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Sciences in Cold and Arid Regions

Intersection-pavement de-icing: comprehensive reviewand the state of the practice

ZhaoHui Joey Yang *

University of Alaska Anchorage, Anchorage, Alaska, USA

*Correspondence to: Dr. ZhaoHui Joey Yang, Department of Civil Engineering, University of Alaska Anchorage, 3211Providence Drive, Anchorage, AK 99608, USA. E-mail: [email protected]

Received: December 7, 2018 Accepted: December 29, 2018

ABSTRACT

Winter maintenance operations are crucial for pedestrian and motorist safety and public mobility on urban streets and high‐ways in cold regions, especially during winter storms. This study provides a comprehensive literature review of existingdeicing technologies, with emphasis on electrical resistance-heating deicing technologies for possible applications in areaswith concentrated traffic, such as street intersections and crosswalks. A thorough review of existing and emerging deicingtechnology for snow/ice melting was conducted. The performance of various deicing methods was evaluated and the in‐stallation and operation cost of the electrical resistance-heating methods compared. Finally, current state of the practice ofintersection/crosswalk winter maintenance was surveyed among state departments of transportation in North America. Theintersection / crosswalk winter maintenance procedure adopted by the State of Alaska Department of Transportation andPublic Facilities was described, and the annual winter maintenance and operation cost per intersection was estimated. Itwas found that the annual energy cost of an electrical resistance-heating method such as the carbon-fiber-tape deicing tech‐nology is about the same as the average annual maintenance and operation cost of current practice. In addition, an automat‐ic electrical resistance-heating deicing system will bring benefits such as minimized delay time and improved safety forpedestrian and vehicular traffic in an urban application.Keywords: deicing technology; intersection; crosswalk; electric resistance heating; state of the practice

1 Introduction

Winter maintenance operations are crucial forpedestrian and motorist safety and public mobilityon urban streets and highways in cold regions, es‐pecially during winter storms. Hansen et al. (2014)predicted global warming will cause warmer andwetter winters and more icing events in the arctic,which would likely result in an increased burdenof winter maintenance and operation for the broadcold regions, including Alaska. Shi et al. (2014)conducted a review of highway winter mainte‐nance operations at extremely low temperatures.Study on urban crosswalk and street-intersectionmaintenance in winter is very limited. For exam‐

ple, Anastasio (2016) reported issues with cross‐walks and sidewalks in New York City as being apersistent problem; as one comment reads, "This isa truly disgusting problem—one that makes NewYork City look like a third-world country wheneverit snows".

2 Review of existing and emerging deicingmethods

Traditional deicing has been accomplished by me‐chanical, chemical, and thermal methods. This sectionprovide a comprehensive review of these methods,with the emphasis on emerging new technologies.

Volume 11, Issue 1, February, 2019

Citation: Joey Yang ZH,2019. Intersection-pavement de-icing: comprehensive review and the state of the practice. Sciences in Cold and AridRegions, 11(1): 0001−0012. DOI: 10.3724/SP.J.1226.2019.00001.

ZhaoHui Joey Yang., 2019 / Sciences in Cold and Arid Regions, 11(1): 0001-0012

2.1 Mechanical and chemical deicing methods

In mechanical ice removal, large equipment andvehicles are used to plow and scrape snow and icefrom the pavement. The expense of employing equip‐ment operators is a major factor contributing to thehigh cost of mechanical deicing. Removing compact‐ed snow and ice with shovels or snow blowers is notalways an easy task due to the strong bond betweenice and pavement. Chemical treatment helps break thebond by melting the ice (Henderson, 1963). Deicingof roads has traditionally been done by a combinationof mechanical and chemical methods. Salt, oftenmixed with sand and gravel, is spread on slick roadsby snowplows or dump trucks; and the ice loosenedby salting is plowed from roadways. Chloride-basedsalts including sodium chloride, magnesium chloride,and calcium chloride are the most common chemicalsused for ice and snow control because they are inex‐pensive and effective (Menzies, 1992). These salts,however, can corrode vehicles and reinforcing steel inthe concrete and pollute the environment (Jones et al.,1992; Williams et al., 2000; Shi et al., 2009b).

To reduce damage to concrete structures, somecomplex chemical solutions have been applied (Zene‐witz, 1977; Kuemmel, 1994). In recent years, acetate-based deicers such as potassium acetate, calcium-mag‐nesium acetate, or calcium-magnesium-potassium ace‐tate have been given preference as deicers, as theytend to decompose faster and do not contain chloride.However, acetates pose a risk to the durability of con‐crete and asphalt pavements and are costly (Hassan etal., 2002; Fay et al., 2008; Pan et al., 2008; Shi et al.,2009a, 2011). Calcium-magnesium acetate (CMA) isnoncorrosive to steel reinforcement; but it requireslarge trucks for transport, and is less effective thansalts, that is, it performs more slowly than salts; andits application temperature range is smaller (Slick,1988; Fay et al., 2008).

More recently, organic compounds generated asby-products of agricultural operations, such as the re‐fining of sugar beets or the distilling process that pro‐duces ethanol, have been applied for ice and snowcontrol. When mixed with other chlorides, such asmagnesium chloride, these organic compounds havelonger residual effects when spread on roadways. Ad‐ditionally, mixing common rock salt with some of theorganic compounds and magnesium chloride resultsin spreadable materials that are effective at coldertemperatures (−34 °C) and require lower overall ratesof spreading per unit area (http://www.magicsalt. info /Magic%20Salt.htm). Nevertheless, organic compoundsmixed with chloride can harm the environment and arecostly. It is worth mentioning that urea, a soluble nitro‐gen compound, is commonly used for airport-pave‐ment deicing because of its low corrosiveness.

2.2 Thermal methods

A number of alternative thermal methods havebeen developed to control snow and ice formation onramps and bridge decks. Yehia and Tuan (1999) haveprovided a comprehensive literature survey of roaddeicing / anti-icing methods used over the past 30years. The thermal methods are categorized into twogroups, i. e., internal and external, depending on howthe heating elements are installed.

2.2.1 Pavement deicing with internal heatingelements

2.2.1.1 Ground-source heat pipe

Initial experimental testing of ground heat pipeswas conducted in 1970 by the Dynatherm Corporationat the Federal Highway Administration (FHWA) Fair‐banks Highway Research Station (Bienert et al.,1974). In 1975, Long and Baldwin (1980) conductedexperiments using a heating system that had 1, 213heat pipes extending 18 m into the ground on a high‐way ramp in Oak Hill, West Virginia. This systemwas successfully used to prevent snow and ice accu‐mulation, except when drifting snow occurred. Thefar-field ground temperature in this case averagedaround 13 °C. A gravity-operated heating pipe systemthat used a manifold ground-heat exchanger was im‐plemented for a bridge deck in 1981 in Laramie, Wyo‐ming (Lee et al., 1984). This system used field-assem‐bled heat pipes to transfer energy from 30-m verticalevaporators in the ground. The results show that theheated surface was approximately 2 − 14 ° C warmerthan the unheated portion of the bridge during opera‐tion, which was sufficient to prevent preferentialfreezing of the bridge-deck surface and providedsome snow-melting function. The main disadvantagewas that the assembly of the heat pipes was complicat‐ed, and 40% of the total cost was for drilling andgrouting the pipes. Zenewitz (1977) described anotherexample of using a geothermal source in snow and icecontrol in Oregon. In this case, a hot-water heatingsystem with copper pipes containing antifreeze heatedby a geothermal source was installed in reinforced-concrete pavement approximately 122 m long on thedeck of a canal bridge to keep the deck free of ice.

2.2.1.2 Hot-fluid heat pipe

In 1993, rubber hoses containing antifreeze fluidheated by a gas boiler were embedded in a concrete pe‐destrian overpass in Lincoln, Nebraska (Cress, 1995).The installation cost of the system was $161/m2 (here‐after all such figures refer to U.S. dollars if not other‐wise specified), and the operating cost per storm was

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about $250 to melt snow 76-mm thick. A heating sys‐tem that consisted of steel pipes and carried Freonheated to 149 ° C by a propane-fired boiler was in‐stalled in the Buffalo River Bridge at Amherst, Virgin‐ia, in 1996 (ASCE, 1998). This system used the latentheat released during condensation of the evaporatedFreon for deicing, and the estimated annual operatingcost was approximately $1,000. Similar hydronic sys‐tems have been installed in Ohio, Oregon, Pennsylva‐nia, South Dakota, and Texas. Nowadays, a hydronicsystem consisting of plastic pipes embedded in Port‐land cement concrete (PCC) pavement and glycolheated by gas - or oil-burning boilers is commonlyused in Anchorage, Alaska (e.g., Downtown Anchor‐age intersections and sidewalks) and other cold re‐gions for deicing and anti-icing purposes (Wheeler etal., 2012). Heating fluid leakage in the supply and re‐turn lines is a common issue observed in a hydronicsystem. In addition, such system requires a fairlylarge space to install a boiler.

2.2.1.3 Solar-source heat pipe

Zhao et al. (2010) reported a deicing system in Ja‐pan that uses solar energy. The solar energy is collect‐ed from the road surface by a water pump when thetemperature is high in summer and stored under‐ground by horizontal and vertical pipes embedded inthe pavement. In winter, the water pump brings warmwater through the pipes to the pavement for deicing.Only the water pump consumes electric energy in thissystem. The energy used for deicing comes from solarradiation and a geothermal heat source.

Wu et al. (2009) and Chen et al. (2011a, b) de‐scribed a similar system, called an asphalt solar col‐lector, based on thermally conductive asphalt con‐crete (AC). The idea was to add thermally conduc‐tive fillers such as graphite powders (Wu et al.,2005) to an asphalt-concrete mixture to improve itsthermal conductivity, which facilitates harvestingduring summer of the solar-radiation energy throughwater circulating in copper tubes embedded in the as‐phalt. The heated water is stored underground for ice/snow melting in winter. The circulating fluid can alsohelp cool the asphalt concrete, hence reducing its riskof permanent deformation due to high temperature insummer months.

A system such as this is essentially a hydronic sys‐tem that is used to harvest solar energy in summer andmelt snow/ice in winter. This type of system utilizes re‐newable energy and is environmentally friendly. How‐ever, the melting process is quite slow if not coupledwith another energy source such as geothermal heat, asthe temperature of the stored water is not very high. Italso inherits all the disadvantages of a hydronic sys‐tem, such as high maintenance cost, vulnerability to

cracks / deformation in the pavement, the requirementof a large underground water storage, etc..

2.2.1.4 Electric heating cable

Electric heating cables were installed on the ap‐proach and the deck of a highway drawbridge to re‐move snow/ice in Newark, New Jersey, in 1961 (Hen‐derson, 1963). Power density was 378 W / m2 for thebridge deck and 430 W/m2 for the road pavement. Theheat generated by electric current was sufficient tomelt a layer of 25-mm-thick snow per hour. However,the installation was later abandoned because the elec‐tric cables pulled out of the asphalt-concrete (AC)overlay due to the traffic load on the pavement. A sim‐ilar system was installed in two ramps and a bridgedeck in Teterboro, New Jersey, in 1964 (Zenewitz,1977). This system was reported to work well for de‐icing. The power density was about 375 W / m2, andthe annual operating cost was approximately $5 / m2.Installation of similar systems can be found in Nebras‐ka, Ohio, Oregon, Pennsylvania, South Dakota, Tex‐as, and West Virginia.

2.2.1.5 Carbon-fiber heating wire

Carbon-fiber wires have been used as a heating el‐ement for deicing. Zhao et al. (2010, 2011) reported afield experiment in which carbon-fiber heating wireswere embedded in a PCC slab for a pavement-deicingstudy. The slab of 1m×2m×0.25m (L×W×H) was castusing C40 PCC concrete. Carbon-fiber heating wireswere wound around the reinforcing mesh longitudinal‐ly, and the interval between the reinforcing bars was100 mm. The power density was in the range of 500−800 W / m2, and the annual operating cost was in therange of $0.375−2.8/m2 per storm. Xiang (2014) wasgranted a patent on using carbon heating wires for de‐icing of AC sidewalks. The carbon-fiber heating wiresare embedded in the AC layer to generate heat forsnow/ice melting. No field studies were found for ACpavement. Lai et al. (2015) and Liu et al. (2015) re‐ported a larger-scale field experiment to study thesnow-melting performance of carbon-fiber heatingwires. In this experiment, PCC slabs of 4.6m×4.6m×0.4m were built with a carbon-fiber grille (or mesh)assembled with reinforcing steel mesh and 48k car‐bon-fiber heating wires and buried 5 cm below thepavement surface. The heating wires were spaced at10 cm, and the power density was 350 W/m2.

This method has the advantage of easy installa‐tion, as it can be combined with the reinforcing mesh.The key issue is that the heat power is not uniformlydistributed within the pavement, creating a tempera‐ture gradient and thermal stress, which could lead tothermal cracking. In addition, the effects of the insu‐

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lated-carbon heating wire wound around reinforcingsteel bars on the steel − PCC pavement bondage andstructural function of the pavement are not clear. If in‐stalled by itself in the AC pavement, the heating wirescould be pulled out of the AC overlay due to the traf‐fic load on the pavement, as happened with metalheating wires (Henderson, 1963).

2.2.1.6 Magnetic snowmelt device

Zhang et al. (2011) described a quite interestingsnowmelt method that utilizes a magnetic heating de‐vice embedded in pavement for highway-pavementdeicing. The magnetic heating device takes advantageof the so-called magneto-caloric effect, which causestemperature change of certain ferromagnetic or ferri‐magnetic material when it is exposed to a changingmagnetic field. This method was represented as beingfast, easy to operate, and energy efficient. The fieldexperiment indicated the segment with the heating de‐vice melted the snow much sooner than the segmentswithout a snow-melting device. However, the snowthat fell the first day did not completely melt until thethird day.

2.2.1.7 Carbon-nanofiber polymer sheet (CNFP)and graphite-PET sheet

Li et al. (2013) reported a novel deicing systemconsisting of a carbon-nanofiber polymer thermalsource and multiwall-carbon-nanotube (MWCNT) ce‐ment-based thermal conductive composite. This sys‐tem utilized a thermally insulated substrate made ofan Aluminum Nitride (AIN) - ceramic wafer to im‐prove the energy efficiency. The power density usedin the limited-scale field experiment was 600 W/m2 to1,800 W/m2, and the snow melting performance wasvery impressive. However the heating source, i.e., car‐bon-nanofiber polymer, is very expensive and haspoor mechanical properties. This system is quite com‐plex and still far from large-scale field application.Recently, Zhang et al. (2016) developed a thin, flexi‐ble, sandwiched-graphite-laminate with Polyester In‐sert (PET) heating element for deicing. A waterproofmembrane was used to protect the heating element. Aheating element of this type has improved mechanicalproperties. However, its long-term durability remainsto be verified by field application.

2.2.1.8 Electrically conductive Portland cementconcrete

Conventional PCC is not electrically conductive. Inelectrically conductive concrete, a certain amount ofelectronically conductive components replaces a cer‐tain portion of the fine and coarse aggregates to attain

stable and relatively high electrical conductivity. Elec‐trically conductive (EC) concrete is a patented technol‐ogy developed at the National Research Council ofCanada (Xie et al., 1995, U. S. Patent No. 5447564;Pye et al., 2003, U.S. Patent No. 6503318 B2).

EC concrete can be classified into two types: fiber-reinforced EC concrete with higher mechanicalstrength and lower conductivity (100 Ω⋅cm), and ag‐gregate-containing EC concrete with lower compres‐sive strength and higher conductivity (10 to 30 Ω⋅cm)(Xie and Beaudoin, 1995; Xie et al., 1996). EC-con‐crete cement-based composites with both high con‐ductivity and mechanical strength were applied tomelt snow / ice in the laboratory and in the field (Xieand Beaudoin, 1995; Xie et al., 1996). A composite-concrete slab consisting of a base ECC layer and aPCC overlay was used to melt snow. The overlay hada w/c ratio of 0.325 and a mix design of cement/fineaggregate /coarse aggregate of 1:2:2. The dimensionsof the experiment slab were 0.24m×0.31m×0.05m (L×W×H). For typical applications, voltages were alwaysless than 15 V; and the primary current through theECC layer was less than 30 A (Pye et al., 2003). Thecurrent through the overlay was extremely small(0.012 mA). Alternately, the thickness of the overlaycan be increased to reduce the current through theoverlay. However, the energy efficiency for snowmelting would be compromised with a very thickoverlay (Tumidajski et al., 2003).

Yehia and Tuan (1998) developed an EC-concretemix with steel fibers and steel shavings specificallyfor bridge-deck deicing. Over 50 trial mixes of ECconcrete were prepared using steel fibers and steelshavings. The heat generated by the EC concrete wasstable and uniform, using 15%−20% conductive mate‐rial (i.e., steel fibers and shavings) by volume. Experi‐ments using small-scale slabs showed that an averagepower density of approximately 520 W/m2 was gener‐ated by the EC concrete; and it took 30 min to raisethe slab temperature from −1.1 °C to 15.6 °C (Yehiaand Tuan, 1998, 1999). In 1998, Yehia and Tuan con‐ducted several groups of laboratory deicing and anti-icing experiments. They found that steel shavings of20% per volume and steel fibers of 1.5% per volumewere the upper bound; a higher amount of shavings orsteel fibers results in poor workability and surface fin‐ishability (Yehia and Tuan, 2000; Yehia et al., 2000).

Two 9-cm-thick EC-concrete overlays, 2m×2m and1.2m × 3.6m, were cast on top of 15-cm-thick conven‐tional concrete slabs for conducting deicing experimentsin the natural environment. Deicing and anti-icing exper‐iments were conducted in five snowstorms in 1998. Anaverage power density of about 590 W/m2 was generat‐ed by the EC-concrete overlays to prevent snow and iceaccumulation (Yehia and Tuan, 2000). The average unit-energy cost was about $0.8/m2 for each storm, with an

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assumed electricity cost of $0.08/(kW⋅h) (Yehia and Tu‐an, 2000; Tuan, 2004).

In spring 2001, carbon products were used to re‐place the steel shavings in the EC concrete. Based onthe findings from laboratory tests, the EC concretewith carbon products was applied on a bridge deck atRoca, Nebraska (referred to as the Roca Spur Bridge)for deicing (Tuan and Yehia, 2004). A 36-m-long and8.5-m-wide EC-concrete inlay was built and instru‐mented with temperature and current sensors for heat‐ing-performance monitoring during winter storms.The inlay was divided into 52 isolated slabs of 1.2m×4.1m (Tuan, 2008). Three-phase 208-V, 600-A ACpower was supplied to the EC-concrete slabs for deic‐ing. All mixes contained 1.5% steel fibers and 25%carbon products per volume of EC concrete. Opera‐tion of this deicing system in four winter seasons hasshown that power density was in the range of 203 −431 W / m2; and the unit-energy cost was about $250per snowstorm, or about $0.8/m2 (Tuan, 2008).

Heymsfield et al. (2014) reported a Federal Avia‐tion Administration (FAA) - sponsored pilot study us‐ing an EC-concrete-overlay panel and renewable ener‐gy to develop an anti-icing airfield runway. Ten over‐lay panels of 1.22m×3.05m were constructed with ECconcrete in Arkansas to conduct anti-icing tests withphotovoltaic panels and a battery storage system. Itwas concluded that the energy warranted to sustainthe thermal mass of ten large overlay panels at anabove-freezing temperature is difficult to attain by asolar-based renewable-energy system. The authors fur‐ther proposed to attach heat wires, such as copperwires, to concrete pavement surface and power it bysolar energy to develop an anti-icing system. Howev‐er, practical issues of installing and protecting wiresunder vehicular loads exist.

In summary, the EC-concrete-overlay approachshows promise for deicing and anti-icing application.However, it has not been widely used for deicing /snow melting to date due to issues such as high resis‐tivity, low electrothermal efficiency, and steel-fibercorrosion. In addition, practical issues such as thermal(transverse) and longitudinal cracking, deteriorationof electrical properties, and rutting of the overlay willsignificantly impact the reliability and life-span costof the EC-concrete-overlay method.

2.2.1.9 Electrically conductive asphalt concrete

EC-asphalt concrete (AC) can be used to generateheat and hence provide another method for snow melt‐ing and deicing. Pan et al. (2015) provided a review onthe structure design, performance, and engineering ap‐plications of EC AC. Conventional AC contains coarseand fine aggregates, asphalt binder, and mineral filler.It behaves as an electrical insulator with a resistivity

value between 108 and 1012 Ω⋅m. EC materials have tobe added to an AC mixture to make it conductive; andthese materials include: (1) powders, including graph‐ite, carbon black, and aluminum chips (Wen andChung, 2004; Huang et al., 2009); (2) fibers, includingcarbon fiber, steel fiber, steel wool, and carbon nanofi‐ber (García et al., 2009); and (3) solid particles, suchas steel slag, substituting for the coarse and fine aggre‐gates (Ahmedzade and Sengoz, 2009).

Derwin et al. (2003) reported a field applicationof an EC-AC pavement system (with the commercialname Snowfree®) for snow melting at O'Hare Interna‐tional Airport. The Snowfree® EC-AC pavement con‐sists a blend of graphite and asphalt; copper buses, al‐ternating between live and ground, were placed at in‐tervals of 4.9 m and cast within a 5-cm layer of thegraphite-infused AC. In collaboration with the FederalAviation Administration (FAA), this type of systemwas installed on 697 m2 of a taxiway in November1994. The installation costs were $161.5/m2 (no infla‐tion adjustment). During the three and a half years ofoperation, the EC-AC system consistently produced apower density of 484 W/m2 while in operation and sat‐isfactorily cleared snow and ice. Throughout the eval‐uation period, 200,000 aircrafts travelled on the graph‐ite-infused AC; and no significant cracking was ob‐served. However, the FAA deemed that the operatingcost was high, and no other airport has utilized thistechnology (Lopez, 2012).

However, the addition of EC materials would re‐quire a substantial change of the mixing procedureand would also impact the mechanical performance ofthe pavement. Furthermore, asphalt as a typical visco‐elastic material is extremely sensitive to temperature;thermal cracking will deteriorate the conductive net‐work, hence resulting in increased resistivity overtime. In addition, cold regions' pavement are subject‐ed to intense loading by climatic and environmentalfactors, which intensify the damaging effect of heavyloads acting on the pavement structure, leading to ac‐celerated deterioration, and hence more frequentmaintenance and even replacement of the pavement(Doré and Zubeck, 2009). These factors could renderthe EC-AC approach unreliable and expensive.

2.2.1.10 Carbon-fiber-tape deicing method

The carbon-fiber-tape (CFT)-based deicing meth‐od is a recently patented technology (Yang, 2012;Yang et al., 2012; Zhou et al., 2012; Singla et al.,2014). This method takes advantage of CFT's uniqueproperties, including low resistivity, high strength,and light weight, to assemble commercially availableCFT into heating panels with CFT strips connected bytwo bus bars in parallel. The heating panels can be ofrectangular or other shapes to suit deicing needs of ar‐

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eas with different geometry. The CFT-panel bus barsare then connected to a low-voltage (less than 36 V)AC-power source to heat the pavement for anti-icingor deicing purposes. The heating panels are embeddedabout two inches below the pavement surface so theyare protected against pavement-surface damages, andthey can be reused even if the surface pavement hasto be milled and replaced.

The advantage of CFT-based deicing can be sum‐marized as being safe, durable, easy to maintain, andefficient; and the approach has received favorable re‐views from recent studies (e. g., Ceylan et al., 2014;Shi et al., 2014). As a low voltage (less than 36 V) issupplied to power the system and the heating panelsare embedded in the pavement, it poses minimum riskfor pedestrians. The carbon-fiber material is light‐weight, strong and durable, and free of corrosion. Asthe carbon-fiber tape can distribute the heat more uni‐formly than the wires in a carbon-fiber or metal-wiremesh, or the pipes in a hydronic system, CFT heatingpanels induce minimal thermal stress in the pavement.All these features lead to a very durable system. Asthere is no fluid or moving parts, the CFT deicing sys‐tem requires a minimal amount of maintenance. Theheat can be uniformly distributed on the pavement sur‐face to melt the snow/ ice. Coupled with a snow/ ice-detection sensor and automatic controller, this systemis quite efficient in operation, as will be evidenced inthe operation-cost comparison with hydronic systemspresented hereafter.

2.2.2 Pavement deicing with external heatingelements

2.2.2.1 Microwave

Hopstock (2003) conceived the idea of testingmagnetite-bearing taconite aggregate and microwavetechnology for two potential road-use applications:(1) all-season, hot-mix pothole patching and curing;and (2) chemical-free deicing of surfaces paved withAC, including highways, bridge decks, pedestrianwalkways, and airport runways. Results from a pre‐liminary bench-scale assessment of this idea using aconventional microwave oven show that magnetite-bearing taconite aggregate is indeed an excellent mi‐crowave absorber (Hopstock, 2003; Hopstock andZanko, 2005). When a truck-mounted microwave gen‐erator is driven over an ice-covered roadway con‐structed with crushed taconite as the aggregate, the mi‐crowaves should pass through the ice and be absorbedas heat at the road/ice interface, allowing the ice to beeasily detached and scraped away. However, thesefindings have not been validated in a full-scale, practi‐cal testing program (Hopstock and Zanko, 2005).

2.2.2.2 Infrared-heat lamp

An infrared heat-lamp was used as an externalheating element in an ice-prevention system installedon the Mississippi Avenue Bridge in Denver, Colora‐do (Zenewitz, 1977). The infrared lamps were used toheat the underside of the bridge deck with a powerdensity of 75 W /m2. It was found that the heat-lampsystem was insufficient to prevent ice formation onthe road surface, due to excessive lag time and inade‐quate power density.

3 Performance evaluation and cost comparison

3.1 Evaluation of mechanical, chemical, andthermal methods

Deicing has traditionally been accomplished by me‐chanical, chemical, and thermal methods. These meth‐ods have drawbacks in that some of them damage thepavement, pollute the environment, and corrode vehi‐cles and reinforcing steel in concrete; and some requirecomplicated installation or are too expensive to installand operate. Table 1 presents an evaluation of the ad‐vantages of combined chemical /mechanical, hydronic,and various electrical resistance-heating (ERH) deicingmethods. Although the mechanical/chemical method re‐mains the most cost-effective for winter-road mainte‐nance, heated pavement, particularly the ERH meth‐ods, offers many promising benefits such as being envi‐ronmentally friendly, as well as the potential for inno‐vation. In addition, heated pavement can reach areasoutside the plow track / brine application area, such ascurb to curb. It could also expose crosswalk stripingmore consistently throughout winter than the plow /brine applications, to further define the crosswalk forall users. Although the operation cost may prohibit ap‐plication of the ERH method in very large areas suchas highways, it offers a great alternative snow/ice-melt‐ing technology for small areas with concentrated traf‐fic, such as urban crosswalks, sidewalks, bus stops, andbridge decks prone to icing.

3.2 Evaluation of existing ERH deicing systems

Various ERH deicing systems have been re‐viewed. To help understand the advantages and disad‐vantages of these systems, Table 2 presents an evalua‐tion of different electrical heating deicing methodsthat have been field-tested, including the heating-wiremethod using metal or carbon-fiber wires, EC-PCC or-AC pavement methods, magnetic snowmelt devices,and CFT heating-panel method. Different aspects in‐cluding constructability, durability, safety, field perfor‐mance, and application examples are addressed. Com‐pared with other field-tested ERH methods, CFT has

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certain advantages in terms of being easy to install, noneed to change the AC mix, durable, safe, and satis‐

factory performance. However, its performance in ACpavement is yet to be verified.

3.3 Cost comparison

Cost-effectiveness is always an important factor af‐fecting the applicability of a deicing system. The instal‐lation and operation costs are compared among theelectrical resistance systems whenever such data isavailable. As discussed in the previous section, the de‐icing cost is very sensitive to air temperature. The ex‐periments conducted in the CFT deicing system had airtemperatures that varied from −17.7 to 2.2 ° C, whilethe data of other deicing systems reported in the litera‐ture were for narrower air-temperature ranges. To makea reasonable cost comparison, it is necessary to selectan air-temperature range, say from −6 to 3 °C, for com‐paring average unit-energy cost with other systems.

Table 3 compares the various reported ERH deic‐ing systems in terms of installation cost, annual oper‐ating costs, power density, and unit-energy cost. Theoperating cost per storm is defined as the average costfor operating a deicing system to melt snow on a unit-surface area (m2) during each deicing/anti-icing exper‐iment. The annual operating cost indicates the aver‐age operating cost of all deicing and anti-icing experi‐ments conducted during one year. Note that the elec‐tricity cost was assumed to be $0.08/(kW∙h) in order

to compare all systems reported in the literature onthe same basis.

The installation cost for the CFT deicing systemwas calculated based on the sum of the costs of theheating panels, electrical and control equipment, andinsulation boards used in the three test-sidewalkblocks of 1.83m×1.22m. It did not include the laborcost and the cost of the sidewalk materials. For theelectric heating-cable system (Henderson, 1963), thecost of the installation was calculated so as to inte‐grate the cost of laying the cable, installing electricaland control equipment including transformers, andelectric service facilities. For the EC-concrete heat‐ing system (Tuan, 2008), the installation cost in‐cludes the cost of building and installing control fa‐cilities, and the cost of integrating and programmingthe deicing operation controller. For the hot-waterdeicing system reported by Cress (1995) and the EC-concrete deicing system reported by Yehia and Tuan(1999), the installation costs were quoted directlyfrom the literature. The installation cost of the car‐bon-fiber heating-wire system reported by Zhao etal. (2010) was not available and was not consideredin this comparison.

It can be seen in Table 3 that the CFT deicing sys‐

Table 1 Evaluation of advantages between mechanical/chemical and various heated-pavement snowmelt methods in PCC

Snowmelt technology

Mechanical/chemical

Hydronic heated pavement

Electrical resistance- heated pavement

Initial

cost

√

Operation and

maintenance

cost

√

Construct-

ability

N/A

TBD

Durability

√

Safety

√√

Potential for

innovation

√

Environmentally

friendly/

green energy

√√

Table 2 Evaluation of different ERH deicing methods

Electrical heating

deicing method

Heating-wire

method

EC-PCC/AC

pavement method

Magnetic heating-

device method

CFT heating-panel

method

Constructability

Easy

Change of pave‐

ment-mix formula

Easy

Easy

Durability

Fair

Good

N/A

Good

Safety

Safe

Safe

N/A

Safe

Field

performance

Poor

Good

Poor

Good

Application examples

AC pavement in Newark, New Jersey; abandoned due to

cable pulled out of pavement by traffic load

Bridge deck (Roc Spur Bridge), Snowfree® technology

at O'Hare Interl. Airport (demolished)

Unknown

Multiple applications in PCC pathways; not yet applied

in AC pavement

7


tem has the lowest power density and unit-energy cost,and a relatively lower installation cost among the sys‐tems compared. The high efficiency of the CFT deicingsystem is likely due to the use of an insulation layer,and the system's rather uniform heating, coupled with

its low power density. For applications in Alaska, theaverage air temperature will be lower than −6 °C; andthe unit-energy cost will be higher. The data show thatthe CFT deicing system has the potential to becomequite a cost-effective deicing technology in the future.

4 Intersection /crosswalk maintenance: the stateof the practice

4.1 DOT survey and results

Intersections and crosswalks are prone to beingthe site of traffic accidents during winter storms. It istherefore important to understand the current practiceof their maintenance. This section presents a surveydesigned to find out the state of the practice on cross‐walk maintenance at the state departments of transpor‐tation (DOT) level. Note that municipalities were notsurveyed because their practices and road inventoryvary too greatly from traditional DOT roads and re‐sponsibilities. This survey including a total of sevenquestions was designed to gather information regard‐ing the state of the practice on how state DOTs aredealing with crosswalk winter maintenance (Yang,2016) and was sent to all state DOTs for survey inJanuary 2016 via the American Association of StateHighway and Transportation Officials (AASHTO) Re‐search Survey Advisory Committee List Serv.

Seventeen states or provinces responded to thesurvey (Yang, 2016). Among these states, six states in‐dicated they do not need to clear crosswalks, as theseare left to municipalities or towns; nine indicated thatthey do not treat crosswalks, if any, differently fromthe highway itself in their states. Only two states/prov‐inces, i.e., Alaska and British Columbia, Canada, indi‐

cated they treat crosswalks differently and maintain acertain standard for crosswalks during winter season.A typical snow / ice-treatment procedure for cross‐walks would include plowing and applying salt andsand, depending on weather conditions and tempera‐tures. In some states, anti-icing is used pre-storm inthe form of MgChl and salt brine. Some states (for ex‐ample, Montana) indicated that it has been used insidewalks to melt snow and ice. A hydronic systemhas been used on some occasion. In at least some loca‐tions, the heat generated from computer servers hasbeen used to heat the sidewalks around the building.It is interesting to note that no ERH methods havebeen applied by any state DOT in maintaining cross‐walks/intersections.

4.2 Current state of the practice in Alaska andcost estimation

The survey result from the Central Region Mainte‐nance and Operations (M&O) of the State of AlaskaDepartment of Transportation and Public Facilities(AK DOT&PF) collected in this survey provided agood example of the state of the practice for cost anal‐ysis (WWH, 2003; Yang, 2016). For Alaska, the Cen‐tral Region M&O maintains quite a large number ofcrosswalks on the Seward and Minnesota freewaysand major arterials throughout Anchorage. Priority isgiven to freeways (same day), then major arterials (1

Table 3 Cost comparison of different ERH deicing systems

Deicing system and year built

Electric heating cable, 1961 (Henderson, 1963)

Hot water, 1993 (Cress, 1995)

EC-concrete mixed with steel shavings and steel fiber,

1998 (Yehia and Tuan, 1999)

EC-concrete mixed with steel fibers and carbon particles,

2003−2007 (Tuan and Yehia, 2004; Tuan, 2008)

Carbon-fiber heating wire, 2008 (Zhao et al., 2010)

Carbon-fiber tape heating panel, 2010−2011

(Yang et al., 2012)

Installation

cost ($/m2)

b 23.6

a 161

a 48

b 205

N/A

145

Annual operating

cost ($/m2)

b 2.8

a 250/storm

a 0.8/storm

b 0.74/storm

b 0.38−2.8/storm

0.27/storm

Power density

(W/m2)

b 323−430

a 473

a 590

a 350

a 500−800

about 300

Unit-energy cost at −6

to −3 °C air temp.

($/(m2⋅cm))

b 0.368

N/A

b 0.075

b 0.033

b 0.025

0.030

a Cost value and power density were quoted directly from the literature; b cost value and power density were converted into uniform unit.

8


day), and then other streets (2 + days) maintained byAK DOT&PF. There is a specific procedure for inter‐section/crosswalk maintenance. For fresh snow, a noseplow with a belly blade is used to plow a 30-m ap‐proach and the intersection, and to dispense the sand /brine mixture. This operation requires one employeeand one truck. If ice is packed on the intersection, itwould require another employee and a grader to treatthe surface first. Brine solution is applied at cross‐walks and intersection approaches pre-storm or dur‐ing freeze/thaw events. No other method is used cur‐rently for snow/ ice management. The personnel-timeestimation for intersection winter maintenance can befound in Yang (2016). The time estimation rangesfrom about 10-min travel time for a two-lane intersec‐tion to 25 min for a five-lane intersection. For compar‐ison, a two-lane intersection was assumed. Table 4summarizes the personnel, equipment, and amount ofmaterials used for each two-lane intersection for the

central region. Depending on the nature of the snow/ice event, the cost of intersection maintenance is esti‐mated to be in the range of $46.77 to $88.41 perstorm. Assuming three events per month and five win‐ter months per year, the cost of winter maintenance isin the range of $701.55−$1,326 per year.

If a CFT deicing system is used, for a two-lane in‐tersection, the area of the intersection itself plus pe‐destrian walkway is about 107 m2 (area = 7.31m ×3.65m×4, assume no approach is covered); the annualoperation cost due to electricity consumption wouldbe around $1,080, which is about the average annualM&O cost of the current practice. The manageable op‐eration cost and the benefits of an automatic deicingsystem, such as the minimized delay time and im‐proved safety for pedestrian and vehicular traffic,show that an ERH deicing system, such as the CFTsystem, might be well worth consideration and the ini‐tial investment in future intersection/crosswalk design.

5 Conclusions

The purpose of this study was to provide a com‐prehensive literature review of existing deicing tech‐nologies with an emphasis on the electrical resis‐tance-heating methods for possible application in as‐phalt approaches and crosswalks. A comprehensive re‐view of existing and emerging deicing technology forsnow/ice melting was conducted. The performance ofvarious deicing methods was evaluated, and the costof various ERH systems were compared. Finally, cur‐rent state of the practice of intersection / crosswalkmaintenance was surveyed among state DOTs; andthe results were summarized. The intersection / cross‐walk winter maintenance procedure adopted by theCentral Region Maintenance & Operation of AKDOT&PF was described, and the cost of annual win‐ter maintenance was estimated and compared with

that of a CFT deicing system. The following conclu‐sions can be drawn:

1. Deicing has traditionally been accomplished bymechanical, chemical, and thermal methods. The me‐chanical / chemical method is the most cost-effective,but heated pavement methods—particularly the elec‐trical resistance-heated-pavement—offer many prom‐ising benefits such as being environmentally friendlyand stimulating the potential for innovation.

2. Although the operation cost may prohibit appli‐cation of an ERH method in very large areas, it offersa great alternative snow / ice-melting technology forsmall areas with concentrated traffic, such as urbancrosswalks, sidewalks, bus stops, and bridge decks.

3. Compared with other field-tested ERH meth‐ods, the CFT method has certain advantages in termsof being easy to install, no need to modify AC-mix ra‐

Table 4 Per-storm cost for personnel, equipment, and amount of materials for winter maintenance

of a two-lane intersection with crosswalk

Winter events

Fresh snow

Ice pack

Pre-storm or

freeze/thaw event

Avg. wage with FHWA

overhead rate1

($69.01/h)

One employee

$11.50

Two employees

$23.00

One employee

$11.50

Equipment

Plow truck

($91.63/h)

$15.27

$15.27

$15.27

Grader

($117.25/h)

N/A

$19.54

N/A

Brine tank

(16.07/h)

N/A

N/A

$2.68

Materials

(sand w/ brine = $14.14/ton;

brine = $0.045/L)

Sand/brine mixture, one yard/

intersection, $20 ($14.14/ton × 1.45

ton/yard × 1 yard/intersection = $20)

N/A

151 L/lane-km, $1.15/intersection

Cost

$46.77

$57.81

$30.60

1 Average wage is 36.71/h, FHWA overhead rate is 88%, and the total rate is $69.01/h. No overtime is considered.

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tio, durability, safety, and observed satisfactory perfor‐mance. However, its performance in AC pavement isyet to be verified.

4. The survey results show that most DOTs do nothave responsibility for intersection / crosswalk wintermaintenance or do not treat intersections / crosswalksdifferently than a highway. Only Alaska and BritishColumbia treat crosswalks differently and maintain acertain standard for winter maintenance of intersec‐tions/crosswalks.

5. A typical snow / ice-treatment procedure for in‐tersections/crosswalks would include plow and appli‐cation of a sand/brine mixture, depending on weatherconditions and temperatures. Anti-icing treatment isused pre-storm or during freeze/thaw events.

6. The energy cost of the CFT deicing system isabout the same as the average annual M&O cost ofcurrent practice in Anchorage. In addition, an auto‐matic ERH deicing system would bring the benefitssuch as minimized delay time and improved safety forpedestrian and vehicular traffic.

As AK DOT&PF maintains quite a large invento‐ry of intersections / crosswalks—and global warmingmight bring warmer and wetter winters to and in‐crease the burden of winter maintenance in the arctic,including Alaska—an ERH deicing system such asthe CFT system is well worth consideration and theinvestment in future design of intersections / cross‐walks and is recommended to be tested in asphaltpavement to verify its suitability for applications in in‐tersection/crosswalk winter maintenance.

Acknowledgments:The research reported herein was supported by AKDOT&PF and FHWA (Project #64006). The authorwould like to express his appreciation to Ms. Anna Bo‐sin, P. E., Research Engineer, Research Developmentand Technology Transfer of AK DOT&PF, for her con‐tinuous support during the entire course of the study.

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