BIM UTILIZATION FOR OPTIMIZING MILLING QUANTITY … · bim utilization for optimizing milling quantity ... bim utilization for optimizing milling quantity and hma pavement ... (cim)

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BIM UTILIZATION FOR OPTIMIZING MILLING QUANTITY

AND HMA PAVEMENT OVERLAY QUALITY

Journal: Canadian Journal of Civil Engineering

Manuscript ID cjce-2015-0001.R2

Manuscript Type: Article

Date Submitted by the Author: 24-Jun-2016

Complete List of Authors: Bae, Abraham; Samsung C&T Corporation, Construction Engineering Group, Civil Infra Biz Unit Lee, David; Samsung C&T Coriporation, Civil Project Management Team, Civil Infra Biz Unit Park, ByoungYck; Samsung C&T Corporation, Construction Engineering Group, Civil Infra Biz Unit

Keyword: construction (CA) < Computer Applications, highways < Transportation, constr. management < Construction, transportation structures < Construction, transportation < Computer Applications

https://mc06.manuscriptcentral.com/cjce-pubs

Canadian Journal of Civil Engineering

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Manuscript DOI No: 10.1139/cjce-2015-0001

Title: BIM UTILIZATION FOR OPTIMIZING MILLING QUANTITY AND HMA PAVEMENT OVERLAY QUALITY

Authors:

Abraham Bae, Ph.D., P.E. (Corresponding Author)

Deputy General Manager, Samsung C&T Corporation

(Address) Construction Engineering Group, Civil Infra Biz Unit

(E-Mail) [email protected], [email protected]

(Tel) +82-10-4222-7980, +82-2-2145-6013

David Lee, M.S., P.E.

General Manager, Samsung C&T Corporation (Project Manager in MCE C486 Project in Singapore)

(Address) Civil Project Management Team, Civil Infra Biz Unit

(E-Mail) [email protected]

(Tel) +82-2-3458-4291

ByoungYck Park

Assitant Manager, Samsung C&T Corporation

(Address) Construction Engineering Group, Civil Infra Biz Unit

(E-Mail) [email protected]

(Tel) +82-2-2145-7989

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ABSTRACT: An approach to a practice paving technique using Building Information Modeling (BIM) was

developed. When planning hot mix asphalt (HMA) overlay on a concrete slab, in-advance paving simulations

can help to preemptively evaluate pavement quality, such as HMA thickness, and prevent excessive HMA

quantity. The BIM technique has the capabilities of ‘In-advance Simulation,’ ‘3-D Visualization,’ ‘Interference

Identification,’ and ‘Quantification.’ BIM could be successfully implemented to optimize milling quantity and

improve HMA pavement quality in an actual paving project. Based on the established BIM model, alternative

paving levels were derived and paving sequences were simulated. Through 3-D visualized images, locations

where HMA thickness was inadequate could be effectively identified. Quantified information for simulation

results enabled optimization of milling and paving options. Milling was selectively conducted for the

identified undulations. The cost was reduced by approximately 12%. Paving thickness and density had

coefficients of variation (COV) of about 15% and 0.2%, respectively.

Key Words: BIM, HMA, overlay, simulation, 3-D visualization, interference, quantification, milling,

optimization

RÉSUMÉ: Développement d’une approche d’une technique de revétement de chaussée pratique en utilisant la

“Building Information Modeling” (BIM). Lors de la phase d’études pour un projet d’enrobé bitumineux à

chaud (Hot Mix Asphalt / HMA) en surcouche sur une dalle de béton, des simulations préalables peuvent aider à

évaluer à l’avance la qualité du revêtement, telle que l'épaisseur de HMA, et d’éviter les quantités excessives de

HMA. La technique BIM offre des possibilités de “Simulation En-Avance”, de “Visualisation 3D”,

d’“Identification d’Interférence” et de “Quantification”. La BIM pourrait être mise en œuvre avec succès pour

optimiser la quantité de rabotage et pour améliorer la qualité du revétement en HMA dans un projet de

revétement de chaussée réel. Basées sur un modèle de BIM prédéfini, les épaisseurs de revétement possibles ont

été déduites et le phasage du revétement a été simulé. Grâce à la visualization d’images 3D, les emplacements

où l'épaisseur de HMA était insuffisante ont pu être efficacement identifiés. La quantification des informations

pour la simulation de résultats a permis l'optimisation des possibilités de rabotage et de revétement. Le rabotage

a été réalisé de manière sélective pour les ondulations identifiées. Le coût a été réduit d'environ 12%.

L’épaisseur et la densité du revétement ont eu des coefficients de variation (Coefficient Of Variation / COV)

d'environ 15% et 0,2%, respectivement.

Mots-clés: BIM, enrobé, HMA, revétement, simulation, 3D visualisation, interférence, quantification,

optimization, rabotage

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1. INTRODUCTION

For pavement inside tunnel, one or two layers of hot mix asphalt (HMA) overlay are generally designed on the

top of the concrete base slab. Similar to concrete deck slab surfaces on bridges, the as-built base slab surfaces

at the bottom of the tunnel exhibit some undulations. To have uniform overlaid pavement qualities such as

thickness, milling of the pre-overlay surface is usually conducted before overlaying. In current practice,

milling would be seldom selectively performed, and consecutive overlaying is usually conducted based on a 2-D

survey. The approach outlined here can potentially reduce milling and HMA overlaying costs.

A BIM has several capabilities, including ‘In-advance Simulation,’ ‘3-D Visualization,’ ‘Interference

Identification,’ and ‘Quantification.’ In this study, a state-of-the-practice method based on the BIM technique

for milling and HMA overlay is developed. The methodology was initiated by modeling the as-built pre-

overlay surface. To optimize paving, alternative paving levels were derived from the BIM model. Paving

sequences were successfully simulated in the BIM model before field paving was completed. The simulated

outputs for pre-overlay conditions and virtual HMA overlaying were quantified exactly. Based on the

quantified information, an optimized milling and paving option was chosen based on the paving quality. 3-D

visualized results helped to identify interferences that could affect HMA thickness quality. This prevented

unnecessary milling and waste of HMA materials. A series of developed processes was reflected in cost

savings in field milling and paving. The developed method was implemented for tunnel road pavement of the

C486 site in the Marina Coastal Expressway (MCE) in Singapore.

2. BACKGROUND

2.1. BIM Implementation in Civil Infrastructure Projects

The BIM technique is widely implemented and used by architectural engineers for building projects. Civil

infrastructure projects have been relatively late in implementing BIM due to its lower efficiency for smaller

projects, costs, training time required, lack of internal understanding of BIM, and other factors. Nevertheless,

the incidence of BIM implementation in infrastructure projects has increased drastically in recent years. In the

U.S., 79% of current BIM users in 2012 anticipated the adoption of BIM in more than 25% of their

infrastructure projects by 2013 (McGraw-Hill Construction, 2012). Note that, in 2011, only 43% of users

forecast the same level of implementation. This increase in demand for BIM appears to be correlated to the

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improvement in return on investment (ROI) that use of BIM yields. A positive ROI was reported by 67% of all

BIM users for infrastructure projects in 2011. Note that ROI for building projects was reported to be 63% in

that same year. Japan has implemented BIM in civil projects as construction information

modeling/management (CIM). The Ministry of Land, Transport and Tourism of Japan (MLIT) promoted an

information and communication technology (ICT) civil engineering production process to improve construction

productivity, and have carried out CIM projects since 2012. Moreover, the Japan construction information

center (JACIC), which is an academic organization, was established to support the MLIT’s CIM projects

(JACIC, 2014). Singapore is one of the global leaders in BIM implementation. The building and construction

authority (BCA) in Singapore made BIM submissions mandatory for architectural projects by 2013, structural

and mechanical & electrical (M&E) projects by 2014, and ultimately all projects with a gross floor area of more

than 5,000 m2 by 2015 (BCA, 2011).

Various civil infrastructure projects such as road and highway projects, airport projects, transit projects,

dams, water and wastewater facilities, and others are implementing BIM. U.K. Crossrail would be the first

infrastructure project to comprehensively implement BIM (Crossrail Ltd, 2016). The roles of BIM in the

project are primarily to facilitate cost saving for all assets during the lifecycle, and to create an integrated 3D

information model that will facilitate multidisciplinary collaboration through design, construction, operations,

and maintenance. The Crossrail project is expected to be a reference project that will influence future

worldwide infrastructure projects. Subway stations are also very important civil infrastructures for which BIM

has been adopted because of the complexity of the various construction sectors e.g. architectural, structural, and

M&E facilities. In road and highway projects, BIM implementation has becomes more prevalent in bridge

structures, because the design shape for bridges is more standardized than for other road elements such as

tunnels or road geometry. For example, in bridge construction in the Denver metropolitan area, 5 to 9% cost

savings were predicted based on use of BIM to reduce change orders or reworks (Fanning et al., 2015).

Graphical in-advance simulation implemented in a BIM improved detection of design flaws in a cable-stayed

bridge (Kim et al., 2011). Road surveys, road geometry design, and cut and fill evaluations have recently

begun to adopt 3-D engineering techniques (Redder and Nelson, 2015), and modeling of tunnel shape was

attempted for standardization purposes (Yabuki et al., 2007). However, pavement element, no remarkable

studies have been documented on BIM application. This is because pavement structural geometry and design

are relatively simpler than other elements, and thus there is not much demand for asset management or as-built

drawing documentation management. However, the benefits of BIM during paving construction may be

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underappreciated. In this study, it is presented that BIM tool can be effectively utilized in terms of cost-saving

and that improves the quality of paving.

2.2. Relationship between Milling and HMA Overlaying Thickness

There are proper compaction thickness ranges associated with HMA Nominal Maximum Aggregate Size

(NMAS) (FHWA, 2001). If the thickness is too thin compared to NMAS, the composition of aggregate sizes

in the mat HMA layer may be inadequate, causing unwanted segregation and sometimes large aggregates to be

broken during compaction. On the other hand, a thicker mat lowers the compaction energy efficiency. In

order to achieve admissible HMA density, proper mat thickness should be secured before HMA overlaying.

Prior to HMA overlaying, milling is usually conducted in order to remove distress and to level

irregular higher elevations on the existing pavement (Brown et al., 1996). When HMA is overlaid without

milling under irregular pre-overlay surfaces, NMAS and the thickness ratio are not constant over the entire

paving surface. This obviously causes differential compaction, resulting in lower density. Thus, milling is

usually recommended as a prerequisite in order to guarantee overlaid HMA quality. Other concerns are milling

quantity and HMA material costs.

2.3. 2-D and 3-D Milling on Concrete Slab Surfaces

On highways or local roads, milling is conducted for an entire lane with a certain cut depth. Once cutting

depth is set for the anticipated elevation level, milling equipment moves forward along the road track and keeps

producing constant level surfaces. The ‘traditional’ milling process is completed two-dimensionally.

However, in the case of HMA overlay on concrete slab surface in tunnel, 2-D milling would not be the best

option. A review of the case study in the MCE C483 and C486 projects shows two primary limitations. First,

2-D milling for the entire concrete slab surface is expensive. Concrete slab surface usually has wide, broad

irregularities, and correspondingly, the required milling volume and area are quite large. Second, milling

should be selectively conducted since the cover thickness for steel wire embedded in the concrete slab should be

maintained within a certain tolerance. In addition, the working environment inside the tunnel is not supportive

for milling work. Milling with a 2-D method might cause large amounts of dust and atmospheric pollution

inside the tunnel.

Milling efficiency is of interest to the paving industries since it is primarily dependent on equipment.

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It is mostly focused on improving milling equipment capability or operation techniques (Sidlar, 2006, Schwarz

2006, Ensell, 2012). However, correct recognition of the pre-overlay surface condition is an important factor

for enhancing the milling efficiency, and seems to be neglected in some pavement situations. If milling is

selectively conducted in areas that exceed the allowable elevation level, the costs would be considerably

reduced. Selective milling can be regarded as ‘3-D milling.’ Recently, 3-D milling was attempted as a

pioneering technique in Europe (Woof, 2011). Using a 3-D monitoring system, cut depth is instantly altered

according to the monitored elevation profile, and only areas that need to be milled are removed. Utilization of

BIM tool can enhance the 3-D milling efficiency. A BIM tool provides better 3-D profiles than surveying

output for pre-overlay surface irregularities, and milling location and quantity become more precise. Beyond

the precision, BIM offers integrated paving information that improves the overlay HMA quality.

3. CONCRETE SLAB CONDITION AS PRE-OVERLAY SURFACE

3.1. Open-Cut Tunnel and Overlay Pavement Design

Figure 1(a) displays a typical box tunnel structure in the Marina Coastal Expressway C486 site in Singapore.

The twin cell box tunnel is placed over soft ground. For ground improvement, Deep Soil Mixing (DSM) and

Jet Grouted Pile (JGP) were applied for about 10 m beneath driving lanes and tunnel edges, respectively. In

spite of the improvements, deep ground mass was expected to keep consolidating even after completion of

construction. For tunnel structure support, bored piles were installed around 50 − 60 m deep.

Concrete slab is an element at the base at the bottom of the box tunnel. Its thickness varies by about

1.0 − 2.0 m depending on construction geometry. Although the concrete base slab is not regarded as pavement,

it comprehensively compensates for the pavement structural capability for the expected design traffic volume.

One or two HMA layer(s) are usually designed for driving comfort and final surfacing. The proposed HMA

overlay design, which is two HMA layers, each 4 cm-thick with a NMAS of 19 mm, is shown in Figure 1 (b)

(Bae et al., 2015).

[Figure 1. Open-Cut Tunnel Design]

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3.2. Base Slab Surface Condition

Concrete base slab is cast under complex conditions such as improved grounds and bored piles. Construction

is mostly conducted in the dark, and equipment is operated in narrow spaces. The concrete base slab is

constructed using form-casting method after reinforced steel installation (Figure 2(a)), and the surface is

manually finished (Figure 2(b)). Due to these restrictions, the concrete base slab surface usually has

undulations.

[Figure 2. Construction Condition of Concrete Base Slab]

Figure 3 displays the as-built base slab surface. The concrete base slab in the tunnel expressway is

regarded as a structural part, not pavement. Undulation of the surface is not a critical quality control item.

However, the undulation influences pavement overlay quality and cost. Pre-overlay surface irregularity is a

challenge for paving work.

[Figure 3. As-Built Concrete Base Slab Surface]

Figure 4(a) presents a section of the plan view for the as-built base slab surface undulation of the

MCE C486 site. The pre-overlay surface contains various lower (‘valley’) and higher (‘hill’) spots. Colored

contours represent elevation differences in both horizontal and longitudinal directions. Figure 4(b) presents a

schematic section view of undulations in the horizontal direction as well. If an HMA design thickness of 80

mm is applied at the basis of the design level, the ‘valley’ part requires surplus HMA materials and the ‘hill’ part

produces insufficient thickness. The ‘valley’ is not a challenge for conforming to HMA thickness and

smoothness requirements since it can be easily leveled out by filling with additional HMA. Construction cost

and NMAS for the increased thickness are the only concerns. On the other hand, the ‘hill’ should be

eliminated in order to secure the HMA thickness. Milling is a fundamental treatment to remove elevation

deviation. A challenge is to estimate the milling quantity. Overestimation of the milling quantity increases

the cost and time, and underestimation results in lower pavement quality. In order to exactly estimate the 3-D

milling volume, a technical approach with the BIM tool was implemented.

[Figure 4. As-Built Base Slab Surface Undulation]

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4. METHOD

4.1. Summary of Method Development

Figure 5 presents the BIM utilization process developed in order to optimize milling and HMA quantity. As an

initiation process, the elevation of the pre-overlay surface should be surveyed. Using the surveyed elevation

data, the BIM tool creates a Digital Terrain Model (DTM) that is a fundamental geometry format for BIM

simulation. Based on the DTM, several paving level alternatives are derived to improve thickness or density

qualities. Virtual paving can then be simulated in the BIM model. The percent area and volume for the secured

HMA thickness (or undulation condition) can be visually identified and quantitatively computed in the BIM

model. The quantified information is used in quality and cost optimization analysis, and finally, construction

paving level and milling quantity are determined.

[Figure 5. BIM Utilization Methodology for Optimized Paving]

4.2. Digital Terrain Modeling of Pre-Overlay Surface

For the paving simulation in BIM, a basic frame needs to be established. The frame is called the DTM.

When modeling a typical highway, the frame is usually composed of geological topography. Figure 6(a)

presents a typical DTM for a highway project before any structural objects are added in the BIM model.

Substantial BIM modeling may include various civil structures such as bridges or tunnels in the DTM, and BIM

may evaluate constructability and efficiency. With any types of spatial elevation data, the BIM tool can

generate DTM model. Obviously, as the resolution of the spatial data increases, the DTM becomes more

refined.

In this study, DTM was established for the as-built concrete base slab in the tunnel. In order to

collect spatial data, the as-built base slab surface elevation was surveyed at the interval of 3 m and 10 m in

transverse and longitudinal directions, respectively. The surveyed data was digitized and transferred to the

BIM tool. Figures 6(b) and 6(c) show the DTM for an 800 m-long expressway section of the MCE C486 site.

The contour represents variation of the as-built slab surface elevations. In the BIM tool, the contour interval

can be adjusted by users.

[Figure 6. Digital Terrain Model]

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4.3. Derivation of Alternative Paving Level

The primary purpose of deriving paving level alternatives is to find optimized milling quantity and HMA

overlay quality. In order to evaluate the as-built surface condition, the difference between the as-built and

design level of the base slab was computed. Figure 7(a) shows the computed data for a specific section. Note

that the data in Figure 7(a) were extracted from the center of the east bound highway, which is about 30 m wide

with 5 lanes. Many points along the station number were found to exceed the design level. If an 80 mm

design thickness is applied, the required thickness would not be guaranteed for locations with points exceeding

that thickness. They would be milled by a ‘zero’ difference in order to achieve the required HMA compaction

thickness. Such an approach would increase milling costs.

[Figure 7. Adjustment for Excessive Elevations on the As-Built Concrete Slab Surface]

Instead, if the original paving level were adjusted within the tolerance, the quantity of milling required

could be reduced. This treatment is facilitated in the BIM model. Note that the Singapore LTA elevation

tolerance for pavement formation is ±25 mm (Engineering Group, 2010). Figure 7(b) shows the corrected as-

built elevations (line with filled legend) within less than +20 mm difference. If the magnitude of adjustment is

higher, corrected elevation profiles would be flatter (i.e., conservative) as the design level. It requires more

HMA, but less milling work is expected. The paving level was created by the overlay design thickness of 80

mm to the corrected as-built elevations. Two alternatives were derived based on the different degrees of

adjustment. Note that alternative 2 was derived to be more conservative than alternative 1.

4.4. Paving Simulation

Paving simulation identifies locations with insufficient HMA thickness to provide quantified information for

paving work afterwards. After BIM processing, HMA overlaying layers were newly added onto the DTM

frame that was previously modeled by an as-built slab surface. This step can be regarded as a BIM technique

to detect interference during construction. In this study, ‘interference’ means insufficient HMA overlaying

thickness due to undulations in the concrete base slab surface.

Figure 8 demonstrates the BIM simulation process of HMA overlaying. Figure 8(a) represents the

DTM for a specific section, where the colored areas represent higher elevations. For section A-A, transverse

surface profiles are shown in Figures 8(b) and 8(c). In Figure 8(c), the as-built and design surfaces are

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displayed together, and the elevation differences are noticeable. Engineers can easily detect ‘hill’ and ‘valley’

spots. Note that excessive levels observed adjacent to the median in the east bound lane in section A-A in

Figure 8(a) are confirmed in detail in Figure 8(c). Figure 8(d) shows the paving simulation after applying an

alternative paving level for section A’-A’. Paving thickness security after overlaying can be visually identified.

Note that in section A’-A’, excessive elevations at the edge of the east-bound lane produced insufficient HMA

thickness (Figure 8(d)).

[Figure 8. BIM Simulation of HMA overlaying]

In addition to the visual identifications, the simulated HMA overlaying quantity can be automatically

calculated in terms of volume and area. The required milling quantity can also be computed in the BIM model.

The combined quantified information for milling and HMA will be used for optimizing paving work in terms of

quality and cost.

4.5. Quantification of Simulated Paving Works

One primary advantage of utilizing BIM is the capability to extract quantitative information for construction

objectives. Quantified information for virtual paving works enables milling to be optimized and HMA paving

quantity to be known. Since paving costs can be directly estimated in BIM, information on paving quantity

and cost can be integrated and instantly analyzed. HMA thickness conditions observed in the visual

identification process can be confirmed and related to quantified information.

4.6. Cost Optimization

There are several ways to achieve the allowable compaction thickness. One way is to pave the surface at a

very conservative paving level, that is to say, thicker overlaying. This is convenient in that milling work can

be minimized. However, the uniformity of the HMA thickness might be inadequate. Costs would be much

higher since the HMA overlay has to mask all undulations. In addition, the paving level cannot be raised as

high as required since there is an elevation tolerance for the pavement structure.

The other approach is, without a paving level adjustment, to mill the surface until excessive elevation

is completely removed. This should result in more uniform thickness and smoother pavement. Traditional 2-

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D milling with only a single setting for the cutting depth is one approach. However, milling all excessive

elevations requires extensive work hours and costs and is impractical inside a tunnel. In addition, for very

excessive elevations, milling thickness is limited because the cover thickness from the concrete slab surface

should be maintained for reinforced steel. Therefore, the best combination of paving level and milling quantity

is sought in the optimization process, as measured by the pavement quality and cost.

5. FIELD WORK - Milling and HMA Overlaying at Paving Site

According to the optimized paving plan, milling was conducted and the HMA overlay level was set. In field

paving work, milling locations were designated by 3-D visualized information. Field engineers transformed

identified high elevations in the 3-D view into 2-D CAD file. Then, the field operator located milling

equipment in the designated area and conducted ‘selective’ milling. Undulation areas in the drawing were not

always coincident with the as-built surface. This was inferred to be due to the resolution of the BIM model

with spatial data of 3 m by 10 m. In addition, as mentioned before, a sizable milling area exists along the

edges of the main driving lanes. In the edge area, steel drainage gratings are embedded at regular intervals,

and thus milling equipment is difficult to access in those areas. Consequently, milling equipment could not be

placed on those areas. Instead, the high elevations in those areas were manually removed by field workers.

Figures 9(a) and (b) show milling equipment placement based on BIM analysis as well as selectively milled

surfaces.

After milling work, HMA materials were overlaid. As designed, two layers, 40 mm each, were

separately laid down. For overlay paving, a string stick was installed at the bottom of the concrete base slab at

intervals of 10 m in the longitudinal direction and with both paving edges over entire paving lanes (Figure 9 (c)).

For the first lift, a string line was set to the sticks based on 19 mm of NMAS and paving alternative 1. The

paver was maneuvered along with the string line level. For the second lift, the string line was not used for the

paver. However, mat thickness paving was conducted during surveying for the first lift layer surface elevation.

Figure 9 (d) shows HMA overlay paving.

[Figure 9. Milling and Paving Works]

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6. ANALYSIS AND RESULTS

6.1. Analysis Results for the Paving Simulation

Detection of the ‘thin area’ contributes to improved pavement quality in advance. Three paving levels,

alternatives 1 and 2 and the original paving level, were virtually simulated using BIM. Table 1 displays the

simulation views for STA 4+670 to STA 4+910. Two colors distinguish areas in which the thickness is secured

at thicknesses of 80 mm, 70 mm and 60 mm. Alternative 2 produces the largest area when the 80 mm design

thickness is secured for required compaction density and the original level is the smallest. Alternatives 1 and 2

were found to provide over 60 mm thickness in most paving areas, but the original level still contains some thin

areas.

In further analysis, various simulation results were examined at any thickness level, although they were not

illustrated in Table 1. There were some locations with 40 mm or 50 mm thickness are not secured, but the

percentage of area affected was insignificant. In the field paving stage, the extreme irregular elevations were

completely removed by the milling work.

In addition, the lower edge of each bound was commonly observed to exhibit higher elevations than

designed. It is inferred that during base slab casting and curing, the concrete mass formed is gravitationally

pushed out toward the lower edges of expressway sides. This detection is a valuable outcome resulting from

BIM utilization.

[Table 1. Virtual 3-D Paving Simulation Results Using BIM]

6.2. Analysis Results for Quantification

Table 2 presents paving area and volume with regard to secured thicknesses. As identified in visual

examination, most east and west bound lanes exhibited over 70 mm overlay thickness. The total area is the

same for the original and alternative levels since the 2-D area does not change for different vertical paving levels.

On the other hand, the total volumes are different for all levels since the volume of HMA overlay changes

reflects a vertical elevation difference. Alternative 2 obviously produces the largest total paving volume since

its level was established the most conservatively. However, area or volume requiring milling is the smallest in

alternative 2. The original level has an advantage in terms of HMA quantity, but not in milling quantity.

[Table 2. Quantitative Information from Paving Simulation]

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Figure10 presents the cumulative percent areas with respect to secured thickness for each paving level.

If the original paving level under the as-built concrete slab surface is applied, only about 65% of the total paving

area satisfies the design thickness, 80 mm for both east and west bound lanes. About 85% and 95% are

guaranteed for 70 mm and 60 mm thickness, respectively. However, alternative levels 1 and 2 after elevation

correction distinctively improved the percentage. Alternative 2 overlaying can produce about 85% and 80%

area for 80 mm thicknesses in east and west bound lanes, respectively. Particularly, alternatives 1 and 2

already achieve about 95% for 70 mm thicknesses, which means that milling work is required for only about 5%

of the total paving to ensure thickness quality assurance. Note that the original level needs to have about 15%

of the area milled to achieve the same level of thickness quality.

[Figure 10. The Percent Area for Secured HMA Thickness]

6.3. Analysis Results for Cost Optimization

6.3.1. Factors for Optimization Analysis

Table 3 presents an optimization matrix with 9 options. The options are composed of paving level, design

thickness security, HMA quantity, and milling work. HMA material quantities and milling work were

computed under the assumption that the corresponding paving level is applied and the percentage of design

thickness security is achieved.

Thickness quality was categorized with 3 levels, 80%, 90%, and 100% for securing design thickness

As shown in Figure 9, virtual paving simulation indicates that over 70 mm thickness covered more than 80% of

the area for all paving levels. Eighty percent coverage was the lowest level chosen for optimization analysis.

Milling area was computed for the corresponding percent of secured thickness, 80%, 90%, and 100%. Unit

cost of milling work was $9 Singapore dollars per 25 mm depth, and overall milling cost was estimated for the

corresponding milling area. Note that milled concrete volume was assumed to be a third of the milling area

multiplied by the 25 mm milling depth. HMA tonnage was computed by multiplying the simulated volume by

2.3 ton/m3 of unit HMA weight. Milled concrete volume was also added in the HMA tonnage since the milled

volume will be replaced by HMA. The unit cost of HMA was $95 Singapore dollars per ton.

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6.3.2. Optimization Results

Cost cannot be the only criterion to select the final paving option. Pavement quality is the priority in the

optimization process. The degree of pavement quality should be simultaneously examined. In addition,

construction period by milling should be carefully taken into consideration, although that factor was not listed in

Table 3.

Options with original levels were excluded since they cause significant milling work. A smaller

HMA quantity than the original level is not expected to compensate for the construction time delay associated

with milling work. Options with alternative 2 have the advantage of reducing the milling quantity compared to

alternative 1. On the other hand, alternative 1 seems to be favorable for pavement qualities such as uniformity

of HMA overlay thickness, compaction efficiency, and smoothness. Consequently, alternative 1 with milling

for 90% thickness security, option 5 in Table 3, was recommended as the optimized option. Note that this

choice does not mean that paving works were limited to the pavement quality of 90% thickness security. The

optimized choice was used as a reference plan to prevent surpluses from being wasted. In field milling work, a

higher degree of undulations could be removed.

[Table 3 Cost Optimization Matrix]

6.4. Expenses for Milling and Paving in the Field

Table 4 summarizes the expenses for milling and paving. Selective milling using 3-D BIM reduced the cost by

a third compared to the original milling cost. Extension of the construction period by the amount of milling

work was not considered in this cost evaluation. If the effect was included in the cost analysis, the actual cost

benefits would be much higher.

As explained, due to use of a thickness paving method for the 2nd lift overlay, the HMA overlay

quantity consumed more than the optimized plan or the original plan. However, in those plans, thickness

paving was not counted. If the plans had been applied during field paving, they would increase HMA quantity

as well.

[Table 4. Summary of Milling and Paving Expenses]

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6.5. Quality Assurance (QA) Results for Thickness and Density after Field Paving

Table 5 presents quality assurance data for the thickness and density of the paved HMA core samples. A total

of 24 core samples were collected from the completed HMA overlay pavement. Thickness data shows that 22

out of 24 samples satisfy design thickness criteria. Mean thicknesses are 9.07 cm and 9.67 cm, east and west

bound, respectively. Most data is thicker than the design thickness, 80 mm. As mentioned, HMA quantity

was reduced slightly more than planned. The thicker results are consistent with the supplied HMA quantity.

Considering the LTA specification thickness range for the single lift, 40 mm − 65 mm, the thickness data for two

lifts can be regarded as satisfactory. Moreover, the coefficients of variation for both bounds are 14.7% and

15.1%, respectively. Thickness uniformity can be regarded as successfully achieved. Selective milling

contributes to the uniformity.

In addition, data for all samples indicates bulk dry densities, Gmb, over 2.30 kg/m3. The density

requirement was 98% of the reference density. The density results reflect that the 19 mm NMAS mix was

compacted within proper HMA mat thickness ranges.

[Table 5. Overlaid HMA Thickness and Density Test Results]

7. CONCLUSIONS AND FUTURE RECOMMENDATIONS

The primary significance of this study is to show that BIM can be effectively utilized to optimize quality and

cost in ‘pavement engineering’ just as in other civil structure(s). The ‘In-advance Simulation,’ ‘3-D

Visualization’, ‘Interference Identification,’ and ‘Quantification’ capabilities of BIM enhance the efficiencies of

individual paving sequences. Implementation of BIM in HMA overlaying work resulted in an obvious

improvement in pavement quality and reduced paving costs. The developed method can be regarded as state-

of-practice for pavement engineering. Detailed achievements include

� In-Advance Simulation:

Paving sequences could be successfully simulated in BIM. Condition of the pre-overlay surface was

accurately modeled. Paving level alternatives could be derived from the BIM model. Diverse HMA

overlaying patterns could be readily simulated in the BIM model.

� 3-D Visualization:

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BIM produced 3-D visualized displays or drawings for simulated paving conditions. During simulation

and quantification processes, engineers were able to observe paving results on a 3-D display. The 3-D

display helps to identify potential sources of interference such as paving thickness. In the field paving

process, based on the 3-D outputs, interferences were marked in 2-D drawings, and field engineers

selectively operated milling equipment only at those locations that had excessive elevation. Selective

milling reduced project costs.

� Interference Identification:

Interference identification is one of the primary functions of BIM. Interference items in paving work

include thickness security, elevation tolerance, and paving equipment accessibility. This study proved

that interferences in paving work, as in other civil structures, can be detected using BIM.

� Quantification:

Simulated paving results were quantified in terms of volume and area, particularly for milling and

overlaying. The quantified information was used to optimize pavement quality and cost. BIM was

easily capable of computing every possible realistic paving case. The amount of quantified information

from BIM allows the best paving option to be determined.

The BIM model in this study was established with a survey resolution of 3 m x 10 m. If a higher resolution

had been used, outputs would have been more defined. Undulation conditions on a concrete bridge deck

surface are similar to those on a tunnel concrete base slab surface. The BIM paving technique developed in this

study can therefore be applied to HMA overlay on a concrete bridge deck surface.

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REFERENCES

Bae, A, Lee, D, and Tan., J. 2015. IRI reduction of HMA overlay on concrete base slab in urban tunnel

expressway. TRB 94th Annual Meeting, Washington D.C.

Brown, E.R., Kandhal, P.S., Roberts, F.L., Kim, Y.R., Lee, D.Y., and Kennedy, T.W. 2009. Hot mix asphalt

materials, mixture design, and construction. Third Edition. National Asphalt Paving Association Research

and Education Foundation. Lanham, MD.↵

Building and Construction Authority (BCA). 2011. BCA’s building information modelling roadmap. Available

from https://www.bca.gov.sg/newsroom/others/pr02112011_bib.pdf, Singapore Government [accessed 03 June

2016]

Building Information Modeling. 2008. BIM Handbook: A guide to building information modeling for owners,

managers, designers, engineers, and contractors. John Wiley & Sons, Inc.

Crossrail Ltd. 2016. Driving industry standards for design innovation on major infrastructure projects,. Available

from http://www.crossrail.co.uk/construction/building-information-modelling [accessed 02 June 2016]

Engineering Group. 2010. Materials and workmanship specification for civil and structural works, Land

Transport Authority, Singapore.

Ensell, J. 2012. Milling and paving operations for smoothness and uniformity. J. the Association of Asphalt

Technologists, 51: 769-772.

Fanning, B, Clevenger, M. C., Ozbek, E. M., and Mahmoud, H. 2015. Implementing BIM on infrastructure:

comparison of two bridge construction projects, ASCE, The Practice Periodical on Structural Design and

Construction, DOI: 10.1061/(ASCE)SC.1943-5576.0000239.

Federal Highways Administration (FHWA) and National Asphalt Pavement Association (NAPA). 2001.

HMA pavement mix type selection guide, Information Series 128, U.S. Department of Transportation.

Japan Construction Information Center (JACIC). 2016. The key-base information station for the construction

industry to pave way for the future japan construction information center - General Incorporated Foundation.

Available from http://www.jacic.or.jp/english/count31.html [accessed 02 June 2016]

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Kim, C., Kim, H., Park, T., and Kim, M. 2011. Applicability of 4D CAD in civil engineering construction: Case

study of a cable-stayed bridge project,” ASCE, J. Computing in Civil Engineering, 25(1): 98-107 DOI:

10.1061/(ASCE)CP.1943-5487.0000074.

McGraw-Hill Construction. 2012. The business value of BIM for infrastructure – Addressing America’s

infrastructure challenges with collaboration and technology, Smart Market Report.

Reeder D. G. and Nelson, A. G. 2015. Implementation manual - 3D engineered models for highway construction:

The Iowa experience,” Report no. RB33-014, National Concrete Pavement Technology Center Institute for

Transportation, Iowa State University.

Schwarz, J. 2006. Three degrees of cold: today's milling contractor needs to stock up on latest and most

complete line of equipment. Roads and Bridges, 44(5): 54-56.

Sidlar, G. 2006. Must be exact: when done right, precision milling carries heavy benefits in urban areas. Roads

and Bridges, 44(5): 50-52.

Woof, M. 2011. Milling sophistication, World Highways/Routes du Monde, July/August:48-50. Available from

http://www.worldhighways.com/categories/measurement-survey-design-software/features/asphalt-milling-

optimised-by-3d-controls [accessed 21 July 2016]

Yabuki, N., Azumaya, Y., Akiyama, M., Kawanai, Y., and Miya, T. (2007). Fundamental study on development

of a shield tunnel product model. J. Applied Computing in Civil Engineering, 16: 261-268.

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TABLES

Table 1. Virtual 3-D Paving Simulation Results Using BIM

HMA Thickness Security

Original Paving Level Paving Level Alternative 1 Paving Level Alternative 2

80mm

70mm

60mm

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Table 2. Quantitative Information from Paving Simulation

(a) Area (m2)

Secured Thickness

Original Level

Alternative 1 Level

Alternative 2 Level

East West

East West

East West

Over 80 mm

13620 12612

15172 14270

17985 15215

70mm ~ 80mm

4189 3609

4569 3958

2728 3396

60mm ~ 70mm

2376 1940

1141 788

334 542

50mm ~ 60mm

742 735

190 156

26 22

40mm ~ 50mm

149 286

3 10

3 7

30mm ~ 40mm

0 20

0 4

0 0

Total Area

21076 19182

21076 19182

21076 19182

(b) Volume (m3)

Secured Thickness

Original Level

Alternative 1 Level

Alternative 2 Level

East West

East West

East West

Over 80 mm

1686.1 1509.5

1816.9 1698.8

1947.6 1765.9

70mm ~ 80mm

51.8 42.2

30.3 20.5

12.2 15.2

60mm ~ 70mm

20.0 18.2

7.0 4.9

1.1 2.2

50mm ~ 60mm

5.1 6.3

0.4 0.5

0.1 0.1

40mm ~ 50mm

0.5 1.5

0.0 0.1

0.0 0.0

30mm ~ 40mm

0.0 0.2

0.0 0.0

0.0 0.0

Total Area

1763.47 1577.83

1854.6 1724.87

1961.03 1783.46

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Table 3 Cost Optimization Matrix

Option

Paving

Level

Design

Thickness

Security

(% Area

of 80 mm)

Milling

HMA Paving

Total Cost

($, Singapore) Milling

Area

(m2)

Cost

($, Singapore)

HMA

(ton) Cost

($, Singapore)

1 Original 80% 5974.8 $53,773 7914.0 $751,832 $805,605

2 Original 90% 10000.6 $90,006 8067.7 $766,429 $856,435

3 Original 100% 14026.4 $126,238 8221.9 $781,084 $907,322

4 Alternative 1 80% 2764.6 $24,881 8338.8 $792,185 $817,066

5 Alternative 1 90% 6790.4 $61,114 8491.9 $806,735 $867,849

6 Alternative 1 100% 10816.2 $97,346 8646.3 $821,399 $918,745

7 Alternative 2 80% 130.2 $1,172 8617.3 $818,643 $819,815

8 Alternative 2 90% 3032.3 $27,291 8727.4 $829,105 $856,396

9 Alternative 2 100% 7058.1 $63,523 8881.8 $843,769 $907,292

a % is the result based on corresponding paving level before milling

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Table 4. Summary of Milling and Paving Expenses

Items Plan with Original Levela Optimized Plan Field Paving Results

Milling Cost $126,238 $ 61,114 $ 41,949

HMA Overlay Cost $781,084 $806,735 $ 854,810

Total Cost $907,322 $867,849 $ 896,759

a Option no. 3 in the previous Table 3

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Table 5. Overlaid HMA Thickness and Density Test Results

East Bound West Bound

No. Test Sample

No.

Thickness

(cm)

Density

(kg/cm3) No.

Test Sample

No.

Thickness

(cm)

Density

(kg/cm3)

1 C486/W3B/E/C1T&B 8.06 2.31 1 C486/W3B/W/C1T&B 8.69 2.30

2 C486/W3B/E/C2T&B 9.23 2.30 2 C486/W3B/W/C2T&B 9.56 2.30

3 C486/W3B/E/C3T&B 8.25 2.30 3 C486/W3B/W/C3T&B 11.21 2.30

4 C486/W3B/E/C4T&B 8.06 2.30 4 C486/W3B/W/C4T&B 10.66 2.32

5 C486/W3B/E/C5T&B 11.76 2.30 5 C486/W3B/W/C5T&B 10.59 2.30

6 C486/W3B/E/C6T&B 10.32 2.30 6 C486/W3B/W/C6T&B 9.49 2.30

7 C486/W3B/E/C7T&B 9.95 2.30 7 C486/W3B/W/C7T&B 10.43 2.30

8 C486/W3B/E/C8T&B 7.19 2.30 8 C486/W3B/W/C8T&B 8.67 2.30

9 C486/W3B/E/C9T&B 8.06 2.31 9 C486/W3B/W/C9T&B 11.04 2.30

10 C486/W3B/E/C10T&B 8.36 2.31 10 C486/W3B/W/C10T&B 8.31 2.31

11 C486/W3B/E/C11T&B 10.57 2.30 11 C486/W3B/W/C11T&B 11.06 2.30

12 C486/W3B/E/C12T&B 8.98 2.30 12 C486/W3B/W/C12T&B 6.36 2.30

Statistics

Mean 9.07 2.30

Statistics

Mean 9.67 2.30

SD 1.34 0.005 SD 1.46 0.01

COV (%) 14.7 0.2 COV (%) 15.1 0.3

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Lists of Figure Captions

Figure 1. Open-Cut Tunnel Design

Figure 2. Construction Condition of Concrete Base Slab

Figure 3. As-Built Concrete Base Slab Surface

Figure 4. As-Built Base Slab Surface Undulation

Figure 5. BIM Utilization Methodology for Optimized Paving

Figure 6. Digital Terrain Model

Figure 7. Adjustment for Excessive Elevations on the As-Built Concrete Slab Surface

Figure 8. BIM Simulation of HMA overlaying

Figure 9. Milling and Paving Works

Figure 10. The Percent Area for Secured HMA Thickness

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(a) Open-Cut Tunnel Geometry

(b) Pavement Design

Figure 1. Open-Cut Tunnel Design

Fill

Trunk

Sewer

Φ2.5m

Manhole

Strut 2

Strut 1

56.0~80.5m

Tubular

Pile

DSM (Deep Soil Mixing) JGP (Jet Grouting)

9~10m

Bored Pile (Earth Drill)

East Bound West Bound

Concrete Base Slab

Soft

Ground

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(a) Reinforced Steel Installation for Form Casting (b) Surface Finishing

Figure 2. Construction Condition of Concrete Base Slab

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Figure 3. As-Built Concrete Base Slab Surface

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(a) Plan View (b) Section View

Figure 4. As-Built Base Slab Surface Undulation

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Figure 5. BIM Utilization Methodology for Optimized Paving

Derivation of

Alternative Paving Levels

Establishment of BIM

Digital Terrain Model

→ Identification of Pre-Overlay Condition

Survey for

Pre-Overlay Surface

(3-D Scan or Survey)

Paving Cost Optimization

Analysis

→ Selection of Paving Level and Milling Quantity

Quantification of

Paving Volume and Area

→ Evaluating % Area

of Secured Thickness

Paving Simulation

for Alternative Levels

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(a) DTM of General Highway Topography

(b) Side View of DTM of MCE C486 Expressway

(c) Plan View of DTM of MCE C486 Expressway

Figure 6. Digital Terrain Model

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(a) Elevation Difference between As-Built Level and Original Design Level

(b) Elevation Difference between Corrected Alternative Level and Design Level

Figure 7. Adjustment for Excessive Elevations on the As-Built Concrete Slab Surface

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4+330

4+340

4+350

4+360

4+370

4+380

4+390

4+400

4+410

4+420

4+430

4+440

4+450

4+460

4+470

4+480

4+490

4+500

4+510

4+520

4+530

4+540

4+550

4+560

4+570

4+580

4+590

4+600

4+610

4+620

4+630

4+640

4+650

As-

Built -D

esign L

evel

(cm

)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4+330

4+340

4+350

4+360

4+370

4+380

4+390

4+400

4+410

4+420

4+430

4+440

4+450

4+460

4+470

4+480

4+490

4+500

4+510

4+520

4+530

4+540

4+550

4+560

4+570

4+580

4+590

4+600

4+610

4+620

4+630

4+640

4+650

Alternative -

Design L

evel

(cm

)

As-Built Surface Level

Corrected Alternative Level

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(a) Digital Terrain Model for the As-Built Concrete Slab Surface

(b) The As-Built Profile of Section A-A (c) The As-Built and Design Surface Profiles

(d) HMA Overlaying Simulation for Section A’-A’

Figure 8. BIM Simulation of HMA overlaying

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(a) Milling Equipment Placement (b) Selectively Milled Surface

(c) Preparation of Overlay Level (d) HMA Overlaying

Figure 9. Milling and Paving Works

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(a) East Bound (b) West Bound

Figure 10. The Percent Area for Secured HMA Thickness

60

70

80

90

100

80 mm 70 mm 60 mm 50 mm 40 mm

% Area for Secured Thickness

(%)

HMA Overlay Thickness

Original Paving Level

Alternative Level 1

Alternative Level 2

60

70

80

90

100

80 mm 70 mm 60 mm 50 mm 40 mm

% Area for Secured Thickness

(%)

HMA Overlay Thickness

Original Paving Level

Alternative Level 1

Alternative Level 2

Page 34 of 34



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