An Overview of Approaches for Utilizing RFID in

Construction IndustryEsin Ergen , Burcu Akinci2

1 Assistant Professor, Istanbul Technical University, Civil Engineering Department, Construction Management Division, AyazagaKampusu, 34469, Istanbul, Turkey

2 Associate Professor, Carnegie Mellon University, Department of Civil and Environmental Engineering, 5000 Forbes Ave.,Pittsburgh, PA 15213-3890 USA

Abstract-Construction industry has dynamic and uncontrolledenvironments, where tracking components/materials andaccessing related information are challenging tasks. Failure ineffectively tracking components/materials and in accessing therelated information on demand results in schedule delays andadditional labor costs. Due to long read ranges, radio frequencyidentification (RFID) technology holds the potential for enablingautomated tracking of components/materials in dynamic anduncontrolled environments. Also, on-board storage capacity ofRFID allows for making information related to a component of abulk of material readily available to the persons who arehandling components and materials. This paper provides anoverview of possible applications for RFID use and describes thefield tests conducted in several research studies on utilization ofRFID in construction industry. The field tests described wereperformed for tracking pipe spools and precast componentsduring delivery and receipt, tracking precast components in amanufacturer's storage yard, tracking tools, locating materialsand transferring material information to construction site. Theresults of those tests demonstrated that despite some limitationsof the current technology, active UHF RFID meets the needs forthe selected cases provided that some reasoning mechanisms aredeveloped and implemented for data cleaning and processingpurposes.

I. INTRODUCTION

Construction industry has dynamic and uncontrolledenvironments, where tracking components/materials and tools,and accessing related information are challenging tasks.Current approaches for managing components/materials andtools mostly use labor-intensive methods to collect and recordrelated tracking information. Data collected using manualmethods are not reliable or complete because they aredependent on the motivation and skills of the people (typicallyworkers) who are tasked for data collection [1]. Moreover,data collected through these methods are usually transferredand stored in paper-based format, which is difficult to searchand access, and which makes processing them into usefulinformation expensive and unreliable. Thus, some informationitems end up being not readily available to the parties, whoneed to access the information in a timely fashion to makeeffective decisions. Failure in effectively trackingcomponents/materials and tools and in accessing the related

information on demand results in schedule delays andadditional labor costs.Due to long read ranges, radio frequency identification

(RFID) technology holds the potential for enabling automatedtracking of components/materials in dynamic and uncontrolledenvironments. Also, on-board storage capacity ofRFID allowsfor making information related to a component or a bulk ofmaterial readily available to the persons, who are handlingcomponents and materials. This paper provides an overview ofpossible applications for using RFID in construction industryand describes the field tests conducted in several researchstudies summarizing the functional requirements for RFID tobe used in construction domain. The field tests described wereperformed tracking pipe spools and precast components duringdelivery and receipt, tracking precast components in amanufacturer's storage yard, tracking tools on a constructionsite, locating materials and transferring material information toconstruction site.

ii.BACKGROUND - OVERVIEW OF CONSTRUCTION INDUSTRYAND THE NEED FOR RFID

It has been known that it is challenging to trackmaterials/components, tools and labors and relatedinformation since environments are mostly dynamic,uncontrolled and subjected to harsh conditions. An example ofsuch an environment is a construction site. Construction sitesare very dynamic since materials, which might arrive on adaily basis, are staged at various laydown areas and theirlocations can be changed several times before they areinstalled in their final locations within a facility. Unlikefactories, construction sites have uncontrolled environments,where pieces of equipment do not follow pre-determined pathswhen moving or do not operate in a pre-determined way. Inaddition, since production is performed in open air, harshconditions are observed such as rain and dust. Within suchdynamic and harsh environments, it is obvious that currentmanual and paper-based way of tracking resources andcomponents are ineffective and inefficient. There is a need foran automated resource tracking system that will function wellin dynamic and harsh environments observed in constructionindustry.

Another challenging characteristic of construction industryis that there are many unique materials/components that needto be uniquely tracked and that require unique handling andinstallation techniques. Workers that are handling thosematerials/components at site currently search for paper-baseddocuments related to each component to get the instructionsfor handling and installation. This results in time-consumingsearches to identify the related information. Thus, there is aneed to have component related information to be easilyaccessible and readily available at construction sites.

Various automated identification technologies, such asbarcodes, two dimensional barcodes, RFID, optical characterrecognition, and contact memories are available for trackingresources and related information in construction [2, 3, 4, 5].However, most of these technologies require line-of-sight tocapture identification information, and require a labor-intensive scanning activity to be performed on each object.Labor-intensive approaches rely on workers' judgment andskill for data collection [1]. Since construction workersconsider data collection to be a secondary task and try to avoidit [6], these approaches result in incomplete and inaccuratedata. As a result, systems utilizing such approaches typicallyhave reliability issues on the information they provide. Inaddition, some of the technologies used cannot survive inharsh conditions encountered in open-air production andconstruction environments.RFID technology does not require line-of-sight for data

collection, and some types have long read ranges and largedata storage capacities. Also, RFID tags can be encapsulatedfor protection in harsh construction conditions. All of thesecharacteristics of RFID technology make it an attractivetechnology that has potential to address the challengesassociated with tracking resources on construction sites.Recently several studies in construction industry proposedutilization of RFID technology for resource and relatedinformation tracking. The next section provides an overviewof such research studies.

III.OVERVIEW OF THE PROPOSED APPLICATIONS OF RFID ANDCORRESPONDING FIELD TESTS

Researchers in construction industry have proposed toutilize RFID technology mostly for trackingmaterials/components and related information. Tracking toolsand related information, and activities of labor were alsoconsidered. Following paragraphs provides information onapplictions of RFID in construction industry that wereenvisioned by the researchers and the related field tests thatwere performed. The results of the field tests are discussed inthe following section.

Tracking materialslcomponents and related information: Inthis group of studies, several systems were envisioned, withinwhich materials/components were tracked in an automated ora semi-automated way through a construction supply chain,i.e., as they are relocated at manufacturing plant's storageyard, sent to/received at the construction site, relocated beforeinstallation and installed to the facility [7, 8, 9]. The

information on where the materials are, would be used forlocating materials/components and progress monitoring bydifferent parties. In the vision developed by Ergen et al.(2006), it was proposed to use RFID to store componentrelated information with the component at site, (i.e., qualitycontrol information, handling instructions) [8]. This approachmakes the related information readily available for theworkers who are handling the materials/components in themanufacturer's storage yard or at the construction site. Suchdecentralized information storage approach was suggestedsince current paper-based information access at site needsimprovement and wireless LAN, which would provide accessto a centralized database, might not be available and might bechallenging to implement on a construction sites where thetopography is changing significantly as constructionprogresses.

Researchers focused on different aspects of the envisionedsystems and conducted some field experiments to test howwell RFID technology performs in construction environmentfor the determined purposes. Peyret and Tasky (2002)identified that quality control information of asphalt, which isneeded during paving and compaction, is not transferred frombatch plant to construction site [10]. Thus, a prototype systemwas developed where quality control information of asphaltwas entered to an active UHF tag attached to an asphalt truckat the batch plant and transferred to on-board computer systemon an asphalt paver. The quality control parameters that wererecorded included bitumen and asphalt temperatures at variousstages of production and spreading; ratios of asphaltcomponents (aggregates, bitumen) in each production batch;average asphalt weight per unit area; and theoretical thicknessof each layer. As the asphalt was being poured, thecoordinates of the paver, received from the GPS, were pairedwith the quality control information of the asphalt. Thisprototype was tested in real-life conditions.

In two other studies, problem of missing components, pipespools and precast concrete components, were observed bothat the manufacturing plant and at the construction site due topoor tracking of components during shipping. Therefore, twoportal tests were performed for determining the technicalfeasibility of using RFID for automated identification ofcomponents during delivery and receipt. In the first study,active UHF tags were attached to 50-83 pipe spools that wereloaded on a trailer, and as the trailer passed through a gatewhere four antennas were installed, the pipe spools wereautomatically identified at different truck sppeds. Thechallenge in this test was that some components might not beidentified since the pipe spools were made of metal and theywere in a very congested environment. In the second study, anactive UHF tag was attached to a precast concrete componentwhich was loaded on a trailer and the component wasautomatically identified as the trailer passed through afictional gate where an antenna was installed. For both portalapplications, identification of tags was tested at different truckspeeds to determine the most appropriate speed.

A similar problem was identified in precast concretemanufacturer's storage yard where precast components were

mislocated [11]. Precast components were stored in a largestorage area and since they were relocated multiple times,precast manufacturer lost track of some components. In thisstorage area, the components were stored at fixed locationsand mobile cranes were used to relocate the components. Toovercome the misplaced component problem, researchersdeveloped an approach and a corresponding prototype thatidentified the precast component being picked up by a crane

and integrated the ID information with the locationinformation received from GPS. The prototype was tested in a

precast storage yard as a piece was relocated by a crane.

Active tags were attached to components and RFID reader,antenna and GPS were placed on the crane that is used torelocate the components.Another study focused on the problem of mislocated

materials at a construction site. Construction site is a lesscontrolled environment when compared with a manufacturer'sstorage yard, i.e., at construction site materials can be stored atany location and are relocated both by workers or equipment.To locate the materials that are scattered at a construction site,Song (2006) developed an approach that combined RFID andGPS [12]. This approach leveraged automatic reading oftagged materials by field supervisors or materials handlingequipment that are equipped with a RFID reader and a globalpositioning system receiver. To assess the technical feasibilityof this approach, a mathematical model has been formulatedwhere the job site is represented as a grid and the location ofmaterials within the grid is determined by combiningproximity reads from a discrete range.

Tracking tools and related information: Goodrum et al.(2006) proposed to use RFID for improving efficiency of tooltracking at construction sites and for storing operations andmaintenance information on the tools [13]. To test thetechnical feasibility of this system, RFID tags were installed inthe tool handles and these tools were identified at varying

distances using a handheld reader. Also, ability of the tags tostore uncorrupted data was tested by storing some data andaccessing it during site visits.

Tracking activies of labor: Navon and Goldschmidt (2003)highlighted the need for automatically identifying labor inputs,which is an important project performance indicator inconstruction projects [14]. They developed a conceptual RFIDbased data collection system, which is designed for indoorenvironments to automatically collect worker's location dataat regular time intervals. This location information will beconverted into labor inputs using algorithms. In this approach,RFID tags would be attached to building elements andworkers would carry personal units that have RFID readers,which record the information from the tags that the workerpasses by. This data would be downloaded once a day andworkers' locations would be calculated.

IV. REQUIREMENTS AND FIELD TEST SETTINGS

The functional requirements that were identified for theapplications described in the previous section are given inTable 1. In most of the cases, medium to long read range was

required since the minimum reading range required was more

than 1 m and up to 3 m. In all the cases, active UHFtechnology was utilized. In some cases, passive UHFtechnology was also tested but it was not selected since it didnot reliably meet the identified read distance.

For tracking and locating materials and components, read-only tags with minimum memory that stores ID were required.Read/write tags allows for updating the data that were storedin the tag. Thus, they were used for storing component/toolrelated information with the component or with the tool andfor making this information readily available for field workers.Examples of this kind of information are quality control (QC)data of asphalt and tool's operations and maintenance data.

TABLE 1GOALS AND REQUIREMENTS FOR UTILIZING RFID IN DIFFERENT CASES

Tracking asphalt QC Storage yard Shipping Shipping Tool tracking Locating materials(Precast) (Precast) (Pipe spools)

Goal Transfer asphalt QC Track precast Identify the Identify the pipe Track tools and Automatically identifyinfo to construction components at precast spools during store O&M data and locate materials atsite and integrate storage yard in an components delivery construction siteswith asphalts' automated way during deliverylocation info

Min. reading range Close (<im) 3 m 3 m 3 m Not very close Not very closerequired >1 m >1 mMemory Read/VWrite Read-only Read-only Read-only Read/VWrite Read-only

Encapsulated/ Yes Yes Yes Yes No Yesinsulated tagsAccompanying GPS GPS GPStechnologyAccompanying Selective reading Proximity methodapproaches

Almost in all cases encapsulated or insulated tags were

required to provide better performance around metal andconcrete and to provide durability in harsh constructionenvironments. In half of the cases, RFID was integrated withGPS technology to track the location of materials/components.GPS was not required at portal applications, where the goalwas not locating the components but determining if thecomponents left the site or arrived at the site.

To automate identification or location process in dynamicand less controlled environments, two approaches were used.In the precast tracking case, selective identification was

required to automate the identification process. Selectiveidentification means that a specific ID (e.g., which belongs tothe carried piece) identified and other irrelevant IDs, whichare detected since they are in the range of the reader, are

ignored., In material locating case, proximity method was usedfor determining the location of materials in an automated wayat a construction site. In this approach, a mathematical modelwas developed where the job site is represented as a grid andthe location of materials within the grid is determined bycombining proximity reads from a discrete range. Bothapproaches enable automated identification which minimizesthe worker input.

Based on the goals and requirements identified in Table 1,test settings were determined as given in Table 2. Sincemobile reading is required in the dynamic and relativelyuncontrolled environments in construction supply chains,mostly mobile reading devices were used; either readers andantennas were integrated with portable devices or fixedantennas were attached on mobile equipment (e.g., gantrycrane). Only in portal applications fixed antennas and readerswere used since the goal was identifying the components as

they leave or arrive.In one of the portal applications, four antennas were used to

ensure that all the components were detected in a metallic andvery congested environment where 50-83 pipe spools were

placed on a trailer. In the other portal application, where onlyone piece of precast piece was being shipped, one antenna wassufficient. In all the tests, active UHF technology was used.The tags that were used were not specifically designed to beattached to construction materials, components and tools. Intool tracking test, the tag was modified to be inseted into toolhandles. The outer casing and LED power indicator were

removed, and battery attachment was modified. In precastcase, the tags were attached to the component using duct tapeand plastic wire.The results of the tests were successful in providing the

required read range, and in identification and tracking ofcomponents and transferring the related information. In termsof data storage, RFID was successfully used in transferringasphalt QC data from the manufacturing plant to constructionsite and in storing operations and maintenance data related totools over long periods of time. RFID also performed well inidentifying the precast piece that was sent to the constructionsite on a trailer. During shipping pipe spools on a trailer,RFID was successfully used in identifying all the pipe spoolson a trailer if the truck speed was under 3.2 km/h For thestorage yard case, by using an approach for selectiveidentification, all the precast pieces were successfullyidentified for all the relocation actions, in which the crane

moves from one location to another. In the test that simulatedthe process of locating materials that were scattered in a

construction site, the results showed that the approximate 2Dlocation of materials (i.e. 3.6-3.7 m) can be determined usingRFID and the proximity localization techniques.Read range of RFID around concrete and metal reduced but

encapsulated active UHF RFID tags with still could providethe necessary read ranges shown in Table 2. As expected, theread range varied for different components and in differentenvironments. For example, in the precast storage yard case

the actual reading range of the RFID tags was reduced to 1/4 -

1 5th of the nominal reading range for open air environments(6-8 m instead of 30 m) whereas for tool tracking case itvaried from 3-9 m for different environments and tools. RFIDperformed well in terms of long term data storage capacity inharsh construction environments. For the tool tracking case, a

longevity test was conducted to determine if the data in thetags would stay uncorrupted over a long period of time and theresults showed that no data was lost.

The overall results of the field tests showed that RFID couldbe used in construction supply chains for tracking and locatingmaterials and components and for storing historical or

operations and maintenance data over a long period of time. Insome cases where selected identification or locating is needed,some approaches and methods need to be developed for thespecified purpose.

TABLE 1TEST SETTINGS

Tracking Storage yard Shipping Shipping Tool tracking Locating materialsasphalt QC (Precast) (Precast) (Pipe spools)

Antenna location Handheld Mobile gantry crane Gate Gate Handheld Rover

Antenna type Mobile Fixed Fixed Fixed Mobile Mobile

Number of antennas 1 1 1 4 1 1

Number of tests Not specified 18 relocations of 12 truck passes 9 truck passes Not specified Not specifiedprecast pieces

Number of 1 8 1 50-83 N/A 6components tagged

CONCLUSIONS

Unlike many other industries (e.g., retail, automotive),construction industry mostly has dynamic and uncontrolledenvironments where tracking and locating materials andaccessing related information is challenging. The overallresults of RFID field tests that were performed in theseenvironments for tracking and locating materials andcomponents and tracking the related information showed thatactive UHF RFID was successful in meeting the basicrequirements. Some limitations of the current technology canbe overcome by using some reasoning mechanisms that aredeveloped and implemented for data cleaning and processingpurposes. In the future, RFID technology developers need towork with construction practitioners for identifying the needsfor different cases and for designing and developing thetechnology based on these needs.

ACKNOWLEDGMENT

This work was partially funded by High Concrete, Inc.,Pennsylvania Infrastructure Technology Alliance (PITA), andPrecast/Prestressed Concrete Institute (PCI). The authors alsogreatly appreciate the assistance and support received fromHigh Concrete, Inc. Any opinions, findings, and conclusionsor recommendations expressed in this material are those of theauthors and do not necessarily reflect the views of the HighConcrete, PITA, or PCI.

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