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Federal Highway Administration Research and Technology
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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
At both sites, the full-depth PCC repairs are performing very well. None of the repairs exhibited any material problems at either 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.
The observed changes in the Ohio sections (since the follow-up survey conducted during SHRP C-206) consist of:
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.
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.
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.
The observed changes in the Ohio sections consist of:
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.
In 1996, the Ohio site was surveyed on September 19, and the Georgia sections were surveyed on November 13.
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.
1 MPa = 145.04 psi
Figure A1. Backcalculation results for the GADOT section.
1 MPa = 6.89.45.04 (psi)
Figure A2. Backcalculation results for the FT 1 section.
1 MPa = 145.04 psi
Figure A3. Backcalculation results for the VES section.
1 MPa = 6.89145 psi
1 m = 3.28 ft
1 m = 3.28 ft
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.
1 in = 25.4 mm
Figure A5. Void detection test results for section FT 1.
1 in = 25.4 mm
Figure A6. Void detection test results for section VES.
1 in = 25.4 mm
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:
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.
In 1997, the Georgia sections were surveyed on October 30, and the Ohio sections were surveyed on November 6-7.
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.
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.
In 1998, the Ohio sections were surveyed on October 22-23, and the Georgia sections were surveyed on November 4.
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.
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.