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Publication Number: FHWA-RD-02-082
Date: August 2006

Highway Concrete Technology Development and Testing Volume I: Field Evaluation of SHRP C-202 Test Sites (Hpc)

Chapter 4

INTRODUCTION

This site consists of two eastbound lanes of State Route 58 eastbound in Boron, CA, as well as an overhead structure carrying State Route 58 over a rail spur immediately before the test section. The individual test sites and test results are described in the following sections.

BORON OVERHEAD

The Boron overhead, Bridge No. 50-353R 9-KER-58-R141.5, consists of two parallel structures carrying State Route 58 over the rail spur leading to the U.S. Borax mine in Boron, CA. Each structure consists of a three-span continuous bridge with no expansion joints. Each bridge has two traffic lanes and a shoulder. The bridge beams were cast integrally with the deck slab. The entire deck appears to be undergoing significant ASR, as manifested by widespread visible map cracking. The deck surface was treated with a methacrylate (HMWM) in 1995, into which a coarse, rounded sand was broadcast. Figure 35 shows a photograph of the deck surface.

Figure 35. Treated section on Boron overhead structure over State Route 58 looking east (Boron, CA).

The figure consists of a photograph of the treated section of the Boron overhead structure. There are two lanes of traffic and a shoulder.

Pavement Sections

The following information was excerpted from the CTL report (Stark to Surdahl letter, dated October 8, 1997):

This pavement section is located on State Route 58 between Barstow and Mojave near Boron on the Kern-San Bernardino county line in California. The pavement of interest was built between 1971 and 1974 as part of a four-lane divided section with 20.32-cm (8-inch) portland cement concrete slip-formed onto 10.16 to 15.24 cm (4 to 6 inches) of cement-treated base. The concrete was made using low-alkali cement (less than 0.60 percent equivalent to Na2O) and natural sand and gravel from a source in Barstow. In the early to middle 1980s, observations of this and several other concrete structures containing aggregate from the same source revealed deleterious ASR. In 1991, SHRP discussion with CALTRANS [California Department of Transportation] personnel revealed major surface cracking had been observed in the State Route 58 pavement. In 1988, a high molecular weight methacrylate (HMWM) had been applied to the pavement wearing surface in selected westbound sections near Boron to minimize cracking development and improve and prolong traffic service life, particularly with truck loading. A side effect would be to minimize any effects of deleterious ASR. In 1991, cores were taken as part of the SHRP program to confirm the occurrence of ASR and estimate the depth of penetration of the HMWM into the pavement concrete.

Observations

As noted in SHRP-C-343, six full-depth 10.16-cm (4-inch) diameter cores were taken from the experimental pavement section of Route 58, and sawed and finely lapped in the longitudinal direction for microscopic examination. The examinations confirmed that deleterious ASR had developed in the pavement concrete, and that the reactive aggregate constituents were cryptocrystalline volcanics of rhyolite to andesite composition. These were evidenced by reaction rims on aggregate particles, microcracks in the concrete, and ASR gel in cracks and voids. The examinations revealed that the applied HMWM penetrated and filled surface cracks to maximum depths of 51 to 62 mm (2 to 2.25 inch). Also, HMWM was found to have penetrated and filled cracks as little as 0.05 m (0.002 in) wide.

Status of Test Sections

For a period of years since 1988 when HMWM was applied, improved performance was noted, compared with sections with no treatment. For more than 5 years, only minor additional surface cracking appeared, while more severe surface cracks continued to develop along transverse joints, and adjacent to other random cracks in untreated sections. Also, numerous small surface spalls continued to develop in the untreated sections but not in the treated sections.

By 1995, 7 years after application of HMWM on State Route 58, it became apparent to CALTRANS that pavement performance both with and without the treatment reached a state of deterioration that required full-surface overlay. In 1996, this asphalt overlay was completed. However, CALTRANS agreed to retain a short section of exposed pavement with HMWM. This is presently the only section still available for visual inspection.

The test section described herein consists of two lanes of U.S. Route 52. Figures 36 and 37 show different views of the test pavement site, and figure 38 shows a plan of the test sections. The original test sections consisted of control 1, methacrylate 1, and methacrylate 2, all of which are located in the travel lane (number 2). Sections methacrylate 1 and methacrylate 2 were treated with a single coat of methacrylate into which a sand was broadcast. In 1995, three test sections in the passing lane (number 1); control 2, control 3, and methacrylate 3 were added alongside the existing test areas in the travel lane (number 2) by CALTRANS to evaluate the effect of traffic loading on the ASR damage. The Boron Overhead section was also added at this time. Lane 1 does not have the extreme damage present at the joints that lane 2 had. A coat of methacrylate was applied to the methacrylate 3 section in 1995, at the same time the bridge deck was treated. At that time, a second coat of methacrylate was added to section methacrylate 2 in the travel lane. Also, in 1995, the pavement on either side of the test section was overlayed with asphaltic concrete. The asphalt overlays were placed to reduce the maintenance liability of the large length of exposed ASR pavement adjacent to the test sections.

Figure 36. Photograph showing part of Boron, CA, test site, M2, Station 250.

In the photograph, two lanes and a shoulder are visible and the station designation parenthesis M2 Station 250) is written on the pavement shoulder.

Figure 37. Photograph showing part of Boron, CA, test site, M3, Station 160.

In the photograph, two lanes and the shoulder are visible.

Figure 38. Plan view of Boron, CA, test site.

The figure consists of a drawing with traffic direction going from left to right. The left lane is the passing lane and designated number 1. It consists of first Control 2, then Control 3, and then Methacrylate 3. The right lane is the travel lane, number 2 and starts with Control 1, followed by Methacrylate 1, and Methacrylate 2.

MAP CRACKING

All the sections making up the Boron, CA, test site had map cracking over 100 percent of their area in 1998. Most of the map cracking was of low severity, but there was some medium and high severity also. Figure 39 shows an example of high-severity map cracking. Figure 40 shows a close-up view of typical map cracking at the Boron site. Figures 41 through 44 show the amount of each level of severity as a percentage of the total area for each section for all 5 years of the study. In the travel lane, control section 1 (C1) had more severe map cracking than the methacrylate sections (M1 and M2). The cracking was less severe in M2 than in M1. It appears that the second application of methacrylate to section M2 in 1995 has helped reduce cracking. In the passing lane, methacrylate section 3 (M3) is performing better than control section 3 (C3). Overall, the passing lane sections are performing better than the travel lane sections. A description of the map cracking in each section is as follows:

Figure 39. Example of high-severity map cracking (Boron, CA).

The figure consists of a photograph showing high severity cracking in the travel lane of the test section.

Figure 40. Close-up photograph showing typical map cracking (Boron, CA).

Close-up photograph showing typical map cracking Boron, California.

Figure 41. Map cracking as a percentage for each level of severity (Boron, CA, 1995).

The figure consists of a bar graph of map cracking in 1995. Section designation is on the horizontal axis and map cracking (area at severity as a percent) is on the vertical axis. Section C 1 had about 90 percent low level severity, 9 percent medium level, and 1 percent high level cracking. Section M 1 had about 92 percent low level and 8 percent medium level cracking. M 2 had about 95 percent low level and 5 percent medium level cracking. C 3 had 100 percent low level cracking. Section M 3 had about 99 percent low level and 1 percent medium level cracking.

Figure 42. Map cracking as a percentage for each level of severity (Boron, CA, 1996).

The figure consists of a bar graph of map cracking in 1996. Section designation is on the horizontal axis and map cracking (area at severity as a percent) is on the vertical axis. Section C 1 had about 80 percent low level severity, 17 percent medium level, and 3 percent high level cracking. Section M1 had about 92 percent low level and 8 percent medium level cracking. M 2 had about 95 percent low level and 5 percent medium level cracking. C 3 had 98 percent low level and 2 percent medium level cracking. Section M 3 had about 99 percent low level and 1 percent medium level cracking.

Figure 43. Map cracking as a percentage for each level of severity (Boron, CA, 1997).

The figure consists of a bar graph of map cracking in 1997. Section designation is on the horizontal axis and map cracking (area at severity as a percent) is on the vertical axis. Section C 1 had about 80 percent low level severity, 15 percent medium level, and 5 percent high level cracking. Section M 1 had about 87 percent low level and 13 percent medium level cracking. M 2 had about 90 percent low level and 10 percent medium level cracking. C 3 and M 3 had 95 percent low level and 5 percent medium level cracking.

Figure 44. Map cracking as a percentage for each level of severity (Boron, CA, 1998).

The figure consists of a bar graph of map cracking in 1998. Section designation is on the horizontal axis and map cracking (area at severity as a percent) is on the vertical axis. Section C 1 had about 70 percent low level severity, 15 percent medium level, and 15 percent high level cracking. Section M 1 had about 82 percent low level and 8 percent medium level cracking. M 2 and C 3 had about 90 percent low level and 10 percent medium level cracking. M 3 had 95 percent low level and 5 percent medium level cracking.

JOINT DISTRESS

The widespread map cracking in the test sections made exact crack recording impossible. Therefore, only the large, clearly visible cracks were noted. The transverse joints were all completely distressed, with cracks and spalled areas occurring over the entire length of the joints. Figure 45 shows a photograph with an example of medium-severity joint distress. Figure 46 shows an example of high-severity joint distress. According to the LTPP criteria for rating joint distress, the entire length of each joint was rated at the highest severity level if at least 10 percent of the joint length had the higher severity distress.

Figure 45. Photograph showing medium-severity joint distress (Boron, CA).

The photograph shows a concrete pavement at a transverse joint with medium-severity distress cracking.

Figure 46. Photograph showing an example of high-severity joint distress (Boron, CA).

The photograph shows a concrete pavement at a transverse joint with numerous deep cracks and an actual hole in the pavement caused by cracking. An individual is shown in the photograph holding pieces of he disintegrated pavement from the hole.

Figures 47 through 50 are a series of graphs illustrating the amount and severity of joint distress for each section. There is also a series of graphs showing the actual lengths of distress at each level in figures 51 through 54. Both series compare all sections for each year. The 1998 observations of the joint distress for individual sections are as follows:

Figure 47. Amount and severity of joint distress (Boron, CA, 1995).

The figure consists of a bar graph of 1995 joint distress using the 10 percent rule. Section designation is on the horizontal axis and length of joint spalls in meters is on the vertical axis.  Sections C 1, M 1, M 2, C 3, and M 3 had 0, 0, 0, 118, and 5 meters of low level severity distress, respectively; and 112, 118, 62, 0, and 13 meters of medium level distress. C 1 had 8 percent high level distress.

Figure 48. Amount and severity of joint distress (Boron, CA, 1996).

The figure consists of a bar graph of 1996 joint distress using the 10 percent rule is on the vertical axis. Section designation is on the horizontal axis and length of joint spalls in meters.  Sections C 1, M 1, M 2, C 3, and M 3 had 0, 0, 12, 70, and 25 meters of low level severity distress, respectively; and 40, 118, 106, 48, and 31 meters of medium level distress. C 1 had 80 percent high level distress.

Figure 49. Amount and severity of joint distress (Boron, CA, 1997).

The figure consists of a bar graph of 1997 joint distress using the 10 percent rule. Section designation is on the horizontal axis and length of joint spalls in meters is on the vertical axis.  Sections C 1, M 1, M 2, C 3, and M 3 had 0, 0, 0, 7, and 3 meters of low level severity distress, respectively; and 60, 110, 118, 111, and 107 meters of medium level distress. C 1 had 60, M 1 had 5, and M 3 had 10 percent high level distress.

Figure 50. Amount and severity of joint distress (Boron, CA, 1998).

The figure consists of a bar graph of 1998 joint distress using the 10 percent rule. Section designation is on the horizontal axis and length of joint spalls in meters is on the vertical axis.  Sections M 3 had only 3 percent low level severity distress. Sections C 1, M 1, M 2, C 3, and M 3 had 17, 87, 113, 118, and 107 meters of medium level severity distress, respectively; and 103, 30, 3, 0, and 10 meters of high level distress.

Figure 51. True length of joint spalls at each level of severity (Boron, CA, 1995).

The figure consists of a bar graph of 1995 joint distress. Section designation is on the horizontal axis and true length of joint spalls in meters is on the vertical axis. Sections C 1, M 1, M 2, C 3, and M 3 had 60, 40, 18, 118, and 8 meters of low level severity distress, respectively; and 54, 80, 43, 0, and 13 meters of medium level distress. Section C 1 had 4 meters of high level distress.

Figure 52. True length of joint spalls at each level of severity (Boron, CA, 1996).

The figure consists of a bar graph of 1996 joint distress. Section designation is on the horizontal axis and true length of joint spalls in meters is on the vertical axis. Sections C 1, M 1, M 2, C 3, and M 3 had 36, 63, 81, 100, and 43 meters of low level severity distress, respectively; and 73, 55, 38, 18, and 6 meters of medium level distress. Section C 1 had 10 meters and M 1 had 1 meter of high level distress.

Figure 53. True length of joint spalls at each level of severity (Boron, CA, 1997).

The figure consists of a bar graph of 1997 joint distress. Section designation is on the horizontal axis and true length of joint spalls in meters is on the vertical axis. Sections C 1, M 1, M 2, C 3, and M 3 had 30, 52, 70, 80, and 82 meters of low level severity distress, respectively; and 83, 62, 43, 37, and 38 meters of medium level distress. Sections C 1, M 1, and M 3 had 8, 2, and 2 meters of high level distress.

Figure 54. True length of joint spalls at each level of severity (Boron, CA, 1998).

The figure consists of a bar graph of 1998 joint distress. Section designation is on the horizontal axis and true length of joint spalls in meters is on the vertical axis. Sections C 1, M 1, M 2, C 3, and M 3 had 0, 30, 40, 3, and 82 meters of low level severity distress, respectively; and 100, 81, 78, 105, and 38 meters of medium level distress. Sections C 1, M 1, and M 3 had 11, 4, and 1 meters of high level distress.

In general, the sections in the travel lane had more severe joint distress than those sections in the passing lane. The control sections had the most severe joint distress in each lane relative to the treated areas. The second application of methacrylate to section M2 appeared to have helped, the severity of distress in M2 being less than that in section M1.

WHEELPATH DISTRESS

Visual surveys of the pavement sections were performed as previously done, with the wheelpath and centerline grading system changed to include sections with small, loose pieces in the high-severity (H) category. The wheelpaths and centerline were rated as follows:

Table 24 shows the number of slabs in each section at each level of severity for all years of the study. Some variability in the ratings occurred due to site lighting conditions and other inspection variations. In 1997, all the methacrylate-treated systems had a combination of low-and medium-severity cracking. There was little difference between section M2, which had the second application of methacrylate, and section M1, which only had one application. Both control sections had the most severe cracking with control section C1, which is in the No. 2 travel (truck) lane, having the most severe cracking. Section C1 had medium- and high-severity cracking while C3 had mostly medium severity with a small amount of low-severity cracking. In 1998, C1 still had the most severe cracking. The severity of cracking in all the other sections but M3 had increased. Sections M1 and M2 had medium-severity cracking over the wheelpaths of all slabs in 1998.

Table 24. Wheelpath ratings for all sections, Boron, CA.
YearC1M1M2C3M3
LMHLMHLMHLMHLMH
1994027513200321
19950032033003302310
1996062633001715152803220
1997010222211019140132017170
19980102203300330029417170

CENTERLINE DISTRESS

Table 25 shows the number of slabs in each section at each level of severity for all 5 years of the study for the centerline area of the sections. The same trend is evident here as in the wheelpath ratings. The ratings for all sections except M3 were more severe in 1998. Sections M1 and M2 were actually rated less severe than M3 in 1997, but in 1998 they were rated more severe then in previous years. The two control sections were rated the most severely distressed with C1 rated more severe than C3. Overall, the ratings in the centerline areas were much less severe than for the wheelpath areas.

Table 25. Centerline ratings for all sections, Boron, CA.
YearC1M1M2C3M3
LMHLMHLMHLMHLMH
1994266031203300
199503201320033003210
19963 2273300303030303300
199712653300330030303030
19987250 825027604290303 0

ELASTIC MODULUS AND COMPRESSIVE STRENGTH

At least four cores were removed from each section, with many of the removed cores extracted in small, already fractured pieces. The cores were 1.22 and 1.83 m from the shoulder stripe to reflect wheelpath and centerline areas, respectively. The specific locations were chosen to avoid interfering with previous cores. If a core was retrieved in a broken or damaged condition, another core was taken approximately 0.61 m east of the original core at the same distance from the shoulder stripe.

The cores were tested to determine the compressive strength and elastic modulus of the concrete in both wet and dry conditions. The cores were tested in a dry as-received condition, then soaked in lime-saturated water for 2 weeks and retested. After the wet modulus tests were performed, the cores were tested to determine their compressive strength. The results of the dry modulus testing are shown in table 26. The results of the wet modulus testing are shown in table 27.

Table 26. Modulus dry tested elastic modulus (psi x 106), Boron, CA.
Section1995199619971998
Control 1(C1)1.600.981.151.25
Methacrylate 1(M1)1.281.131.141.47
Methacrylate 2 (M2)1.421.341.161.18
Control 3 (C3)0.921.261.28
Methacrylate 3 (M3)0.691.091.18

1 psi = 6.89 kPa

Table 27. Modulus wet tested elastic modulus (psi x 106), Boron, CA.
Section1995199619971998
Control 1 (C1)1.281.101.081.47
Methacrylate 1 (M1)1.000.991.121.82
Methacrylate 2 (M2)1.191.301.091.49
Control 3 (C3)0.901.051.50
Methacrylate 3 (M3)0.720.991.12

1 psi = 6.89 kPa

The results of the modulus testing show there is not much difference in modulus from one section to another. The wet and dry modulus values were generally similar. The one consistent trend is that the modulus for section M3 was the lowest in every year.

The wet lime-saturated compressive strength results are given in table 28. The compressive strength results show no significant difference between the sections. Generally, there has been a decrease in strength of each section over the test years.

Table 28. Compressive strength test results (Boron, CA).
Section1995199619971998
Control 1 (C1)4788427036053731
Methacrylate 1 (M1)4052451040414371
Methacrylate 2 (M2)4302513738033609
Control 3 (C3)398534953684
Methacrylate 3 (M3)428036883744

The cores tested may represent a minimum strength or modulus for intact cores. If a core was taken and it fell apart as it was being removed, another core was drilled. This biases the results because only solid cores can be tested.

RELATIVE HUMIDITY MEASUREMENTS

Relative humidity samples were removed from one or two locations in each section at various depth intervals, using a 38.1-mm-diameter bit and rotary hammer. The depth intervals and results of the relative humidity testing are shown in tables 29 through 33. Most of the relative humidity measurements were above 80 percent, especially below a depth of 10.2 cm. These results indicate that even though the pavement is located in a very dry climate, sufficient moisture is still present to sustain the ASR. The humidity results for the bridge were much lower than the pavement. This is encouraging and indicates that methacrylate treatment of bridge decks may be much more effective at slowing ASR than when treating pavements.

Table 29. Relative humidity testing (1994).
Test Area and Section NumberRelative Humidity, Percent (at given depth interval) (inches)
0.5–1 2–2.5 4–4.5 6–6.5
Number 1 (Passing) LaneC388899392
M369818787
Number 2 (Passing) LaneC193879390
M178919792
M259979690

1 inch = 2.54 cm

Table 30. Relative humidity testing (1995).
Test Area and Section NumberRelative Humidity, Percent (at given depth interval) (inches)
0.5–12–2.54–4.5 6–6.5
Number 1(Passing) LaneC336636286
M346728690
Number 2 (Travel) LaneM145706289
M272848689
C168649089
Bridge37556665

1 inch = 2.54 cm

Table 31. Relative humidity testing (1996).
Test Area and Section NumberRelative Humidity, Percent (at given depth interval) (inches)
0.5–12–2.54–4.5 6–6.5
Number 1 (Passing) LaneC365909287
M369798783
Number 2 (Travel) LaneC156898480
M181908672
M244747078

1 inch = 2.54 cm

Table 32. Relative humidity testing (1997).
Test Area and Section NumberRelative Humidity, Percent (at given depth interval) (inches)
0.5–12–2.54–4.5 6–6.5
Number 1 (Passing) LaneC3
M340628696
Number 2 (Travel) LaneM146938198
M243487987
C150769290
Bridge32464456

1 inch = 2.54 cm

Table 33. Relative humidity testing (1998).
Test Area and Section NumberRelative Humidity, Percent (at given depth interval) (inches)
0.5–12–2.54–4.5 6–6.5
Number 1 (Passing) LaneC34875100100
M358769796
Number 2 (Travel) LaneM1100100100100
M21005410093
C1100100100100
Bridge32395262

1 inch = 2.54 cm

PETROGRAPHIC EXAMINATION

Two cores from each section were examined petrographically to document the condition of the concrete. The cores were cut length-wise and polished. These sections were then soaked overnight and dried, and the entire lapped surface was traversed under a stereo microscope. Each lapped surface was divided into five or more traverse areas and examined at magnifications of 10 to 30 times. Because of their smaller diameters (6.99 cm (2.75 inches)), the Boron overhead bridge cores were divided into four traverses. All instances of cracks, alkali-silica gel, and deteriorated or reacted aggregate particles were counted. The petrographer’s notes for each year are included in appendix C. Table 34 gives a numerical summary of the findings for 1997 and 1998.

Table 34. Summary of petrographic findings for 1997 and 1998, Boron, CA.
Core IDYearCracksReactive ParticlesGel Locations
MicroLargeFine Coarse
C1-11997
1998
190
86
0
5
20
21
8
22
67
49
C1-21997
1998

60

0

21

23

41
C3-11997
1998
174
50
0
3
23
8
11
11
24
28
C3-21997
1998
190
63
0
23
30
10
26
12
44
14
M1-11997
1998
191
51
0
1
33
9
23
9
65
20
M1-21997
1998

84

6

15

17

32
M2-11997
1998
135
72
0
3
24
7
29
12
59
12
M2-21997
1998

89

3

16

8

23
M3-11997
1998
134
66
0
0
32
7
31
14
46
29
M3-21997
1998

67

0

13

10

24
OH-1 Bridge1997
1998
22
29
0
2
0
8
0
7
0
29
OH-2 Bridge1997
1998

29

1

7

11

36

A summary description of the cores from each section follows:

SUMMARY OF BORON, CA TEST SITE

HMWM resin was topically applied to desert pavement sections with moderate to severe ASR distress. The methacrylate has extended the pavement life by filling cracks bonding the pieces of concrete and reducing spalling, especially near joints. The service life extension of one coat of HMWM appears to be about 3 to 5 years. Two coats of resin improved performance further. It is envisioned that periodic reapplication of HMWM would reduce future concrete spalling and continue to extend the pavement life.

HMWM resin was also applied to a bridge deck having low to moderate ASR distress. The resin had been effective in bonding and sealing almost all of the cracks. No new visible cracking was noted over the study period. The relative humidity in the deck concrete is moderately low and to a level that should slow ASR deterioration. Preliminary results are promising and continued monitoring of this structure is recommended.

 


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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). 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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