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Shed the Shovel, Halt the Salt

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

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



HYDRONIC OR ELECTRIC?

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

THE INSULATION FACTOR

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

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

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



PERFORMANCE PLANNING

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

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

LAYOUT AND CONSTRUCTION

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

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

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

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

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

ts12INSTRUCTION AND GUIDANCE

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

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New Product Spotlight

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

provenceslabsPROVENCE SLABS

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

ADJUSTABLE HEIGHT PEDESTALS

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

starlitesSOLAR-POWERED LED STARLITES

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

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The Best of the Best

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

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

 

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

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

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

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

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

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

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

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

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

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What If?

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

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

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

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

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

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

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Geosynthetics Part 1: Geotextiles

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

Table_1

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

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

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

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

Table_2

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

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And the Survey Says…

Thanks to continued construction growth, industry survey results from the Interlocking Concrete Pavement Institute (ICPI) indicate a repeat of last year’s double-digit growth. New home construction, acceleration in sales of existing homes, a rebound in public section construction spending, and an increase in commercial construction all contributed to strong growth last year for U.S. and Canadian segmental concrete pavement. Survey respondents, including 29 companies representing 141 paver-producing machines, report shipments across all segmental concrete pavement categories up 15.4% in the U.S. and 8.9% in Canada compared to 2014 figures.

The Industry Survey encompasses interlocking concrete pavers, permeable interlocking concrete pavers, concrete grid paving units, paving slabs, and related concrete paving products. In the principal category of concrete pavers as defined by ASTM and CSA, U.S. production increased 15.2% year-over-year from 517 million to 595 million square feet, while Canadian output grew 10.6% from 85 million to 94 million square feet. At just over 78% of all sales, the residential market continues to drive segmental concrete pavement. Commercial sales, including municipal and industrial projects, claimed almost 22% of the total 2015 market.

Robust year-over-year sales activity, notes ICPI Chairman and Oldcastle APG Northeast President Matt Lynch, “demonstrates continued demand for segmental concrete pavement systems with versatile design options, low maintenance and environmental benefits. The construction industry is experiencing an economic recovery that supports the expansion of our market share in residential and commercial applications.”

Order the survey report from icpi.org. $20 for ICPI members; $99 for non-members.

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A Higher Degree of Assurance

The American Society for Testing and Materials International (ASTM) recently approved revisions to C936 Standard Specification for Solid Concrete Interlocking Paving Units that include an optional lower temperature for laboratory freeze-thaw durability testing while paver units are immersed in a 3% saline solution. For freeze-thaw durability testing, C936 references C1645 Standard Test Method for Freeze-thaw and De-icing Salt Durability of Solid Concrete Interlocking Paving Units. This test method includes a minimal freezing temperature of -5° C (23° F) though 49 freeze-thaw cycles. Mass lost is measured from the tested paver units and that loss is divided by the total surface area expressed in square meters to determine if the pavers meet the requirements in ASTM C936.

This standard now includes the optional use of -15° C (5° F) as the lowest temperature in C1645. Deciding to use the -15 ° C option is supported by a map identifying geographic cold climate zones for project locations where the specifier might want to use this colder temperature in freeze-thaw durability testing per C1645. The reason for introducing this option is that some areas of the U.S. see colder temperatures than -5° C and use deicing materials. The colder temperature option of -15° C can help provide a higher degree of assurance for winter paver durability to manufacturers and specifiers.

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Resilient Infrastructure

Procrastination seems endemic to human nature. However, there may be some evidence to the contrary. Most of us might recall Superstorm Sandy in October 2012. Millions in New Jersey and New York sure do. Local governments, insurance companies, businesses and homeowners also remember some $80 billion in destruction. And this event wasn’t a hurricane.

The evidence against procrastination appears to be emerging from within the highest levels of government and among business leaders. Katrina and Sandy were catalysts. Leaders are asking how to build better to reduce damage from storms and earthquakes and accelerate recovery. Most of the discussion is on making buildings stronger, i.e., more wind-, flood- and earthquake-resistant. The conversation must soon turn to how to better build things outside buildings such as parking lots, roads, utilities and communication infrastructure.

Even flooding from smaller storms, the ones with no names, are costing millions. While investments in resilient infrastructure solutions are long-term, we are seeing an emerging trend of using permeable interlocking concrete pavement (PICP) as a means to reduce flooding. Such is the case with the Southeast Atlanta Green Infrastructure Initiative that aims to capture seven million gallons under miles of PICP streets. The first six miles are already built. This exemplifies resilient infrastructure where roads also do flood control: They mitigate it rather than contribute to it.

Another little known aspect is resilience from interlocking concrete pavement. That type of segmental pavement isn’t designed to permeate due to sand joints, bedding, and a dense-graded aggregate or stabilized base. There are reports in Canada and Italy on the ability of this system to not crack when inundated, unlike monolithic asphalt or concrete. ICP doesn’t crack when flooded because it has “cracks” in it; joints between the paving units relieve the water pressure as it builds under the pavers. And the surface can be reinstated without requiring deliveries from a ready-mix concrete or asphalt plant. (They might be flooded, too.) Rapid recovery of roads from floods or earthquakes is a prerequisite to building repair.

While lots of beautiful patios are being built, the segmental concrete pavement industry is at the threshold of entirely different conversation and market opportunity. It is poised to more readily establish and institutionalize segmental pavements as part of resilient infrastructure that yields economic, environmental and social benefits to property owners, municipalities and wider society.

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Clearing the Air

Repeated exposure to respirable silica poses long-term health risks, according to medical studies. How much exposure is considered safe? In 1971, OSHA established 250 micrograms per cubic meter of air (µg/m³) per 8-hour workday as the permissible exposure limit (PEL) to respirable silica dust for the construction industry. In March, OSHA published a final rule lowering the PEL to 50 µg/m³ averaged per 8-hour day effective June 23, 2016, with compliance required by June 23, 2017. The construction industry in general has rejected this rule on the basis of technological infeasibility plus the untenable costs related to reducing exposure by 80%.

In an effort to educate contractors, ICPI has approved new language for inclusion in its contractor courses and manuals (see sidebar). Though OSHA might rarely visit residential jobsites, an estimated 75% of all pavers and paver products see use in residential applications. Thus, raising awareness and providing knowledge on jobsite protection are important responsibilities for ICPI. A resource webpage on respirable silica is in the works for the new ICPI.org website. It will include links to research and reports on the issue.

Worker health and safety are universal priorities on which everyone can agree. Workers understand why protecting their eyes, backs, knees, elbows and hands are important because there is a fairly immediate cause and effect if they do not. However, effects from repeated exposure to respirable silica can become manifest over a long period of time. When risks are not immediately apparent, prevention may seem less imperative. That is why knowledge and awareness are so important, as well as safety training. A worker’s lungs need protection too.

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Couldn’t Stand the Weather

Mark Twain said, “Everybody talks about the weather, but nobody does anything about it.”

Global climate change might be altering the implications of Mr. Twain’s saying because we are likely doing something to the climate and maybe something about it. While the causes and effects of climate change receive endless debate in scientific and political spheres, regional-scale rainfall patterns are changing for certain. The result has been wetter weather in some parts of North America, drier in others.

The weather changes have been so dramatic that rainfall statistics defining storm recurrences are seeing realignment. A hypothetical example explains this shift. Say there are 80 years of storm data and some indicates that very occasionally, a city receives five inches rainfall in 24 hours. Some statistics are run and they conclude that the city has 4% probability of that rainfall depth occurring in any given year. So it’s called a 25-year storm. But data gathered over the past two decades now indicate a 10% probability. So that rain event has shifted to a 10-year storm recurrence. The old 10-year storm with maybe three inches of rain is now five inches.

This shift directly affects cities because storm sewers back up and can’t immediately drain the additional water. When that happens, it can end up in someone’s basement. Besides property damage, the city can be liable for damages. Storm sewers originally designed to manage a 10-year storm are now obsolete as confirmed by revised rainfall statistics.

Hurricanes plague the East, tornadoes the Midwest and South, and earthquakes the West. Because of natural disasters like the earthquakes in Northridge and Loma Prieta, and Hurricanes Katrina, Irene and Sandy, governments at all levels are seeking resilient designs and technologies to resist excessive wind, rain and tectonic plate movements. Resilient infrastructure resists these onslaughts from nature by designs that minimize damage to private property and society’s productivity. As urban infrastructure is rebuilt, resilient technologies and designs are increasingly included.

One city implementing resilient infrastructure is Atlanta, GA. It recently completed the Southeast Atlanta Green Infrastructure Project. Infrastructure renovation involved replacing century-old water lines, storm and sanitary sewers in two neighborhoods. The ‘green’ portion reduced stormwater runoff, a fundamental goal in most GI projects, with permeable interlocking concrete pavement. Atlanta went beyond reducing runoff. It installed around 700,000 sf (65,000 m²) of permeable interlocking concrete pavement with enormous water storage capacity to reduce increasing flood events.

According to Todd Hill, P.E., Atlanta’s Director of Watershed Management, the pavement stores about 7 million gallons. That approaches one million cubic feet of water in over 10 Olympic-sized swimming pools. As an extra bonus, maybe a fourth of that water is infiltrated back into Atlanta’s clay soils. A portion of the $66 million invested will be returned in spared litigation costs, not to mention increased property values and resulting taxes.

In their present state, many urban drainage systems simply can’t stand the weather. In response, resilient urban infrastructure is an intentional public investment goal. As they rebuild, cities and neighborhoods can resist bad weather by providing permeable pavements that control flooding while remaining un-flooded and useable during the worst storms. Atlanta certainly magnifies and affirms the role of permeable interlocking concrete pavement in resilient infrastructure.