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Publication Number: FHWA-RD-02-085
Date: July 2006

Highway Concrete Technology Development and Testing Volume IV:Field Evaluation of SHRP C-206 Test Sites (Early Opening of Full-Depth Pavement Repairs)

 

APPENDIX A. SUMMARY OF ANNUAL SURVEY RESULTS

1994 Survey

At both sites, the full-depth PCC repairs are performing very well. None of the repairs exhibited any material problems at either site.

Georgia Site

At the Georgia site, only two of the long (4.6-m or longer) repairs developed cracks. No other repair distresses were observed. The surrounding pavement at the Georgia site did not show any significant further deterioration, but it exhibited very high deflection under load. The deflection of the pavement under truck wheel loads was readily visible.

Ohio Site

The observed changes in the Ohio sections (since the follow-up survey conducted during SHRP C-206) consist of:

  • Further progression of longitudinal cracking that developed shortly after opening of the test sections to traffic.
  • Development of transverse cracking in one slab.
  • Development of corner breaks in two slabs (both VES).

Two of the repairs in the Pyrament 1 section (PC 1) had been removed and replaced. The most likely reason for this replacement is the deterioration of the surrounding pavement and not the repairs themselves. Many of the C-206 repairs are surrounded by very short slabs (1.8 to 2.4 m), resulting from the placement of the repairs. If the deterioration of the original joint in the surrounding slabs is excessive (due to D-cracking, which is a widespread problem at this site), the only way the repairs can be made is by removing all of the short slabs in the immediate area and replacing them with full slabs. The other important noticeable change at the Ohio site was the deterioration of the surrounding pavement. D-cracking in the surrounding pavement had progressed significantly since the placement of the repairs. Virtually all original joints in the surrounding pavement exhibited extensive D-cracking.

1995 Survey

In 1995, the Ohio sections were surveyed on November 15, and the Georgia sections were surveyed on November 30. At both sites, the PCC repairs are performing well. None of the repairs exhibited any material problems at either site.

Georgia Site

Considering the length of some of the Georgia repairs, the Georgia sections are performing very well. The GADOT section contained the longest repairs (repair lengths up to 4.9 m). During the 1994 survey, a transverse crack was observed on two of the 4.6-m repairs in this section (one medium- and one high-severity). Both repairs had been partially replaced before the 1995 survey to repair the cracked portion. The remaining portions of these two repairs are now 2.7 m and 3.7 m. Full-depth repairs have also been made adjacent to two of the 1.8-m repairs in the FT 1 section. No other distresses were observed at this site. Faulting in all sections was minimal (less than 1.0 mm (0.04 in)).

The shoulders at the Georgia site were replaced with a new asphalt shoulder in November 1995. The contractor was just finishing the construction of the new shoulder in section 3 when it was surveyed. Because of the construction work in the area, the FWD testing originally planned for this section could not be completed. That testing will be completed next year.

Ohio Site

The observed changes in the Ohio sections consist of:

  • One repair in the FT1 section (B5) developed a longitudinal crack. The longitudinal cracking is prevalent in all Ohio sections. The likely cause of these cracks is the excessive temperature gradients that were present in the slabs when the concrete hardened.
  • One repair in the VES section (E3) developed a transverse crack. This repair also has a longitudinal crack at about 1.8 m from the lane-shoulder joint.
  • With the exception of RSC 1, which has an average faulting of -4.6 mm on the approach side and 4.8 mm on the leave side, faulting in all sections is minimal (less than 1.3 mm).

Another noticeable change at the Ohio site is the general condition of the surrounding pavement. A significant number of transverse joints in the surrounding pavement were badly deteriorated due to D-cracking. All of these joints had been repaired since the last survey, either by full-depth repair, patching, or sealing. Many of the cracks in the surrounding pavement were also repaired by full-depth repair.

1996 Survey

In 1996, the Ohio site was surveyed on September 19, and the Georgia sections were surveyed on November 13.

Georgia Site

This year, FWD testing was conducted in addition to the visual distress survey to detect changes in LTE and PCC modulus (EPCC). The results of the visual distress survey and faulting measurements are shown in table B1. Since last year, only one 4.5-m repair in section 1 (GADOT mix) developed a crack. This amounts to 30 percent of 4.5-m repairs, but this is substantially better than the predicted performance. None of the shorter repairs developed cracks. The level of faulting in all sections remains about the same.

The FWD testing results are summarized in table A1. The backcalculated moduli from this year’s test results show that PCC properties have not changed significantly over the 4 years the repairs have been in place. The backcalculated subgrade k-values from this year’s test results appear high. The variability of the backcalculated k-value and EPCC is illustrated in figures A1, A2, and A3 for the three sections. The variability of subgrade k shown on these figures appears reasonable, but the variability of EPCC is more likely due to slab thickness variations rather than the actual variability of EPCC.

The deflection measurements from the testing conducted at the transverse edges were used to determine deflection LTE. The deflection LTEs also appear to have remained about the same. Table A1 shows improved LTE in some cases. This anomaly is most likely due to the difference in the mix of joints tested, but the temperature and moisture conditions during testing can also affect the deflection testing results. More slabs were tested this year than during SHRP, but not all of the slabs tested during SHRP were tested this year. Tables A2, A3, and A4 provide more details of the LTE testing results.

Table A1. Summary of Falling Weight Deflectometer test results.
Section Subgrade k psi/in EPCC million psi LTE w/Load Plate On, % Average LTE
Approach Side Leave Side
SHRP 1996 SHRP 1996 SHRP 1996 SHRP 1996 SHRP 1996
GA 1, GADOT 199 275 6.12 6.03 62% 74% 83% 77% 73% 75%
GA 2, FT1 218 328 5.64 5.38 72% 70% 81% 75% 77% 72%
GA 3, VES 299 309 5.27 5.13 71% 76% 84% 84% 77% 80%

1 MPa = 145.04 psi

Figure A1. Backcalculation results for the GADOT section.

. This figure is a line graph. Location from the beginning of the section is graphed on the horizontal axis, from 0 to 3,500 feet. Subgrade K is graphed on the left vertical axis from 0 to 450 P S I per inches. P C C modulus is graphed on the right vertical side from 0 to 8 mega P S I. Subgrade K begins at 350 P S I per inches and decreases to 225. After 1,250 feet, subgrade K increases back to 350. P C C modulus begins at 4.5 mega P S I and increases to 5 mega P S I at 250 feet. The modulus starts to decline at 1,250 feet to 2.5 mega P S I at 2,500 feet. P C C increases rapidly to 7 mega P S I at 2,500 feet. Whenever subgrade K increases in P S I, P C C modulus decreases in mega P S I.

1 MPa = 6.89.45.04 (psi)
1 m = .3053.28 ft

Figure A2. Backcalculation results for the FT 1 section.

This figure is a line graph. Location from the beginning of the section is graphed on the horizontal axis, from 400 to 800 feet. Subgrade K is graphed on the left vertical side of the graph, from 0 to 450 P S I per inches. P C C modulus is graphed on the right vertical side, from 0 to 7 mega P S I. Subgrade K begins at 375 P S I per inches at 526 feet from the beginning of the section. It gradually decreases to 310 P S I at 675 feet. Subgrade K increases dramatically to 400 P S I at 700 feet, and then decreases dramatically to 275 P S I at 725 feet. P C C modulus begins at 4.5 mega P S I at 425 feet from the beginning of the section, and it gradually increases to 6.5 mega P S I at 575 feet. The P C C modulus starts to decrease at 6.5 mega P S I to 4 P S I at 700 feet and then increases dramatically. As subgrade K increases in P S I per inches, P C C modulus decreases in mega P S I.

1 MPa = 145.04 psi
1 m = 3.28 ft

Figure A3. Backcalculation results for the VES section.

This figure is a line graph. Location from the beginning of the section is graphed on the horizontal axis, from 0 to 3,000 feet. Subgrade K is graphed on the left vertical axis, from 0 to 450 P S I per inches. P C C modulus is graphed on the right vertical side, from 0 to 7 mega P S I. Subgrade K begins at 350 P S I per inches at 200 feet from the beginning of the section, and it starts to fluctuate up and down. After 500 feet, subgrade K decreases to 200 P S I at 1,500 feet and then slowly increases to 300 P S I at 2,800 feet. P C C modulus begins at 4.25 mega P S I at 200 feet from the beginning of the section. It increases to 5 mega P S I at 700 feet and stays above 5 mega P S I for the remainder of the location. Whenever subgrade K has a high level of P S I, P C C modulus has a low level of mega P S I.

1 MPa = 6.89145 psi
1 m = .3053.28 ft

Table A2. Deflection load transfer test results of section GA 1, GADOT.
Section ID Slab Size, ft Joint Relative Station LTE w/ Load Plate On Average LTE
Approach Side Leave Side
1-1 8 Approach 0+00 83% 88% 86%
1-1 8 Leave 0+05 69% 66% 68%
1-2 8 Approach 1+06 34% 61% 48%
1-2 8 Leave 1+22 84% 81% 82%
1-3 8 Approach 2+69 70% 79% 75%
1-3 8 Leave 2+76 85% 85% 85%
1-4 8 Approach 5+57 71% 86% 78%
1-4 8 Leave 5+65 83% 89% 86%
1-5 8 Approach 11+28 78% 72% 75%
1-5 8 Leave 11+39 82% 80% 81%
1-6 8 Approach 11+61 53% 53% 53%
1-6 8 Leave 11+69 86% 83% 85%
1-8 15 Approach 15+22 56% 59% 57%
1-8 15 Leave 15+37 85% 92% 88%
1-16 16 Approach 19+73 54% 60% 57%
1-16 16 Leave 19+89 85% 77% 81%
1-17 15 Approach 20+34 72% 72% 72%
1-17 15 Leave 20+48 89% 90% 90%
1-18 15 Approach 24+24 70% 75% 73%
1-18 15 Leave 24+39 87% 90% 88%
Average LTE 74% 77% 75%

1 m = 3.28 ft

Table A3. Deflection load transfer test results of section FT 1.
Section ID Slab Size, ft Joint Relative Station LTE w/ Load Plate On Average LTE
Approach Side Leave Side
2-3A 7 Approach 0+00 63% 70% 67%
2-3A 7 Leave 0+08 86% 84% 85%
2-4 10 Approach 4+19 73% 74% 74%
2-4 10 Leave 4+28 88% 89% 89%
2-5 6 Approach 4+57 65% 71% 68%
2-5 6 Leave 4+62 71% 72% 72%
2-7 10 Approach 5+71 60% 61% 61%
2-7 10 Leave 5+82 78% 76% 77%
2-9 10 Approach 6+60 59% 69% 64%
2-9 10 Leave 6+70 88% 89% 88%
2-10 10 Approach 6+91 74% 71% 73%
2-10 10 Leave 7+01 78% 81% 80%
2-11 10 Approach 7+23 69% 85% 77%
2-11 10 Leave 7+33 81% 85% 83%
2-12 6 Approach 7+83 19% 24% 22%
2-12 6 Leave 7+90 86% 93% 89%
2-13 11 Approach 10+50 74% 79% 77%
2-13 11 Leave 10+62 10% 37% 23%
2-15 6 Approach 11+86 79% 86% 83%
2-15 6 Leave 11+91 93% 93% 93%
Average LTE 70% 75% 72%

1 m = 3.28 ft

Table A4. Deflection load transfer test results of section GA 3, VES.
Section ID Slab Size, ft Joint Relative Station LTE w/ Load Plate On Average LTE
Approach Side Leave Side
3-2 12 Approach 2+10 65% 79% 72%
3-2 12 Leave 2+23 85% 88% 86%
3-5 12 Approach 3+92 72% 80% 76%
3-5 12 Leave 4+03 94% 84% 89%
3-7 12 Approach 6+03 67% 82% 74%
3-7 12 Leave 6+16 83% 85% 84%
3-9 8 Approach 7+25 76% 97% 86%
3-9 8 Leave 7+33 85% 88% 86%
3-12 8 Approach 8+87 87% 75% 81%
3-12 8 Leave 8+95 80% 79% 80%
3-13 8 Approach 9+09 70% 89% 80%
3-13 8 Leave 9+17 85% 97% 91%
3-15 9 Approach 12+70 59% 77% 68%
3-15 9 Leave 12+78 82% 81% 82%
3-16 12 Approach 15+40 52% 74% 63%
3-16 12 Leave 15+54 89% 101% 95%
3-18 8 Approach 22+43 51% 57% 54%
3-18 8 Leave 22+52 88% 90% 89%
3-19 8 Approach 28+46 63% 81% 72%
3-19 8 Leave 28+59 86% 86% 86%
Average LTE 76% 84% 80%

1 m = 3.28 ft

These tables show that the approach joints are consistently faulted more than the leave joints, and the repair size does not appear to be a factor on this effect.

The FWD testing was conducted at different load levels to determine the presence of voids under the repair joints. The void detection is possible because the presence of voids causes nonlinear response of pavement deflections. If edge deflections were plotted against applied load, the bestfit line through the data points should go through zero if the pavement response is linear. However, if voids are present, then a certain amount of deflection will take place with minimal applied load until the slab comes in full contact with the subgrade. Hence, the presence of voids causes increased deflection at all load levels, causing an upward shifting of the plot of load versus deflection.

A positive intercept on the load versus deflection plot, therefore, indicates a possible presence of voids under the joint, and the value of the intercept is related to the magnitude of the voids. However, the best-fit line on the load-deflection plot may not always go through zero even when no voids are present because other factors can cause nonlinear response of pavement deflections (e.g., load response of the subgrade and the base layers). Depending on the temperature conditions, upward curling of the slabs may also show up as voids, because the curling can cause the slab corners to lift off the foundation. In general, a positive y-intercept greater than about 0.05 mm may be a possible indication of the presence of voids.

The intercept values from the load-deflection plots are shown in figures A4, A5, and A6. The figures show possible voids under the repairs 1-3, 2-13, 2-15, 3-13, and 3-15, but most joints tested show good support under the joints. These results show that the slabs were not curled up at the time of testing.

Figure A4. Void detection test results for section GA 1.

This figure is a line graph. Sections are graphed on the horizontal axis, from 1-1 to 1-18. The void, in 10 to the negative cubed inches, is graphed on the vertical axis, from negative 6 to 8. Sections 1-2 and 1-3 had between 3-5 possible voids. Every other section had below two possible voids. All the points below the possible voids zigzag up and down.

1 in = 25.4 mm

Figure A5. Void detection test results for section FT 1.

This figure is a line graph. Sections are graphed on the horizontal axis from 2-3A to 2-15. The void, in 10 to the negative cubed inches, is graphed on the vertical axis, from negative 6 to 8. The points begin below the possible voids line, which is 2 inches, and zigzag slightly between negative 2 and 0 inches. The points increase above the possible voids line at section 2-13.

1 in = 25.4 mm

Figure A6. Void detection test results for section VES.

This figure is a line graph. Sections are graphed on the horizontal axis from 3-2 to 3-19. The void, in 10 to the negative cubed inches, is graphed on the vertical axis from negative 6 to 8. The points begin below the possible voids line, which is 2 inches. The points remain below 0 inches but increase to 3 inches at section 3-6, which is above the possible voids section. Then, the points drop below the line and zigzag up and down until section 3-13 to 3-16. After section 3-16, the points drop again below the possible voids line to continue the zigzag pattern.

1 in = 25.4 mm

Ohio Site

In general, the condition of the test patches had not changed significantly from the previous year. The surface cracking in some areas appeared to have progressed somewhat, but none of these cracks are severe enough to be called block cracking yet. The distress data from the Ohio site are summarized in table B2, and the faulting measurements are summarized in table B3. The faulting remained virtually unchanged, but the following changes in slab cracking were noted:

  • FT 1—two longitudinal cracks (patches B7 and B8) went from low to medium severity.
  • RSC 1—two longitudinal cracks (patches D5 and D9) went from low to medium severity. This section was overlaid shortly after the 1996 survey.
  • VES—Patch E3 was partially replaced with asphalt concrete (AC). This patch contained a longitudinal crack and a transverse crack that divided the outer half of the patch into two pieces. The quartered portion of the patch was replaced with AC.

The condition of the surrounding pavement had not changed significantly since the last survey. Very few original joints remain at this site. Virtually all joints had been replaced with full-depth repairs because of severe D-cracking problems. Most cracks in the original pavement have also been repaired, so very few slabs are long enough to develop transverse cracks. Since the last survey, the ODOT apparently went through a cycle of AC patching at this site. Any areas showing spalling had been filled with AC patching material.

The original concrete near the patch joints started to show signs of D-cracking in some areas. Fine cracks in the D-cracking pattern were found at several repair joints at the corners of the original concrete. So far, these cracks are very tight. Similar cracks were also found on a few of the repairs, but most of the repairs are free of this type of cracking.

1997 Survey

In 1997, the Georgia sections were surveyed on October 30, and the Ohio sections were surveyed on November 6-7.

Georgia Site

At the Georgia sections, the only significant change from last year is the additional cracking in section 1 (GADOT mix). Two of the 4.5-m repairs had developed a crack. One of the 2.4-m repairs also was lost from this section, apparently because of the failure adjacent to the repair slab; the whole area had been removed and replaced with a new repair slab. No significant change in faulting was noted, and no material-related problems were observed.

Ohio Site

At the Ohio site, the only significant change is the noticeable increase in map cracking in the VES and ODOT FS mix sections (sections E, H, and I). As discussed under task B, delayed ettringite formation is the suspect cause of the noticeable increase in map cracking in these sections. In 1997, it was planned that additional cores would be taken in 1998 to verify the cause of the map cracking. As previously reported, the RSC 1 section was overlaid after the 1996 survey.

1998 Survey

In 1998, the Ohio sections were surveyed on October 22-23, and the Georgia sections were surveyed on November 4.

Georgia Site

The Georgia sections did not show any change in either structural or material condition since the last survey. Faulting levels remain very low and virtually unchanged throughout the entire monitoring period.

Ohio Site

The structural condition of the Ohio sections remained largely unchanged since the last survey, but some of the sections showed modest increase in map cracking that first became significantly noticeable in 1997. The only changes in structural condition were in section B (FT I) and section E (VES). Each section developed two additional transverse cracks. Faulting levels were again very low and virtually unchanged throughout the entire monitoring period. Sections E, H, and I (VES and FS mix sections) showed a modest increase in map cracking. Delayed ettringite formation was the suspected cause of the map cracking in these sections. Additional cores were taken from those sections to verify the cause of the map cracking. Both Pyrament sections (sections C and F) also exhibited some map cracking.

 

FHWA-RD-02-085

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