Safety Edge SM

PCC Demonstration Project

County Highway E34 

Fairview, Iowa 

Field Report 

June 10, 2011 
FOREWORD 

The purpose of this field report is to provide a summary of observations made during the 

construction of the portland cement concrete (PCC) Safety EdgeSM project near Fairview, 

Iowa, east of Cedar Rapids. These observations and data are to be used with similar 

information from other Safety EdgeSM projects to facilitate the development of standards and 

guidance for Safety EdgeSM construction and long-term performance. 

This field report is a summary of the observations and field data measured during 

construction on May 14, 2010 to evaluate the use of the Safety EdgeSM during paving, 

determine the slope of the Safety EdgeSM, recommend design adjustments, and identify 

benefits and complications with the use of the edge device
ii

1. Report No. 2. Government Accession No 3. Recipient’s Catalog No

3. Title and Subtitle 

Safety EdgeSM PCC Demonstration Project, County Highway E34 

Fairview, Iowa 

5. Report Date 

 June 10, 2011 

6. Performing Organization Code 

7. Authors 

Joe Pitlik and Jagannath Mallela 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 

 Applied Research Associates, Inc. 

 100 Trade Centre Drive, Suite 200 

 Champaign, IL 61820 

10. Work Unit No. 

11. Contract or Grant No. 

12. Sponsoring Agency Name and Address 

 Office of Infrastructure 

 Federal Highway Administration 

 1200 New Jersey Avenue, SE 

 Washington, DC 20590 

13. Type of Report and Period Covered 

 Field Report 

 May – June 2011 

14. Sponsoring Agency Code 

15. Supplementary Notes 

Contracting Officer’s Technical Representative: Byron Lord and Mary Huie

Contracting Officer’s Technical Manager: Andy Mergenmeier

16. Abstract 

In a coordinated effort with highway authorities and industry leaders, the Every Day Counts initiative serves as a catalyst to 

identify and promote cost effective innovations to bring about rapid change to increase safety of our nations highway 

system, decrease project delivery time, and protect our environment. The Safety EdgeSM concept is an example of one such 

initiative in which the edge of the road is beveled during construction for the purpose of helping drivers who migrate off the 

roadways to more easily return to the road without over correcting and running into the path of oncoming traffic or running 

off the other side of the roadway. 

This field report documents the observations made on the construction of the Safety EdgeSM on a two lane highway PCC 

overlay project on County Highway E34 (a.k.a. Fairview Road) in the vicinity of Fairview, Iowa. Details regarding the 

fabrication and performance of a custom device used to shape the Safety EdgeSM along with the shape and physical 

properties of the finished Safety EdgeSM are presented for the purpose of understanding what processes and techniques were 

most successful in forming the Safety EdgeSM. 

The findings from this overlay project and other similar ongoing projects form the basis for understanding the construction 

process and material performance necessary to bring this innovation into common highway practice and make our Nation’s 

highways safer. 

17. Key Words 

Safety EdgeSM, Slope, PCC 

18. Distribution Statement 

No restriction. 

19. Security Classif.(of this report) 

Unclassified 

20. Security Classif. (of this page) 

Unclassified 

21. No. of Pages 

23 

22. Price 

Form DOT F 1700.7 (8-72)
iii

SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

LENGTH 

(none) mil 25.4 micrometers μm

in inches 25.4 millimeters mm

ft feet 0.305 meters m 

yd yards 0.914 meters m 

mi miles 1.61 kilometers km

AREA 

in2square inches 645.2 square millimeters mm2

ft2square feet 0.093 square meters m

2

yd2square yards 0.836 square meters m

2

ac acres 0.405 hectares ha

mi2square miles 2.59 square kilometers km2

VOLUME 

fl oz fluid ounces 29.57 millimeters mL 

gal gallons 3.785 liters L 

ft3cubic feet 0.028 cubic meters m

3

yd3cubic yards 0.765 cubic meters m

3

NOTE: volumes greater than 1000 L shall be shown in m3

MASS 

oz ounces 28.35 grams g 

lb pounds 0.454 kilograms kg 

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

TEMPERATURE (exact degrees) 

°F Fahrenheit 5 (F-32)/9 

or (F-32)/1.8 

Celsius °C

ILLUMINATION 

fc foot-candles 10.76 lux lx

fl foot-Lamberts 3.426 candela per square meter cd/m2

FORCE and PRESSURE or STRESS 

lbf poundforce 4.45 Newtons N 

lbf/in2 (psi) poundforce per square inch 6.89 kiloPascals kPa 

k/in2 (ksi) kips per square inch 6.89 megaPascals MPa 

DENSITY 

lb/ft3 (pcf) pounds per cubic foot 16.02 kilograms per cubic meter kg/m3

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

LENGTH

μm micrometers 0.039 mil (none) 

mm millimeters 0.039 inches in

m meters 3.28 feet ft

m meters 1.09 yards yd

km kilometers 0.621 miles mi

AREA 

mm2square millimeters 0.0016 square inches in2

m

2

square meters 10.764 square feet ft2

m

2

square meters 1.195 square yards yd2

ha hectares 2.47 acres ac

km2square kilometers 0.386 square miles mi2

VOLUME 

mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal 

m

3

cubic meters 35.314 cubic feet ft3

m

3

cubic meters 1.307 cubic yards yd3

MASS 

g grams 0.035 ounces oz 

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T 

TEMPERATURE 

°C Celsius 1.8C+32 Fahrenheit °F

ILLUMINATION 

lx lux 0.0929 foot-candles fc

cd/m2candela per square meter 0.2919 foot-Lamberts fl

FORCE and PRESSURE or STRESS 

N Newtons 0.225 poundforce lbf 

kPA kiloPascals 0.145 poundforce per square inch lbf/in2 (psi) 

MPa megaPascals 0.145 kips per square inch k/in2 (ksi) 

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. (Revised March 

2003) 
iv

Table of Contents 

Topic Page 

FOREWORD........................................................................................................................... 1

SUMMARY OF OBSERVATIONS ...................................................................................... 1

Overall Opinion of the Safety EdgeSM ............................................................................... 1

Slope of Safety EdgeSM ...................................................................................................... 1

Placement .......................................................................................................................... 1

Shoulder Construction ...................................................................................................... 1

PCC and Safety EdgeSM .................................................................................................... 2

FIELD EVALUATION OF PCC OVERLAY WITH SAFETY EDGESM ........................ 3

INTRODUCTION................................................................................................................... 3

FIELD EVALUATION .......................................................................................................... 5

Slope Measurements ......................................................................................................... 5

Portable Seismic Pavement Analyzer ............................................................................... 7

Free-Free Resonant Column Testing .............................................................................. 11

Compressive Strength Testing ......................................................................................... 12

Unit Weight and Air Void Analysis ................................................................................. 13

OBSERVATIONS MADE DURING PAVING WITH THE SAFETY EDGESM ........... 16

Paver/Placement Operations .......................................................................................... 16

Shoulder Construction .................................................................................................... 21

Material/Structural Performance Issues of the Safety EdgeSM ....................................... 21

Tie Bar Placement ........................................................................................................... 21

Random Cracking ........................................................................................................... 22

FINDINGS AND CONCLUSIONS..................................................................................... 23

APPENDIX A. DATA TABLES FROM FIELD MEASUREMENTS .......................... A-1

The Portable Seismic Pavement Analyzer ..................................................................... A-1

Free-Free Resonant Column .......................................................................................... A-4

References ...................................................................................................................... A-5
1

Summary of Observations 

This section of the field report provides a summary and listing of important observations 

made during the paving operations, interview with paving personnel and findings from the 

field measurements taken during paving that are expected to have a significant impact on the 

performance of the Safety EdgeSM. 

Overall Opinion of the Safety EdgeSM

 The Safety EdgeSM does not appear to have a major impact on the contractor’s paving 

operation during mainline open paving. Some minor issues were encountered by the 

contractor and the construction method may require some refinement to resolve these 

issues, however. 

Slope of Safety EdgeSM

 The average slope of the Safety EdgeSM was found to be 31.5° with a maximum value 

of 34.0° and a minimum value of 28.5°.

Placement 

 The sloped face of the Safety EdgeSM was slightly concave or convex at some 

locations. This condition may be caused by either flex in the device during paving or 

due to issues during finishing. The deviation from flat surface is generally considered 

to be minor and is not expected to have a significant impact on the performance of the 

Safety EdgeSM. 

 The fixed nature of the Safety EdgeSM device lead to additional labor needed to form 

the Safety EdgeSM at locations where the mainline crosses existing roads. 

Sawcutting of the transverse joints stopped at the sloped face of the Safety EdgeSM. 

Joints were observed forming at the proper location through the Safety EdgeSM where 

the sawcut ended. 



 The contractor experienced minor difficulty placing the tie bars at the lane to shoulder 

joint but this turned out to be an equipment issue rather than the design of the Safety 

EdgeSM. 

 Minor random cracking was observed but was not directly related to the Safety 

EdgeSM. 

Shoulder Construction 

 The thickness at the outside edge of Safety EdgeSM varied due to variability of the 

concrete overlay thickness and shoulder base material grading and was not due to 

Safety EdgeSM construction. 
2

PCC and Safety Edge SM

 The results of the air voids and modulus testing of the hardened concrete indicate that 

the quality of the concrete is reasonably uniform between the Safety EdgeSM and 

away from the Safety EdgeSM. 

This Safety EdgeSM project should be monitored over time to determine its long-term 

performance and the frequency of any required maintenance operations, as well as the life 

cycle cost of the Safety EdgeSM and its effectiveness over time. Attention should be given to 

how well the granular shoulder dressing remains in place. 
3

FIELD EVALUATION OF PCC OVERLAY WITH SAFETY EDGESM

Introduction 

The project was located along County Highway E34 (a.k.a. Fairview Road) in the vicinity of 

Fairview, Iowa. The objective of this study was to evaluate the quality of Safety EdgeSM

constructed as well as that of the in-place concrete material. The location of the project is 

shown in Figure 1. The length of the project was approximately 14,055 ft between Quaker 

Lane and Fairview Road. 

Figure 1. Location of site. 

Figure 2 presents a view of a completed section of the roadway. The construction included a 

6 inch overlay of unbonded PCC over an existing 6 inch PCC pavement. The overlay 

included a tied 9-inch thick shoulder 2.75 ft wide, with a 30° sloped Safety EdgeSM in both 

the westbound and eastbound direction. A schematic of the cross section of the pavement is 

shown in Figure 3. 

Project location 
4

Figure 2. General view of the project showing the Safety EdgeSM.

Figure 3. Cross section of concrete pavement overlay. 
5

Field Evaluation 

Field evaluation of this pavement included: 

 Safety EdgeSM slope measurements. 

 Testing the modulus of the concrete within the Safety EdgeSM and away from the 

edge using the portable seismic pavement analyzer (PSPA). 

 Free-free resonant column (FFRC) testing conducted to compare the moduli 

measured in the field with the PSPA. 

 Core samples taken to analyze the compressive strength, unit weight, and air void 

content of the hardened concrete within the Safety EdgeSM and away from the edge.

Construction of the Safety EdgeSM was observed over two days to record the paving process 

and any peculiarities associated with the inclusion of the Safety EdgeSM.

Slope Measurements 

Measurements were taken along the length of the Safety EdgeSM in both directions for the 

first two days of paving at 50-ft intervals. The pavement was placed and saw cut prior to the 

field evaluation crew arriving on site. The edge of the pavement was generally found to be 

well formed. The slope of the Safety EdgeSM varied along the length of the pavement due to 

curve elevations, flexing of the paver device that forms the Safety EdgeSM, and other related 

issues; however, the slope was generally found to be within a reasonable range. The average 

slope measured was 31.5° with a maximum value of 34.0° and a minimum value of 28.5°. 

Some deviation in the flatness of the slope face was observed. The flatness was measured by 

placing a straightedge on the face as shown in Figure 4. The face was found to be concave in 

some cases and convex in other cases. This condition may be caused by either flexing of the 

device or issues during finishing. The deviation from flat is generally considered minor and 

is not expected to have a significant impact on the performance of the Safety EdgeSM. 

Similarly, the vertical edge face of the pavement was found to have defects from forming. 

The Safety EdgeSM device did not always seal tightly against the end gate, leaving a ridge in 

the face. Figure 5, shows an example of this. The vertical face is bowed and the marks 

created by the end of the device and the end gate can be clearly observed. 
6

Figure 4. Measuring the slope and flatness of the Safety EdgeSM.

Ridge and slight 

bow in the PCC left 

by the Safety 

EdgeSM device. 

Figure 5. Slope face showing ridge and bow. 
7

Portable Seismic Pavement Analyzer 

The PSPA was utilized to provide a measure of quality by determining the variation in 

modulus with depth of the concrete in the field. Details of this nondestructive test procedure 

are explained in Appendix A. PSPA testing was conducted on the sloped edge, at 1 ft from 

the edge, and on the right wheelpath as illustrated in Figure 6. This was done to compare the 

quality of the concrete within the edge and at points gradually moving towards the interior of 

the pavement. 

Location of PSPA Tests

Widening Unit

Existing 6” PCC Slab

Right Wheelpath

Sloped Edge 

(Midpoint)

1 ft 3 ft

6” New PCC Slab

Shoulder

Joint

Figure 6. Location of PSPA test points. 

PSPA tests were conducted on the westbound and eastbound lanes from Stations 19+00 to 

53+00 of Linn County and from Stations 11+00 to 19+00 of Jones County. Spacing between 

stations was 100 ft. This portion of the project was paved over two days. The first section 

that was tested was paved on May 5 and tested on May 10 (Day 1 of testing) and included 

stations 19+00 to 36+00. The second section that was tested was paved on May 6 and tested 

on May 11 (Day 2 of testing) and included station from 11+00 to 19+00 and from 37+00 to 

53+00. In total, tests were conducted at 44 stations. In addition to the PSPA tests, nine cores 

were obtained at three different locations for laboratory analysis of the concrete's modulus 

for comparison with the PSPA results. 

Moduli for the 44 stations investigated in each direction and representative statistics are 

summarized in Table 1. The full set of data are presented in Appendix A. The section that 

2 was paved on Day 1 exhibited an average modulus of 4,200 k/in , slightly higher than the 

section constructed on Day 2 (4,050 ksi). Coefficients of variation (COV) of the modulus for 

all stations were small and between 3 and 6 percent. Figure 7 and Figure 8 graphically 

present the variation of moduli at the three lateral points tested along the project. 
8

Table 1. PSPA statistical results. 

Day 

Tested 

Average Modulus (ksi) 

Eastbound Westbound 

Slope Shoulder Wheelpath Slope Shoulder Wheelpath 

May 10 

(Day 1) 

4,238 

(4)* 

4,185 

(3) 

4,169 

(3) 

4,192 

(4) 

4,222 

(5) 

4,215 

(5) 

May 11

(Day 2)

4,046 

(5) 

4,036 

(4) 

4,059 

(5) 

3,999 

(6) 

4,111 

(5) 

4,012 

(5) 

 *Numbers in parentheses are the COV of the 44 points.

3000

3250

3500

3750

4000

4250

4500

4750

5000

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Station Number

Seismic Modulus, ksi

Slope Shoulder RWP

3000

3250

3500

3750

4000

4250

4500

4750

5000

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Station Number

Seismic Modulus, ksi

a) Eastbound

b) Westbound

Figure 7. Variations of the moduli for the sections tested on Day 1. 
9

3000

3250

3500

3750

4000

4250

4500

4750

5000

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 11 12 13 14 15 16 17 18 19

Station Number

Seismic Modulus, ksi

Slope Shoulder RWP

3000

3250

3500

3750

4000

4250

4500

4750

5000

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 11 12 13 14 15 16 17 18 19

Station Number

Seismic Modulus, ksi

b) Westbound

b) Eastbound

Figure 8. Variations of the moduli for the sections tested on Day 2. 

Table 2 through Table 4 present the results of a paired t-test and a single factor analysis of 

variance (ANOVA) on the test data from the eastbound direction, westbound direction, and 

pooled east and westbound directions. There are no statistical differences among different 

data groups as indicated by the statistical analysis with one exception. The calculated t-value 

for westbound slope versus shoulder data pairs is higher than the critical t-value indicating 

that there exists significant difference between the two groups. However, this difference is 

caused by the variations in the ―westbound shoulder‖ data rather than the ―westbound (Safety 

EdgeSM) slope‖ data. Note that the paired t-value for westbound slope vs right wheelpath 

(RWP) is -0.48, whereas the t-value for the westbound shoulder vs RWP is 1.73. The results 

of the statistical analysis therefore indicates that the concrete across the pavement is uniform 

suggesting that the Safety EdgeSM concrete is no different than interior concrete. 
10

Table 2. Paired t-test and ANOVA results for the eastbound dataset. 

Eastbound 

 Slope Shoulder RWP

Mean 4128.6 4093.6 4104.2 

Std dev. 215.6 170.3 180.9 

 

Slope vs 

Shoulder 

 Shoulder vs 

RWP

Slope vs 

RWP

t Stat 1.32 -0.24 0.57 

P(T<=t) 0.20 0.81 0.57 

t Critical 2.02 2.02 2.02 

Anova: Single Factor 

 F P-value F crit 

 0.36 0.70 3.07 

Table 3. Paired t-test and ANOVA results for the westbound dataset. 

Westbound 

 Slope Shoulder RWP

Mean 4077.9 4156.6 4095.4 

Std dev. 218.3 203.7 231.0 

 

Slope vs 

Shoulder 

 Shoulder 

vs RWP 

Slope vs 

RWP

t Stat -2.47 1.73 -0.48 

P(T<=t) 0.02 0.09 0.63 

t Critical 2.02 2.02 2.02 

Anova: Single Factor 

 F P-value F crit 

 1.58 0.21 3.07 

Table 4. Paired t-test and ANOVA results for the combined east and westbound dataset. 

Both lanes 

Slope Shoulder RWP

Mean 4102.7 4125.8 4102.1 

Std dev. 217.2 189.7 208.1 

Slope vs 

Shoulder 

 Shoulder 

vs RWP 

Slope vs 

RWP

t Stat -1.07 1.03 0.02 

P(T<=t) 0.29 0.31 0.98 

t Critical 1.99 1.99 1.99 

Anova: Single Factor 

F P-value F crit 

0.37 0.69 3.03 
11

Free-Free Resonant Column Testing 

Three random stations tested with the PSPA were selected for core extraction. At each 

station, three samples were obtained—one on the sloped edge, one on the shoulder and one 

on the wheelpath. The three stations were: 

 Eastbound 21+00 (samples 1 to 3). 

 Westbound 50+00 (samples 14 to 16). 

 Eastbound Station 18+00 (samples 19 to 21). 

As an example, the cores from station 21+00 are shown in Figure 9. The cores were first 

trimmed to remove either the rough ends (if needed) or the sloped portions. 

 

Figure 9. Cores retrieved from station 21+00. 

The seismic moduli of the cores were determined by measuring the resonant frequency of 

vibration (standing waves) according to the FFRC test for comparison with the moduli 

measured in the field with the PSPA. Details of the FFRC test procedure are included in 

Appendix A. At the time of FFRC testing, the specimens had cured for approximately seven 

days. The comparisons of the lab and field moduli for the nine cores are presented in Figure 

10. The results of the PSPA and FFRC testing were similar with the average difference of 7 

percent and a range of 1 to 13 percent. 
12

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

1 2 3 14 15 16 19 20 21

Core Number

Seismic Modulus, ksi

FFRC PSPA

Figure 10. Comparison of the moduli obtained with PSPA and FFRC. 

Compressive Strength Testing 

The nine cores tested for seismic modulus were further tested to measure their compressive 

strengths (ASTM C39) approximately 22 days after construction. The compressive strengths 

of the cores are summarized in Table 5. Because cores had different length-to-diameter 

ratios (L/D), adjustment factors were applied to convert the strengths to those for L/D ratios 

2

of 2 as per ASTM C39/C39M. The average compressive strength was 6,200 lbf/in with a 

2 COV of 12 percent. Similarly, the average seismic modulus was 4,368 k/in with a COV of 6 

percent. Considering the low COV for both parameters, the concrete can be considered to be 

relatively uniform. 

Table 5. Compressive strength and FFRC modulus results. 

Core No. and 

Location 

Station 

Number and 

Bound 

Raw 

Compressive 

Strength, lbf/in2

Length/ 

Diameter 

Adjustment 

Factor 

Adjusted 

Compressive 

Strength, lbf/in2

1 (wheelpath) 21+00 (EB) 6,250 1.47 0.958 5,987 

2 (shoulder) 21+00 (EB) 6,738 2.00 1.000 6,738 

3 (edge) 21+00 (EB) 5,682 1.20 0.920 5,229 

14 (edge) 50+00 (WB) 5,394 1.90 0.991 5,343 

15 (shoulder) 50+00 (WB) 5,891 2.01 1.001 5,897 

16 (wheelpath) 50+00 (WB) 5,963 1.72 0.977 5,827 

19 (edge) 18+00 (EB) 6,976 1.23 0.926 6,459 

20 (shoulder) 18+00 (EB) 7,592 2.01 1.001 7,600 

21 (wheelpath) 18+00 (EB) 7,189 1.28 0.934 6,717 

Average 6,200 

COV 12

Eastbound (EB), Westbound (WB) 
13

Before conducting strength tests, the cores longer than 8 inches were further trimmed to 8 

inches and all cores were tested again with the FFRC. The comparisons of the FFRC moduli 

at ages of 7 and 22 days are shown in Figure 11. On average, the moduli increased by 5 

percent in that time frame. 

0

1000

2000

3000

4000

5000

6000

1 2 3 14 15 16 19 20 21

Core #

Seismic Modulus, ksi

Modulus after 7 Days

Modulus after 22 Days

Figure 11. Comparison of the FFRC Moduli. 

Unit Weight and Air Void Analysis 

A total of six pairs of additional cores were taken (each pair containing one core from the 

edge and one core from the shoulder) to determine if there were any differences in unit 

weight or air voids that could lead to differences in their respective durability performances 

over the life of the pavement. The shoulder concrete was supposed to be representative of 

the mainline pavement. ASTM C457 standard test procedures were followed to determine 

the parameters of the air-void system in the cores. 

Observations of the surface of the cores suggested that the concrete in the Safety EdgeSM was 

of good quality but had inconsistent consolidation that resulted in differences in the 

entrapped air contents. Two of the shoulder cores appear to have not been vibrated 

sufficiently because entrapped air voids are distributed throughout the core sample. In most 

of the other cores, the entrapped air occurs in higher concentrations several inches from the 

top surface and slightly below the bottom surface. This distribution of entrapped air was 

likely the result of the paver's vibrator penetrating to a fixed depth slightly above the granular 

base. The entrapped air is the lowest at the top because of vibration inherent to the screeding 

process. The vibrator did not seem to be contacting the granular base because there is no 

apparent incorporation of foreign materials into the bottom of the concrete. 

Two of the cores at the Safety EdgeSM contained irregular air-void channels (or tears during 

placement) that may lead to lower durability if they didn't occur a couple of inches below the 

surface. The location of these defects, inches below the surface, suggests that they will have 

no effect upon the durability of the concrete because they are protected by a layer of denser 

concrete. 
14

Generally, laboratory testing revealed that the air void systems in the edge cores had both a 

greater percentage of entrapped air voids greater than 1.0 mm and more air void chords 

greater than 0.5mm in comparison to the shoulder cores (Figure 12).

R2 = 0.6234

R2 = 0.8029

0

10

20

30

40

50

60

70

80

0.00 0.50 1.00 1.50 2.00

Number of Void Chords > 0.5mm

Percent of Entrapped Air Voids >1.0mm

Edge Shoulder

Figure 12. Comparison of the percentage of entrapped air and the number of void chords 

greater than 0.5mm. 

The only consistent difference found in the pairs of cores is that the Safety EdgeSM cores had

a somewhat greater amount of entrapped air voids in regards to the spacing factors as 

compared to the shoulder cores (Figure 13). This observation appears in both the amount of 

entrapped air voids as determined by both the linear traverse method (where the length of all 

traverse chord across air voids was observed) and the point count method. 

On average, the edge cores had a lower unit weight, a higher air content, a slightly higher 

spacing factor, and more air voids over 0.5mm. Despite the differences, however, the 

spacing factors and other parameters were reasonable and the concrete at the edge as well as 

from the shoulder appears to be durable. Table 6 summarizes these results. 
15

Figure 13. Comparison of the number of large air voids (> 0.5 mm) and the spacing factors. 

Table 6. Results of the air voids analysis. 

Core 

Pair 

No. 

Position Unit Weight, pcf Avg. Hardened Air, 

percent 

Spacing Factor, 

in.

No. of Chords 

Over 0.5mm 

Shoulder Edge Shoulder Edge Shoulder Edge Shoulder Edge 

1 Edge 

137.3 

135.6 

6.3 

6.4 0.0042 47

Shoulder 

138.7 

0.0053 47

66 2 Edge 

138.2 6.0 

6.6 0.0058 

Shoulder 0.0037 22

3 Edge 

139.1 

138.6 

4.5 

6.4 0.0060 

32

66

Shoulder 

6.4 

0.0041 

4 Edge 

140.9 

139.7 

5.1 

0.0067 

35

61

Shoulder 0.0058 

0.0056 5 Edge 

139.9 

138.6 

6.4 

6.0 

0.0049

57

Shoulder 

136.5 7.6 

34

76 6 Edge 

139.0 5.8 0.0050 

0.0058 

Shoulder 29

Average 139.1 138.4 5.7 6.6 0.0048 0.0060 33.2 65.2 

COV 0.89 1.13 13.05 8.22 16.14 13.73 24.8 15.0 

R2 = 0.388

R2 = 0.438

0

10

20

30

40

50

60

70

80

0.0020 0.0030 0.0040 0.0050 0.0060 0.0070 0.0080 No. of Intersected Void Chords > 0.5 mm 

Spacing Factor, in.

Edge Shoulder
16

Observations Made During Paving with the Safety EdgeSM

This section provides an overview of the observations made during the paving operations. 

Paver/Placement Operations 

The contractor made a custom Safety EdgeSM device or profile for their Gomaco paver. 

discussion of the fabrication process is provided by the contractor as follows: 

As far as the fabrication process on a Gomaco machine, there is an insert 

section on the end drive portion of the pan that allows the use of different 

profiles, such as curb profiles, flat sections, or in this case a Safety EdgeSM

profile....

One idea we had was to weld the Safety EdgeSM profile to the bottom of the 

existing profile section, after much discussion we decided against this as we 

felt we may get tearing of the finished product at the welds. Also with this 

method we would not have any edge slump adjustment as the adjusting bolts 

would be in the wrong location. 

The second idea [and the idea used on this project] was to cut out the existing 

profile and fabricate in the Safety EdgeSM profile. This method seemed the 

best because we were able to incorporate some adjustment into the profile, 

and all edges would be smooth to hopefully eliminate any tearing of the 

finished edge. We were also able to fabricate in the edge slump adjustments 

to the new section. Although the inserts would only be able to be reused as a 

Safety EdgeSM profile in the future or a complete rebuild would have to be 

done again, unlike if we welded the profile beneath the existing profile, we 

still felt this was the best way to go. 

After the decision was made to rework the existing profile, our fabricator cut 

the profile out of rigid cardboard first to get the correct dimensions. He then 

removed the portions of the existing profile needed to fit in the new Safety 

EdgeSM profile. He then took the cardboard template and cut out and rolled 

the new profile into shape. He then made the same profile out of stainless 

steel for the finish portion of the pan. We decided to leave a 2 inch finish tail 

on the stainless steel profile to help finish the portion of the edge where it 

goes from slope to vertical. When he was done with the profile fabrication, 

he then made the adjusting bolts fit where we thought the adjusting points 

needed to be. One spot was on the sloped section itself as this way we had 

some adjustment if the edge was not finishing properly. 

When the first side was complete, and all measurements were checked we 

mirrored the same process for the other side.... 

A 
17

When the time came to setting up the paver, we made sure that the vibrators 

were positioned in the correct locations for proper consolidation at the point 

where the slope angled at the top. One thing that benefited us on this project 

was the fact that we had done a lot of urban paving also, so we had previous 

experience with vibrator placement on different profile types. 

We encountered a few challenges as we progressed down the road. One was 

the two inch tail we had left at the point on the profile where it went from 

slope to vertical. When going through existing intersections, drives, or if the 

grade was not exact on the very outside edge, this would drag. We 

eventually cut one inch off of this and it still performed well. I believe a half 

inch would work also. 

With the use of the Safety EdgeSM on an overlay, one consideration that has 

to be taken into account is the outside edge thickness of the pavement. This 

thickness must be as thick or thicker than design. Once the Safety EdgeSM

[profile] is attached to the paver there is no way of reducing the outside 

thickness as the profile is stationary on the machine. 

Another challenge with the use of the Safety EdgeSM [profile] was paving 

through intersections or drives that required a vertical edge. The first 

intersection we went through we decided to pave through and come back and 

saw off 9 inches to create a vertical edge. This method worked but wasted 

concrete. Another option would be to box out the intersections before we 

went through. We decided at the drives to place forms, fill in and consolidate 

the sloped edge with fresh concrete right behind the paver. This worked 

well, so before we went through the next intersection we laid out forms and 

did it the same as we had done the drives. 

Another thing that we had to watch out for was the profile protruded beneath 

the main pan section. This created extra height to the machine when moving 

to, and on the job. The operator had to make sure the machine was in the 

right location or the edges could be damaged. If width adjustments on the 

main pan needed to be done, the inserts had to be removed first unlike other 

profiles. 

We had good luck using the Safety EdgeSM profile and believe the level of 

difficulty of using it is low, if you do the preparation ahead of time. 

The Safety EdgeSM device can be seen in Figure 14. The device in Figure 15 is shown 

welded to the back of the pan and sits closely to the end gate. It is evident that the device has 

been bent. The contractor indicated the device was bent during transport operations. This 

bend in the device can be seen in the pavement as a bow in the exposed vertical face of the 

pavement edge. 
18

The contractor indicated there may be a benefit to using the Safety EdgeSM versus a 

conventional vertical face. It is expected a more workable concrete mix can be used that 

would facilitate improved concrete quality. 

Safety EdgeSM device. 

Figure 14. View of the Safety EdgeSM device from front of paver. 

Note the bow in 

the face of the 

Safety EdgeSM

device. 

Figure 15. Viewed from the rear of paver showing the bend in the Safety EdgeSM device. 
19

An example of saw cutting and removing the Safety EdgeSM at an intersection is shown in 

Figure 16. The alternative was to build up the Safety EdgeSM by hand (see Figure 17) in 

order to tie into pavement intersections. 

Figure 16. Saw cut edge at an intersection. 

Figure 17. Edge formed and prepared for intersection paving. 
20
21

Shoulder Construction 

The plan for the Safety EdgeSM called for a nominal 9 inch thickness for the widened 

shoulder section. Measurements revealed that the average thickness of the shoulder over the 

first two days of paving was 11.0 inches. The additional concrete thickness in the shoulder 

may benefit the performance of the pavement, but indicates that the shoulder preparation was 

not as precise as the contractor or engineers may have wished. Additional material costs may 

be reflected in the final payout. This issue is more likely due to the widening of the roadway 

than the presence of the Safety EdgeSM itself.

Material/Structural Performance Issues of the Safety EdgeSM

The primary concerns for failure from a structural aspect of the Safety EdgeSM will be 

material issues such as segregation or under-consolidation in the Safety EdgeSM, and lack of

support under the widened roadway, which may cause the Safety EdgeSM and shoulder to 

break away from the mainline pavement. 

Unlike with hot mix asphalt (HMA), which requires a rolling operation to produce material 

density, the PCC Safety EdgeSM achieves density, or consolidation through the vibration an

extrusion process. While a vibrator was not placed within the steeply sloped portion of the 

Safety EdgeSM, the nearest vibrator is still quite close the edge. No obvious signs of 

consolidation issues were observed at either the exposed edge face or in the surface of the 

cores cut from the Safety EdgeSM. Laboratory and nondestructive testing of the in-place 

concrete confirmed that consolidation was not a major issue. 

d 

Tie Bar Placement 

The contractor experienced problems with one of the tie bar launchers for the tie bar located 

between the shoulder and mainline pavement. The launcher repeatedly failed to release the 

bars inside the pavement resulting the bars being bent and partially removed from the 

pavement. The net result when a bar was misplaced is that the bar was removed and not 

replaced. The contractor resolved this issue by placing a laborer on the bridge of the paver to 

manually pause the launcher with the bar at depth. Once the paver moved past the bar, the 

laborer would restart the launcher and reload the device. This significantly reduced, but did 

not completely eliminate, the problem. Several misplaced bars were observed during a few 

hours of paving. 
22

Random Cracking 

A decision was made to saw cut only the top of the pavement and not saw cut the slope of the 

Safety EdgeSM as shown in Figure 18. The reason for not saw cutting the slope was that it 

would be easier to retain the joint sealant with only the sawcut on top. Another reason was 

the joint would crack straight down which was what was observed. Figure 18 also shows 

that the joint formed properly at this location. 

Figure 18: Photo of saw cut and formed joint. 

Figure 19 shows one of two locations along the project where random cracking was observed 

parallel to the sawed joint. It is unknown if the Safety EdgeSM contributed to the formation 

of these cracks, however, given the location and orientation it appears unlikely that the Safety 

EdgeSM contributed to these cracks. 

A mid-panel crack was also observed in a slab at approximate station 52+40. The cause of 

the crack is not believed to be related to the presence of the Safety EdgeSM. Saw cut timing 

may have played a role in this. 
23

Figure 19. Random crack formed near joint. 

Findings and Conclusions 

As previously stated, the objective of this field study was to evaluate the quality of the inplace PCC pavement and Safety EdgeSM by investigating three features. 

1. Correct use of the Safety EdgeSM device during paving. 

2. PCC properties at the Safety EdgeSM.

3. Slope of the Safety EdgeSM.

This section of the field report summarizes the findings and conclusions made during the 

paving operations. 

 The slope was generally found to be appropriate. The average slope was 31.5° with a 

maximum value of 34.0° and a minimum value of 28.5°. 

 A slight hump or bow in the slope face was produced by the Safety EdgeSM device. 

Modifications to the device and a more robust design should be considered to prevent 

this problem on future projects. Unlike the Safety EdgeSM attachments for asphalt 

pavers, the PCC device on the concrete paver requires more time and effort to install 

or modify once paving begins. 
24

 Additional labor was required to cut and remove the Safety EdgeSM or form the 

Safety EdgeSM to tie into connecting pavements. 

The results of field and laboratory test results indicate the quality, as indicated by 

PCC modulus and compressive strength testing, is reasonably uniform throughout the 

pavement. 



 Laboratory test results of cores taken at the Safety EdgeSM show, on average, a lower 

unit weight, a higher air content, a slightly higher spacing factor, and more 0.5 mm 

air voids in comparison to cores taken from the shoulder. Despite the differences, 

however, the concrete within the edge appears to be as durable as that in the mainline 

pavement. 

The pavement should be inspected after the final shoulder backing material has been placed 

to determine if the Safety EdgeSM promotes the retention of the backing material. Monitoring 

of this site would be beneficial in evaluating the long-term performance of the Safety 

EdgeSM. 
A-1 

APPENDIX A. DATA TABLES FROM FIELD MEASUREMENTS 

The Portable Seismic Pavement Analyzer 

The PSPA, shown in Figure 20, consists of two ultrasonic sensors or transducers and a 

hammer or source packaged into a hand-portable system, which can determine the variation 

in modulus of the material with depth using the Ultrasonic Surface Wave (USW) method 

(Nazarian et al., 2006). The PSPA is operable from a laptop computer tethered to the handcarried transducer unit through a cable that carries power to the hammer and transducers and 

returns the measured signals to the data acquisition board in the computer. To collect data 

the user initiates the testing sequence through the computer. The high-frequency source is 

activated four to six times. The outputs of the two transducers from the last three impacts are 

saved and averaged (stacked). The other (pre-recording) impacts are used to adjust the gains 

of the pre-amplifiers to optimize the dynamic range. 

Figure 20. Portable seismic pavement analyzer. 

The time records collected are subjected to signal processing and spectral analyses. In the 

USW method, the surface or Rayleigh wave velocity, VR, is measured without an inversion 

algorithm. After VR is measured, the modulus of the top layer, Efield, can be determined from 

(Nazarian et al., 2002): 

2

Efield  2 VR

1.13 0.16 1 

(1) 

where ρ is mass density, and  is Poisson's ratio. 

Source

Near 

Receiver

Far 

Receiver

Data Acquisitio

Box

n 

Connecting Cable
A-2 

Typical time records of the receivers are shown in Figure A-3. These records are analyzed to 

obtain a dispersion curve, a plot of the modulus vs. wavelength (or depth), as shown in 

Figure A-3. At wavelengths less than or equal to the thickness of the uppermost layer, the 

travel time and velocity of surface waves is independent of wavelength, as long as the 

modulus of the layer is constant. If the pavement structure is composed of several layers, 

voids are present or poorly-constructed layers exist, the velocity will vary with wavelength in 

the dispersion curve. In that manner, the operator of the PSPA can get a qualitative feel for 

the variation in modulus with depth. In Figure A-3 the modulus remains constant for the top 

5 inches, and slightly decreases below that depth and remains constant below 6 inches. To 

obtain the average modulus, the moduli from a wavelength of about 2 to 6 inches (nominal 

thickness of the overlay) is used. The results of the PSPA testing are in Table A-1. 

a) Time Records

Source

Near 

Receiver

Far Receiver

b) Reduced Data

Figure A-2. PSPA time records shown on 

Dispersion Curve

Range used 

for average 

Modulus

Measured

Modulus, ksi

Depth (in.)

Figure A-3. Reduced data shown on the PSPA interface screen. 
A-3 

Table A-1. PSPA test results.

 

Eastbound

Station Slope Shoulder RWP

19+00 3955 4060 4113

20+00 3995 4150 4115

21+00** 4287 4140 4135

22+00 4257 4250 4510

23+00 4517 4177 3967

24+00 4063 4235 4240

25+00 4263 4013 4385

26+00 3925 4060 4013

27+00 4180 4055 3990

28+00 4050 4210 4160

29+00 4317 3987 4310

30+00 4517 4288 4077

31+00 4290 4217 4133

32+00 4430 4273 4210

33+00 4250 4460 4245

34+00 4227 4380 4310

35+00 4405 4267 4023

36+00 4365 4117 4110

37+00 3825 3973 4297

38+00 4187 4153 4345

39+00 3940 4055 4100

40+00 4135 4027 4160

41+00 4100 4135 4255

42+00 4420 4325 4250

43+00 4185 3988 4045

44+00 3843 4045 4170

45+00 3665 3995 3790

46+00 4040 3903 4013

47+00 4315 4320 4040

48+00 3935 4040 4073

49+00 4123 4210 3823

50+00 4085 3763 4000

51+00 3635 3713 3925

52+00 3975 4143 3855

53+00 3950 3883 3815

11+00 N/A 4230 3965

12+00 N/A 4125 4033

13+00 4020 3850 4005

14+00 3890 3893 4040

15+00 4020 3903 4020

16+00 3895 3877 3763

17+00 4273 3928 3875

18+00** 4300 4173 4495

19+00 4353 4297 4387 1Day Day 2

Westbound

Station Slope Shoulder RWP

19+00 4085 4137 4073

20+00 4125 4230 4523

21+00 3897 4110 4130

22+00 4230 4355 4320

23+00 4390 4305 3940

24+00 4237 3940 4100

25+00 4437 4203 4165

26+00 4007 4140 3980

27+00 4090 3678 4020

28+00 4013 4095 4260

29+00 4270 4400 3927

30+00 4190 4097 4490

31+00 4287 4420 4358

32+00 4125 4458 3947

33+00 4025 4190 4217

34+00 4260 4400 4530

35+00 4447 4535 4465

36+00 4340 4305 4430

37+00 3607 3897 3933

38+00 3890 4180 4453

39+00 4363 4395 4220

40+00 3780 4295 4070

41+00 4210 3937 4105

42+00 4165 4270 4467

43+00 4315 4127 3927

44+00 4095 4120 4023

45+00 4327 4490 3946

46+00 3980 3995 4005

47+00 3940 4125 3747

48+00 4113 4230 4010

49+00 4253 3833 3877

50+00** 3740 4135 3620

51+00 3870 3970 4030

52+00 3873 3767 3885

53+00 4120 4010 3938

11+00 3910 4250 3965

12+00 3865 4065 3790

13+00 3840 3917 4103

14+00 3835 3800 3760

15+00 3580 3953 3913

16+00 3900 4243 3810

17+00 4368 4340 4247

18+00 4005 4340 4300

19+00 4030 4210 4177

** Core LocationDay 1 Day 2 
A-4 

Free-Free Resonant Column 

The FFRC test (ASTM C215) measures the resonant frequency of vibration (standing waves) 

and thus the modulus of a cylindrical or prismatic specimen in the laboratory. In recent years, 

the test has been simplified and enhanced (Nazarian et al., 2006) and a setup example is 

shown in Figure A-4. A typical system includes an instrumented hammer that is connected 

to a load cell and a broadband receiving transducer (accelerometer) that detects waves 

propagating inside the specimen. To conduct a test, the specimen is placed on a pedestal and 

impacted on one end with the instrumented hammer. The accelerometer is securely placed 

on either end of the specimen to measure the time records of the compression wave (or Pwave) and the reflections inside the specimen generated by the impact. The signals collected 

from the accelerometer and load cell are used to determine the resonant frequency of the 

reflecting wave inside the specimen, f. An example of time records and the resonant 

frequency obtained of a typical sample are illustrated in data plots in Figure A-4. The 

Young's modulus (Elab) can be obtained from: 

E  2

lab   2 fL

(2) 

where ρ, is mass density and L, is the length of the specimen. 

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

0

0.2

0.4

0.6

0.8

1

Frequency (Hz)

Normalized Amplitude

Instrumented 

Hammer

Accelerometer

Sensor 

Box

a) Setup

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

-150

-100

-50

0

50

100

150

Time (s)

Amplitude (mV)

b) Time Record

c) Phase Spectrum

Specimen

Figure A-4. FFRC setup and example of the time records output. 
A-5 

References 

ASTM C39 / C39M - 09a. Standard Test Method for Compressive Strength of Cylindrical 

Concrete Specimens. ASTM International, West Conshohocken, PA, 2009. 

ASTM C215 - 08. Standard Test Method for Fundamental Transverse, Longitudinal, 

and Torsional Resonant Frequencies of Concrete Specimens. ASTM International, West 

Conshohocken, PA, 2008. 

Nazarian, S., Yuan, D., and Arellano, M. (2002), ―Quality Management of Base and 

Subgrade Materials with Seismic Methods.‖ Transportation Research Record No. 1786, 

Washington, D.C., pp. 3-10.

Nazarian, S., Yuan, D., Smith, K., Ansari, F., Gonzalez, C. (2006), ―Acceptance Criteria of 

Airfield Concrete Pavement Using Seismic and Maturity Concepts.‖ ―Innovative Pavement 

Research Foundation, Airport Concrete Pavement Technology Program. Report IPRF-01-G002-02-2.