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Publication Number: FHWA-04-044
Date: February 2004

Incremental Costs and Performance Benefits of Various Features of Concrete Pavements

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CHAPTER 2. DATA COLLECTION ACTIVITIES

Introduction

A significant data collection effort was required to obtain the information needed to fulfill the overall project objectives. This data collection effort consisted of:

The development, distribution, and collection of the questionnaire surveys as well as the overall processing of the data represented a major work effort. The processed and summarized performance and cost data serve as the "default" database (i.e., default cost and performance data sets) for use in evaluating the relative cost and performance benefits of each PCC pavement design feature.

This chapter describes each of the primary data collection activities mentioned above. The overall approach and methodology used in each activity are described, along with a summary of how the collected data were used in this project.

Literature Review

The detailed literature review for this project aimed to identify pertinent reference documents discussing the costs and performance benefits of different PCC pavement design features. A previous literature search conducted for a National Highway Institute (NHI) training course was the basis for the search conducted for this project.(5) However, the previous search by Smith and Hall targeted pavement design and performance information for the three major PCC pavement types (jointed plain concrete pavements (JPCP), jointed reinforced concrete pavements (JRCP), and continuously reinforced concrete pavements (CRCP)), so portions were not necessarily applicable to the current study which focuses primarily on JPCP designs and on the costs and performance benefits of PCC design features. Moreover, additional information was sought on pavement cross sections, PCC strength, PCC materials, and ride specifications, as these saw limited coverage in the original literature review.

To supplement the applicable documents identified in the original literature review, additional targeted searches were completed using the Transportation Research Information Services (TRIS), National Technical Information Services (NTIS), and Engineering Index (EI Compendex) national bibliographic databases. These searches were limited to recent publications (TRIS: 1995 to 2000; NTIS: 1990 to 2000; EI Compendex: 1998 to 2000). The search identified more than 100 additional records that were deemed potentially useful to the project.

After reviewing the records identified in the new literature searches, the researchers prepared a short annotation describing the record's content. A final annotated bibliography was prepared and grouped by the following topics:

The final annotated bibliography (appendix A) is not intended to be a comprehensive coverage of every PCC pavement design and performance study; instead, it is a listing of pertinent recent reports and papers (those published within the past 10 years) that provide guidance on the costs and performance of PCC pavement design features. The key documents were reviewed and used as a foundation for the pavement design categories and design features to be evaluated in the study, and also provided insight into general cost and performance trends.

Questionnaire Survey Development

This section describes the data collection effort for the performance and cost surveys conducted for this project. First, general background information is provided on the PCC pavement design features included in the surveys and on the construction of the surveys themselves. This is followed by a description of the data collection processes utilized in both the SHA (relative performance) surveys and the PCC paving contractor (relative cost) surveys.

Design Categories and Alternative Design Features

Based on the literature review, 10 primary categories of PCC pavement design features were identified, along with a list of possible design feature alternatives within each category. Because pavement designs can vary considerably within each of the design feature categories, one feature was selected to be the "standard" feature within that category. The collection of "standard" features from all design feature categories then represents the Standard PCC pavement cross section. The Standard PCC pavement cross section is the basis for comparison and allows for the determination of the incremental increase (or decrease) in cost and performance relative to that standard design (instead of, for example, each agency's standard design).

The final design feature categories and alternative design features considered within each category are summarized below. Those design features included as part of the Standard pavement design are indicated by "STD." A two-lane roadway (two lanes in one direction and part of a four-lane divided highway) is assumed as the Standard construction section.

Clearly, a virtually unlimited number of design feature alternatives could have been selected for this project. However, the number of alternatives was limited to not only facilitate the questionnaire survey process but also to represent more established design practices (although a few unique design features were included to reflect new or innovative practices).

Questionnaire Survey Forms

After the design feature categories were identified and the various design feature alternatives selected, questionnaire surveys were developed: one targeted at highway agencies (to solicit relative performance data) and one targeted at PCC paving contractors (to solicit relative cost data). Although these were separate surveys, the pavement design variables presented in each questionnaire are identical. This allows the results from each data collection effort to be directly paired for analysis. Additional data (including a short summary of the agency's PCC pavement maintenance activities and the ranking of the design categories in terms of their impact on pavement performance) were also a part of the relative performance questionnaire surveys.

Both surveys were structured so that only one design feature (from the Standard design) was changed at a time, and the survey participants were then asked to assess what effect that change might have in terms of the relative performance (agency questionnaire) or costs (contractor questionnaire). In this way, the relative effects of the change in that one design feature could be determined. For example, one scenario is to change the base from the 150-mm (6-inch) aggregate base in the Standard design to a 150-mm (6-inch) CTB. Considering this single change, the highway agencies were asked to assess what effect this would have on the relative performance of the modified pavement design in comparison to the Standard design. Assigning the relative performance of the Standard design as 1.0, if the modified pavement (with the CTB) is believed to be capable of carrying 5 percent more 80-kN (18-kip) equivalent single-axle load (ESAL) applications than the Standard pavement, the relative performance rating is 1.05. On the other hand, if the design feature change is believed to result in a 5-percent decrease in the number of 80-kN (18-kip) ESAL applications that the pavement can carry, the relative performance rating is 0.95. Again, all performance ratings are made relative to the Standard design performance rating of 1.0.

A similar approach is employed for the cost surveys. Using the same example (changing the aggregate base of the Standard section to a CTB), PCC paving contractors were asked to estimate what the change in relative cost of the modified pavement design might be, assuming a relative cost of 1.0 for the Standard section. If the cost for the modified pavement (containing the CTB) is believed to be 15 percent more than the Standard section, the relative cost rating is then 1.15.

Survey respondents provided these relative ratings for the entire group of design feature alternative changes listed above. Respondents were asked to not enter a rating if they had no experience with a particular design feature.

As part of the survey development, several design and construction assumptions were established to provide a common foundation for all respondents and to help to maintain overall consistency in the responses. These assumptions include the following:

Appendix B contains the final questionnaires used in conducting both surveys.

Desired Number of Survey Responses

Prior to sending out the questionnaire surveys, the researchers performed an initial statistical evaluation to determine the desired number of questionnaire responses required to have a reasonable estimate of the relative performance and cost. In determining the desired sample size, it is assumed that the total population has a normal distribution. The purpose of the questionnaires is to predict the average of the population (for example, the average PCC pavement life or the average PCC pavement relative construction cost). Thus the following equation is applicable to estimate the desired sample size:

Equation 1. The desired number of survey samples, lowercase N, equals the quotient of the product of the estimated standard deviation, sigma, times the number of standard error units, lowercase Z, divided by the required precision or tolerance, T, all raised to the second power.(1)

where:

n = desired number of survey samples.

s = estimated standard deviation.

z = number of standard error units (based on the desired confidence level and obtained from a normal probability table).

T = required precision or tolerance.

With this approach, the standard deviation of the to-be-determined average value is yet unknown. Furthermore, the desired confidence levels and the desired precision levels must also be selected. However, by running a range of values with an initially assumed, reasonable average, the effects of these inputs on the resulting number of samples can be determined and reasonable target values can be selected.

For the purposes of estimating the number of samples, the analyses for the performance and cost questionnaires are broken out separately, as described below.

Table 1. Summary of the required number of samples for performance questionnaires.
   

Number of Required Samples

   

90% Confidence (z = 1.645)

95% Confidence (z = 1.960)

   

Precision of Average Performance Life Estimate (T)

Precision of Average Performance Life Estimate (T)

   

Within 2 years

Within 5 years

Within 10 years

Within 2 years

Within 5 years

Within 10 years

Estimated Standard Deviation of Performance Life Estimates (σ)

4 years

10.8

1.7

0.4

15.4

2.5

0.6

6 years

24.4

3.9

1.0

34.6

5.5

1.4

10 years

67.7

10.8

2.7

96.0

15.4

3.8

As expected, table 1 shows that for higher levels of precision, higher standard deviation values, and higher confidence levels, greater numbers of relative performance responses are needed. For this project, a 95 percent confidence level and a precision level of 5 years are considered appropriate. Assuming a high variability in the life estimates (10 years), a minimum of 16 surveys (rounded up from the corresponding value of 15.4 in table 1) is desirable for the performance surveys.

Similarly, table 2 shows that for higher levels of precision, higher standard deviation values, and higher confidence levels, more relative cost responses are needed. For this project, a 95 percent confidence level and a precision level of $4.80/m2 ($4.00/yd2) are probably appropriate. Assuming a high variability in the responses ($10.80/m2 ($9.00/yd2)), a minimum of 20 surveys (rounded up from the corresponding value of 19.4 in table 2) is desirable for the cost surveys.

Table 2. Summary of the required number of samples for relative cost questionnaires.
   

Number of Required Samples

   

90% Confidence (z = 1.645)

95% Confidence (z = 1.96)

   

Precision of Average Cost Estimate (T)

Precision of Average Cost Estimate (T)

   

Within $2.40/m2 ($2.00/yd2)

Within $4.80/m2 ($4.00/yd2)

Within $7.20/m2 ($6.00/yd2)

Within $2.40/m2 ($2.00/yd2)

Within $4.80/m2 ($4.00/yd2)

Within $7.20/m2 ($6.00/yd2)

Estimated Standard Deviation of Cost Estimates (σ)

$3.60/m2 ($3.00/yd2)

6.1

1.5

0.7

8.6

2.2

1.0

$7.20/m2 ($6.00/yd2)

24.4

6.1

2.7

34.6

8.6

3.8

$10.80/m2 ($9.00/yd2)

54.8

13.7

6.1

77.8

19.4

8.6

The above analysis is very approximate, but it was used as an initial goal for the number of questionnaires to be obtained for the performance and cost surveys.

SHA Performance Questionnaire Survey

A project summary and request for participation was faxed to 43 SHAs; 25 agencies ultimately agreed to participate. Once appropriate contacts within each agency had been identified, the relative performance questionnaire forms were faxed or mailed to the participants; 45 days were allotted to them to submit completed forms. During this time, typically three deadline reminders were faxed to the volunteers. These reminders were sent during the third and fourth weeks and on the survey completion date.

A total of 12 SHA responses were received, despite several concentrated efforts to increase that number. This falls slightly lower than the original target of 16, but is believed to still be sufficiently high to provide meaningful results. Agencies providing responses to the questionnaire surveys were:

A summary of the raw SHA relative performance ratings is provided in appendix C; a concise summary of the responses is shown in table 3. This table shows several different columns of information related to the relative performance ratings. The column titled Average Survey Results contains the direct averages of the performance ratings provided by all SHAs. However, because of the considerable variability associated with many of these responses, perceived outlier data points were removed and the resultant performance ratings presented under the column titled Modified Survey Results. Outlying data points were identified as those performance values that 1) grossly contradicted the expected performance trends or 2) were greatly different in magnitude from the reasonable performance range.

The column titled Average Model Results in table 3 presents the average performance ratings as computed by available performance models; it is used as a basis for checking the reasonableness of the survey results (see Performance Model Evaluation section below). Based on the consideration of the survey results and the performance models, the recommended ranges of performance ratings for each design feature category are presented in the column titled Recommended Values.

A quick review of the recommended values shown in table 3 indicates that slab thickness has the largest effect on relative pavement performance, as might be expected. Other factors noted to have a major effect on relative pavement performance include the type of base (including the absence of a base course), drainage, dowel bars (the absence of dowel bars considerably decreased performance), and widened slabs.

Performance Model Evaluation

Due to the variability observed in the performance-related survey responses, available PCC pavement performance models were used to develop relative performance ratings for certain design features that may be added to or deleted from the Standard pavement section. Unfortunately, not all design features could be evaluated using these models because many features are not direct input variables in the models. Table 4 summarizes the models that were used in this study and the corresponding design features that could be evaluated with each model.

The average performance ratios coming from an investigation of all of the aforementioned models are presented in the Average Model Results column of table 3. As previously mentioned, using a combination of the results from the modified performance ratings and the results from the available performance models, recommended ranges for each design feature category were developed and are presented in table 3. The recommended ranges are used to define the default performance changes (i.e., the default performance data set) used in the analytical software tool developed for this project.

Table 3. Summary of performance ratings.

Design Feature Category

Design Feature

Average Survey Results

Modified Survey Results

Average Model Results

Recommended Values

Comments

Subgrade

Untreated prepared subgrade (STD)

1.00

1.00

1.00

1.00

Standard section.

300-mm (12-in) lime treated subgrade (and elimination of aggregate base)

0.86

0.86

0.93

0.85 to 0.95

Base course eliminated.

Base

150-mm (6-in) dense-graded aggregate base on prepared subgrade (STD)

1.00

1.00

1.00

1.00

Standard section.

No base (placed directly on prepared subgrade)

0.76

0.83

0.89

0.70 to 0.90

150-mm (6-in) dense-graded ATB

1.11

1.16

1.25

1.00 to 1.20

150-mm (6-in) dense-graded CTB

0.88

1.09

1.29

1.00 to 1.20

Drainage 

No drainage layers, no underdrains (STD)

1.00

1.00

1.00

1.00

Standard section.

150-mm (6-in) open-graded, nonstabilized aggregate base (with underdrains)

1.32

1.22

1.19

1.00 to 1.20

High survey performance results not validated with field data. Performance of permeable bases without underdrains not substantiated with field data.

150-mm (6-in) ATPB (with underdrains)

1.52

1.34

1.33

1.00 to 1.20

150-mm (6-in) ATPB (without underdrains)

1.27

1.17

n/a

0.90 to 1.20

150-mm (6-in) CTPB (with underdrains)

1.28

1.24

1.33

1.00 to 1.20

150-mm (6-in) CTPB (without underdrains)

1.28

1.17

n/a

0.90 to 1.20

Thickness/ Slab Size

250-mm (10-in) JPCP with 4.6-m (15-ft) joint spacing (STD)

1.00

1.00

1.00

1.00

Standard section.

200-mm (8-in) JPCP with 3.7-m (12-ft) joint spacing

0.57

0.82

0.44

0.40 to 0.80

300-mm (12-in) JPCP with 5.5-m (18-ft) joint spacing

2.05

1.17

13.64

1.20 to 1.80

Models largely consider effects of thickness on fatigue damage.

250-mm (10-in) JRCP with 9.1-m (30-ft) joint spacing (32-mm (1.25-in) epoxy-coated dowels, 150- x 300-mm (6-x 12-in) mesh)

0.91

0.91

0.79

0.80 to 1.00

Long joint spacing detracts from performance in models.

240-mm (9.5-in) CRCP (19-mm (0.75-in) epoxy-coated deformed bars, 200-mm (8-in) o.c. longitudinal, 914-mm (36-in) o.c. transverse)

1.05

1.05

0.74

0.90 to 1.10

American Association of State Highway and Transportation Officials (AASHTO) models assume same thickness required for all pavement types.

240-mm (9.5-in) CRCP (19-mm (0.75-in) noncoated deformed bars, 200-mm (8-in) o.c. longitudinal, 914-mm (36-in) o.c. transverse)

1.12

1.12

0.74

0.90 to 1.10

Cross Section

250-mm (10-in) thick uniform cross section (STD)

1.00

1.00

1.00

1.00

Standard section.

Trapezoidal cross section, 275 to 200 mm (11 to 8 in)

1.00

1.00

n/a

0.95 to 1.05

Thickened edge cross section, 200 mm (8 in) at centerline to 275 mm (11 in)

1.00

1.00

n/a

0.95 to 1.05

Joints/Load Transfer

250-mm (10-in) JPCP, 32-mm (1.25-in) epoxy-coated dowels, 4.6-m (15-ft) perpendicular joints (STD)

1.00

1.00

1.00

1.00

Standard section.

250-mm (10-in) JPCP, 32-mm (1.25-in) noncoated dowels, 4.6-m (15-ft) perpendicular joints

0.97

0.97

0.86

0.90 to 1.00

250-mm (10-in) JPCP, 32-mm (1.25-in) epoxy-coated dowels, 4.6-m (15-ft) skewed joints

0.96

0.96

n/a

0.95 to 1.00

250-mm (10-in) JPCP, no dowels, 4.6-m (15-ft) perpendicular joints

0.59

0.59

0.50

0.50 to 0.60

250-mm (10-in) JPCP, reduced # of 32-mm (1.25-in) epoxy-coated dowels, 4.6-m (15-ft) perpendicular joints

0.85

0.85

n/a

0.80 to 0.95

Design Feature Category

Design Feature

Average Survey Results

Modified Survey Results

Average Model Results

Recommended Values

Comments

Joint Sealing

Hot-poured rubberized asphalt with widening cut (4.6-m (15-ft) joints) (STD)

1.00

1.00

1.00

1.00

Standard section.

Hot-poured rubberized asphalt without widening cut (4.6-m (15-ft) joints)

0.99

0.99

n/a

0.95 to 1.00

Silicone sealant with widening cut (4.6-m (15-ft) joints)

1.06

1.06

0.64

1.00 to 1.05

Models show reduced performance from silicone sealants.

Silicone sealant without widening cut (4.6-m (15-ft) joints)

0.98

0.98

n/a

0.95 to 1.05

Preformed compression sealant (4.6-m (15-ft) joints)

1.05

1.07

2.97

1.00 to 1.10

Models show extremely high performance from preformed seals.

No sealant

0.86

0.95

0.56

0.90 to 1.00

Shoulders

150-mm (6-in) HMA over 250-mm (10-in) dense graded aggregate base (STD)

1.00

1.00

1.00

1.00

Standard section.

400-mm (16-in) gravel

0.98

0.98

1.00

0.95 to 1.00

150-mm (6-in) partial-depth tied PCC over 250-mm (10-in) aggregate base

1.14

1.14

1.73

1.00 to 1.15

Models show extremely high performance from tied shoulders and widened slabs.

250-mm (10-in) full-depth tied PCC over 150-mm (6-in) aggregate base

1.30

1.18

1.73

1.00 to 1.30

0.6-m (2-ft) widened PCC slab and a 2.4-m (8-ft) HMA shoulder

1.34

1.21

2.74

1.10 to 1.40

Strength/ Materials

4.5-MPa (650 lb/in2) flexural strength (STD)

1.00

1.00

1.00

1.00

Standard section.

5.2-MPa (750 lb/in2) flexural strength

1.17

1.17

4.35

1.00 to 1.20

Models largely consider effects of strength on fatigue damage.

High-early strength

0.97

0.97

n/a

0.95 to 1.05

Well-graded mix

1.26

1.08

n/a

1.00 to 1.10

Initial Smoothness

Note: These smoothness performance values are assumed to be the same regardless of the base type used. Reported smoothness values assume measurement with a 5-mm (0.20-in) blanking band.

110 to 142 mm/km (7 to 9 in/mi) (STD)

1.00

1.00

1.00

1.00

Standard section.

79 to 110 mm/km (5 to 7 in/mi)

1.03

1.03

1.04

1.00 to 1.05

47 to 79 mm/km (3 to 5 in/mi)

1.08

1.08

1.07

1.00 to 1.10

16 to 47 mm/km (1 to 3 in/mi)

1.12

1.12

1.10

1.00 to 1.14

< 16 mm/km (1 in/mi)

1.10

1.10

1.13

1.00 to 1.16

Key: STD = Standard; ATB = asphalt-treated base; CTB = cement-treated base; ATPB = asphalt-treated permeable base; CTPB = cement-treated permeable base; o.c. = on center; n/a = not available.

All ratings are relative to the performance of the Standard pavement section.

Key: STD = Standard; n/a = not available.

Table 4. PCC pavement performance models used to evaluate effect of design features.

Model

Performance Indicator

Design Features Evaluated

1993 AASHTO(6)

Serviceability

Base
Drainage
Slab Thickness
Load Transfer
Shoulder Type
PCC Strength
Initial Smoothness

1998 AASHTO(7)

Serviceability

Subgrade
Base
Slab Thickness/Slab Size
Shoulder Type
PCC Strength
Initial Smoothness

1990 Ripper(8)

Slab Cracking

Slab Thickness/Slab Size
PCC Strength
Shoulder Type

1997 Ripper(9)

Slab Cracking

Base Type
Slab Thickness/Slab Size
PCC Strength
Shoulder Type

Joint Faulting

Base Type
Drainage
Slab Thickness/Slab Size
Load Transfer
Shoulder Type

Joint Spalling

Slab Size
Joint Sealant

SHA Design Category Ranking Survey

In addition to the relative performance ratings, SHA respondents were asked to rank the relative importance of each design feature category to PCC pavement performance. That is, of the 10 design feature categories (see below) respondents were asked to rank each factor on an integer scale of 1 to 10, with 10 representing the most important and 1 the least important. No two design features were allowed to share the same ranking, so the result was a "forced ranking" of the importance of each design feature category. These rankings were incorporated into the analysis approach as a way of accounting for the effects of multiple design feature changes on pavement performance (see discussion in chapter 3).

The final recommended category rankings are presented in table 5 and are based on the collected survey results. It is readily acknowledged that a designer or agency could have different opinions about the ranking factors. Therefore, although the category ranking factor set displayed in table 5 is used as the default ranking factor set in the software, an agency may create their own ranking factor set that reflects their expected relationships between design categories and concrete pavement performance.

Table 5. Details of the recommended category ranking factor set.

Design Category

Ranking Factor

Most Important
Down Arrow
Least Important

Joints/Load Transfer

10

Thickness/Slab Size

9

Base/Subbase

8

Drainage

7

Strength/Materials

6

Subgrade

5

Initial Smoothness

4

Joint Sealing

3

Cross Section

2

Shoulders

1

Contractor Cost Questionnaire Survey

A project summary and request for participation was faxed to 216 contracting companies provided by the American Concrete Pavement Association (ACPA). A total of 53 firms responded to the request; 38 volunteered to participate in the study. The relative cost questionnaire forms were faxed or mailed to each volunteer. Forty-five days were allotted to complete the questionnaire surveys. As with the relative performance questionnaire surveys, typically three deadline reminders were faxed to the volunteers. These reminders were sent during the third and fourth weeks and on the survey completion date.

Sixteen responses were received from contractors. As with the SHA surveys, this value falls slightly lower than the original target of 20, but it is believed to be sufficiently large to provide meaningful results. Paving contractors responding were:

A summary of the raw relative cost data collection responses is provided in appendix C. The averages of all survey results for each alternative design feature are displayed in table 6. An initial review of the data indicates that comprehensive drainage systems result in a substantial increase in pavement costs. Other design features that contribute significantly to pavement costs are PCC shoulders and high-early strength PCC mixtures. On the other hand, factors such as pavement cross sections (trapezoid or thickened edge), widened slabs, and joint sealing appear to have very little effect on pavement construction costs. Note that the cost associated with achieving different levels of initial smoothness is dependent on the selected base type.

Summary

This chapter summarizes the data collection activities for this project. A description of the literature search is first presented, which provided many useful resource documents that served as the basis for the development of the questionnaire surveys. The approach used in developing the questionnaire surveys is also provided, which produced two separate questionnaire surveys: one targeted to state highway agencies and intended to collect relative performance ratings for changes in design features, and one targeted to PCC paving contractors and intended to collect relative cost ratings for changes in design features. Each questionnaire survey was structured in the same manner so that the performance and cost data could be matched up for each design feature.

The results of the performance and cost surveys are summarized in this chapter, with raw survey results presented in appendix C. The performance ratings that were received from the highway agencies were evaluated in conjunction with available performance models to check their validity and reasonableness. Overall, these data serve as one "data set" for use in the computer program developed under this project (see chapter 3).

Table 6. Summary of contractor initial cost ratings.

Design Feature Category

Design Feature

Average Survey Results

Subgrade

Untreated prepared subgrade (STD)

1.00

300-mm (12-in) lime treated subgrade (and elimination of aggregate base)

0.98

Base

150-mm (6-in) dense-graded aggregate base on prepared subgrade (STD)

1.00

No base (placed directly on prepared subgrade)

0.85

150-mm (6-in) dense-graded ATB

1.16

150-mm (6-in) dense-graded CTB

1.06

Drainage 

No drainage layers, no underdrains (STD)

1.00

150-mm (6-in) open-graded, nonstabilized aggregate base (with underdrains)

1.22

150-mm (6-in) ATPB (with underdrains)

1.33

150-mm (6-in) ATPB (without underdrains)

1.28

150-mm (6-in) CTPB (with underdrains)

1.28

150-mm (6-in) CTPB (without underdrains)

1.27

Thickness/ Slab Size

250-mm (10-in) JPCP with 4.6-m (15-ft) joint spacing (STD)

1.00

200-mm (8-in) JPCP with 3.7-m (12-ft) joint spacing

0.87

300-mm (12-in) JPCP with 5.5-m (18-ft) joint spacing

1.09

250-mm (10-in) JRCP with 9.1-m (30-ft) joint spacing (32-mm (1.25-in) epoxy-coated dowels, 150- x 300-mm (6-x 12-in) mesh)

1.08

240-mm (9.5-in) CRCP (19-mm (0.75-in) epoxy-coated deformed bars, 200-mm (8-in) o.c. longitudinal, 914-mm (36-in) o.c. transverse)

1.20

240-mm (9.5-in) CRCP (19-mm (0.75-in) non-coated deformed bars, 200-mm (8-in) o.c. longitudinal, 914-mm (36-in) o.c. transverse)

1.15

Cross Section

250-mm (10-in) thick uniform cross section (STD)

1.00

Trapezoidal cross section, 275 to 200 mm (11 to 8 in)

0.99

Thickened edge cross section, 200 mm (8 in) at centerline to 275 mm (11 in) edges

1.00

Joints/Load Transfer

250-mm (10-in) JPCP, 32-mm (1.25-in) epoxy-coated dowels, 4.6-m (15-ft) perpendicular joints (STD)

1.00

250-mm (10-in) JPCP, 32-mm (1.25-in) noncoated dowels, 4.6-m (15-ft) perpendicular joints

0.99

250-mm (10-in) JPCP, 32-mm (1.25-in) epoxy-coated dowels, 4.6-m (15-ft) skewed joints

1.01

250-mm (10-in) JPCP, no dowels, 4.6-m (15-ft) perpendicular joints

0.94

250-mm (10-in) JPCP, reduced # of 32-mm (1.25-in) epoxy-coated dowels, 4.6-m (15-ft) perpendicular joints

0.97

Joint Sealing

Hot-poured rubberized asphalt with widening cut (4.6-m (15-ft) joints) (STD)

1.00

Hot-poured rubberized asphalt without widening cut (4.6-m (15-ft) joints)

0.99

Silicone sealant with widening cut (4.6-m (15-ft) joints)

1.03

Silicone sealant without widening cut (4.6-m (15-ft) joints)

1.02

Preformed compression sealant (4.6-m (15-ft) joints)

1.07

No sealant

0.95

Shoulders

150-mm (6-in) HMA over 250-mm (10-in) dense graded aggregate base (STD)

1.00

400-mm (16-in) gravel

0.90

150-mm (6-in) partial-depth tied PCC over 250-mm (10-in) aggregate base

1.13

250-mm (10-in) full-depth tied PCC over 150-mm (6-in) aggregate base

1.17

0.6-m (2-ft) widened PCC slab and a 2.4-m (8-ft) HMA shoulder

1.07

Strength/ Materials

4.5-MPa (650 lb/in2) flexural strength (STD)

1.00

5.2-MPa (750 lb/in2) flexural strength

1.05

High-early strength

1.12

Well-graded mix

1.01

Design Feature Category

Design Feature

Average Survey Results

Note: these smoothness performance values differ based on the base type used. Reported smoothness values assume measurement with a 5-mm (0.20-in) blanking band.

Initial Smoothness (measured with a 5-mm (0.20-in) blanking band)

150-mm (6-in) dense-graded aggregate base on prepared subgrade (STD)

-

110 to 142 mm/km (7 to 9 in/mi) (STD)

1.00

79 to 110 mm/km (5 to 7 in/mi)

1.00

47 to 79 mm/km (3 to 5 in/mi)

1.00

16 to 47 mm/km (1 to 3 in/mi)

1.02

< 16 mm/km (1 in/mi)

1.04

No base (placed directly on prepared subgrade)

-

110 to 142 mm/km (7 to 9 in/mi) (STD)

Base type not included in survey. Assumed to be similar to costs associated with the 150-mm dense-graded aggregate base.

79 to 110 mm/km (5 to 7 in/mi)

47 to 79 mm/km (3 to 5 in/mi)

16 to 47 mm/km (1 to 3 in/mi)

< 16 mm/km (1 in/mi)

150-mm (6-in) ATB

-

110 to 142 mm/km (7 to 9 in/mi) (STD)

1.03

79 to 110 mm/km (5 to 7 in/mi)

1.04

47 to 79 mm/km (3 to 5 in/mi)

1.04

16 to 47 mm/km (1 to 3 in/mi)

1.05

< 16 mm/km (1 in/mi)

1.07

150-mm (6-in) CTB

-

110 to 142 mm/km (7 to 9 in/mi) (STD)

1.01

79 to 110 mm/km (5 to 7 in/mi)

1.01

47 to 79 mm/km (3 to 5 in/mi)

1.01

16 to 47 mm/km (1 to 3 in/mi)

1.03

< 16 mm/km (1 in/mi)

1.04

150-mm (6-in) open-graded, nonstabilized aggregate base

-

110 to 142 mm/km (7 to 9 in/mi) (STD)

Base type not included in survey. Assumed to have higher costs than any of the other included base types due to the difficulty of constructing on this base type.

79 to 110 mm/km (5 to 7 in/mi)

47 to 79 mm/km (3 to 5 in/mi)

16 to 47 mm/km (1 to 3 in/mi)

< 16 mm/km (1 in/mi)

Open-graded stabilized drainage layers

-

110 to 142 mm/km (7 to 9 in/mi) (STD)

1.03

79 to 110 mm/km (5 to 7 in/mi)

1.03

47 to 79 mm/km (3 to 5 in/mi)

1.03

16 to 47 mm/km (1 to 3 in/mi)

1.05

< 16 mm/km (1 in/mi)

1.06

Key: STD = Standard; ATB = asphalt-treated base; CTB = cement-treated base; ATPB = asphalt-treated permeable base; CTPB = cement-treated permeable base; o.c. = on center.

All ratings are relative to the cost of the Standard pavement section.

Key: STD = Standard; ATB = asphalt-treated base; CTB = cement-treated base.

 

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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