of the slabs and planks set on aggregate and concrete bases will be monitored to see how quickly or slowly the slabs will crack, as that defines failure. The testing will likely begin in spring 2017 and run for a few years.

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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