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The Following chapter summarizes observations and evaluations resulting
from the site visits to each of the 18 sulfur-extended asphalt pavements noted in Table 3.
Visual manual distress surveys were conducted at each of the sites in
accordance with FHWA's Long Term Pavement Performance Distress Identification Manual.
Summaries of all surveys are provided in Appendix A. A comparison of the distress
quantities for sections with and without sulfur is provided in Table 4.
An initial evaluation on the previously completed laboratory testing
was conducted when possible, to gain insight on anticipated condition at the various
locations. The Asphalt-Aggregate Mixture Analysis System (AAMAS) models were used with the
1990 lab data to give an indication of the types of distresses (rutting, fatigue cracking
and/or low temperature cracking) that may be present and the possible severity, prior to
visiting the sites. These analyses are discussed for each site visit under the heading
"Comparison of Field Data to Laboratory Data". Previous distress surveys
conducted in 1986 were also used for this purpose, but by using the lab information it was
anticipated that predictions of progression may be possible (if traffic data for the past
10 years was available).
Coring was conducted to verify layer thicknesses and check for any
material deficiencies (i.e. stripping). Detailed laboratory evaluations of these cores
were conducted by the FHWA to evaluate the effects of moisture on asphalt concrete paving
mixtures. The results are reported in FHWA-RD97-098 (5).
A brief summary of the observations from each visit are provided in the
following pages along with discussion on the comparison of model predictions versus the
actual observations. Further details about each site visit can be found in technical
memorandums completed for each site visit.
Boulder City, Nevada, Section 853201, April 12, 1994
SITE LOCATION
This section is located at the junction of US-93 and 95 near Boulder
City, Nevada. The test sections are located on the southbound Railroad Pass ramp of US-95.
Upon arrival, it was noted that the site was in excellent condition. It
was immediately determined that some sort of rehabilitation had taken place on the
pavement. However, since the exact type of rehabilitation was unknown, it was decided to
continue with the coring operations and determine what rehabilitation had taken place.
Pavement sections were marked based upon the Sulfur Institute Construction Report written
in 1977. Figures from this report were used to determine the beginning station and to
determine where the sulfur-extended asphalt thicknesses varied.
The first core was taken at Station 6+50 in the mid-lane. After
drilling approximately 4 inches, the core split at the interface between two lifts and
could not be extracted. A second core was taken approximately 18 inches away from the
first and ended up being approximately 12 1/2 inches thick. Visual observations of the
core confirmed that the project had been overlaid. Delineations of the original 4 inches
of sulfur-extended asphalt, the 1-inch friction course and the overlay material could be
seen on the core.
In an effort to get a clearer picture of exactly what had occurred
during rehabilitation, several other cores were taken throughout the project. Cores were
taken at Stations 7+50, 10+00, 15+00 and 20+00. It was determined from this operation that
the overlay tapered from about a 6-inch overlay at the beginning station to approximately
a 2-inch overlay at the ending station. Pictures of the cores taken are included in the
technical memorandum completed for the site visit.
After the second core was taken, Mr. Tom Sullivan arrived at the
project. He was present on the original construction project and provided good information
about the project. Mr. Sullivan originally worked for the US Department of Interior,
Bureau of Mines which was responsible for construction of the sections and confirmed that
the sections selected were exactly in the right locations. He had no knowledge of the
overlay that had occurred but he also noted that he had not been on the site in
approximately 2 years. Mr. Sullivan's arrival was extremely helpful in confirming the
location of the sites. Upon completion of the coring operation, several pictures of the
site were taken and a video walk-through was conducted. No distress surveys were conducted
due to the overlay.
OBSERVATIONS
Based upon the phone survey conducted under Phase I of this contract,
it was relayed to us that no overlay existed on the site. However, upon completion of the
coring it was determined that an overlay was present.
After further contact with State DOT research personnel it was
determined that the overlay on the ramp was most likely placed during the 1991
construction season. During this season the mainline lanes received a significant overlay
rehabilitation and it was planned for the US 95 ramp (where the SEA sections were located)
to receive a thin surface friction coarse overlay. It is the State DOT's conclusion that a
project level decision was made to continue the mainline overlay down the ramp (tapering
to the thin friction coarse) for some unspecified reason. District personnel were also
contacted to try and determine why the overlay was continued down the ramp and they were
unable to locate that information as well.
EVALUATIONS
Because of the overlay, no significant performance evaluations can be
made at this time.
COMPARISON OF FIELD DATA TO LABORATORY DATA
Because of the presence of the overlay, no distress surveys were
completed. Therefore, no comparisons (based upon new information) may be made. Also, there
is no lab data from FHWARD-90-110 because this site was not included in the original lab
evaluations. Therefore, due to these limitations no comparisons or evaluations may be made
for this site other than observations from the surveys in 1989 (Beatty, et al) or any
state observations.
SH 29, near Wittenberg, Wisconsin, Section 865501, July 7,1994
SITE LOCATION
This section is located on State Highway 29 in Shawan County between
Witterberg and Tilleda and was placed in 1982. The project contained a single SEA mix
placed in four different cross-sections and also includes four asphalt concrete control
sections. The SEA mix remained as the surface layer, but was in poor condition at the time
of the site visit. Some milling (3/4" deep) was performed to remove minor rutting
(1/4" to 1/2" in depth), but only occurred in a few areas. State Highway 29 was
being redesigned as a superhighway and the roadway containing the SEA pavement was to be
completely reconstructed at the start of the 1994 construction season.
The Wisconsin Department of Transportation provided a location map and
plan sheets for the site and had placed sign markers identifying the test sections. With
assistance from State DOT personnel, the test sections were located that had been
previously studied in the 1986 survey.
Initially, the virgin sulfur-extended asphalt mix over the 12 inches of
granular base located in the eastbound lane was cored and surveyed. The test section was
located at approximately the same stationing that was used in the 1986 survey. The
500-foot test section was located from Station 385+50 to 390+50. Six cores were taken at
this site with three in the outer wheelpath and three in the mid-lane. Six 6-inch diameter
cores were taken from the pavement.
The control section consisted of an unmodified AC over the same 12
inches of granular base material and was located further east in the eastbound lane. Six
cores were also taken from this test section. This section was also located in the same
approximate location as the 1986 survey. The test section stations began at 567+00 and
ended at 572+00. The last 26 meters of the section crossed an intersection.
OBSERVATIONS
Based on the phone survey conducted under Phase I, it was relayed that
the sections were in poor condition. It was also noted that some milling had occurred to
remove some of the surface distress and roughness. The SEA mix had been milled
approximately 3/4 of an inch to remove some rutting and cracking. The control section had
been milled approximately one inch and inlaid with one inch of asphalt concrete. The
control section had some pretty severe ruts of over one inch before the inlay, and
therefore, the State chose to do some rehabilitation around 1990. The previous survey
conducted in 1986 indicated that both sections had some rutting with the control being the
more severe. This again was noted during the Phase II visit. There was only slight rutting
in the sulfur mix with an average of about 7.7 millimeters in the outer wheelpath. The
control section had rutting with an average of over 11.5 millimeters and some points over
20mm.
Both the SEA and control mix exhibited some transverse cracking,
however, it was very difficult to get a good indication of the progression of cracking due
to the rehabilitations that had occurred on both sections. From all indications it seems
as though the SEA section had more transverse cracks and the cracks at some locations
seemed to be more severe. This may be due to the fact that there was a two-foot extended
lane that made up part of the shoulder. This extended lane in the sulfur section had
several wide transverse cracks (49 in the 500-foot test section) that started on the edge
of pavement and progressed all the way up to the edge stripe. Some of the cracks had
progressed past the edge stripe but did not extend all the way across the lane. These
transverse cracks at one point probably did extend all the way across the lane to the
center stripe because there were also several cracks that emanated from the center stripe
at the same approximate station as the transverse crack that extended out past the edge
stripe across the adjacent lane. The milling that occurred on the SEA pavement must have
removed the wide surface crack and left only the micro-crack. Due to the rain during the
survey and the water that was standing on the pavement, this type of crack would have been
very difficult to see and therefore may not have been traceable.
The control section also exhibited transverse cracking but due to the
inlay the cracks were only detectable on the extended lane edge. The frequency of the
transverse cracks on the extended lane edge, however, was considerably lower on the
control section than on the sulfur section. Also, the severity of the transverse cracks on
the control section was not as high on the SEA section.
Raveling was present on both sections and was located in the mid-lane
and was approximately one meter wide. The raveling was rated as low severity and did not
exist in either of the wheel paths. There was no fatigue cracking present on the SEA
section, however there was a considerable amount of fatigue cracking on the control
section. The control section exhibited some portions of fatigue cracking in both
wheelpaths that was in excess of a half a meter wide, however, most of the fatigue
cracking was less than a tenth of a meter wide. It is unknown whether the fatigue cracking
initiated at the bottom of the inlay or at the bottom of the existing asphalt concrete
surface coarse. Therefore, any comparisons of the fatigue cracking between the SEA and
control section may be misleading.
EVALUATIONS
Due to the rehabilitation that occurred on both sections, an evaluation
will be very subjective in nature. However, it seems as though the sulfur-extended asphalt
section was performing much better in terms of rutting than the control section and at
present there are more transverse cracks on the SEA section than there are on the control
section. Also, the severity of the transverse cracks on the SEA section seem to be greater
than on the control section.
COMPARISON OF FIELD DATA TO LABORATORY DATA
From the initial evaluation of this Wisconsin site, it was predicted
that there should be a very high amount of rutting in the AC control section and a
moderate amount in the SEA section based on the accumulated permanent strain in the
asphalt concrete layer from the 1990 laboratory testing. This was consistent with the
observations made in the field and the previous distress surveys. However, fatigue
cracking was not predicted for the control or the SEA sections. This was definitely not
the case with the control because fatigue cracking was found in both wheelpaths and at
times was greater than a half meter wide and of moderate severity. Fatigue cracking was
not found in the SEA section. Low temperature cracking was predicted to occur at lower to
moderate test temperatures because a slight change in temperature could produce transverse
cracks. The distresses noted did indicate that the pavements (SEA and control) probably
did contain low temperature cracking because of the numerous transverse cracks that were
present.
Loop 495, Nacogdoches, Texas, Section 854803. September 6, 1994
SITE LOCATION
The site is located just north of downtown on Loop 495, which is also
known as Business Route 59 (or North Avenue) in Nacogdoches. Construction was completed in
1983 and consisted of one SEA section and one AC control section. The original surface was
still present and was in fair condition at the time of the survey. The SEA mix was placed
as a plant-mixed seal on the surface (2.5 cm thick). Rehabilitation of the roadway was
planned for late 1994.
The sulfur mix was placed in the northbound lanes and the AC control
section was directly adjacent in the southbound lanes. The previous sampling areas used
for Report FHWA-RD-90-110 were easily located and the 152 1/2-meter test sections and
sampling areas were located in these areas. It should be noted that FM-343 (also known as
Industrial Drive), intersects Loop 495 within the project location. The test sections that
were surveyed and sampled for the conventional AC control section were located in the
southbound, outside lane, approximately 142 meters south of the intersection with FM 343.
The SEA section, was located in the northbound, outside lanes approximately 150 meters
north of the intersection with FM 343.
A total of eight cores were retrieved from the control section, four in
the outside wheelpath and four in the inside wheelpath. The open-graded friction course,
the surface layer and the binder layer cored with no problems. However, the asphalt
material below these layers had experienced significant stripping and generally was not
retrievable. A total of eight cores were also retrieved for the SEA section, and the same
stripping problem was encountered on this section.
OBSERVATIONS
It was found that while the rut measurements were comparable between
the two sections, the surface distress was much worse on the AC control section than on
the SEA section. While both sections exhibited bleeding and had a number of transverse
cracks, the AC control section had a significantly higher number of transverse cracks than
the SEA section. Fatigue cracking was also present throughout a large portion of the AC
section that was not present on the SEA section.
EVALUATIONS
Initial observations indicated that although both sections did exhibit
various distresses, the AC control section was significantly more distressed than the SEA
section. On average, the rutting was slightly higher on the AC control section than on the
SEA section. Fatigue cracking was also noted in the AC control section but was not noted
on the SEA section. There were also significantly more transverse cracks in the AC control
section than in the SEA section.
COMPARISON OF FIELD DATA TO LABORATORY DATA
There was no initial evaluation for this site, because data did not
exist in the FHWA-RD-90-110 Report. However, a comparison with the distress data from the
1986 survey did show that alligator (fatigue) cracking had developed in the control
section that had not developed in the SEA section. Bleeding in the SEA section had
increased considerably but had stayed at about the same level in the control section.
Rutting had begun to develop in both sections, which was not noted in the 1986 survey.
Longitudinal cracking in the control section had decreased considerably. However,
at the time of the 1986 survey, these cracks were more than likely the beginning of
fatigue cracks. Therefore, it is anticipated that a drop in longitudinal cracking and an
increase in fatigue cracking would occur.
In summary, the SEA section was performing better than the AC control
section when comparing the amount of fatigue cracking (and severity) and the number of
reported transverse cracks. Rutting between the two sections was not statistically
different and therefore could be considered the same.
MH 153 (Wellborn Road), College Station, Texas, Section 854802, November 17, 1994
SITE LOCATION
This section is located on MH 153 or Welborn Road in Bryan/College
Station. The section was placed during the years of 1976 to 1978. There are two different
SEA mixes, each containing three sections and there are two asphalt concrete control
sections. State Personnel were not familiar with the SEA projects and initially indicated
that no rehabilitation had occurred on the site. However, BRE personnel familiar with the
section of roadway containing the SEA mixes indicated that a chip-seal had been placed in
1988 by the City of Bryan. The State Personnel confirmed this with the city and obtained
information regarding the chip seal. The condition of the roadway during the Phase II
survey was poor. Rehabilitation at this particular site was planned for 1995.
The Texas DOT had provided excerpts from a construction report written
at the Texas Transportation Institute (TTI) and had also obtained records from the Texas
DOT Record Management Branch that showed the location of the site on Welborn Road. From
previous inquiries, the test section that had been cored and surveyed during the 1986
survey was located and marked for the Phase II surveys. Dr. Don Saylak, a TTI Research
Engineer who worked on the original construction project, was also present during this
survey and confirmed the test section locations.
The TTI construction report showed that there were several different
SEA test sections located along the 3,000-foot roadway that contained the SEA sections and
the control sections. Interest was focused primarily on the 30/70 SEA mix that had an
aggregate blend of 75% bank run river gravel and 25% sand. Other test sections included a
40/60 SEA mix with an aggregate blend of 75% bank river gravel and 25% sand, a 40/60 SEA
sand mix and a 30/70 SEA sand mix. Only the 30/70 aggregate test section was surveyed and
mapped previously, therefore, efforts were concentrated on locating and mapping that
section for the Phase II surveys.
Eight 4-inch diameter cores (four midlane and four wheelpath) on both
the SEA and AC control sections. Coring was completed by TxDOT personnel and no problems
were encountered during the coring operations.
OBSERVATIONS
Based on the phone survey conducted under Phase I, it had been relayed
that both the SEA and the control sections were in poor condition. Based on information
provided by TxDOT personnel from the City of Bryan, a chip seal had been placed on the SEA
and control sections around 1988 or 1989. The coring operation confirmed the presence of
the chip seal and could be observed on cores from the SEA and AC control sections.
Total pavement thickness was approximately seven inches with six inches of a bituminous
base course material and a one-inch friction course.
The SEA site had a moderate amount of low severity fatigue cracking and
several wheelpath longitudinal cracks. The control section had a greater amount of fatigue
cracking and also the severity level was classified as medium. There were also several
wheelpath longitudinal cracks in the control section and none of these cracks had been
sealed like the SEA section. There were approximately the same number of transverse cracks
between the two sections and the severity between the two was approximately the same.
One major difference between the control and the SEA section was the
amount of rutting. The SEA section had an average rutting measurement that was higher than
the control section. Also, there were several areas along the SEA section where the
rutting was much more severe than the average. This did not show up in the calculation of
the average because measurements were only taken every 15.3m. The SEA section had low
severity bleeding in the wheelpaths existing throughout the entire section. The AC control
section did not exhibit this bleeding. The existence of the bleeding probably has nothing
to do with the inclusion of sulfur in the SEA mix but was probably due to the chip seal
that was placed in 1988.
One item to note is that the chip seal that was placed on the SEA
section was placed at a different time than the chip seal placed on the control section.
The reason that this occurred was due to the fact that maintenance of portions of Welborn
Road was handed over to the cities of Bryan and College Station. The AC control section
that was cored (due to the configuration of the test section in relation to the traffic
signals) was located in College Station and the SEA control section was located in the
city of Bryan. Therefore, the chip seals were placed at different times and by personnel
from each city.
EVALUATIONS
Rutting in the SEA sections was more severe than the control section
and although there was plenty of fatigue cracking in the SEA section, it was not as severe
as the control section. In terms of performance, both sections seemed to be performing
very poorly. This may be due to the underdesign on the road with the level of traffic that
was being carried. It was understood that maintenance of this particular roadway section
had been transferred back to the state and therefore some major rehabilitation may take
place.
COMPARISON OF FIELD DATA TO LABORATORY DATA
After conferring with state DOT personnel it was determined that the
average daily traffic (ADT) for this particular section of roadway ranged from
18,000-20,000 vehicles per day. Therefore, from this estimate a total number of cycles
that had been applied to the pavement was determined using the beginning traffic from the
construction report. The AAMAS system identified that low temperature cracking for this
particular site should not be a problem and that was certainly the case because no low
temperature cracks were found during the site evaluation. However, the AAMAS system did
indicate that rutting and fatigue cracking would be a problem.
Visual inspection of the cores indicated that stripping was evident and was mainly at
the bottom of the core near the subgrade. The stripping was probably due to the bank run
river gravel that was used in the asphalt concrete mix. As a side note, one core from the
40/60 sand mix test sections was taken at the request of the TTI Research Engineer. This
core was in very good shape and did not indicate any underlying failures from the SEA mix.
IH 10, Pecos County, Texas, Section 854801, April 13,1995
SITE LOCATION
This section is located on Interstate 10 in Pecos County and was placed
in September of 1981. There was only one SEA mix placed with one AC control section and
one SEA section. Two seal coats have been placed on the SEA section and the condition of
the roadway at the time of the survey is good. Rehabilitation was anticipated during 1995.
The Texas Department of Transportation in Odessa, Texas provided
information for the specific location of the sulfur project and personnel from Texas DOT
to assist in coring operations for this site visit.
The project is located on Interstate 10 between Mileposts 297.5 and
306.7. The sulfur-extended asphalt mix portion of the project is located between Mileposts
302.8 and 306.7. The AC control section is no longer in service for this project, because
it was overlaid in 1988 and microsurfaced in 1990. The 152.5 meter SEA test section and
sampling area was located at Milepost 306. This is one mile west of the intersection with
U.S. Highway 190. The test section was located in the westbound direction in the outside
travel lane.
As previously mentioned, the AC control section was no longer in
service and was not cored. The SEA section consisted of a 1-inch Type D mix over a 2-inch
Type C sulfur modified mix. During coring operations, although the cores were all
retrievable, stripping was evident in the bottom SEA (Type C) lift. A total of eight cores
were retrieved from this test section. A visual inspection of the cores and pavement
showed that a surface treatment was placed on the test section. Review of report DP54-01
(Beatty et al) indicated that this seal coat was placed in June, 1985.
OBSERVATIONS
The predominant distress found on the SEA test section was bleeding.
There was approximately 76 meters of longitudinal cracking in the wheel paths, most of
which was sealed. There were also a number of transverse cracks that were sealed. Rutting
existed in both wheel paths and was on the average of 4-6 millimeters, with no rutting
greater than 10 millimeters measured.
EVALUATIONS
With only one section remaining at this location, there are no other
sections for comparison purposes. It can be speculated that the removal and replacement of
the control section is an indication of poor performance. Discussions with local TXDOT
personnel confirmed this speculation, however, actual distress data was unavailable for AC
control sections prior to the overlay.
COMPARISON OF FIELD DATA TO LABORATORY DATA
From the AAMAS system, it was predicted that rutting and fatigue
cracking should be present for this site. Rutting did exist but was minor and there was
limited longitudinal cracking in the wheel paths. The seal coat and the associated
bleeding may mask distresses that existed on the original surface. As previously
mentioned, stripping was evident in the cores (bottom layer) retrieved from the test
section.
US 2, Minot, North Dakota, Section 853801, May 10, 1995
SITE LOCATION
This project is located on combined Routes U.S. 2-52 and was placed in
September of 1982. There are four different SEA mixes present each having an AC control
section. There are two sections of a 20/80 mix, five sections of a 30/70 mix, one section
of a 40/60 mix and three sections of a 25/75 mix. All SEA surface layers are still present
and were in fair to poor condition at the time of the survey. Rehabilitation of the SEA
pavement was expected in 1996. The original field survey report prepared by the FHWA
indicated that a chip-seal had been placed in 1985 but the survey completed in Phase I of
this project did not indicate this rehabilitation or any other. The rehabilitation noted
in the field survey report was later verified with the state.
Project plans and typical sections for the sulfur-extended asphalt
project on US-2 just northwest of Minot, North Dakota and excerpts from a research report
provided by the NDDOT Materials Division, were used to locate and lay out the asphalt
concrete control section and two sulfur-extended asphalt sections. Previous core locations
were not readily apparent on the roadway because of minor patching and chip seals that had
occurred over the years.
Three test sections were surveyed and cored which included the asphalt
control section, a 30/70 SEA mixture found in both the surface and base course and a 25/75
SEA mixture that was also found in the surface and base course. It should be noted that
there were several other SEA test sections located on this 6-mile stretch of pavement,
however, efforts were concentrated only on those sections that had been previously
reviewed and surveyed by the FHWA. The asphalt control section and the 25/75 SEA section
were located on the driving or outside lane and the 30/70 SEA mixture was located on the
passing or inside lane.
Eight, 4-inch diameter cores (four midlane and four wheelpatli) on both
SEA sections and the control section were taken. Four cores were taken at approximately
Station 0-10 and four more at approximately Station 5+10. Coring was completed by NDDOT
personnel and no problems were encountered during the coring operations. One core was also
taken in the 30/70 SEA mix over a transverse crack in an effort to determine the possible
formation of the crack and also show if any stripping was occurring along the depth of the
crack. It was noted that cores taken from the SEA sections did not have the pungent smell
of sulfur that had been identified in many of the other SEA sections during other site
visits. One possible explanation for this may have been that liquid sulfur was used in
these sections which may have blended better with the asphalt cement than the colloid
mixtures that were used on several of the previous projects.
It was understood that NDDOT will provide some sort of significant
rehabilitation in the next 1-2 years on this particular project. This may include an
overlay because the northbound lanes were overlaid in previous years.
OBSERVATIONS
Based on the phone survey conducted under Phase I, it had been relayed
that the control and SEA sections were in fair to poor condition. Conclusions were also
drawn from previous site surveys and from NDDOT personnel that a chip seal and other
surface patching had been placed on the control and SEA sections from 1985 to present. The
most. recent repair was on the AC control section and included a surface seal in the
driving lane (the lane where the visual distress surveys were completed). It was observed
that there were some transverse cracks that started in the passing lane of the control
section that were covered up by the surface seal as they migrated across the lane and into
the driving lane. All sections also included some rut level-up rehabilitation in the wheel
paths.
From the coring operations, the surface seals could be observed on the
SEA and control sections. Total pavement thickness ranged from 11.0cm (4.3 inches) to
17.5cm (6.9 inches). The typical sections provided by the state indicate that when
constructed in 1979, the pavement was 8.9cm (3.5 inches) asphalt concrete over 29.2cm
(11.5 inches) of aggregate base. These typical sections include both the SEA sections and
the asphalt control section. The thicknesses recorded are consistent with those as
reported in FHWA-RD-90-110.
EVALUATIONS
In comparison, all three test sections seemed to possess the same types
of distress. Transverse or thermal cracks seemed to be the most prevalent distress type
present. The 30/70 SEA sections had the highest number of occurrences of these t-cracks
however, the 25/75 SEA sections had. the greatest number of high severity t-cracks. As
mentioned previously, the AC control section did have a surface seal present and therefore
some of the t-cracks were covered up. This would seem to skew the results somewhat but it
is still believed that a fairly accurate assessment of the comparable performance can be
maintained. The AC control and 25/75 SEA sections exhibited a fair amount of pumping along
the transverse cracks. The 30/70 SEA mix did not show this type of pumping. Rutting
measurements were essentially the same between the three sections however, district
personnel indicated that rutting and shoving had been a significant problem along the
entire 14-mile project which included the six miles of the SEA. Therefore, the chip seal
and rut level-up were used to remedy this situation. All three sections exhibited some
bleeding however that may have been due to the tack coat that was placed for the chip
seals.
COMPARISON OF FIELD DATA TO LABORATORY DATA
After conferring with State DOT personnel, it was determined that the
Average Daily Traffic (ADT) for this particular section ranged from 8,000-12,000 vehicles
per day with approximately 10% trucks. Therefore, from this estimate the total number of
cycles that have been applied to the pavement were determined using the beginning traffic
from the construction report. The AAMAS System determined that all three distresses
(rutting, fatigue cracking and low temperature cracking) for this particular site could be
problematic. Observations of rutting and low temperature cracking seemed to agree with the
AAMAS analysis. Fatigue cracking was predicted by the AAMAS System to be fairly
significant (based upon the low number of cycles to failure) however, fatigue cracking was
not observed as a significant distress during the site evaluation.
Visual inspection of the cores indicated that there was very little
stripping present throughout the entire 6-mile section. However, the four cores taken at
the 0+00 end of the 25/75 SEA test section had evidence of stripping. Upon moving to the
5+00 end of the test section, the stripping that was noted in the previous cores was not
present. Due to time constraints on the coring rig, more coring was not completed around
the SEA section to determine where the stripping problems began and ended.
Lincoln Ave., Anaheim, California, Sections 860601 and 860602, June 5, 1995
SITE LOCATION
The sites on Lincoln Avenue arc located approximately 2.4 kilometers
apart and were both still available for study. Section 860602 was the only project that
was included in the FHWA laboratory study, and rehabilitation was indicated to possibly
occur within two years.
The Anaheim City Civil Engineer, provided project construction plans
detailing the location of the sulfur-extended asphalt sites as well as the control
sections.
The first sulfur-extended asphalt section (SEA #1) was located just
east of Villa Place Street, in front of the Norm's Restaurant. The corresponding asphalt
control section was located just east of West Street and is intersected by Illinois Street
(AC Control #I). The second sulfur-extended asphalt section (SEA #2) began in the
eastbound lanes of Lincoln Avenue where Evergreen Street intersects with Lincoln Avenue.
The second asphalt control section (AC Control #2) was located just west of State College
Boulevard in the eastbound lane. It should be noted that the two asphalt control sections
were marked on the eastbound lane curbs by use of benchmark pins. All test sections were
located on the outside lanes of the eastbound direction on Lincoln Avenue. The sections
were marked to be 300-foot long sections because the asphalt control sections were built
as only 300-foot sections.
Eight, 4-inch diameter cores (four mid-lane and four wheelpath) on both
the SEA and control sections were taken. Coring was split up by taking four cores at
approximately Station 0-10 (west end) and four more at approximately Station 3+10 (east
end).
OBSERVATIONS
Based on the phone survey conducted under Phase I, it had been relayed
that the controls and sulfur-extended asphalt sections were in good condition, however,
rehabilitation on Lincoln Avenue could possibly be occurring in the near future. The
previous site surveys conducted in 1986 showed that there was very little distress on any
of the four test sections and the distress that was present was only minor. During the
Phase II survey, it was noticed that there was some distress development in the test
section lanes that was due to extreme circumstances and did not really reflect the
performance of the pavement. For example, there were utility patches and maintenance hole
covers on some of the sections that caused some cracking to occur off of the patched
areas. Also, it was noticed that there was some raveling in the driving lanes in front of
business driveways where several turning movements were occurring. The sulfur-extended
asphalt test sections were located on relatively straight portions of Lincoln Avenue,
however, the asphalt control sections (which were preset by the City) were located on
areas of Lincoln Avenue with slight horizontal curvature (which may cause distress to
develop differently). It was also noticed on one of the sulfur-extended asphalt sections,
that a patch of fatigue cracking had occurred outward from a previous core hole location.
The coring operations provided information where discrepancies in
pavement layer thickness on SEA #1 and its corresponding control section were noted. The
total pavement thicknesses for these two sections ranged from 32.0cm (12.6 inches) to
8.0cm (3.1 inches). However, thickness of the sulfur-extended asphalt overlay averaged
about 5.0cm (2 inches) on SEA #1 with very little variation. The overlay thickness data
agrees with the information provided by the City of Anaheim and specifically the design
and construction report written by Ralph Harp in 1983. The second SEA section (located
between State College Boulevard and East Street) had varying sulfur-extended asphalt
thicknesses across the lanes. This is detailed in the City of Anaheim design and
construction report. A portion of the lanes had approximately 10.5cm (4.2 inches) of
sulfur-extended asphalt while the other portions of the lanes had approximately 3.0cm (1.2
inches) of sulfur-extended asphalt mix. From the cores that were taken during the Phase II
site visit, our evaluations were conducted on the lane that contained the 10.5cm overlay
of SEA mix.
Traffic between the sections varied in terms of Average Daily Traffic
(ADT). The section from Citron Street to Interstate 5 had approximately 23,000 ADT and the
sections from State College Boulevard to East Street had approximately 27,000 ADT. Both
sections seem to be carrying approximately 3-4% trucks.
EVALUATIONS
In comparison, all four test sections seem to possess the same types of
distress and three out of the four had very little distress present. The only section with
a significant amount of distress was the second asphalt control section located just west
of State College Boulevard. One possible explanation for the increased distress could be
that this section is near a busy intersection. Portions of the pavement immediately
adjacent to the intersection were not included in the visual distress surveys, because
during the high traffic periods a significant amount of traffic is backed up on to the
asphalt control section with slower speeds and stopping movements. The asphalt control
section is also located, as previously mentioned, on a slight horizontal curve which may
also cause an increase in the amount of distress present.
Rutting measurements were not taken on any of the test sections for two
separate reasons. The first reason being that there was very little discernible rutting
present on any of the sections along Lincoln Avenue. This is probably due to the fairly
low percentage of trucks that travel on Lincoln Avenue and those trucks that do travel are
not the very heavy 18-wheeler trucks. The second reason was due to the significant cross
slope that is present across the lanes. All of the test sections have an outer lane that
is used as a parking lane. The cross slope to this parking lane is fairly significant and
also causes a fair amount of vehicle wander along the outside lane. Due to the significant
wander it is very difficult to locate true wheel paths in which to take the rut depth
measurement.
COMPARISON OF FIELD DATA TO LABORATORY DATA
The AAMAS System, indicated that all three distresses (rutting, fatigue
cracking and load temperature cracking) for this particular site would not be a
problem. Field evaluations on the sites seemed to agree with the AAMAS analysis, however,
the distress noted in AC Control #2 did indicate that there may be something else
occurring that was causing it to perform differently than the others.
Visual inspection of the cores was hampered slightly by the fact that
the cores were extracted with an unstable coring rig. However, there was no indication
that significant stripping was occurring in the sulfur-extended asphalt portions of the
cores. It was noted that some stripping had occurred in the lower layers of several of the
cores, but this may have been due to the age of the asphalt pavement itself.
IH 15, Barstow/Baker, California, Section 850601, June 6, 1995
SITE LOCATION
This project is located on Interstate 15 west of Baker and has two
different SEA mixes with corresponding control sections. The surfaces have been
chip-sealed twice; once in 1987 or 1988 and then another chip-seal placed in 1992. The
current condition of the two sections had been classified as fair with a lot of alligator
cracking that is reflecting through the chip seal but with no apparent rutting. There were
no rehabilitation plans scheduled for the next five years. Reports were obtained that
outlined the construction and monitoring that the State of California did on this section
and a corresponding section on Route 6, near Benton. From that research report, the exact
locations of the test sections was identified.
Three test sections were surveyed and cored which included an asphalt
control section, a 20/80 SEA mixture and a 40/60 SEA mixture. It should be noted that
there were several other SEA test sections located along the project, however, the Phase
II survey efforts were concentrated only on those sections that had been previously
reviewed and surveyed. The SEA sections that were surveyed were located in the outside
northbound lane of Interstate 15. The 20/80 SEA section was located between Milepost
109.15 and Milepost 109.58. The 40/60 SEA section was located between Milepost 109.58 and
Milepost 109.94. These two SEA sections had approximately 7.6cm (3 inches) of SEA placed
in a single lift. The asphalt control section was located between Milepost 107.75 and
Milepost 108.25 and was built with an AR-4000 asphalt cement. The outside northbound lane
was again surveyed for this project and included a 7.6cm (3-inch) layer placed in one
lift.
There was a second asphalt control section that was constructed with an
AR-2000 asphalt cement that was not surveyed. This was an oversight because the
sulfur-extended asphalt sections were actually constructed with a mixture of sulfur and
the AR-2000 asphalt cement. Therefore comparison between the control and the sulfur
sections may be somewhat skewed, however, it was noticed that the entire length of the
project that included all of the test sections was performing about the same. Therefore,
this oversight hopefully will not bias the results substantially.
Eight, 4-inch diameter cores (four mid-lane and four wheelpath) on both
SEA sections and the control sections were taken. Four cores were taken by at
approximately Station 0-10 (the lower milepost) and four more at approximately Station
5+10. It should be noted that the first two cores extracted out of the asphalt control
sections were full depth cores whereas, subsequent cores were taken to include only the
top 7.6cm (3.0 inches) overlay.
OBSERVATIONS
During conversations with State personnel it was noted that prior to
the chip seals there was a fair amount of fatigue cracking on the pavement. However, in
test sections surveyed in Phase II fatigue cracking was not noted to be reflecting through
the chip seals.
From the coring operations, the chip seal could be observed on both SEA
and control sections. Total pavement thickness from the first two cores is approximately
26cm (10.2 inches). The typical pavement sections provided by the State indicated that
when constructed in 1982, 7.6cm (three inches) of asphalt concrete or SEA was placed over
16.5cm (6.5 inches) of dense-graded asphalt concrete over 20.4cm (8 inches) of aggregate
base over 22.9cm (9 inches) of aggregate subbase. The sections were originally constructed
in 1964 with an open-graded asphalt concrete on the surface. This open-graded course was
milled off and replaced with the 7.6cm (3 inches) of SEA or asphalt concrete in 1982. As
mentioned, the sections also had two chip seals placed in the last few years. The overall
pavement thicknesses recorded from the cores were consistent with those as reported in
FHWA-RD90-110.
EVALUATIOINS
In comparison, all three test sections seemed to possess the same types
of distress. The distresses found most often were longitudinal cracks and transverse
cracks. The asphalt control section did exhibit some longitudinal cracking along the edge
almost the entire length of this section. As noted previously, there was very little
fatigue cracking noted in any of the sections. On all three sections, raveling of the chip
seal was noted along the inside lane edge. The raveling and the longitudinal cracking was
not believed to be indicative of the performance of the asphalt concrete mixture but would
indicate a problem with the chip seal in the case of the raveling and a problem with the
shoulder conditions in the case of the longitudinal edge cracking. Each test section
exhibited approximately the same number of transverse cracks and approximate total length
of cracking with the 20/80 SEA section exhibiting the least amount. In terms of the
longitudinal cracking, the asphalt control section exhibited the highest amount of
cracking and most of this occurred in the wheelpath. The two SEA sections exhibited almost
the same amount of longitudinal cracking, however, the 20/80 SEA section had the higher of
severity cracking than the 40/60 SEA section.
COMPARISON OF FIELD DATA TO LABORATORY DATA
After conferring with CALTRANS personnel, it was determined that the
average daily traffic (ADT) for this particular section is approximately 26,000 (ADT) and
truck traffic accounts for 15% of the ADT. Therefore, from this estimate a total number of
cycles that has been applied to the pavement since overlay construction was determined.
The AAMAS System determined that low temperature cracking might be a problem for the 20/80
SEA section, fatigue cracking may also be a problem for the 20/80 SEA mix and rutting
should not be a problem in any of the sections.
From the field evaluations it was noted that AAMAS correctly identified
that rutting would not be a problem as well as correctly identified that low temperature
cracking and fatigue cracking should not create a problem in the controls or the 40/60 SEA
mix. In the 20/80 SEA section that AAMAS did predict to have some fatigue and thermal
cracking, it was observed that very little fatigue and very few transverse cracks were
actually present but it should be kept in mind that these distress may have been present
prior to the chip seals.
Visual inspection of the cores did not indicate that either the SEA or asphalt control
sections were stripping. However, there is a possibility that after splitting the cores
may have indicated that some
stripping may be present. It was difficult to determine from the extracted cores
whether or not stripping was actually a problem.
US 50A, Fernley, Nevada, Section 853202, June 8, 1995
SITE LOCATION
The Nevada DOT in Carson City provided information on previous core
locations that Nevada DOT had taken on previous studies. These notes assisted in locating
the appropriate sections for the surveys.
Two test sections were surveyed and cored which included the asphalt
control section and a 26/74 SEA mixture. This project was built as a 7.6cm (3-inch)
overlay over an existing asphalt concrete surface and a granular base. The project
consisted of approximately one mile of SEA pavement and eight miles of AC control
pavement. The test section lane was located in the westbound direction and the control was
located from Milepost 72.9 to Milepost 73.0. The 26/74 SEA section was located from
Milepost 70.9 to Milepost 71.0.
Eight, 4-inch diameter cores (four mid-lane and four wheelpath) on both
the SEA section and the control section were taken. Four cores were taken at approximately
Station 0-10 (the high Milepost) and four more at approximately Station 5+10.
OBSERVATIONS
Based on the phone survey conducted under Phase I, it had been relayed
that the control and SEA sections were in good condition. However, upon arrival at the
sites it was noticed that the test sections were actually in very poor condition. It had
become apparent that since the last site visit in 1985 that a significant amount of
distress development has occurred. Several of the transverse and longitudinal cracks had
become quite fatigued. This phenomenon is probably caused by a weak base structure
underlying the pavement and the inclusion of moisture in that base.
The coring operations revealed several underlying asphalt concrete
layers. Total pavement thickness on the asphalt control section ranged from 27.0cm (10.5
inches) to 23.5cm (9.2 inches) and pavement thickness on the SEA section ranged from
17.0cm (6.7 inches) to 22.0cm (8.7 inches). There were no typical sections provided by the
State to indicate the as-built constructed thicknesses for this overlay and since this
site was not included in the FHWA-RD-90-110 there is no way to verify the overlay
thickness and the underlying pavement thicknesses.
EVALUATIONS
In comparison, the two test sections seemed to possess the same types
of distress. Transverse or thermal cracks and longitudinal cracks seemed to be the most
prevalent distress present. The AC control section had the higher quantities and severity
of both the transverse and longitudinal cracks. There was more fatigue cracking (as
related to the underlying failures) on the sulfur-extended asphalt section, however, the
fatigue cracking on the control section was more severe. It was also noted that around
Station 2+50 on the SEA section that a culvert was present. On either side of the culvert
there seemed to be a significant increase in the distress that was present on the
pavement. There was slight rutting noticed in both the control and SEA sections with the
SEA exhibiting slightly more (but not statistically different) than the asphalt control.
COMPARISON OF FIELD DATA TO LABORATORY DATA
Because this section was not previously cored and included in
FHWA-RD-90-110 there is no way to compare the field data collected during the Phase II
survey to any laboratory data. Therefore, use of the Asphalt Aggregate Mixture Analysis
System (AAMAS) to predict occurrences of the distresses was not possible.
Visual inspection of the cores did not indicate stripping in the
sulfur-extended asphalt or conventional asphalt layers. However, it was observed that
several different asphalt concrete layers under the 7.6cm (3-inch) overlay did exist. This
would indicate some type of stage construction over the past several years. The cores
indicated that several different types of aggregate and possibly asphalt cements were used
for construction of the AC layers underlying the current surface. Splitting of the cores
may have provided more insight into the stripping evaluations.
Southwest 16th Ave., Gainesville, Florida, Section 861201, November 7,
1995
SITE LOCATION
The Florida DOT in Gainesville marked the test sections based on
information gathered from Florida DOT records and reports. Four test sections were
surveyed which included two sulfur-extended asphalt sections and two control sections. The
SEA sections consisted of a 30/70 blend of sulfur to asphalt and was incorporated into the
base layer. The first two sections surveyed consisted of a 3-inch base layer, the first
section containing the straight asphalt and the second section containing the 30/70 SEA
blend. The next two sections consisted of a 5-inch base layer with the first section
consisting of the 30/70 SEA blend and the second section containing the straight asphalt.
Both sections had a 1-inch dense-graded friction course on top of the bases. Each section
was approximately 600 feet in length and section 2 (3-inch SEA base) and section 4 (5-inch
asphalt base) had intersections within the experimental test section. These intersections
were not included in the overall distress survey.
The sections were never cored by the FHWA and were not included in the
evaluation from FHWA Report RD-90-110. Therefore, no cores were taken as part of this
evaluation.
OBSERVATIONS
Based on the phone survey conducted under Phase I, it had been relayed
that the sections were in good condition. Based on the field survey and assessment
completed by Beatty et al, reflective cracking in the sections was expected. However,
there was not a discernable pattern of reflective cracking in any of the sections and very
little cracking on any of the sections (with the exception of the 3-inch base control
section). The previous survey noted that rutting was observed in design section three
which is the 5-incb base control section and this was consistent with the observations of
the Phase II survey completed.
EVALUATIONS
In comparing the control sections to the sulfur-extended asphalt
sections, there seemed to be some slight discrepancies that may or may not relate to the
inclusion of sulfur into the pavement. One of the notable exceptions was the excessive
amount of fatigue cracking noted on the 3-inch base control section. This did not follow
the same trend that was noted on the other three sections and very possibly could have
been a result of the underlying structure. Another notable exception was the presence of
potholes in the 3-inch SEA section whereas there were no other potholes noticed on any of
the other sections. These potholes also could have been a result of the underlying
pavement structure. Rutting also seemed to be fairly consistent throughout the sections
with only one exception. This exception is noted in the 5-inch SEA section where the inner
wheelpath had a much lower measured rutting than the rest of the inner wheelpath
measurements.
COMPARISON OF FIELD DATA TO LABORATORY DATA
Because this section was not previously cored and included in
FHWA-RD-90-110 there is no way to compare the Phase II field data to any laboratory data.
Therefore, use of the AAMAS to predict any of the distresses that may be present was not
attempted.
Route 225, Cheyenne, Wyoming, Section 865601, April 23, 1996
SITE LOCATION
This section is located on Route 225 west of Cheyenne and was placed in
1978. There is one SEA section and one AC control section. The SEA mix is still the
surface layer and was in good to fair condition at the time of the survey. Some minor
maintenance had been performed which included some crack sealing and patching. There were
no plans for rehabilitation in the next five years. This section is a 16.4 kilometers
section on a rural road that is basically divided into two sections in terms of traffic.
One section has approximately 100 ADT and the other has approximately 1,000 ADT.
The Wyoming DOT provided information containing the milepost
information for the sulfur sections and the asphalt control section. Sections that
contained an AC control section and a 20/80 SEA section were marked based on this
information. The AC control section was located from Milepost 356.5 to 356.4, and the SEA
section was located from Milepost 356.0 to 355.9.
As mentioned, two sections were surveyed and cored, which included the
asphalt control and the 20/80 sulfur-extended asphalt mixture. The survey was conducted on
the westbound lanes of Route 225, which is also called Otto Road. It should be noted that
on the east side of Otto Road, located around Milepost 355, is an industrial plant of some
kind. Traffic coming out of the plant, which headed east toward the interstate was much
higher than traffic headed west out of the plant. The decision was made to survey the road
west of the plant due to the fact that it was only a two-lane road and safety could have
been a problem because of the trucks coming out of the plant heading towards the
interstate.
OBSERVATIONS
Based on the phone survey conducted under -Phase I, it had been relayed
that the control and SEA sections were in fair condition. Information from the previous
site surveys and from the Wyoming DOT personnel indicated that some patching and crack
sealing had been applied over the life of the pavement. As noted previously, traffic
estimates differ considerably on different sections of this road. Visual inspection of the
higher trafficked road showed that there was considerably more distress present.
From the coring operations, the average total pavement thickness ranged
from 16cm to 20cm. The sections were designed to have approximately 5cm of either the HMAC
or SEA mix placed over an existing pavement. It is unknown what the existing pavement
cross-section was supposed to be from the information provided by the state. However, the
upper 5cm thickness recorded from the cores is consistent with those reported in
FHWA-RD-90-110.
EVALUATIONS
In comparison, the two sections seem to possess the same types of
distress but in different quantities. Prevalent distresses were longitudinal and
transverse cracking and rutting. The SEA section contained more longitudinal and
transverse cracks, and the longitudinal cracks were predominantly outside the wheelpath.
Rutting was shown to be slightly less in the SEA section as compared to the control,
however, there were measurements within the SEA section that were quite high.
COMPARISON OF FIELD DATA TO LABORATORY DATA
After conferring with state DOT personnel, it was determined that the
accumulated 18-kip ESAL loading from construction to present (on the section that was
surveyed) was estimated at 100,000 ESALS. Therefore, the AAMAS prediction system and the
material characteristics determined from the 1990 report were used to determine which
distresses may be present prior to the site visit.
From the AAMAS system and materials characterization, it was determined
that neither fatigue cracking nor rutting for this particular site would be problematic.
Field observations of rutting seemed to agree with the AAMAS system, however, cracking
seemed to be underpredicted by the AAMAS system. Upon evaluation, both the SEA and AC
control had significant amounts of longitudinal and transverse tracking, all of which, was
classified as low severity. This could possibly indicate either environmental distress
development or a loss in tensile strength due to stripping.
Visual inspection of the cores did not indicate that either the SEA or
asphalt control section was stripping.
US 62/180, Carlsbad, New Mexico, Section 853501, May 1, 1996
SITE LOCATION
This project is located on combined Route U.S. 62-180 near Carlsbad and
was placed during the years of 1981 and 1982. There was only one SEA mix placed with one
AC control section. It was discovered during the Phase I phone survey that this section
was seal coated shortly after construction. There were no plans for rehabilitation in the
next five years.
Prior to the site visit, NMSHTD had provided information containing the
stationing and Milepost locations of the sulfur sections. The specific stationing for the
previously reviewed (1986) and surveyed sections did not contain an AC control. The NMSHTD
information indicated that at the end of the sulfur sections, from Station 860+00 to
870+00, the pavement did not have sulfur present but did have identical cross-sectional
thicknesses, therefore this area was used as a control.
Two sections were surveyed and cored which included the asphalt control
section as mentioned and a 30/70 Sulfur-Extended Asphalt (SEA) mixture. It should be noted
that the sulfur site was located from Station 780+00 to 860+00. The sections surveyed were
located in the outside, northbound lane of U.S. 62/180. The 30/70 SEA section was located
between Station 847+00 and 852+00. The AC control section, built with an AC-10 (modified),
was marked between Station 863+00 and 868+00. The stationing was referenced from Chapman
Road (Station 873+57).
Eight, 4-inch diameter cores (four midlane and four wheelpath) on both
the SEA and control sections were taken. The sampling was split with four cores taken at
approximately Station 0-20 and four at approximately Station 5+20. It should be noted that
core holes from previous studies were located on both the SEA and control sections.
OBSERVATIONS
Based on the phone survey conducted under Phase I, it had been relayed
that the control and SEA sections were in fair/good condition. Information from the
previous site surveys and from NMSHTD's personnel indicated that a fog seal was applied
shortly after construction in 1982. State personnel also indicated that the sulfur section
was more deteriorated than the AC control section. This was confirmed with the visual
distress survey performed under Phase II.
From the coring operations, the Open-Graded Friction Course could be
observed on both the SEA and control sections. The average total pavement thickness from
the sections was 19.5cm (7.7 in). The two sections were designed to have approximately a
1.6cm (5/8 in) Open-Graded Friction Course, over a 5.1 cm (2 in) AC or SEA Surfacing
Course, over a 14cm (5.5 in) AC or SEA Treated Aggregate Base, over a 15.25cm (6 in)
Untreated Aggregate Base. The overall pavement thickness recorded from the cores were
consistent with those reported in the NMSHTD Research Report MBRR-85/1 and FHWA-RD-90-110.
EVALUATIONS
In comparison, the two sections seemed to possess the same types of
distress, but in differing quantity and severity. The prevalent distresses were
longitudinal and transverse cracking. The SEA section contained more longitudinal and
transverse cracks, at a higher severity and predominantly outside the wheelpath. Both
sections contained low severity raveling in the wheelpaths throughout the section. It was
assumed that the raveling throughout the sections is attributed to the quality of the
open-graded friction course and not the performance of the asphalt concrete mixture. Also,
rutting in the outer wheelpath was compared. At 95% significance, the measured rutting
between the sections was statistically different with the SEA having greater rut depth
measurements.
COMPARISON OF FIELD DATA TO LABORATORY DATA
After conferring with State DOT personnel, it was determined that the
Annual Average Daily Traffic (AADT) for this particular section ranged from 1,000-2,000
vehicles per day with an estimated percent trucks at less than 10%. Therefore, a total
number of cycles that have been applied to the pavement could be determined based on the
beginning traffic from the Construction Report. The AAMAS System, determined that only
fatigue cracking for this particular site would be problematic. Rutting seemed to agree
with the AAMAS System. Fatigue cracking was predicted by the AAMAS System to be a possible
problem in the SEA sections and should not be significant in the AC control. However, upon
evaluation, both the SEA and AC control had significant amounts of longitudinal and
transverse cracking and some of this distress was categorized as moderate to high
severity. This would indicate either environmental distress development or a loss in
tensile strength due to stripping.
Visual inspection of the cores did not indicate that either the SEA or
asphalt control section was stripping,
Emmaus Ave., Allentown, Pennsylvania, Section 854201, may 15, 1996
SITE LOCATION
Prior to the site visit, PEN-NDOT had provided information containing
the station location of the HMAC and sulfur sections. The specific stationing for the
previously reviewed (1986) sections were Station 200+00 - 205+00 for the sulfur-extended
asphalt section and 265+00 - 270+00 for the control section. It was observed that the
first 200 feet of the previously surveyed sulfur-extended asphalt section was covered with
an overlay. Therefore, it was decided to begin the Phase II survey 250 feet to the east,
where the State had not overlaid, between Stations 202+50 - 207+50.
Two sections were surveyed and cored which included an asphalt control
section and a 30/70 sulfur-extended asphalt SEA mixture. The sections surveyed were
located in the eastbound lane of Emmaus Avenue (Route 39013). State personnel indicated
that the entire site would be overlaid by the end of August, 1996.
Eight, 6-inch diameter cores (four midlane and four wheelpath) on both
the SEA and control sections were taken. The sampling was split with four cores taken at
approximately Station 0-20 and four at approximately Station 5+10 for each section.
OBSERVATIONS
Based on the phone survey conducted under Phase I, it had been relayed
that the control and SEA sections had received some patching. During conversations with
State personnel, they noted that the sulfur sections were in a greater state of
deterioration than the AC control section. This was confirmed with the visual distress
survey performed in Phase II. It should be noted however, that in the adjacent westbound
lane, the State constructed both an SEA and control section as well, in a checkerboard
fashion. It appeared that the sections in the westbound lanes showed opposite conclusions.
The top layer containing the SEA or the AC control mix HMAC for both
sections could be observed from the coring operations. The average total pavement
thicknesses from the sections was 17.5cm (7 in.). The two sections were designed to have
approximately a 1.8cm (1.5 in.) AC or SEA wearing course, over an HMAC scratch course of
varying thicknesses from 2.5 - 7.5cm (1 - 3 in.), over patches consisting of a bituminous
concrete base course seven inches in depth on top of a subbase approximately 4 1/2 inches
thick. The overall pavement thicknesses recorded from the cores are consistent with those
as reported in the PENNDOT Pavement Design Report D/4332A. It should be noted that the
patches were located in various areas throughout the project length and cores were taken
in areas where patches existed and in other areas where there were no patches.
EVALUATIONS
The SEA section that was surveyed showed moderate signs of raveling
throughout the entire section compared to the AC control that had none. The AC control did
however, show greater signs of transverse and longitudinal cracks. It should be noted that
the sections in the westbound lanes immediately adjacent to the eastbound SEA and AC
control sections displayed exactly the same types of distress. It was expected that the
same types of distresses in the two AC controls and similar distresses in the two SEA
sections would occur; instead what was noted was that the distress pattern was the same
over the full 24-foot lane width and was independent of mix type. There is no change in
traffic pattern or climate conditions that can be attributed to this phenomena. Some
explanations for this could be that the plans are incorrect (very doubtful) or the
patching that was completed prior to the SEA overlay attributed to the development of the
distresses over the full pavement width. Also, what this could mean is that the inclusion
of SEA may not be significant in the overall pavement cross-section for this site.
COMPARISON OF FIELD DATA TO LABORATORY DATA
Because this section was not previously cored and included in the FHWA-RD-90-110 there
is no way to compare the Phase II field data to any laboratory data. Therefore, use of
AAMAS to predict any of the distresses that may be present was not completed.
Visual inspection of the cores did not indicate that either the SEA or asphalt control
section was stripping. However, there were one or two sulfur-extended asphalt cores that
showed signs of stripping between the SEA and HMAC base.
SR 15, Near Philadelphia, Mississippi, Section 862801, June 19, 1996
SITE LOCATION
The project is located on Route 15 in Neshoba County from Milepost 2.7
to 8.2. There are two different SEA mixes and three AC control sections. There are three
sections of a 30/70 SEA mix and three sections of a 40/60 SEA mix. The original SEA
surface was still in service but rehabilitation was planned for later in 1996.
MSHD provided as-built plans containing the station location of the
HMAC and two sulfur sections. The stationing selected, corresponded with the previously
reviewed sections. The stationing for the control section was 415+00 - 420+00, for the
30/70 sulfur-extended asphalt section 575+00 - 580+00 and for the 40/60 sulfur-extended
asphalt section 599+50 - 602+00. The sections were all fall-depth with identical
thicknesses. The 40/60 SEA section contained only three hundred and fifty feet of
full-depth SEA. The sections were marked by MSHD personnel.
Three sections were surveyed and cored which included an asphalt
control section, a 30/70 sulfur-extended asphalt SEA mixture, and a 40/60 sulfur-extended
asphalt SEA mixture. The sections that were surveyed were located in the southbound lane
of State Route 15.
Eight, 6-inch (150mm) diameter cores (four midlane and four wheelpath)
were cored on the 40/60 SEA section and eight 4-inch (100mm) diameter cores were taken for
the remaining two sections. The sampling was split with four cores taken approximately
twenty-five (25) feet outside the end of the section.
OBSERVATIONS
Based on the phone survey conducted under Phase I and the as-built
plans, it had been noticed that there were three types of sections each having three
different cross-sectional thicknesses. The HMAC thicknesses varied from 4.5-inches to
9-inches. All of the sections that were surveyed were full-depth 9-inches. The sulfur
sections and the AC control sections contained similar distresses. It should be noted
however, that the distresses found in the control section were higher in severity than the
SEA sections.
The thicknesses of the top layer containing the SEA or the AC control
mix for both sections could be observed from the coring operations. The average total
pavement thicknesses from the sections was 20.9cm (8 1/4 in.). The three sections were
designed to have approximately a 3.8cm (1.5 in.) AC or SEA surface course, over an AC or
SEA binder course approximately 1.8cm (1.5 in.), over 15.25 cm (6 in.) AC or SEA black
base on top of a subbase approximately 15.25 cm (6 in.) thick. The overall pavement
thicknesses recorded from the cores were consistent with those as reported in the MSHD
Report No. FHWA-TS-82, Field Trial with Sulfur-Extended-Asphalt (SEA) Binders in
Mississippi, 1982.
EVALUATIONS
The SEA sections that were surveyed showed moderate signs of raveling
in the wheel path throughout the entire section and light raveling outside the wheel path
throughout the entire section. The AC control section had only light raveling throughout
the entire section. The AC control did however, show a higher severity of transverse
cracks.
COMPARISON OF FIELD DATA TO LABORATORY DATA
Based on the information contained in the FHWA-RD-90-110 and the AAMAS
relationships it was anticipated that fatigue cracking should be more of a concern in the
SEA sections than in the AC control section. Rutting was anticipated to be very similar
between the SEA and AC control. It should be noted that only the AC control and the 30/70
SEA section were tested and no information on the 40/60 SEA mix is contained in
FHWA-RD-90-110. The rutting predictions were confirmed with the distress surveys performed
during Phase II, however, there is more fatigue cracking in the control than in the SEA
which is opposite from what was anticipated.
SR14, Elk City, Idaho, Section 851601
SITE LOCATION
This project is located on the Elk City Highway on State Highway 14.
State Personnel indicated that there was one section of SEA mix with one control section.
The current condition of the roadway was classified as good and State Personnel indicated
that there had been one and possibly two chip-seals placed on the section. The first
chip-seal occurred soon after the project was completed and the next possibly occurred
seven years after the first chip-seal. Specific details were unavailable on these chip
seals but it is speculated that the frictional resistance was not satisfactory based on
the limited amount of time between construction and treatment application. State Personnel
also indicated that there is a monument post indicating where the sulfur project begins
and that reports on the project had been completed.
State DOT personnel reported that rehabilitation was scheduled for
portions of SR 14 in August, 1996. A complete set of plans and a report for the
construction of the sulfur sections was obtained for this site. State personnel were
contacted in July to schedule a site visit, and reported that the entire sulfur site was
currently being overlaid with 3/8 to 1/2 inch hot-mix asphalt. A chip seal was to be added
in August. DOT personnel offered to provide coring and storage of the cores, and mentioned
that the states PMS might contain current distress data for SR 14.
Idaho DOT provided as-built plans containing the station location of
the project from which two HMAC and two sulfur sections were selected. The stationing we
selected corresponded with the previously reviewed sections. The stationing for the
control sections were 827+00 to 832+00 and 1386+00 to 1391+00, for the 30/70
sulfur-extended asphalt sections 975+00 to 980+00 and 1650+00 to 1655+00. The sections
were all full-depth with various aggregate base thicknesses.
Eight, 4-inch (100mm) diameter cores (four midlane and four wheelpath)
were cored for each of the 30/70 SEA sections and AC Control sections. The sampling was
split with four cores taken approximately twenty-five (25) feet outside each end of the
section. The cores arrived were shipped from Idaho and were photographed and examined.
Distress data was obtained from the Idaho DOT Pavement Management System (PMS). The
distress data was collected for the PMS in September 1995 and the rutting data was
collected in July 1993.
OBSERVATIONS
Visual observations of pavement distress were not completed as part of
Phase II. However, distress data representative of the sections was obtained from the
Idaho DOT PMS.
The site was reconstructed and a level-up of hot-mix was used of
varying thickness. The sections were designed to have approximately 7.6cm (3 in.) of
hot-mix with 22.9cm (9 in.) to 30.5cm (12 in.) of aggregate base on a granite subgrade.
The sections had two chip seals since their construction. A 1.0 cm (3/8 in.) to 1.3cm (1/2
in.) overlay was placed on the sections before coring. The average thickness could not be
determined by the cores, because several cores broke or were unable to be fully extracted
from the roadway.
EVALUATIONS
The PMS data indicated that alligator cracking was apparent in all the
sections in equal amount and severity. The AC sections contained a small amount of low
severity longitudinal cracking. The SEA section containing the 23cm (9 in.) aggregate base
showed the only signs of low severity transverse cracking. Rutting data indicated that the
average rutting for AC sections was 1.42cm (0.56 in.) and 1 cm (0.40in.) for the SEA
sections.
Visual inspection of the cores indicated that both the AC and SEA
sections may contain some stripping. Many of the cores that were extracted split along an
interface. This could be signs of delamination occurring between the level-up and AC/SEA
layer or between lifts in the AC/SEA layer. Crystalline deposits of sulfur were visible
along the delamination area.
COMPARISON OF FIELD DATA TO LABORATORY DATA
Data from the previous survey contained in FHWA-RD-90-110 provided the
necessary information to complete an analysis. The AAMAS results indicated that after
approximately five million Equivalent Single Axle Loads (ESALS) that fatigue cracking and
rutting would be present. PMS data provided confirmed this finding with average rutting of
1.25cm (1/2 in.) and low severity alligator cracking.
TH 63. Rochester, Minnesota, Section 862701, August 27, 1996
SITE LOCATION
This section is located on Trunk Highway 63 between Rochester and
Zumbro Falls and was placed in May of 1979. There is one section with one SEA mix and a
corresponding control section. The original SEA surface was still intact and was in good
condition. There were no plans for rehabilitation in the next four years.
State DOT personnel provided information about the construction of the
test sections. From this information it was determined that the existing pavement had been
given a level up course of approximately two inches with a 1-1/2-inch overlay of
sulfur-extended asphalt or regular HMAC. Stationing locations were determined from
construction plans and specs provided and verified by information from previous surveys.
Three sections were identified for this study. The first section
contained a 40/60 SEA blend and was located at Milepost 55.4-55.5. After coring began, it
was noticed that a transverse joint existed within the section signifying two different
mixes had been laid. After cores were extracted, it was determined that the first half of
the section up to Station 1+50 contained the normal HMAC mixture and that the remaining
350 feet of section contained the actual sulfur-extended 40/60 asphalt. The next section
consisted of an HMAC mixture with a 200/300 pen grade located at Milepost 57.0-57.1. The
third section contained an HMAC section with 120/150 pen grade located at Milepost
58.0-58.1. Eight, 4-inch (100mm) diameter cores (four midlane and four wheelpath) were
cored for the 40/60 SEA section and AC control sections. The sampling was split with four
cores taken approximately 25 feet outside each section end.
OBSERVATIONS
Thicknesses of the cores corresponded with the construction plans and
specifications provided by the State. Variations were found in the existing pavement layer
and level up course. Core thicknesses varied 1-2 inches. The average thickness of the
cores extracted from the end of Section No. 1 containing sulfur was 20.25cm (8 inches).
EVALUATIONS
It was clearly visible by the distress surveys that the sulfur-extended
asphalt sections exhibited a greater resistance to rutting and bleeding. This was clearly
apparent in the 40/60 SEA section that had the first 150 feet of regular HMAC. The
bleeding and rutting that was collected for Section No. 1 ended at Station 1+50,
indicating that the HMAC was prone to these types of distresses. Observations of the two
control sections of regular HMAC exhibited similar types of distresses and severities. The
control sections predominantly had bleeding and rutting in the wheel paths with moderate
severity transverse cracking. No sign of raveling was noticed on the control sections
whereas the sulfur-extended asphalt section did contain this type of distress. The cores
extracted from all sections exhibited signs of stripping. However, the HMAC sections
exhibited the greater degree of stripping and advanced deterioration.
COMPARISON OF FIELD DATA TO LABORATORY DATA
Based on the information provided in FHWA-RD-90-110, it was anticipate
that fatigue cracking and rutting would be encountered on all sections during the distress
survey. It was also anticipated that many more thermal cracks (transverse cracks) would be
present on the SEA section than on the control section. The surveys actually did show that
there were more transverse cracks in the SEA section when compared to the 200-300 pen AC
control section. However, rutting and fatigue cracking were not a problem on either of
these two sections. The 150-200 pen AC control section, however, had many more transverse
cracks as well as significantly higher rutting measurements.
Glendale Ave., Phoenix, Arizona, Section 850401
Based on several discussions with personnel at the Arizona DOT, FHWA,
and the Western Research Institute, it was later decided that a visit to this particular
site would not be cost effective. The sulfur extended material was in the base and
distinctions in performance for the various sections would likely be indistinguishable.
With this in mind no visit to this section was conducted.
A clear distinction in performance was not identified between the
sulfur extended asphalt sections and their control counterparts. Distinctions in design
(layer thicknesses and layers selected to contain SEA) and construction made comparisons
between projects inappropriate in some cases. From reviewing Table 2 it does appear that
the sulfur extended sections are more resistant to fatigue and longitudinal cracking and
possibly even somewhat more rut resistant, but no clear distinctions in transverse
cracking or surface defects (such as bleeding and raveling) were detected.
Table 5 has been prepared to summarize the results of the AAMAS
predictions. The "differences" shown denote how much more (or less) was expected
on the control vs. the SEA. For comparison purposes the actual data and its percent
difference are also shown. Although these are very crude approximations for most of the
sections, the predictions of fatigue and rutting matched the actual observations quite
well. The predictions of thermal cracking, however, were not nearly as successful.
Materials data for characterization of thermal cracking was very limited, however, which
might explain the less reasonable predictions for transverse cracking.
Although the study focused on the evaluation of performance for
existing SEA sections, if a decision is to be made regarding the use of sulfur extension
of asphalt, one must also consider the "real costs" associated with:
1.) Worker safety/health,
2.) Emissions during construction and/or environmental impact,
3.) Rehabilitation issues (specifically as they relate to recycling or
reuse of existing material).
Although these issues were not the focus of these investigations, the
importance and impact of these issues was made very clear to the research team by various
highway agencies during the course of these investigations. These issues frequently came
up during discussions and interviews with highway agency personnel associated with these
projects and from the reports provided, documenting the construction of these sections
(where available). |
