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ARCHITECTURAL PAVING SYSTEMSADVANCEMENTS IN SURFACE TECHNOLOGIES AND FINISHES

When the City of Toronto decided to revitalize Yorkville Avenue, arguably Canada’s trendiest shopping district, planners wanted to enhance the sidewalks and the roadway with paving stones that were sophisticated, contemporary and durable.

“The durability of the pavers was of the utmost importance,” said Brett Hoornaert, landscape architect and an associate with The Planning Partnership. Paving stones had been in place outside Yorkville Avenue’s fire station for 40 years, and Hoornaert cited this as evidence that paving stones could deliver the long-term durability required for the project.

Working with the manufacturer, the design team chose a plank style paving stone laid in

a herringbone pattern, with a pleasing mix of grey tones, and umber-colored stones added for the sidewalk. Now, the avenue feels both trendy and historic with paving stones from building face to building face.

Today, the specification of concrete paver systems offers more diverse architectural choices than ever before. However, not all concrete paving materials are created equal. To withstand harsh environments and heavy use with minimal color and surface wear, paving products should employ the latest technologies and manufacturing processes available. This will ensure that the architect, landscape architect, or engineer is specifying concrete pavers that will withstand the test of time. The range of

color and finish options for these products is greater than ever before, allowing the designer to explore creative options in partnership with a supportive manufacturer. This article explores how to recognize, design for, and build with, the highest quality concrete pavers available in the industry.

THE LONG HISTORY OF CONCRETE PAVERS

Segmental paved surfaces have a long history of function and durability. The Romans used paving stones of varying materials, and a layered construction method to build over 50,000 miles of paved roads. Base materials consisted of a bedding layer of fine cement combined with a number of layers of rubble of increasing size to ensure proper drainage.

By Kathy Price-Robinson

Presented by:

LEARNING OBJECTIVES

Upon completion of this course the student will be able to:

1. Describe the history of concrete pavers.

2. Understand the manufacturing process and standards of concrete paving stones.

3. List new paver technology and industry trends.

4. Understand the diversity of application types available.

5. Examine the potential options for contribution to LEED criteria.

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CREDIT: 1 LU

COURSE NUMBER: ARmay2016.3

Use the learning objectives above to focus your study as you read this article. To earn credit and obtain a certificate of completion, visit http://go.hw.net/AR516Course3 and complete the quiz for free as you read this article. If you are new to Hanley Wood University, create a free learner account; returning users log in as usual.

Paving stones laid from building front to building front helped revitalize Toronto’s trendy Yorkville Avenue shopping district.

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Roman segmental paved surfaces were built to resist rain, freezing, and flooding, and to require as little repair as possible. It’s clear that these construction methods worked, as some of these roads are still in use today.

Throughout history, many urban roads were paved in segmental stone or brick. Cobblestones, a commonly used surface, were typically sourced from riverbeds and provided a rough and uneven surface. By the 1700s, this river rock began to be replaced by quarried stone dressed in rectangular shapes. In the U.S., basalt, sandstone, and even limestone were used. This surface stone sat on a bed of course sand; sand was also used to fill joints.

Brick pavements have been used for hundreds of years, most commonly in areas where there wasn’t enough local stone. A similar base of sand and sometimes an additional layer of broken stone was used. Joints were filled with sand or a bituminous material.

The issue with brick pavers was their tendency to suffer surface damage, which limited their lifespan to about 20 years.

The use of concrete block pavers began in Germany prior to World War I. These were seen as a replacement for stone and brick pavers, providing greater uniformity.

PAVERS IN POST-WAR EUROPE

After World War II, Holland began manufacturing concrete pavers in earnest. Because clay bricks were needed for building construction, manufacturers created concrete pavers for use in road repair and rebuilding. Originally, these concrete pavers were manufactured to match clay brick sizes, but eventually new formats and sizes were created. These new concrete pavers were less expensive than their clay counterparts and had greater consistency of size. The concrete paver soon evolved into shapes that were denated, meaning they had “teeth,” which allowed

the blocks to be easily placed without the use of lugs. This reduced the need for skilled installation labor, thus lowering costs.

During the same period, Fritz Von Langsdorff, an engineer from Germany, developed new shapes and integrated colors for concrete pavers that featured tremendous pressure resistance and low moisture content. The first of these new paving stones were installed in Stuttgart, and Germany soon became recognized as the leader in this field. The Germans are responsible for many of the new paver products and much of the manufacturing technology we use today, and concrete pavers remain a very popular choice in Europe.

NORTH AMERICAN PAVER TECHNOLOGY FROM 1970 TO PRESENT

Pavers were introduced to North America in the 1970s, with the first stones made in Barrie, Ontario, Canada. They were made six units at a time, 3,000 per day and palleted by hand. At that time, natural-colored (grey) pavers were the only available option. Here is the timeline:

1970s: First generation pavers all had a standard finish, meaning that the concrete mix was the same from top to bottom. In 1975, new paver shapes were developed that combined the classic shapes of a square and an octagon into one versatile paver.

1980s: The first circle system paver is introduced in 1983. Heavy-duty pavers were developed in 1989 in response to a need for an attractive pavement option capable of sustaining enormous loads. These properties make this type of paver ideal for mechanical installation, which allows for economic paving of large areas.

1990s: Distressed pavers, designed to mimic natural worn stone, were introduced in North America following the popularity of tumbled pavers in Europe. This second generation paver had a different texture, derived from the first generation finish and concrete mix.

Early in the decade, third generation pavers were introduced with face mix technology, where the mix design on the surface of the paver was denser than the base. This allowed for new surface textures to be developed that were more durable over time. As well, an innovative, new paver shape was introduced with larger voids between the pavers, providing drainage for rainwater and runoff into the sub-base. These new pavers were called ‘permeable’.

2000’s: Wetcast manufacturing technologies allowed for new shapes and surface textures that more closely reflected the look of natural stone, with advanced color retention and wear capabilities. This fourth generation of pavers introduced different casting methods that could also take advantage of face mix technology. Built-in surface treatments created pavers that were easier to clean than standard pavers. As well, different formulas allowed for varying degrees of stain resistance.

2010s: New shapes were introduced, allowing for more rapid installation (up to 30 percent faster than regular paving stones). Wetcast products, reminiscent of historical street pavers, were introduced in a permeable version, improving the aesthetic options within this emerging category. And finally, the latest in the permeable line of products are plank-style pavers that are machine installed, allowing a contractor to install 5,000 to 6,000 square feet per day with a two- to three-person crew.

YORKVILLE FIRE HALL AND YORKVILLE AVENUE, TORONTO

In 1974, a first-generation paver was installed at the Fire Hall on Yorkville Avenue in Toronto. Unit pavers were a brand new paving concept in North America at the time, having been introduced to the market only two years prior.

In 2014, the pavers were still intact and enduring the rigors of daily fire truck traffic.

“They have endured for over 40 years,” said Paul Halls, Toronto Fire District Chief, who joined the department just after the pavers were installed.

The history of paving stones dates back to Roman times, and beyond.

Plank-style paving stones are among the latest design trends.

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cementitious material (SCM). These materials may include:

• Fly ashes type C and F—Residue from combustion of pulverized coal.

• Silica fume—Residue resulting from the production of silica.

• Slag cement—Ground granulated blast furnace (GGBF) slag, formed by rapidly chilling molten blast furnace slag.

• Natural pozzolans—Materials that, when finely divided, will react chemically with calcium hydroxide in the presence of water to participate in a cementitious reaction.

The use of supplementary materials decreases the environmental impact associated with concrete production by reducing energy requirements and CO2 emissions.

Importance of Admixture

Another contributor to superior concrete is admixtures, which are dry or liquid additives in the concrete mix that augment performance characteristics based on application requirements. Admixtures are used to plasticize the concrete to make it more fluid, which assists in the filling process and increases densification. They also help control efflorescence, and improve the concrete quality overall.

Admixtures may contain air entrainers. The Portland Cement Association explains that air-entrained concrete contains billions of microscopic air cells in each cubic foot and that these air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes.

Admixtures which improve the quality and durability of the concrete may include water reducers, super plasticizers, retarders, accelerators, viscosity modifiers, alkali-silica reactivity reducers, shrinkage reducers, expansion agents, etc. Some contain chemicals (including calcium stearates) that repel water from the concrete after curing. Note that silane/siloxane technology is now common in admixture development and is permanent, whereas calcium stearates break down over a period of time.

Some admixtures help control efflorescence. Efflorescence is observed as a whitish/grey deposit of soluble salt left behind by water evaporating from the concrete. Most concrete products will have some efflorescence, as it is the natural salt found in the aggregate used to create the concrete. It will disappear in time on its own.

us. We need to rely on this. It doesn’t matter the weather, the time of year. We need this to survive.”

Concurrent with the new Fire Hall project, efforts were in the works to develop a master plan for Yorkville Avenue itself, which is one of the premier shopping districts in Toronto. The design focused on creating a pedestrian-friendly environment using appropriately durable materials and construction methods to ensure the roadway and sidewalks would withstand the harsh winter environment. The road reconstruction consisted of a 10" concrete road base with PVC drainage pipes located along the curb. The pipes were covered with filter cloth at the inlets to prevent clogging and 4"x12"x4" plank pavers were set in a 1" sand setting bed. The next phase included the roadway and sidewalks and here, an additional color was incorporated into the sidewalk for more visual definition and interest.

THE KEYS TO DURABLE PAVERS: COMPOSITION AND MANUFACTURING

The evolution of pavers, and their upward trajectory of style and substance over the decades, is due to continual technological improvements in paver composition.

The combination of coarse and fine aggregates in a concrete mix design is vital to achieve high strength, a low absorption rate, and good surface textures. Only with the proper blending and balancing of fine and coarse aggregates, can a top-quality product be produced.

Cement acts as the “glue” within the mix, bonding together particles of coarse and fine aggregate. With mix designs using a large amount of fine material, more cement is required to coat each aggregate particle, compared to the amount of cement needed with a mix of larger aggregate particles.

The more cement used in the mix, the more expensive the product becomes; finding the right balance is key to producing quality material at a good price.

Cement can be partially replaced with other materials, which are known as supplementary

“Over 250,000 emergency responses in that time have come out these doors and across this platform,” Halls explained. “The stones have withstood so much pounding. The aerial truck, the ladder truck, weighs over 35 tons. So rolling in and out for a quarter of a million responses in the 40 years they’ve been here is huge.”

By 2014, it was determined that the pavers should be replaced. A new style from the original manufacturer’s line was chosen for its aesthetic to fit with the heritage building and accents, as well as its ability to withstand the demands of the fire hall. The proctor density of the original granular base was tested and no modifications were required Therefore, new pavers were installed on top of the existing base. The 4" x 12" x 4" paver was laid in a herringbone pattern for maximum 'lock up', adding strength to handle the rotational forces of the fire trucks.

“We need good equipment, good material,” Halls added. “Part of that is a good platform. The big thing for us is durability. So the way they (the pavers) are built—way thicker—to withstand the pounding of the trucks, that means something to

After more than 40 years of reliable service, the original paving stones were replaced in 2014.

A variety of colors and shades add interest to the Yorkville Avenue paving stones.

The paving stones installed outside the Fire Hall on Toronto’s Yorkville Avenue held up for more than 40 years of heavy traffic from fire trucks weighing more than 35 tons.

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Efflorescence will not directly harm concrete products, but in excess it can be an indication of other potential problems, such as poor curing, high permeability, and low strength.

Color in Concrete

Pavers are available in a wide palette of colors in order to complement nearly any design vision. Some manufacturers use synthetic iron oxides (pigments) to tint concrete. A smaller particle size in the batch allows for higher strength tinting, lower loading, and cost savings.

Even when the same pigments are used, product color can vary based on the source of the aggregates used in the concrete mix. Different regions or quarries produce different aggregates which can have a significant effect on the color of the finished product. Different cements also have an effect on the concrete color.

Ä This article continues on http://go.hw.net/AR516Course3. Go online to read the rest of the article and complete the corresponding quiz for credit.

QUIZ

1. The use of concrete block pavers began prior to World War I. These were seen as a replacement for stone and brick pavers, providing greater uniformity and eliminating the need to dress the stone. In what country did the use of these pavers begin?

a. Japan b. Germany

c. Australia d. Fiji

2. In the 1970s, first generation pavers with a standard finish and a consistent concrete mix from top to bottom were introduced to North America. In the 1990s, a new technology was introduced where the mix design on the surface of the paver was denser than the base, and allowed for new surface textures to be developed. What is that technology called?

a. Stacked mix technology b. Parallel mix technology

c. Face mix technology d. Pancake mix technology

3. Shortly after concrete paving stones were introduced to North America in the 1970s, they were installed outside a Fire Hall in Toronto. With trucks weighing as much as 35 tons rolling over them many times a day, equaling some 250,000 emergency responses, how long did the paving stones last?

a. More than 10 years b. More than 20 years

c. More than 30 years d. More than 40 years

4. Cement can be partially replaced with supplementary materials, which are known as supplementary cementitious material (SCM). The use of these materials decreases the environmental impact associated with concrete production by reducing energy requirements and CO2 emissions. These materials may include:

a. Fly ashes type C and F, which is residue from b. Silica fume or slag cement combustion of pulverized coal.

c. Natural pozzolans, which are materials that when d. All of the above finely divided will react chemically with calcium hydroxide when in the presence of water to participate in a cementitious reaction.

5. There are two types of manufacturing processes for pavers: Drycast and wetcast. In which process is the mix poured into flexible polyurethane molds, which allows manufacturers to create more realistic looking products that resemble stone or old brick?

a. Wetcast b. Drycast

c. Both of the above d. None of the above

6. Absorption is critical to the longevity of a surface. If a surface absorbs high levels of water above 5 percent, freeze thaw durability will be compromised. When comparing concrete, concrete pavers and clay pavers, which has the lowest absorption rate of 4 percent to 5 percent?

a. Poured concrete has lowest absorption rate b. Concrete pavers have lowest absorption rate

c. Clay pavers have the lowest absorption rate d. All absorption rates are equal

7. True or False: Paving stones are also covered under ASTM International C936 Standard Specification for Solid Concrete Interlocking Paving Units.

a. True b. False

8. What shape of paving stone is currently on trend?

a. Rectangular (plank) shape b. Octagon shape

c. Round shape d. Trapezoid shape

9. Concrete pavers can clean themselves with exposure to sunlight and rain when they are made with photocatalytic cement. What is the ingredient in the coating that facilitates this process?

a. Copper b. Titanium dioxide

c. Sodium silicate d. Colloidal silver

10. The renovation of Navy Pier in Illinois includes many sustainable features inspired by the Sustainable Sites Initiative of the Green Building Certification Institute. To increase the project’s sustainability, what supplemental material was used in the production of the pavers that actually increased the strength of the product?

a. 30 percent fly ash b. 30 percent copper slag

c. 30 percent ground glass d. None of the above

SPONSOR INFORMATION

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Modern and ancient technologies make possible a wide range of paving stone colors, including a virtually unlimited number of custom colors.

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Absorption—This factor is critical to the longevity of a surface. If the paver absorbs high levels of water above 5 percent, freeze thaw durability will be compromised. Here is a comparison of the absorption rate of poured concrete, clay pavers, and concrete pavers:

Poured Concrete: 2,000 to 5,500 psi, 15 percent + absorption

Clay pavers: 8,000 to 10,000 psi, 6 to 8 percent absorption

Concrete pavers: 8,500 to 15,000 psi, 4 percent to 5 percent absorption

Excellent dimensional control is also critical for ease of installation, with a height variation between stones ideally limited to +/- 1/8”.

And of course, there must be pleasing aesthetics, which includes color and surface texture.

Standards

For an architect, landscape architect, or engineer specifying paving stones, awareness of durability and strength is supremely important.

CSI Division 32

Paving stones are covered in Construction Specifications Institute (CSI) Division 32–Exterior Improvements. Here are the specifics:

• 32 14 00–Unit Paving

• 32 14 13–Precast Concrete Unit Paving.

• 32 14 13.13–Interlocking Precast Concrete Unit Paving.

• 32 14 13.16–Precast Concrete Unit Paving Slabs

• 32 14 13.19–Porous Precast Concrete Unit Paving.

• 32 14 16–Brick Unit Paving.

• 32 14 23–Asphalt Unit Paving.

• 32 14 26–Wood Paving.

• 32 14 29–Recycled-Rubber Paving.

• 32 14 40–Stone Paving.

• 32 14 43–Porous Unit Paving.

ASTM C936

Paving stones are also covered under ASTM International C936. Standard Specification for Solid Concrete Interlocking Paving Units is specific to interlocking paving units and the specifications they need to conform to.

faded. However, on a face mix product there is no large aggregate to be exposed so even after many years of wear, the impression of color will be maintained.

Although face mix technology is commonly used for drycast products, it can also be utilized in a wetcast product, ensuring a particularly long-lasting, durable finish.

Standards and Specifications

Durability is the most important factor for pavers. Several factors contribute to a quality paver product.

High compressive strength—A quality paver must have high compressive strength combined with high density and low water absorption to have good freeze thaw durability.

Concrete Density—Though the numbers may change, the chart above illustrates the general relationship between concrete density, compressive strength, and absorption percentage. Generally, higher densities increase the compressive strength and lower the water absorption rate, creating a longer-lasting paver. When the compressive strength is roughly 10,400 psi (blue line), the absorption rate is just over 4 percent (red line).

How Pavers Are Manufactured

There are two types of manufacturing processes for pavers: Drycast and wetcast.

Drycast products have less water in their mix design compared to wetcast products. The drycast mix is put into rigid steel molds, vibrated, compacted, and then cured in kilns.

Drycast products are available with many finishes:

• Standard finish

• Tumbled finish.

• Smooth finish.

• Brushed finish.

• Exposed aggregate finish.

Wetcast products, on the other hand, are poured into flexible polyurethane molds, allowing manufacturers to create more realistic looking products that resemble stone or old brick. Wetcast products are available in a wide variety of styles.

Face Mix Technology

Face mix products are made with a top layer of specialized concrete mix representing about 12 percent of the total depth of the product. This layer—made up of either normal fine aggregates or a blend of high-quality minerals and aggregates—has a higher cement content and reduced water absorption. Larger aggregates are used in the base mix to give the paver high-strength. Typically used in drycast products, face mix technology results in a more durable product with long-lasting color.

The aggregates that are used in the surface of the face mix product are much smaller than the aggregates in the traditional stone that is not made with face mix technology. With a traditional product, over time, the concrete surface slowly wears, exposing larger aggregate which eventually makes the paver color appear

Paver manufacturing is precisely controlled for maximum quality, uniformity and durability.

This chart shows the general relationship between concrete density, compressive strength and absorption.

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protection are available and are integrally manufactured in the paver creating a paver that repel dirt, inhibit the growth of algae and moss, reduce chewing gum adherence, and enhance the color on the surface, much like a sealer would. No matter how dirty the pavers get, soap and water power washing can restore them to their original state of cleanliness.

In addition to the integral advanced finishing processes previously mentioned, post-production processing is also available from many manufacturers. Grinding, shot blasting and polishing of standard pavers or face mix pavers can be used to further customize surface textures and the overall look of the end product.

CASE STUDY: MARY BARTELME PARK

In this unique Chicago park, three strong, diagonal paths intersect, creating a fountain plaza zone, children's play area, dog park and open lawn area.

Five large stainless steel structures appear twisted, set in a field of brilliant white permeable pavers. This sculpture-like interactive misting water feature is the park’s signature element. The newest

An advanced smooth finish uses face mix technology, with finer aggregates on the surface. The surface appears smooth, with a tight finish that will wear extremely well. Generally available in a wide range of stock products, this finish can also be customized to create the desired paver color and style.

Washed products, which offer a striking visual effect, are made up of granites and quartz aggregates. These aggregates are introduced into the face mix design and excess concrete is washed off the surface to further expose these durable minerals. The resulting surface provides long-term wear and structural performance. As this product ages in its installation, the aesthetic further improves.

A washed finish is ideal for a myriad of applications, including driveways, walkways, offices, commercial retail plazas, and institutions.

Brushed paving stones offer an attractive, detailed look and are made with angular granite in the face mix which, when brushed, creates irregular lines etched across each paver. Available by select manufacturers in a variety of dimensionally compatible units, this paving stone system features the ability to create an almost unlimited variety of geometric and random pattern designs.

In addition to altering the final texture, techniques have been developed to create unique finishes, such as the random dispersion of color and aggregates on the paver surface. This type of finish can be customized to create a paver for any design vision. This finish can be combined with an easy-to-clean integral sealing process (as part of the manufacturing process) that allows for easy cleanup before stains set in. This feature eliminates the added step of applying a protective sealant further reducing maintenance costs.

For some applications, stain-resistant pavers will be most practical. Various levels of stain

ASTM C936 references include:

• C140 Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units (specification related to absorption and compressive strength)

• C1645 Standard Test Method for Freeze-thaw and De-icing Salt Durability of Solid Concrete Interlocking Paving Units (specification pertaining to freeze-thaw durability)

• C418 Standard Test Method for Abrasion Resistance of Concrete by Sandblasting (specification related to abrasion and durability).

ASTM Standard C140 calls for:

• 8,000 psi average.

• 7,200 psi minimum unit.

• 5 percent absorption average (ASTM only).

• 7 percent absorption maximum (ASTM only).

• Height tolerance less than +/- 1/8”.

Paver Finished

Most manufacturers offer a number of different textures in standard finishes. The variety of finishes offered, in combination with color options, makes for an extensive palette. Standard finishes include standard smooth, tumbled finishes, dimpled and weathered finishes, split and weathered finishes, and flagstone finishes.

Advanced Finishes

While the standard selection offered by most manufacturers is often enough to satisfy design requirements, sometimes a designer needs to create a distinctive look that can only be achieved with an advanced finish solution.

Different aggregates and technologies can be added to face mix products to create different surface effects.

Many factors are considered when choosing the finish for a project—the visual appeal, skid resistance, and the color, or pattern of colors, used.

PAVERS THAT CLEAN THEMSELVES

Concrete produced with photocatalytic cement literally cleans itself. Integrally bonded coatings, made with titanium dioxide, are added during the production of pavers or concrete to allow the surface to clean itself using sunlight and rain, which is particularly useful in commercial settings. This is available by custom order only.

Lab test: Concrete produced with photocatalytic cement on the left, and ordinary cement on the right, was exposed to artificial light over a 24-hour period. At the conclusion of the test, the dirt and discoloration (pink color) is gone from the concrete produced with photocatalytic cement.

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Laying Patterns

Paver patterns can be used to divide large spaces or influence vehicular/pedestrian traffic. Simple and repeated patterns can have a stunning effect. Using a repeating pattern with a decorative element adds visual interest. Create any design vision by mixing or rotating patterns.

The laying pattern is important from a design aspect, but it is also very significant in terms of “lock-up” adding strength to the paver’s performance. Laying patterns are chosen by considering the traffic loads (pedestrian or vehicular) of the application, however, Stacked Bond offers the least added strength. Running Bond and Basket Weave offer more strength due to the staggered joints. Herringbone has the best lock-up, resisting rotational forces, such those produced by tires at a roadway intersection.

Technical Assistance

To facilitate the design process, it is best practice to work with a manufacturer who offers technical assistance. Connecting with suppliers from the early stages of your vision will eliminate unnecessary compromises further into the project. They will help you to work with the standard options for smaller projects and create realistic, on budget, custom options on larger projects. In the end you and your customer will benefit from the collaboration. Some manufacturers also have a full SketchUp library of their products, the ability to provide 3-D design, CAD patterns and additional software to aid in the planning process

CASE STUDY: NAVY PIER

Navy Pier is one of the most popular attractions in the Midwest. When the 1990's design was in need of an overhaul, James Corner Field Operations won the international competition to create an updated year-round urban destination for Chicagoans and tourists alike.

Working closely with a manufacturer, three new plank sizes were created: 3"x6"x4", 3"x12"x4"

Paver Shapes

An extensive line of product shapes is generally available from manufacturers, although all shapes may not be available in all finishes. Common shapes include square, rectangle (plank), L-shape, octagon, etc. They are available in a variety of sizes, which can be combined to create visual interest. Typically, units range in size from 4"x4" to large slabs up to 36"x36".

Heavy-duty pavers designed for rapid mechanized installation are also available. Providing a stronger, more stable pavement surface, these pavers feature an “L” interlocking shape that offers superior resistance to tipping and twisting. Heavy-duty paving stones can withstand the heaviest vehicular loads.

Custom orders are available from some manufacturers to accommodate unique design requirements. Plank pavers are often specified to create a long, linear design element that is growing in popularity. Plank pavers may range from 3"x12" to 12"x36".

Along with custom shapes, most manufacturers offer a variety of standard colors as well as custom colors and custom finishes.

CASE STUDY: CUSTOM COLOR: BROWN UNIVERSITY

When a new master plan was being developed to connect the downtown campus of Brown University in Providence, Rhode Island, to the nearby Jewelry District, design inspiration was needed. A New York City-based architecture firm called “!melk” drew inspiration from the past life of the area, as a seaport with old stone roads. The architecture firm worked with the paving stone manufacturer to create custom colors in the paver style that would fulfill their vision for the space.

The sidewalks and the new public square now energize the former industrial area, creating a new urban destination in the center of the Jewelry District.

technology in architectural paving made it possible to create the brilliant white permeable pavers made with smog-eating concrete that are both pollution-reducing and self-cleaning.

When exposed to sunlight, the paver material destroys several atmospheric pollutants common to urban areas that can dull and streak conventional concrete surfaces over time. While the photocatalytic properties of the pavers clean the air on a clear day, on a rainy day their permeability allows rainwater to flow through the joints, cleaning the paver and filtering water naturally back into the ground, rather than being discharged into local sewers.

This savvy specification by Site Design Group in Chicago will ensure the pavers retain their brilliant white aesthetic far into the future.

Design Considerations

For an architect, landscape architect, or engineer, it is important to understand the application requirements in order to select the paving solution best suited to the project. Here are some considerations:

• Is the paved area subjected to vehicular or pedestrian traffic?

• Are heavy-duty or light-duty pavers required?

• Do pavers need to be permeable or non-permeable?

• Will the pavers be installed on grade or on a roof deck?

• What is the look and feel of the project?

• Is it classic or contemporary?

• Will style influence the architecture?

• Will this paver be integrated with other materials?

• Which colors contrast with, complement, or highlight the space best?

• Which size or sizes fits the space appropriately?

• What is the desired finish or texture?

• What is the aspect ratio?

• What is the laying pattern?

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CASE STUDY: UNITED NATIONS SECRETARIAT

An example is the United Nations Secretariat building in Manhattan, where the building’s 60-year-old single-pane glass window panels were replaced with double-glazed panes as part of the project’s green mandate. The window glass was ground into a pozzolan and used to replace 20 percent of the Portland cement in new permeable pavers that are now installed in front of the UN building. According to the U.S. Environmental Protection Agency, approximately 12 million tons of glass are brought to landfills each year. Using ground glass in architectural materials diverts glass from landfills and helps transform what was once a waste product into a resource that reduces a project’s carbon footprint.

CONCLUSION

Paving stones have been an important part of architecture and landscape architecture throughout human history. Technological advances have made pavers stronger and more durable than ever, and created a virtually unlimited combination of sizes, shapes, colors, textures, and applications. However, they are not all created equally. Beyond the all-important aesthetic, the informed architect, landscape architect, or engineer will understand the manufacturing processes and standards that deliver the best product. As countless projects have shown, working with a manufacturer’s technical and design team can result in a superior project that will enhance a streetscape, pier scape, park or public area far into the future. ◾

ENDNOTESi. http://www.cement.org/cement-concrete-basics/working-with-concrete/air-entrained-concrete

ii. https://navypier.com/sustainable-navy-pier/

• Building Product Disclosure and Optimization—Material Ingredient Reporting—Material Ingredient Optimization: 1 point

• Building Product Disclosure and Optimization—Environmental Product Declaration: 1 point

Heat Island Reduction—Non-Roof: LEED v4

Paving materials with a three-year aged solar reflectance (SR) value of at least 0.28 will qualify. If three-year aged value information is not available, use materials with an initial SR of at least 0.33 at installation OR use an open grid pavement at least 50 percent pervious: 2 points (except Healthcare subtract 1 point). See LEED v4 for more specific site calculations.

Solar Reflectance

Solar Reflectance Index (SRI) is a criterion used by USGBC that measures values of sunlight and radiation bouncing from built surfaces. It is used to measure urban heat island effects in city centers. Dark pavement absorbs heat during the day and then releases it at night. This process causes urban centers to stay warmer all the time which contributes to air pollution and increased energy consumption. Careful selection of materials and colors can help reduce urban heat island effects.

Recycled Content: Supplementary Cementitious Materials (SCM)

Concrete is a mixture of sand, coarse aggregate, water and the principal cementitious material which is Portland cement. Most concrete recipes also contain supplementary cementitious material (SCM) admixtures. These can be by-products from other processes or natural materials that may, or may not, have been further processed for use in concrete. These admixtures can contribute toward achieving the cumulative minimum recycled content criteria for Leadership Extraction Practices.

(one permeable and one non-permeable), and 6"x24"x6". The unique design was achieved using four custom colors. The distinct blend of aggregates allowed for subtle color changes that will uniquely withstand this rigorous environment.

The project includes many sustainable features inspired by the Sustainable Sites Initiative of the Green Building Certification Institute. To increase the project’s sustainability, 30 percent copper slag was used in the production of the pavers which also increased the strength of the product. The re-imagination of Navy Pier has created a contemporary “pier scape” with engaging social spaces that are the center of activity and culture.

Potential for LEED v4 Credits

Paving stones can help achieve a U.S. Green Building Council’s LEED certification. Here are some potential points.

Rainwater Management: LEED v4

Up to 3 points can be achieved for retaining rainwater onsite based on the percentile kept, as follows:

• 85 percent (zero lot line projects only): 3 points

• 95 percent: 2 points

• 98 percent: 3 points (all except Healthcare—subtract one point).

See LEED v4 for more specific project/ site details.

Materials and Resources: LEED V4

• Building Product Disclosure and Optimization—Sourcing of Raw Materials—Sourcing of Raw Materials and Extraction: 1 point

• Building Product Disclosure and Optimization—Sourcing of Raw Materials—Leadership Extraction Practices: 1 point

• Building Product Disclosure and Optimization—Material Ingredient Reporting- Material Ingredient Reporting 1 point