Hot In-Place Recycling of Polymer Modified
Open Graded HMA
Near Big Bar Ranger Station
Trinity-299-PM26.1-PM29.1
Report Number: CP2C-2010-113 February 17, 2011
California Pavement Preservation Center
35 Main Street, Suite 205
California State University
Chico, California 95929-0603
(530) 898-5981
i
PROJECT SUMMARY PAGE Tech Report: 2010 – 113
Title: Hot-In-Place Recycling of Polymer Modified Open Graded HMA: Near Big Bar Ranger
Station Trinity-299-PM26.1-PM29.1
Authors: Brandon Fraser, Ding Cheng, R. Gary Hicks, and Joel Gasik
Prepared For:
California Department of Transportation
Client Reference No.:
56A0243-TO-2
Prepared by: CP2 Center Date: February 4, 2011
Abstract:
This pilot study was intended to expand the technical information about the construction and performance
of the hot in-place recycling (HIR) of an existing asphalt concrete pavement that consisted of a one-inch
open graded wearing course with polymer modified asphalt binder and a one-inch dense-graded asphalt
layer. The HIR process resulted in a two-inch layer of dense-graded asphalt concrete mix. The project had
a number of issues in the beginning, including slow production rates, obtaining the necessary paving
temperatures, safety issues, and achieving compaction. Additionally, the Hveem stabilometer values of
the recycled pavement were inconsistent and were likely influenced by the amount of rejuvenating agent
used and the rate of production.
After trial and refinement, the HIR process in production was able to eliminate the safety issues and
created a uniform pavement mat with proper compaction. The adjusted amount of rejuvenation agent
helped address some of the low stabilometer value issues as well.
Project selection guidelines for HIR are proposed. It is recommended that a cost benefit analysis be
performed, and the long-term performance of pavement produced with this technique be studied.
Keywords:
Hot in place recycling, HIR, open graded mixes, Cyclogen-L rejuvenating agent, polymer modified
asphalt
ii
Acknowledgements
We appreciate the financial support of Caltrans for providing the funding for this important and
meaningful project. We would like to extend our gratitude to Larry Rouen, Hector Romero, and
Haiping Zhou of Caltrans Headquarters in Sacramento, Lance Brown and Wayne Rinard of
Caltrans District 2, and Don Matthews of Pavement Recycling Systems, all of whom provided
continuous support to this project.
Disclaimer
The contents of this report reflect the views of the authors who are responsible for the facts and
accuracy of the data presented herein. The content does not necessarily reflect the official views
or policies of the California Department of Transportation or the State of California.
iii
Table of Contents
LIST OF FIGURES ..................................................................................................................................................... V
LIST OF TABLES ..................................................................................................................................................... VI
1 INTRODUCTION ............................................................................................................................................. 1
1.1 BACKGROUND .................................................................................................................................................. 1
1.1.1 Hot In-Place Recycling Process ................................................................................................................. 1
1.1.2 Project ...................................................................................................................................................... 2
1.1.3 Contractors .............................................................................................................................................. 2
1.1.4 Equipment ................................................................................................................................................ 2
1.1.5 Asphalt Rejuvenator................................................................................................................................. 8
1.2 ORGANIZATION OF THE REPORT............................................................................................................................ 8
2 PRECONSTRUCTION INFORMATION .............................................................................................................. 9
2.1 EXISTING PAVEMENT ......................................................................................................................................... 9
2.2 JOB MIX FORMULA FOR HIR REMIX .................................................................................................................... 14
3 CONSTRUCTION OF THE PROJECT ................................................................................................................ 15
3.1 AGGREGATE PLANTS AND ESTIMATED HAUL TIME/DISTANCES ................................................................................. 15
3.2 CONSTRUCTION OBSERVATIONS AND DISCUSSION ................................................................................................. 16
3.2.1 August 10, 2010 ..................................................................................................................................... 16
3.2.2 September 1, 2010 ................................................................................................................................. 20
3.2.3 September 7, 2010 .................................................................................... Error! Bookmark not defined.
3.2.4 September 21, 2010 ............................................................................................................................... 25
3.3 QUALITY CONTROL AND QUALITY ASSURANCE ...................................................................................................... 28
3.3.1 Quality Control ....................................................................................................................................... 28
3.3.2 Quality Assurance .................................................................................................................................. 28
3.4 PROBLEMS ENCOUNTERED ................................................................................................................................ 31
4 POSTCONSTRUCTION EVALUATION AND LESSONS LEARNED ....................................................................... 33
4.1 POSTCONSTRUCTION EVALUATION...................................................................................................................... 33
4.2 FUTURE PLANS ............................................................................................................................................... 35
4.2.1 Survey in 2011 ........................................................................................................................................ 37
4.2.2 Information Access................................................................................................................................. 39
4.3 LESSONS LEARNED FROM THE HIR PROJECT ......................................................................................................... 39
5 CONCLUSIONS AND RECOMMENDATIONS .................................................................................................. 41
5.1 CONCLUSIONS ................................................................................................................................................ 41
5.2 RECOMMENDATIONS ....................................................................................................................................... 42
5.2.1 Proposed Project Selection Guidelines ................................................................................................... 42
5.2.2 Proposed Work....................................................................................................................................... 42
6 REFERENCES ................................................................................................................................................ 44
iv
7 APPENDICES ................................................................................................................................................ 45
Appendix A - Materials Information Handout
Appendix B - Existing Pavement Coring Information Job Mix Formula
Appendix C - Caltrans nSSP Hot In-Place Recycling (HIPR)
v
List of Figures Figure 1. 1st and 2nd preheaters .................................................................................................................. 3
Figure 2. Grinder at rear of preheater/miller ............................................................................................... 4
Figure 3. Adding rejuvenating agent in front of rear grinder on preheater/miller ...................................... 4
Figure 4. Windrow behind preheater/miller ................................................................................................ 5
Figure 5. Windrow in front of postheater/mixer .......................................................................................... 6
Figure 6. Mixing blades underneath postheater/mixer ................................................................................ 6
Figure 7. Postheater/mixer (center) delivers recycled HMA to paving machine (left) ................................. 7
Figure 8. Paving machine .............................................................................................................................. 7
Figure 9. Gradation Curves of Existing Open Graded and Dense Graded HMAs ........................................ 10
Figure 10. 0.45 Power Gradation Chart of Existing HMA: Open Graded and Dense Graded portions of Top
2 inches mixed ............................................................................................................................................ 11
Figure 11. Pavement surface close-up: Slight raveling shown .................................................................... 11
Figure 12. Cracking and raveling of existing pavement .............................................................................. 12
Figure 13. Transverse and longitudinal cracking ........................................................................................ 12
Figure 14. Longitudinal cracking and raveling ............................................................................................ 13
Figure 15. Alligator, longitudinal, and transverse cracking and raveling .................................................... 13
Figure 16. Aggregate plant location map .................................................................................................... 15
Figure 17. Rear grinder crooked on preheater/miller ................................................................................ 16
Figure 18. Pavement heated excessively behind second preheater .......................................................... 17
Figure 19. Pavement temperature behind 1st preheater .......................................................................... 17
Figure 20. Rejuvenator injected in front of rear grinder on preheater/miller ........................................... 18
Figure 21. Pavement behind paving machine ............................................................................................. 19
Figure 22. Finished pavement in the testing strip, which was not very smooth ........................................ 19
Figure 23. Admix being dumped into hopper ............................................................................................. 21
Figure 24. Mix coming out of paving machine ............................................................................................ 22
Figure 25. Operations running smoothly, note lack of smoke .................................................................... 22
Figure 26. Weeds caught on fire despite being wetted; contractor responded quickly ............................ 23
Figure 27. Newly added watering system to prevent grass fire ................................................................. 23
Figure 28. The temperature behind paver was uniform with highest at 230 degree F .............................. 24
Figure 29. Rut created due to the breakdown roller staying at the hot surface too long .......................... 25
Figure 30. Newly added teeth on the first preheater to let heat penetrate the pavement deeper .......... 26
Figure 31. Water truck wets the grass to prevent possible fire at the HIR job site .................................... 27
Figure 32. Second preheater continued to heat the existing pavement ................................................... 27
Figure 33. 0.45 Power Gradation Chart: Placed Remix ............................................................................... 30
Figure 34. Photo of compacted HIR alongside old pavement .................................................................... 33
Figure 35. Smooth finished mat vs. existing distressed opposite lane ....................................................... 34
Figure 36. Finished HIR pavement section ................................................................................................. 34
Figure 37. HIR construction test sites ......................................................................................................... 35
Figure 38. Raveling of the existing open graded pavement at test site A .................................................. 36
Figure 39. Raveling, transverse and longitudinal cracks on test site B ....................................................... 36
vi
Figure 40. Pavement at test site A -The sections that are lighter in color have been ground ................... 37
Figure 41. EB Lane Remix Density ............................................................................................................... 38
Figure 42. WB Lane Remix Density ............................................................................................................. 38
List of Tables
Table 1. Average Gradation of top 2 inches of HMA .................................................................................... 9
Table 2. Temperature Measurements September 1, 2010 ........................................................................ 20
Table 3. Temperature Measurements on September 7, 2010 ................................................................... 24
Table 4. Temperature Measurements September 21, 2010 ...................................................................... 26
Table 5. Laboratory Testing Results for Cores Taken During Project ......................................................... 29
1 Introduction
1.1 Background
1.1.1 Hot In-Place Recycling Process
Hot In-place Recycling (“HIR”) of existing asphalt pavement is a pavement surface treatment
technique, that is an alternative to cold milling the existing pavement and placing new asphalt mix in the
milled area (commonly referred to as mill and fill). The HIR technique typically recycles the top 1-3
inches of the existing pavement on site, thus eliminating the costs associated with transporting,
stockpiling, handling, and inventorying reclaimed asphalt pavement (“RAP”). In some cases, virgin hot
mix asphalt (often referred to as “admix”) is required to produce the final mixture. Because only 15-
30% of admix is usually required, the total transport and production costs associated with the virgin
HMA are significantly reduced.
The HIR equipment used in this project is in its third generation and uses diesel for all power and
heat generating systems. The first generation equipment was open flame and second generation used
an infrared heating system. This equipment uses hot forced air to heat the existing pavement prior to
and during milling which results in fewer emissions than the first generation equipment that used a
propane-powered open flame heating system. It also reduces the over-heating of the pavement that
was associated with the second generation equipment.
The third generation of equipment also incorporates a propane-powered exhaust combustion
engine that further reduces emissions.[1] This HIR technique incorporates hot milling the existing
pavement. Hot milling does not degrade the aggregates in the existing pavement to the extent that cold
milling does. This is because heat softens the binder, which allows the individual aggregates to be easily
separated and removed from the existing HMA in whole instead of being crushed into smaller sizes. As a
result, fines created by degrading aggregate in the milling process are also reduced.[1]
Pavements that are candidates for HIR are generally pavements that are candidates for
traditional mill and fill techniques. This includes pavements that have existing surface deterioration
such as rutting, corrugations, cracking, raveling, flushing, and loss of surface friction. The HIR process
typically operates at depths of 1-2 inches (25-50mm), but some projects have been reported to be as
deep as 3 inches (75mm). Typical pavement widths are between 10-14.5 feet (3.05-4.42 meters).
Production rates for the HIR process have been reported to be between 10-16 feet per minute
(approximately 3-5 meters per minute), depending on the milling depths involved and the heating
capacity of the existing pavement.[2] Based on the literature, HIR is not recommended for:[3]
Pavements with an overall thickness less than 3 inches (75 mm).
Pavements where the surface course contains aggregates larger than 1 inch (25mm).
Pavements where the underlying material has low load bearing capacity.
2
Pavements where surface cracks extend through the whole pavement thickness and into the
underlying base material.
Using HIR reportedly achieves up to 30-40% cost savings when compared to costs of traditional
cold milling and placing pavements of equal depth.[4] This is dependent on recycling depth, labor costs,
and fuel costs.[5]
1.1.2 Project
Caltrans Distinct 2 designated California State Route 299 in Trinity County between PM 26.1 and
36.9 to receive hot in-place recycling. This route is a two lane rural road in low mountainous terrain
having one lane in each direction. The project has approximately 20 lane miles within the project limits.
The annual average daily traffic (AADT) was estimated in 2009 to range between approximately 3100-
3650 vehicles per day. The monthly peak Average Daily Traffic (“ADT”) was estimated in 2009 to be
between 3800-5100. [6] Truck traffic volume (2008) for this route at a location approximately 20 miles
from the project location was estimated to be between 11.5-12.6% of the AADT.[7]
The HIR technique was used to convert the existing pavement surface (approximately 1-inch
open graded HMA over 1-inch dense graded HMA) into a dense graded final product. This type of
project is typically expected to achieve a design life of 5-10 years, and is typically used as a preventative
maintenance measure. It was estimated that the project would require 20 construction days to
complete, and a total of 35 working days were allotted. The estimated total cost for this innovation
project is $1,500,000.[8]
1.1.3 Contractors
Pavement Coatings Company, a division of Pavement Recycling Systems, was the contractor
selected to perform the HIR on this project. Martec Recycling Corporation was subcontracted to provide
the AR2000 HIR single-pass operation train equipment for the project. JF Shea worked as a paving
subcontractor for Pavement Coatings Company and provided the virgin admix.
Pavement Coatings Co. is based out of Riverside, CA and has several satellite offices in California
and one in Reno, Nevada. Pavement Coatings Co. was the prime contractor for this project. [9] Martec
was the subcontractor who provided the AR2000 HIR train. Martec’s main office is located in
Vancouver, British Columbia, Canada. [10]
JF Shea Co., Inc incorporates multiple smaller “Shea” companies and performs residential and
commercial property development, heavy civil engineering, and aggregate supply and paving, amongst
others. Shea Sand and Gravel was the paving subcontractor for this project. All virgin admix in this
project came from two Shea operated aggregate plants. These plants were Aggregate Products plant
and Fawndale Rock & Asphalt plant.[11]
1.1.4 Equipment
HIR of the pavement was completed by the AR2000 single-pass operation train. This third
generation equipment is manufactured in Japan and owned by the Canadian equipment contractor,
Martec Recycling Corp, Inc. HIR using AR2000 train was accomplished using four unique pieces of
3
equipment that recycle existing pavement on site, in a single pass. The first two pieces of equipment
were preheating machines. The third piece was a preheater/miller machine, and the fourth piece was a
postheater/mixer machine. A conventional paving machine followed this train to place the recycled mix,
and it was then compacted. A truck transporting virgin HMA was also used in this project. Information
has been obtained from the equipment manufacturer and it is supplemented by pictures highlighting
various aspects of this project.[12]
To begin, two preheaters passed over in tandem (shown in Figure 1) to heat and soften the
existing pavement.
Figure 1. 1st and 2nd preheaters
The preheater/miller followed these two preheaters and milled the top 2 inches of the existing
pavement. There is a heating element on the front of this equipment that maintains pavement heat
prior to two rows of grinders which mill the existing pavement at the back of this equipment (Figure 2).
This project involves milling to a depth of two inches. For design purposes, the top 2-inches of existing
pavement were characterized by 1-inch open graded HMA over 1-inch dense graded HMA.[13]
The front milling units mill the existing pavement and direct the millings toward the center of
the pavement lane being milled. A rejuvenating agent is then applied to these millings at a rate just
prior to entering the rear milling unit (Figure 3). The rejuvenating agentfor this project was Tricor
Cyclogen-L. The targeted application rate for this rejuvenating agent was originally 0.133 ± 0.005
gallons per square yard, which was determined by using 0.5% rejuvenating agent based on the weight of
the milled pavement (RAP). After the test strips were completed the targeted rejuvenating agent was
reduced to 0.2% by weight of milled pavement (RAP). This corresponds to an application rate 0.053
4
gallons per square yard. . The rejuvenating agent was to be applied to the millings at a temperature
within ±25°F of the recycled asphalt pavement, which was specified to be between 230-290°F.[8]
Figure 2. Grinder at rear of preheater/miller
Figure 3. Adding rejuvenating agent in front of rear grinder on preheater/miller
5
The recycled millings containing the rejuvenating agent were placed in a windrow behind the
preheater/miller machine (Figure 4).
Figure 4. Windrow behind preheater/miller
This project added virgin HMA (admix) to the recycled millings of the existing pavement. A
dump truck followed the preheater/miller and added this virgin HMA to the hopper at the front end of
the post heater/mixer.
The postheater/mixer was the fourth piece of equipment in the HIR train (Figure 5). The
rejuvenated millings were spread across the width of the milled section using horizontal augers and
were then agitated by a stirring blade system (Figure 6) while applying heat.
A slat conveyor system delivered the recycled millings up into a pug-mill. This material was fed
into a paving machine (Figure 7) which placed the recycled HMA in a single lift (Figure 8).
6
Figure 5. Windrow in front of postheater/mixer
Figure 6. Mixing blades underneath postheater/mixer
7
Figure 7. Postheater/mixer (center) delivers recycled HMA to paving machine (left)
Figure 8. Paving machine
Three rollers were initially used on this project. The first roller was a steel drummed CAT CB-
634-C weighing about 12 tons with vibration mode turned on. The second roller was a rubber tired roller
and weighed about 12 tons. The third roller was a steel-drummed CAT CB-634-C roller used as a finish
roller without vibration. The rubber tired roller was originally designated as an intermediate roller.
8
However, when this roller was used, it picked up the newly placed mat and stuck to the rubber tires. It
was therefore removed based upon the joint opinion of the Caltrans project quality control technician
and contractor. The compaction requirement specified for this job was between 92.0 and 97.0 percent
of maximum theoretical density (Rice). This indicates the density of the HIR remix should be between
154.1 and 161.0 pounds per cubic foot. Based on prior experience with the equipment, the hot in-place
remix must be kept at a temperature between 230°F to 290°F to achieve good compaction.[8]
1.1.5 Asphalt Rejuvenator
The asphalt rejuvenator used for this project was Tricor Cyclogen-L. Rejuvenators help soften the
aged binder in the existing mix. They are liquid petroleum-hydrocarbons that are non transparent with
a dark green/brown color. Cyclogen-L has an initial boiling point of 550°F and a flash point greater than
360°F. It has a specific gravity of 0.9 to 1.03 and is not soluble in water. It is generally non-hazardous
with the exception of overlong, repeated exposure to the skin. It is recommended that the liquid be
stored and handled in places without sparks or open flame and also that it be used in places with
adequate ventilation.[14] This rejuvenating agent is intended to adjust the asphalt viscosity of the
existing pavement by 200-500cSt.[15]
1.2 Organization of the report The report is organized into the following chapters:
Chapter 2: Preconstruction Information. This chapter describes the condition of the
existing pavement and identifies the existing pavement distress and is supplemented with
pictures. The job mix formula developed for this project is also discussed.
Chapter 3: Construction of the Project. This chapter discusses the plants used to supply
the virgin admix in this project and estimates their proximity to the project location. Four
visits during the construction of this project are also discussed. The first three of these
visits were during HIR test strips, and the fourth was during routine production. The
events of each visit are briefly accounted for, including information about the weather on
site, the material temperatures within the HIR train, material densities achieved, and any
modifications or additions to the original HIR system. Problems that were encountered
during construction are also discussed.
Chapter 4: Evaluation of the Finished Project. This chapter discusses the pavement
condition after the HIR process including the lessons learned. Future plans to visit this
project and the two established monitoring sites are also discussed.
Chapter 5: Conclusion and Recommendations. This chapter provides conclusions as to the
constructability HIR process during this project from an analysis of collected data.
Recommendations for future study and development of the HIR process are also
provided.
9
2 Preconstruction Information
2.1 Existing Pavement Fifteen 8-inch cores were taken by Caltrans District 2 and forty-six 4-inch cores were taken by
Pavement Coatings Co. Three of the 8-inch cores were used by Caltrans to determine the existing
aggregate gradation and binder content. The gradation results and binder content are summarized
below in Table 1.
Table 1. Average Gradation of top 2 inches of HMA
Sieve Size Average Percent Passing
3/4" 100
1/2" 97.8
3/8" 92.8
No.4 51.3
No. 8 32.7
No. 16 23.5
No. 30 16.9
No. 50 12.3
No. 100 9
No. 200 6.4
Binder Content 6.8
Six 8-inch cores and forty-six 4-inch cores were sent to Asphalt Pavement And Recycling
Technologies, Inc. (APART, Inc.) who conducted the pavement mix design. The top 2 inches of the
pavement was characterized from these samples. In the top two inches of existing pavement, the open
graded layer varied from 1/2 to 1 1/2 inch. The dense graded layer beneath this varied from 1/2 to 1
1/2 inch.
The gradation of the open and dense graded portions were determined by taking the top two
inches of 4-inch diameter cores obtained from the existing pavement and separating the dense graded
portion from the open graded portion. The gradation of the open and the dense graded portions of the
existing HMA are shown in Figure 9. The upper and lower limits for Caltrans 1/2 inch Type A HMA are
also included in this graph for reference.
Only the top two inches of the existing pavement were going to be recycled and mixed together,
so the gradation for the combined dense and open graded portions was determined. This was
determined by using the top 2 inches of nine 8-inch diameter cores obtained from the existing
pavement. The nine cores used produced enough material to perform three separate gradation
analyses. APART conducted two of these analyses, and Caltrans District 2 Materials Lab conducted the
remaining one. The gradation curves for these three analyses are shown in Figure 10, and the upper and
lower bounds of Caltrans 1/2 inch Type A HMA are included in the figure for reference.
Figure 10 shows that when the open and dense graded portions of the top two inches of the
exiting pavement vary; however the resulting gradations are very close to the lower limit of Caltrans 1/2
inch Type A HMA mix.
10
APART, Inc. used the top two inches of the same 8-inch cores to determine the binder content
of the existing pavement and the viscosity of that binder. The binder was 4.8% by dry weight of
aggregate for the open graded mix of the samples and 5.39% for the dense graded mix. The average
viscosity of the binder at 140°F for the open graded mix was 56,914 Poise and 25,920 Poise for the
dense graded mix.
When the open graded and dense graded portions of the existing HMA were mixed together, the
viscosity ranged from 37,448 to 79,662 Poise. The viscosity was affected by the relative quantity of open
graded HMA to dense graded HMA in the top two inches of pavement. More open graded material
corresponded to a higher measured viscosity.
0
10
20
30
40
50
60
70
80
90
100
0 0.5 1 1.5 2 2.5 3 3.5 4
Pe
rce
nt P
assi
ng
Sieve Size
0.45 Power Gradation Chart: Existing HMA
1/2 inch Type A HMA upper limit
1/2 inch Type A HMA lower limit
Open Graded Mix
Dense Graded Mix
No. 200 30 8 4 3/8 in. 1/2 in. 3/4 in.
Figure 9. Gradation Curves of Existing Open Graded and Dense Graded HMAs
Detailed information about the cores used and the mix design are in the Appendices of this
report. For purposes of mix design, the existing pavement was characterized as 1-inch open graded HMA
over 1-inch dense graded HMA. Additionally, the existing pavement contains polymer modified asphalt.
This was determined by visual inspection and tackiness of binder by APART, Inc.
The existing pavement had moderate alligator cracking, moderate transverse cracking, moderate
longitudinal cracking, and raveling. The existing pavement was also oxidized. Typical condition of the
existing pavement is shown in Figures 11-15.
11
0
10
20
30
40
50
60
70
80
90
100
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
Pe
rcen
t Pas
sin
g
Sieve Size
0.45 Power Gradation Chart of Existing HMA: Open Graded and Dense Graded Portions of Top 2 inches Mixed
1/2 inch Type A HMA upper limit
1/2 inch Type A HMA lower limit
Cores 1,2,3 (APART)
Cores 10,11,12 (Caltrans)
Cores 13,14,15 (APART)
No. 200 30 8 4 3/8 in. 1/2 in. 3/4 in.
Figure 10. 0.45 Power Gradation Chart of Existing HMA: Open Graded and Dense Graded portions of Top 2 inches mixed
Figure 11. Pavement surface close-up: Slight raveling shown
12
Figure 12. Cracking and raveling of existing pavement
Figure 13. Transverse and longitudinal cracking
13
Figure 14. Longitudinal cracking and raveling
Figure 15. Alligator, longitudinal, and transverse cracking and raveling
14
2.2 Job Mix Formula for HIR Remix The initial job mix formula included recycling the top two inches of the existing pavement, adding
0.5% Cyclogen-L (an asphalt rejuvenating agent) by weight of milled pavement and adding 15-30% virgin
HMA. After reviewing the performance of the first test strip, the recycling agent content was decreased
to 0.2% to minimize flushing and increase the stability.
The final pavement was a dense graded mix close to the 1/2 inch Type A HMA specified in the
Caltrans Standard Specifications Section 39 for Hot Mix Asphalt. The virgin HMA also met the 1/2 inch
HMA requirements; however the virgin HMA used in this job (which was originally intended to correct
gradation of the final mix) was often less than the 15% virgin HMA used in the mix design. The
gradations determined from post construction cores also show that the gradation of the final mix was
not significantly altered during the HIR process. The recycled binder target was Caltrans Performance
Grade PG 70-10. The detailed job mix formula is included Appendix B.
15
3 Construction of the Project This chapter details the construction process during this project by summarizing the site visits
made by staff of the California Pavement Preservation Center.
3.1 Aggregate Plants and Estimated Haul Time/Distances There were two aggregate plants used in this project to produce the HMA admix. The two plants
are Aggregate Products Plant and Fawndale Rock and Asphalt. Both are owned by JF Shea and are
located in or near Redding, CA. The haul distance from these plants to the project location is
approximately 75 miles for each site, which is roughly an hour and a half of haul time for each. The
locations of these plants are shown in Figure 16.
Figure 16. Aggregate plant location map
16
3.2 Construction Observations and Discussion The construction project was visited several times during the construction process. The following
provides a summary of the visits.
3.2.1 August 10, 2010
This was a clear and sunny day with the high air temperature of 82°F and a low of 57°F. The first
preheater entered the roadway at approximately 9:40 AM at the Big Bar Ranger Station. The contractor
started a test strip during the day. The test strip attempt started at the eastern entrance to the Big Bar
Ranger Station approximately 25 feet east of PM 28.6. Mechanical issues with the grinder height
adjusting mechanisms prevented forward progress until late that afternoon. By 3:00 PM, the HIR train
had been positioned to begin work, but there was little forward progress due to a succession of
mechanical failures on the equipment. Even after an initial fix, the height positioning system for the rear
grinder on the preheater/miller machine was still not working properly. The grinder on the
preheater/miller is shown in Figure 17.
Figure 17. Rear grinder crooked on preheater/miller
The two preheaters and the dump body truck containing virgin admix were waiting for the
proper operations of the preheater/miller. This caused the virgin admix to cool and the pavement
beneath the preheaters to overheat. The placed pavement should be heated to around 350°F. The
pavement temperature directly behind the second preheater during this waiting period is shown in
Figure 18 indicating the pavement temperature was above 450°F.
17
Figure 18. Pavement heated excessively behind second preheater
Although the previous picture displayed the excessive heating of the pavement surface, this was
probably due to the lack of forward motion of the HIR train. Once in motion, the preheaters appeared
to be capable of adequately and uniformly applying heat to the pavement. The pavement temperature
behind the first preheater, once in motion, is depicted in Figure 19.
Figure 19. Pavement temperature behind 1st preheater
18
The pavement was within a temperature range of 150°F and 242°F prior to the second preheater passing
over the pavement. No thermal images were taken behind the second preheater during normal
operation speeds, as normal operation speeds were not accomplished during this day.
The contractor targeted the temperature of the rejuvenating agent to be between 230°F and
250°F since the specifications call for the rejuvenating agent to be heated to within ±25°F of the recycled
asphalt pavement (acceptable range 230°F-290°F).[8] The temperature of the rejuvenating agent is
depicted in Figure 20. This image suggests that the recycling agent was being applied at a temperature
around 170°F, which is below the acceptable range.
Figure 20. Rejuvenator injected in front of rear grinder on preheater/miller
The millings containing rejuvenating agent and the admix were heated again and blended by the
postheater/mixer, and it was then placed by the paving machine.
The windrow behind the preheater/miller was at a temperature of approximately 160°F which
may have been caused by the train’s slow forward progress. When this temperature was taken, the two
preheaters and the preheater/miller were ahead of the rest of the train by about 80 feet while the
postheater/mixer and the paving machine approached the rest of the train. This is not typical of smooth
operations and contributed to the excessive cooling of the material in this windrow. Additionally, the
truck containing admix had been waiting several hours prior to use (without tarps), causing the
temperature of the admix to be low and the mix to be stiff.
The temperature behind the paver must be between 230°F and 290°F.The recycled asphalt mix
in the hopper was heated and mixed with the rejuvenated millings by a pug mill on the
postheater/mixer and then fed into the paving machine. The temperature of the pavement behind the
paving machine is shown in Figure 21.
19
Figure 21. Pavement behind paving machine
The pavement temperature was approximately 227°F right behind the paver, which was at the low end
of the acceptable temperature range. The finished pavement, after break-down compaction by vibratory
steel-drum rolling, and finish compaction by a static steel-drum rolling is shown in Figure 22. The surface
was very rough because of all the equipment breakdowns.
Figure 22. Finished pavement in the testing strip, which was not very smooth
20
Rubber tired rollers were specified by the contract to be used after breakdown compaction with
a vibratory steel-drummed roller. Rubber tired rollers were not used on this day due to the excessive
time spent to addressing the various mechanical problems encountered. The AR2000 equipment had
trouble with its fuel pump, the pumps used to inject the rejuvenating agents, and problems with the
grinders.
The finished pavement as shown in Figure 22 did not result in a uniform product. Additionally,
the surface of the recycled pavement did not conform to the surface of the adjacent existing pavement
in a uniform manner, as shown by the varying height of the longitudinal joint. The sections of
pavement recycled this day were re-recycled and placed at the end of construction to achieve a more
suitable finished product.
3.2.2 September 1, 2010
The weather was clear and sunny this day. The high air temperature was 73oF and the low was
60oF. The high pavement temperature was 125°F and the low was 98°F. Upon arrival at the job site at
9:30 AM, the work was not going well as the equipment was not completely in balance. From 9:30 AM
to 12:00 noon, the contractor had to make several adjustments to the equipment before target
temperatures were achieved. Initially too much admix was used which caused problems. Additionally,
by the time the admix was dumped it was often too cool due to prolonged waiting times. This caused
problems in some of the feeders.
The temperature of the windrow behind the preheater/miller was supposed to be about 175°F.
The temperature behind the screed was supposed to be about 230°F. The admix was supposed to be
about 260°F. These temperatures were not met in the beginning but increased as operations improved.
The production rate at the end of the day was close to 11 ft/min which was the target. Temperatures at
various points in the operation are shown in Table 2.
Table 2. Temperature Measurements September 1, 2010
Location Temperature range
(°F) Comments
Behind first heater 268-344 Heat increased as operation improved Behind second heater 250-304 Heat increased as operation improved In windrow behind 3rd heater
145-190 Lower temperatures were during equipment breakdowns
Admix 150-264
Should have been 260 F. Lower because of equipment breakdowns
Behind paver 180-210
Should have been 230 F. Polymer could have caused more rapid cooling
At breakdown compaction
180-210 Followed right behind the paver
Breakdown compaction was done with a CAT CB-634-C steel drum roller weighing about 12 tons
and using vibration. The intermediate roller was a CAT pneumatic weighing about 12 tons. Finish rolling
21
was also done with a CAT CB-634-C this time without vibration. Relative densities were measured by
inspectors on site using a nuclear testing device. These values ranged from 134-145 lbs/ft3 which is 87-
94% compaction based on an estimated maximum theoretical density of 154 lbs/ft3. Selected photos of
this day’s construction are shown in Figures 23 through 26.
At first the construction crew needed time to get use to the equipment and the HIR process. In
the end it was working smoothly, although the temperatures were still not consistent at the critical
points in the train.
3.2.3 September 7, 2010
The weather for this day was clear and sunny with a wind of approximately 7mph. The high air
temperature was 80°F and the low was 60°F. The contractor started preparing the job around 8:30 AM
and started paving around 10:45 AM. Initially, the paving train moved slowly and the breakdown roller
stopped many times. From 10:45 AM to 1:30 PM, the contractor paved about 500 ft, which is an average
of 3 ft per minute. From 1:30 PM to 3:30 PM, the paving train traveled about 600 ft, an average of about
5 ft per minute. The process got faster in the end and reached almost 10 ft per minute. The targeted
production rate was 11 ft per minute.
During previous test strip on September 1, a small grass fire happened. To remedy this, the
contractor added a heat shield on the outer side of the heater and watering devices on the outside
edges of the heating units. These improvements proved useful, as the vegetation adjacent to the
heaters did not catch on fire. The watering system is shown in Figure 27.
Figure 23. Admix being dumped into hopper
22
Figure 24. Mix coming out of paving machine
Figure 25. Operations running smoothly, note lack of smoke
23
Figure 26. Weeds caught on fire despite being wetted; contractor responded quickly
Figure 27. Newly added watering system to prevent grass fire
The mix temperature behind the paver screed improved from the test strip on September 1. The
temperature was controlled at around 220°F, which is still lower than specified. Table 3 summarizes the
24
temperatures at different locations within the train. Figure 28 is a thermal image that shows the
temperature of the pavement behind the paving machine.
Table 3. Temperature Measurements on September 7, 2010
Location Temperature range, oF Comments
Behind first heater 268-310 Heat increased as operation improved
Behind second heater 250-304 Heat increased as operation improved
In windrow behind 3rd heater 150-190 Lower temperatures were during stops
Admix 150-240 Should have been 260 F. May have waited too long because of slow paving
Behind paver 210 – 230 Should have been 230 F. Polymer could have caused more rapid cooling
At breakdown compaction 180-210 Followed right behind the paver
Despite some of the temperatures being low, the paving mat achieved good compaction. The
compaction was usually between 88-95% as determined in the field by using a nuclear density gauge
and a maximum theoretical density obtained from recompacted laboratory samples depending on
location.
Figure 28. The temperature behind paver was uniform with highest at 230 degree F
25
The recycled mix seemed relatively easy to work with. There were three rollers on the job site.
The breakdown compaction was done by a CAT CB-634-C vibratory roller weighing about 12 tons. The
CAT rubber tired roller for the intermediate compaction was not used because it picked up the freshly
placed mix. The finish rolling was done with a CAT CB-634-C without vibration. Figure 29 shows an
indentation in the pavement due to the steel drummed roller staying in the same place for too long.
Figure 29. Rut created due to the breakdown roller staying at the hot surface too long
The finished mat appeared to be in very good shape and to have good compaction. The
pavement looked smoother than the test strip completed on September 1. The mix appeared rich in oil
content.
3.2.4 September 21, 2010
This was a cloudy day with air temperature around 62°F and pavement temperature of 74°F at
11:00 AM. Around 3:00 PM, it was still cloudy, and the air temperature was 68°F and existing pavement
surface temperature was 80°F. The wind was about 7 mph. The contractor started paving around 9:30
AM and it was obvious that he was more familiar with the equipment. The construction went smoothly
for the duration of the day. Two test sites were set up during this day. They were each 500 ft in length
and located on either side of the bridge over Manzanita Creek. Test site A is on the west side, and test
site B is on the east side.
The temperatures behind the paver screed were improved from the previous visits. The
temperature was controlled at around 240°F, which was within the range of specified, but the downside
was that the smoke from pre-heaters and post-heater had increased. Table 4 summarizes the
temperatures at various points in the train for this day.
26
Table 4. Temperature Measurements September 21, 2010
Location Temperature range, oF Comments
Behind first heater 340-360 Heat increased as operation improved
Behind second heater 400-420 Heat increased as operation improved
In windrow behind 3rd heater 250-260 Temperatures within specified ranges.
Admix 200-210 Should have been 260 F. May have waited too long
because of slow paving
Recycled mix into the paver 260-270 Temperatures within specified ranges.
Behind paver 237-250 Polymer could have caused more rapid cooling
At breakdown compaction 200-230 Followed right behind the paver
The compaction for this day was usually between 92-95%, based on an estimated maximum
theoretical density of 154 lb/ft3. The recycled mix seemed relatively easy to work with. There were two
rollers on the job site. The breakdown compaction was done by a CAT CB-634-C vibratory roller with
about 12 ton weight. The finish rolling was also done with a CAT CB-634-C without vibration. In the end,
only one roller did all compaction jobs because of the low paving speed. The average speed for test
sites A and B were 6.5 ft/min. Average for the day was 6 ft/min. During a 10 hour work day the
production would be around 3600 feet per day, based on these rates. Selected photos from this day’s
construction are shown in Figures 30-32.
Figure 30. Newly added teeth on the first preheater to let heat penetrate the pavement deeper
27
Figure 31. Water truck wets the grass to prevent possible fire at the HIR job site
Figure 32. Second preheater continued to heat the existing pavement
28
For some spots, water was trapped inside the open graded friction course from a recent rain.
Nonetheless, the finished mat seemed in very good shape with good compaction. The train moved
slowly but smoothly, the pavement looked smoother than those paved on September 1st and 7th.
3.3 Quality Control and Quality Assurance
3.3.1 Quality Control
Asphalt Pavement and Recycling Technologies, Inc. verified that the 1/2 inch HMA mixed at both
the Aggregate Products Plant and the Fawndale Rock and Asphalt plant met the 1/2 inch mix gradation,
on August 7, 2010. The original job mix formula produced stabilometer values ranging between 32 and
37, based on laboratory testing prior to the beginning of work. Although Caltrans typically requires a
minimum stabilometer value for 1/2 inch HMA, there was no performance requirement for stabilometer
values on this project. The contract for this project required the stabilometer value only to be reported.
The air voids and binder content also did not have construction performance requirements and were
items required by contract to be reported only. The amount of recycling agent was reduced from 0.5 to
0.2% during production of the test strips in attempt to increase the stabilometer value.
3.3.2 Quality Assurance
Caltrans took pavement cores and HMA remix samples throughout the project to monitor the
quality of the placed material. The remix material was used to determine the stabilometer value of the
placed material, the air voids of the field compacted and laboratory compacted samples, the binder
content, and the in-place compaction density. This project placed three test strips, which were
necessary to become familiar with the operation of the equipment and to finalize the targeted
pavement mix. The data of this testing is presented in Table 5, along with the calculated air voids
(laboratory and field samples) and the in-place compaction. The equations that were used to calculate
these values are shown in Equations 1-3.
Eq. 1.
Eq. 2.
Eq. 3.
In Place
29
Table 5. Laboratory Testing Results for Cores Taken During Project
Date Stabilometer
Value Air Voids
Binder
Content
Maximum
Theoretical
Density
(Rice)
In-Place
Compaction
(% of
MTD)
Completed
Lane
Miles
Tes
t S
trip
1
9/1/2010 <13 0.9 6.9 2.565 90.3
0.28 9/1/2010 32 4.1 6.8 2.544 91.6
9/1/2010 <13 1.5 7 2.541 93.7
Tes
t S
trip
2
9/7/2010 40 4.1 6.9 2.480 93.1
0.48 9/7/2010 20 2.3 7.05 2.497 86.6
9/7/2010 40 5.7 - 2.510 92.4
Tes
t S
trip
3
9/9/2010 15 1.9 7.41 2.471 94.8
0.77 9/9/2010 43 5.5 5.95 2.551 90.4
9/9/2010 29 2.9 7.23 2.480 93.3
Pro
du
ctio
n
9/13/2010 40 4.7 6.62 2.499 93.8 0.76
9/14/2010 36 3.3 6.77 2.505 92.1 0.78
9/15/2010 33 6 6.81 2.490 92.7 0.65
9/16/2010 40 4.1 6.38 2.523 89.6 0.76
9/20/2010 11 ~2.2 6.74 2.753 90.8 0.38
9/21/2010 15 2.4 6.4 2.580 91.1 0.29
9/22/2010 18 2 6.96 2.563 88.8 0.57
In practice, the laboratory percent air voids are used to compare to the field percent air voids to see if
there are any material differences between them. If there are such differences, then possible
contributions to the differences are explored. In this project, the differences between the percent air
voids in the lab and in the field (1.3-11.1%) are attributed to the high variability in the thickness of the
open graded wearing course in the top two inches of existing pavement. Dense graded HMA is below
this open graded wearing course. The in-place compaction is used to measure the performance of
achieved field compaction against the maximum theoretical density (Rice).
During Test Strip 1 on September 1, 2010, the recycling agent, Cyclogen-L, was targeted at 0.5%.
This produced low stabilometer values, with two of three samples being below 13. The production rate
for this day was also low.
The second test strip on September 9, 2010, utilized two different amounts of added recycling
agent. Both 0.1% and 0.2% Cyclogen-L were used. The cores that represent remix produced using 0.2%
Cyclogen-L both had stabilometer values of 40. The sample that represented the remix using 0.1%
produced a stabilometer value of 20. Because using 0.2% Cyclogen-L produced higher stabilometer
values on this day, this amount of recycling agent was targeted during the rest of construction.
Production rates for this day began low at around 3 feet per minute and by the end of the day it was up
30
to around 11 feet per minute. Just less than one half of a lane mile was completed during this day,
which is half of the originally projected production rate of one lane mile per day.
The third test strip targeted using 0.2% Cyclogen-L. The stability values varied for the cores taken
this day, and so did the air voids. The binder content for the cores taken this day were between 5-7%,
and most of the compaction within targeted range of 92-97%. The production rates for this test strip
were the highest for the whole project, and few problems were encountered.
After the three test strips were completed, the actual production began. Production occurred
between September 13, 2010 and September 22, 2010. The first four days of production went more
smoothly than the last three. Average stabilometer values for the first four days of production were
above 30 and the last three days it was below 30. The average densities of the cores taken during the
first four days were within the compaction range specified by the contract (between 92% and 97% of
maximum theoretical density). For the last three days, the average densities were below this desired
range. Also, the last three days also had lower production rates than the first four days.
The job specifications indicate that the virgin admix (15-30%) was planned to correct the
gradation of the existing pavement. Gradation curves of the top two inches of existing pavement
combining two open graded and dense graded portions were shown earlier in Figure 10. This is prior to
construction. Gradation curves showing the placed remix as a result of HIR are shown in Figure 33. This
is after the HIR process.
0
10
20
30
40
50
60
70
80
90
100
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
Pe
rce
nt P
assi
ng
Sieve Size
0.45 Power Gradation Chart: Placed Remix
1/2 inch Type A HMA upper limit
1/2 inch Type A HMA lower limit
9/13/2010
9/14/2010
9/15/2010
9/16/2010
9/20/2010
9/21/2010
9/22/2010
No. 200 30 8 4 3/8 in. 1/2 in. 3/4 in.
Figure 33. 0.45 Power Gradation Chart: Placed Remix
31
The gradation curves of the placed remix and the existing pavement show that there was little
difference in the gradation that resulted from the HIR process. In some cases, the placed remix did not
conform to the targeted Caltrans 1/2 inch Type A gradation, the most noticeable being from the sample
of the material placed on September 15th, as shown in Figure 33. Although the initial target was to
include 15% virgin admix on this project, the parties involved in this project indicated that throughout
the project less than 15% of virgin admix was actually used, and it was usually used to maintain a proper
amount of material ahead of the equipment during the HIR process. Throughout the construction of this
process, the average binder content of the sampled material was 6.8% and the standard deviation was
0.4%.
3.4 Problems Encountered Many of the problems encountered during this project were mechanical. They included issues
with the pumps to deliver recycling agent to the millings and the grinder positioning system. The
mechanical difficulties encountered for one machine in this train made it difficult to coordinate the
smooth operation of the rest of the train which caused temperatures within the recycling train to vary
(often being too low) and the temperature of the virgin admix to be low because of long waiting times.
Another problem encountered was that the dry grass near the heating units caught fire. A fire
protection plan was included in the scope of work and the contractor was able to put fires out very
quickly. The contractors added spray bars on the outside of the heating units to wet the vegetation
adjacent to the pavement being heated. They also used a water truck to lead the HIR train with the sole
purpose of wetting the vegetation adjacent to the road prior to the rest of the train approaching. No
fires occurred after taking these extra measures.
Differences of materials in the existing pavement could also have led to problems with the final
product. The top portion of the top 2 inches of the existing pavement was open graded and contained a
polymer modified binder and varied from 1/2 inch to 1 1/2 inch thick. Underneath this open graded
mix, the pavement was dense graded. In the top two inches of the existing pavement, the open graded
mix varied from 1/2 inch thick to 1 1/2 inch thick. Because of the difference in the pavement
characteristics with depth, uniformly heating the whole thickness of pavement to be recycled was
challenging. It was noted in the sections of pavement which had a higher proportion of open graded mix
in the top two inches; the pavement was ground more easily and maintained its temperature more
steadily. This resulted in smoother operations and remix which had less bumps in it. The open graded
portion of existing pavement may have lost heat more quickly than the dense graded portion and
prevented the applied heat from properly heating the dense graded portion below. It is also likely that
the differences in the existing pavement contributed to the variability in the maximum theoretical
density (Rice) and the achieved compaction density.
When the remix was at the lower temperatures, spreading, mixing, and lifting the remix from the
ground became difficult. The paving machine tried to assist the forward motion of the postheater/mixer
machine by pushing it from behind. This caused the screed on the paver to be at inconsistent heights
during paving and produced bumps in the placed remix mat large enough to require grinding to restore
smoothness.
32
The most significant problem encountered throughout the project was the low production rates.
Although this was initially due to mechanical difficulties and low material temperatures, once operations
became steadier the production rate was still low, likely due to differences in the existing pavement mat
and difficulties achieving target temperatures to the full depth material prior to milling. The average
production rate was 0.6 lane miles per day (roughly half of the projected rate) and the originally
projected rate of one lane mile per day was never achieved. Because of this, only 30 percent of the 20
lane miles in the project was completed using the HIR process. The remaining 70 percent of the project
is planned to be completed using the traditional mill and fill technique in the 2011 construction season.
It is important to note that although production rate is an important factor in evaluating this recycling
process, the goal is ultimately to achieve a high quality final product with a reasonable, acceptable
production rate.
33
4 Postconstruction Evaluation and Lessons Learned
4.1 Postconstruction Evaluation The pavement that was recycled using the HIR technique produced a good final product once all
the equipment problems were worked out. Figures 34-36 show the recycled pavement next to the
existing pavement. The cracking and raveling apparent prior to the HIR are no longer present.
Figure 34. Photo of compacted HIR alongside old pavement
34
Figure 35. Smooth finished mat vs. existing distressed opposite lane
Figure 36. Finished HIR pavement section
35
No problems or distresses with the newly recycled pavement have been reported, even though
there were some quality issues at the beginning of the project. The project site will be revisited after the
winter season to further evaluate the short-term performance.
4.2 Future Plans Two test sites have been established for future observation and are shown in Figure 37. Both HIR
test sites are in the westbound lane. Site A includes 500 feet of pavement on the west side of the
Manzanita Creek Bridge, and site B includes 500 feet of pavement on the east site of the Manzanita
Creek Bridge. The post mile for the bridge is at PM 29.00 (GPS coordinates: n 40o45’21”, w 123o16’53”).
Figure 37. HIR construction test sites
The existing pavement condition before the HIR process had transverse cracks and raveling.
Figures 38 and 39 illustrate the pavement distresses before construction on site A and site B,
respectively.
Site B Site A
36
Figure 38. Raveling of the existing open graded pavement at test site A
Figure 39. Raveling, transverse and longitudinal cracks on test site B
37
4.2.1 Survey in 2011
CP2 Center conducted a post construction project survey after one winter rainy season. Overall
the pavement had a smooth ride. There was a considerable amount of grinding within the project limits
to correct intermittent pavement smoothness problems that occurred due to issues during
construction. The HIR project produced a good quality mix, and there was no apparent cracking or
significant raveling problems during this visit. Figure 40 shows a pavement photo taken Feb 11, 2011 at
test site A. This photo shows the pavement directly to the west side of the Manzanita Creek Bridge.
Figure 40. Pavement at test site A -The sections that are lighter in color have been ground
During this project survey the pavement density was measured using a Pavement Quality
Indicator in three locations across the width of the pavement at various stations: the westbound outer
wheel path, the center of the roadway, and the eastbound outer wheel path. The density was measured
three times at each location and the values averaged. Although, the average values for each measured
location ranged between 139.4 and 156.2 lbs/ft3, the average of all of the measured density values was
148.8 lbs/ft3 and the standard deviation was 4.2 lbs/ft3.
This seems to be a low standard deviation for the density of the final product considering the
amount of “stop and go” that was encountered during construction due to equipment difficulties, which
is good, but when comparing the achieved density in the field to the performance requirements
specified in the contract, the achieved density was sometimes out of the specified performance range.
The contract specifies that the placed remix should be between 92-97% of the maximum theoretical
density (MTD) achieved when creating a laboratory compacted specimen using material from the field.
Because the thickness of the open graded and dense graded portions of the pavement vary throughout
the limits of the project, so did the MTD. The upper and lower limits of the density requirements for the
38
Eastbound and Westbound lanes are shown in figures 41 and 42, respectively, along with the values for
achieved compaction density in the field for comparison.
Figure 41. EB Lane Remix Density
Figure 42. WB Lane Remix Density
135
140
145
150
155
160
26 26.5 27 27.5 28 28.5 29 29.5
De
nsi
ty (
lb/f
t3 )
Postmile
EB Lane Remix Density
CT EB 92%MTD
CT EB 97% MTD
CT EB Field Compacted Cores
CP2C EB Measured In-place Density
130
135
140
145
150
155
160
26 26.5 27 27.5 28 28.5 29 29.5
De
nsi
ty (
lb/f
t3)
Postmile
WB Lane Remix Density
CT WB 92%MTD
CT WB 97% MTD
CT WB Field Compacted Cores
CP2C WB Measured In-place Density
39
Figures 41 and 42 show that the compaction density achieved in the field varies with location.
This is likely influenced by the differences in the thicknesses of the open graded and dense graded
layers, which influences the rejuvenating agent’s effect on the achieved density, and the stop and go
during construction.
Near the construction limit at the east end of the project (near PM 29.40) there was a significant
amount of grinding required, in addition to noticeable raveling in the westbound lane, as well as some
delaminating of the remix that caused a small pothole. This may have been influenced by the presence
of moisture in the existing pavement prior to recycling, but is not typical for the rest of the pavement
within the project limits.
The condition of the sections of pavement that received hot in-place recycling will be monitored
again during the summer of 2011.
4.2.2 Information Access
Information included in this report can be found on the CP2 Center database located at
http://www.ecst.csuchico.edu/cp2c/software/pptdb.
4.3 Lessons Learned from the HIR Project The following lessons were learned from the D2 SR-299 HIR project:
Construction: Caltrans wanted the equipment be ready at the job site at the beginning
of the project; this was not demonstrated at the beginning of the project. Industry
mentioned that enough time must be allowed for the preliminary mix design and
material testing, as well as for alterations to the mix design for this project. Sanding may
be needed after the HIR work because the finished project looked shiny.
Materials: A big issue associated with this project was the recycling an open graded over
a dense graded HMA. The thickness of the open and dense graded portions varied
throughout the project. The open graded mix was heated quicker and did not retain
heat very long, and prevented the effective heating of the underlying dense graded mix.
The problem with non-uniform heating of the materials caused some construction
difficulties in the milling and scarifying operations. This could be a reason for the non-
uniform pavement surface and low production rates.
Design: The laboratory mix design was not effective for this project. The initial
percentage of rejuvenating agent (Cyclogen-L) was too high (0.5 percent), and was later
arbitrarily adjusted to 0.2 percent after the first test strip. The addition of the
rejuvenating agent reduced the Hveem stability values. The amount of rejuvenating
40
agent should be carefully determined and evaluated during the mix design in the
laboratory. Caltrans mentioned that low stability values may not be a major issue in this
project given that only 2 inches at the surface were recycled. Also, having higher oil
content in the pavement may perform better in the long run. Ultimately, a better mix
design should be developed and approved by both Caltrans and the contractor.
HIR fire prevention plan: The fire prevention plan was very successful, especially with
the addition of water irrigation devices to the heaters to wet the grass adjacent to the
heating units.
41
5 Conclusions and Recommendations
5.1 Conclusions This project demonstrated that hot in-place recycling is a process that can produce pavements of
good quality, but that it is difficult to keep results consistent if existing pavement conditions are not
uniform. Following are the conclusions resulting from this project:
Less than half of the cores taken during production achieved targeted compaction
values of between 92-97%. The average compaction value was 91.3% of the maximum
theoretical density, with a standard deviation of 1.7%. This is not a high standard
deviation, but the average is below the performance range specified. The average
compaction might be increased by using the pneumatic roller originally intended for
intermediate compaction; but it was not used because the tires picked up and stuck to
the freshly laid mat.
Average stabilometer values were determined from cores taken during the construction
(typically three cores per day). The average stabilometer value achieved during
production was 27.6. A minimum stabilometer value of 37 is required for 1/2 Type A
HMA by Caltrans in Section 39 of the Standard Specifications for Hot Mix Asphalt, so this
average value does not meet the standards. However, because this is an innovation
project and only the top two inches of pavement are being recycled, the contract
specifies the stability number for the portions of recycled pavement was to be reported
only and did not have a minimum requirement. Additionally, the standard deviation of
the stabilometer value was 12.5. This is a very high deviation, which indicated that
stability number of the HIR product varied by location. The high standard deviation was
likely caused by the varying thicknesses of the open graded and dense graded portions
in the top two inches of the pavement. Some of the variation of the stability number
may also be attributable to slight variations or uncertainties in the stability test
procedure.
The production rate for this hot in-place recycling process was sensitive to the low
temperatures in the pavement millings and virgin admix. The low temperatures of the
millings and admix were typically caused by the cooling of the recycled asphalt paving
materials and a difficulty attaining the desired temperatures in the existing pavement
prior to milling. During production, a low production rate corresponded to both a low
stabilometer value and low achieved compaction. Pavements produced at higher
production rates showed higher stabilometer values and higher levels of compaction. It
appears that higher production rates also produce a more uniform pavement.
There is considerably less smoke produced by this recycling technique. Low production
rates often produced excess heating in the pavement, which produced more smoke.
Higher production rates did not appear to have as much smoke.
42
The rejuvenating agent blended with aged existing asphalt mixture to reduce the
viscosity and increase elasticity of the oxidized binder. The amount of rejuvenating
agent can not only reduce the viscosity of the binder, but also reduce the stabilometer
number of the mixed asphalt concrete. Because the stabilometer numbers were low at
the beginning of the test section, the amount of rejuvenating agent was reduced from
0.5% of the mix to 0.2%.
It was noted that after compaction the placed remix had a considerable amount of shine
to it from a distance. Applying sanding after the HIR process may help reduce this shine.
5.2 Recommendations With the inconsistent densities, stabilometer values, production rates, and mix temperatures
throughout the project, a few recommendations as to project selection have been established.
Proposed project selection guidelines that resulted from this project are as follows:
5.2.1 Proposed Project Selection Guidelines
Uniform HMA layer for the entire recycled depth with uniform gradation and cross
sections. Variable pavement layers cause non-uniform heating and a variable binder
content. Open graded layer may have prevented heat from penetrating into the dense
graded layer.
Dense graded HMA is suitable candidate for HIR. A 2 inch depth was targeted for
recycling in this project, but future projects should consider recycling at a depth around
1.5-1.75 inches. Open graded HMA thicker than 2 inches may be acceptable.
Dense graded HMA with polymer modified asphalt is a potential candidate for HIR as
demonstrated in this project. HMA containing asphalt rubber or rubber modified
binders are not recommended for HIR because current equipment and technology are
not suitable for this type of material.
ADT’s for HIR projects should be less than 30,000.
Minimum curve radius for HIR projects need to be established. This project had curves
that approached the limit of maneuverability for the large HIR equipment. The tightest
of these curves has a radius of approximately 850 feet.
Types of distresses should be in the category of pavement preservation.
5.2.2 Proposed Work
A cost-benefit analysis could help to evaluate whether HIR is cost-effective or not. This
should include details about the asphalt, fuel, and estimated labor costs involved. It
should also contain details of the existing HMA, depths recycled, quantity of admix and
recycling agent used, as well as address quality of the placed final product.
Long term performance of pavements recycled using this technique should be measured
to help establish life cycle cost analysis.
43
FWD deflection tests on both the HIR pavement and conventional mill and fill pavement
will be helpful to determine the effectiveness of different strategies. It will also be
helpful to compare FWD tests before and after the HIR process to study the differences.
Grinding was required to smooth out the bumps at various locations in the placed
pavement mat. A smoothness test may be needed to address smoothness issue of this
HIR project.
A binder viscosity test on HIR samples from the project location should be conducted to
help determine the final viscosity of the binder. The amount of rejuvenating agent was
adjusted during the test strip. Knowing the final viscosity may help to study the effects
of the rejuvenating agent on the mix design.
44
6 References
[1] Joharifard, M., Kaplun, M., Emery, J. (2005). “Martec’s approach to road maintenance for
sustainable pavements through hot in-place recycling technology.” Proceedings of International
Symposium on Pavement Recycling. Sao Paulo, Brazil.
[2] Hoskokawa, H., Kanzake, Y., Gomi, A., Kasahara, A. “A Case Study of Work done by a Hot In-
Place Recycling (HIR) Machines.”
[3] Lee, S., Siddon, T. (1999). “Advanced Hot In-Place Recycling for Cost Effective Maintenance of
Asphalt Pavements.” International Seminar on Highway Rehabilitation and Maintenance. New
Delhi, India.
[4] Terrel, R., Lee, S. (1997). “Hot In-place Recycling of Asphalt Pavements.” Paper prepared for
Arab Urban Development Institute Symposium. Al-Ain, United Arab Emirates.
[5] Asphalt Recycling and Reclaiming Association. (2001). “Basic Asphalt Recycling Manual.” USA.
[6] California Department of Transportation. (2009). “Average Annual Daily Traffic.” Spreadsheet.
[7] California Department of Transportation. (2008). “Average Annual Daily Truck Traffic.”
Spreadsheet.
[8] California Department of Transportation. (2010). “Notice to Bidders and Special Provisions
Contract No. 02-2E2604.”
[9] Pavement Recycling Systems, Inc. website. http://www.pavementrecycling.com/.
[10] Martec Recycling website. http://martec.ca/.
[11] JF Shea Co., Inc. website. http://www.jfshea.com/.
[12] Terrel, R., Epps, J., Joharifard, M., Wiley, P. (1997). “Progress in Hot In-Place Recycling
Technology.” Paper prepared for 8th International Conference on Asphalt Pavements (ICAP).
Seattle, WA, USA.
[13] APART, Inc. (2010) Job Mix Formula: Tri-299-PM26.18-36.89 Caltrans Contract 02-2E2604.
[14] Tricor Refining, LLC. (2005). “Material Safety Data Sheet Cyclogen L Base Oil.” Bakersfield, CA.
[15] Tricor Refining, LLC. “Cyclogen Recycling Agents Specifications.”
[16] California Department of Transportation. (2010) “Materials Information: Pavement Sample
Coring Record/Pavement Samples Test Report Route: 02-TRI-299-PM 26.18/36.89.”
45
7 Appendices
Appendix A
Materials Information Handout
Appendix B
Existing Pavement Coring Information Job Mix Formula
Appendix C
Caltrans nSSP Hot-In-Place Recycling (HIPR)
Cyclogen® Recycling Agents
10-1.21 HOT-IN-PLACE RECYCLING (HIPR)
GENERAL Summary
This work consists of rehabilitating an asphalt concrete (AC) pavement by heating, then milling the AC pavement surface, collection of the recycled AC pavement, mixing of the recycled asphalt pavement with a recycling agent and between 15 and 30 percent new hot mix asphalt (Corrective HMA), and laying the HIPR Remix as a single, homogeneous mix.
TERMINOLOGY "Recycled asphalt pavement" refers to the removed existing layer of AC pavement,
before it is mixed with recycling agent or Corrective HMA. "Recycling agent" refers to the agent used to rejuvenate the recycled asphalt
pavement. "Corrective HMA" refers to the HMA added to the recycled asphalt pavement, to
correct the aggregate gradation to meet densities after milling. It does not refer to the end product.
"HIPR Remix" refers to the homogeneous mixture of recycled asphalt pavement, recycling agent, and Corrective HMA placed on the project.
"Pavement Establishment Period" refers to the time period between preliminary and final acceptance, see "Final Acceptance" of these special provisions.
MATERIALS The Department has taken 15 cores to characterize the top 0.17 feet of the existing
pavement. An Information Handout with the results of the coring, and subsequent gradations, is available as described in "Supplemental Project Information" of these special provisions.
The recycling agent must comply with the following quality characteristics: 1. Is grade R-1, R-5, R-25, or R-75; or 2. Complies with the quality characteristics in the following table:
Test ASTM Test Method Minimum Maximum Viscosity @ 140 ºF cST D 2170 or D 2171 200 800 Flashpoint COC, ºF D 92 400 n/a Saturates, Wt. % D 2007 n/a 30
Specific Gravity D 70 or D 2198 Report only n/a Viscosity Ratioa n/a n/a 3 Mass Change ± % n/a n/a 4 a Viscosity Ratio = (RTFC Viscosity @ 140 ºF, sCT) / Original Viscosity @ 140 ºF, sCT)
Corrective HMA The Corrective HMA must either meet the requirements for HMA (Type A) of
Section 39, "Hot Mix Asphalt," of the Standard Specifications, and these special provisions; or the aggregate of the Corrective HMA must meet the aggregate quality characteristics in the "Aggregate Quality" table in sub-Section 39-1.02E of Section 39, "Hot Mix Asphalt," of the Standard Specifications.
JOB MIX FORMULA FOR HIPR REMIX You may obtain representative pavement material samples from the existing roadway
by cores or milling. Submit a HIPR Remix job mix formula (JMF) to the Engineer developed from the
existing pavement materials present in the roadway surface at least 7 days before starting recycling work.
The job mix formula report must include:
1. Recycled asphalt pavement gradation (CT 202) and asphalt binder content of the
existing asphalt concrete pavement to be recycled (CT 362, 379 or 382). 2. Recommended Corrective HMA as a percentage of total weight of HIPR Remix. 3. Recommended recycling agent by percent of dry recycled asphalt pavement. 4 Additive, if used, and percentage by weight of dry recycled asphalt pavement. 5. Maximum density (CT 309) 6. Air voids 7. Stability 8. Provide for recycling agent and any additives Designation Company name Location Residue content Certificates of compliance
Job Mix Formula The JMF must comply with:
Design Parameters Test Method Requirement Gradation of Recycled Asphalt Pavement
CT 202 Passing 1-inch
Asphalt Content of Recycled Asphalt Pavement
CT 362 or CT 379 or ASTM D 2172 Method B
Report only
Bulk Specific Gravity CT 308, Method C Report only Maximum Theoretical Specific Gravity
CT 309, including provisions of Section J Report only
Air Voids of Compacted Specimens CT 367 Part B Report only Stability Cured Specimen Report only
Submit samples split from your HIPR Remix, for independent determination of the correlation factor, to the Engineer.
Just-In-Time Training (JITT)
The Engineer's personnel and your personnel must complete JITT. JITT is a formal training class for HIPR Remix work by a qualified instructor you provide. You provide the JITT training class, which may be an extension of the pre-construction conference.
JITT must be: 1. At least 2 hours long 2. Completed within 5 business days before you start HIPR process 3. Conducted during normal working hours You and the Engineer's personnel must attend the formal JITT class before starting
hot-in-place recycling. Personnel include, but are not limited to, individuals involved in hot-in-place recycling mix design and quality control and equipment operators and crew who place, inspect and test recycled in-place material, and the Engineer's representatives including Redding Materials Lab staff, inspectors and testers.
The JITT instructor must be experienced with HIPR methods, materials, and tests. The instructor must not be a Department field staff member. Upon completion of JITT, the instructor must issue a certificate of completion to the participants.
The JITT instructor must submit to Engineer for review and approval a copy of the course syllabus, handouts, and presentation material to the Engineer at least 7 days before the day of training.
The Engineer may waive training for personnel who have completed equivalent training within the 12 months preceding JITT. Submit each certificate of completion for the equivalent training.
Just-In-Time Training participation does not relieve you of responsibility under the contract for the successful completion of the work in conformance with the requirements of the plans and specifications.
Test Strip
On the first day of HIPR activities and within the limits of the project, construct a test strip of HIPR to the specified depth for a single lane width at least 1500 feet long. Use the same equipment, materials, and construction methods for the test strip as the rest of the HIPR Remix.
The test strip section must: 1. Demonstrate that the equipment, materials and processes you proposed and
furnished can produce HIPR Remix in compliance with the specifications 2. Determine the sequence and manner of rolling necessary to obtain the density
requirements in compliance with the specifications 3. Comply with compaction and surface straightedge requirements Measure temperatures for the test strip at the various locations within the continuous
train to assure proper mixtures are provided for the final HIPR product.
Test the test strip for:
1. Gradation 2. Percent of maximum theoretical density 3. Asphalt binder content 4. Stabilometer value 5. Remix temperature behind screen must be over 230 ºF. An approved test strip may remain in place as part of the HIPR work provided it is in
compliance with the Standard Specifications and these special provisions, and approved by the Engineer. A test strip that is not approved will be removed and replaced with HMA (Type A), as directed by the Engineer.
The Engineer has 4 business days to approve or not approve the test strip. If recycling agent requires a cure time, the Engineer has 4 business days plus the number of days required for the recycling agent cure time.
Do not continue HIPR work if your equipment and process fail to meet the requirements and until a test strip is approved by the Engineer. Before starting another test strip, document to the Engineer what corrective actions you will take to ensure that the test strip will be in compliance with the Standard Specifications and these special provisions, and as directed by the Engineer.
QUALITY CONTROL INSPECTION, SAMPLING AND TESTING
General Provide a quality control plan (QCP) at least 14 business days before starting HIPR
work and perform quality control sampling and testing during HIPR work, placement, compaction and finishing. Describe in the QCP the organization and procedures you will use to:
1. Control the quality characteristics 2. Determine when corrective actions are needed (action limits) 3. Implement corrective actions Meet with the Engineer at least 7 days before starting HIPR work to review the QCP.
The Engineer must approve the QCP before HIPR work begins. Manage the QCP testing and results to ensure that HIPR work and placement is in
compliance with the Standard Specifications and these special provisions, and as directed by the Engineer.
In the QCP, identify your Quality Control Manager, who will be on the project site during HIPR work.
Provide testing laboratory and personnel to perform quality control sampling and testing. Provide the Engineer with unrestricted access to the laboratory, sampling and testing sites and all information resulting from mix design and quality control testing activities. Proficiency of testing laboratories and sampling and testing personnel must be reviewed, qualified, and accredited by the Department's Independent Assurance Program before starting HIPR work.
Perform sampling and testing at a rate sufficient to ensure that HIPR work, placement, density and finishing complies with the Standard Specifications and these
special provisions, but in no case less frequently than stated in the paragraphs below. Submit QCP testing results to the Engineer daily.
Quality Control Testing and Sampling
Perform the following once for every 750 tons of HIPR Remix: 1. At a location agreed to by the Engineer, take and split a sample of HIPR Remix
for determining the maximum theoretical density under CT 309, and stabilometer value under CT 366. Determine an asphalt binder content and gradation per LP-9.
2. Label one of the split samples with location by station and deliver to the Engineer. For every 750 tons of HIPR Remix, provide the following information: 1. Length, width and depth of cut, and measured weight (tons) of material processed 2. Amount of recycling agent added (tons), and calculated percentage of recycling
agent by weight compared to the total weight of the recycled asphalt pavement in the lot
To determine density of the HIPR Remix, take two 4-inch or 6-inch diameter density cores for every 250 tons of HIPR Remix from random locations designated by the Engineer. Take density cores in the Engineer's presence and backfill and compact holes with material authorized by the Engineer. Before submitting a density core to the Engineer, mark it with the density core's location and place it in a protective container.
If a density core is damaged, replace it with a density core taken within 1 foot longitudinally from the original density core.
Relocate any density core located within 1 foot of edgeline to 1 foot transversely away from edgeline.
If cure time is required for HIPR Remix, wait for the HIPR Remix to cure before taking cores. If cores become too difficult to take, then, with the permission of the Engineer, calculate percent maximum theoretical density using CT 375.
The density cores above are also used to measure the HIPR Remix layer thickness, as described in "Thickness" below.
Prepare 3 briquettes for each stabilometer value and air voids content determination. Report the average of 3 tests. Prepare new briquettes and test if the range of stability for the 3 briquettes is more than 12 points.
You may use the briquettes used for stability testing to determine bulk specific gravity under CT 308. If you use these briquettes and tests using bulk specific gravity fail, you may prepare 3 new briquettes and determine a new bulk specific gravity.
The Engineer tests the density core you take from each 250 tons of HIPR Remix production. The Engineer determines the percent of maximum theoretical density for each density core by determining the density core's in-place density and dividing by the maximum theoretical density.
One calculated percent of maximum theoretical density represents 250 tons of HIPR Remix. The 250 tons is that HIPR Remix located directly behind the location of the density core that was used to calculate the percent of maximum theoretical density.
When field adjustment for optimum results for a lot of the pavement being recycled requires changes from one lot to the next, document the reason for the change and identify each lot where the changes were made and submit a copy to the Engineer.
Smoothness
Determine HIPR Remix smoothness with a straightedge. The HIPR Remix layer must not vary from the lower edge of a 12-foot long
straightedge: 1. More than 0.02 foot when the straight edge is laid parallel with the centerline 2. More than 0.03 foot when the straightedge is laid perpendicular to the centerline
and extends from edge to edge of a traffic lane 3. More than 0.03 foot when the straightedge is laid within 24 feet of a pavement
conform If the layer of HIPR Remix does not comply with the smoothness specifications,
grind the pavement to within tolerances, or remove and replace with HMA (Type A) as specified in "Hot Mix Asphalt (Type A)," of these special provisions.
HOT-IN-PLACE RECYCLING EQUIPMENT
General The hot-in-place recycling process for this specification is the "Remixing" method, as
defined and described by the Asphalt Recycling and Reclamation Association. The existing asphalt concrete pavement is heated, then the heated asphalt concrete pavement is removed by milling. The asphalt concrete pavement is collected into a windrow, then mixed with recycling agent and corrective HMA in a pug mill. The HIPR Remix is placed as a single, homogeneous mix, and then compacted.
The hot-in-place recycling process is a single pass operation train. Any air emissions from the hot-in-place recycling process must be compliant with
local county air boards and local air quality management districts. Provide hot-in-place recycling equipment train that is continuous, integrated and
delivers a homogeneous mixture of uniformly coated aggregates of unchanging appearance at discharge from the spreading unit that provides the final compacted thickness of HIPR material for the width being spread without resort, spotting, picking up or otherwise shifting the mixture ready for compaction.
Heating Units
Provide heating units that apply thermal energy to existing AC pavement without charring asphalt binder or breaking aggregate particles. Equip heat units with an enclosed or shielded hood to supply heat a minimum of 4 inches beyond the width of recycling. Protect adjacent trees, shrubs or other landscape and other materials that could be damaged from the heat from the heating unit with shields, water spray or other methods.
Attention is directed to "Fire Plan" of these special provisions.
Pavement Removal Units Use 1 or 2 milling machine(s), capable of removing the specified depth of the existing
pavement surface. Each unit must be capable of milling as wide as 12 feet in one pass. These milling unit(s) must uniformly loosen and remove the heated AC pavement to the depth specified that minimizes fracturing of aggregate. Automatic grade and cross slope controls must be used on the final milling unit(s) in the equipment train. The milling unit(s) must be capable of height adjustments in order to clear manholes and other obstructions in the pavement surface.
Pavement removal unit(s) must be capable of feeding removed pavement material into a mixing unit, then thoroughly mix and blend it with recycling agent and corrective HMA material, and feed the resulting mixture into a spreading and leveling unit.
Distribution and Blending Unit(s)
A controlled system shall be used for adding and uniformly blending the recycling agent and corrective HMA at a predetermined rate with the recycled asphalt pavement during remixing and leveling operation.
The recycling system shall be required to provide the following: 1. Application rate for the added materials synchronized with the speed on the
recycling system. 2. Control of the quantity of recycling agent to ±0.05 gallons per square yard of
surface treated within application range of 0.1 to 2.0 percent by weight of the recycled asphalt pavement.
3. Heating the recycling agent to ±25ºF of the temperature of the recycled asphalt pavement.
4. Measurement of the recycling agent by a device capable of recording accumulated gallons to an accuracy of ±2 percent.
5. Twin shaft pug mill capable of thoroughly mixing the recycling agent, corrective HMA and recycled asphalt pavement to produce a uniform, consistent product.
Proportioning Devices Except for continuous weigh belts, provide type approved by the Division of
Measurement Standards, Department of Food and Agriculture, State of California weighing and measuring devices for proportioning recycling mixture ingredients. Provide weighing and measuring devices for proportioning recycled asphalt pavement tested under the Departments Material Plant Quality Program (MPQP), (formerly CT 109 certification).
You must provide the Engineer 10 days notice prior to scheduling the Department to perform an MPQP.
Spreading and Compacting Equipment
Paving equipment for spreading must be: 1. Self-propelled 2. Mechanical 3. Equipped with a screed or strike-off assembly that can distribute HIPR Remix the
full width of a traffic lane
4. Equipped with a full-width compacting device 5. Equipped with automatic screed controls and sensing devices that control the
thickness, longitudinal grade, and transverse screed slope Install and maintain grade and slope references. The screed must produce a uniform HIPR Remix surface texture without tearing,
shoving, or gouging. The paving equipment must not leave marks such as ridges and indentations unless
you can eliminate them by rolling. Each paving equipment spreading HIPR Remix must be followed by 3 rollers: 1. Breakdown Roller – a vibratory roller appropriate for compacting the HIPR
Remix. 2. Pneumatic Roller – an oscillating type pneumatic-tired roller at least 4 feet wide.
Pneumatic tires must be of equal size, diameter, type, and ply. 3. Finish Roller – a steel-tired, 2-axle tandem roller. Each roller must have a separate operator. Rollers must be self-propelled and
reversible.
CONSTRUCTION Spreading and Compacting
Keep HIPR Remix temperature between 290ºF and 230 ºF, but not lower than 230 ºF. Maintain the mixture temperature in the range to provide for compaction prior to opening the recycled pavement to traffic of not less than 92.0 percent nor more than 97.0 percent of maximum theoretical density.
Paving Window HIPR, placement, compaction and finishing may not be done between October 1 and
May 1.
ACCEPTANCE INSPECTION, SAMPLING AND TESTING General
Acceptance of HIPR pavement is based on the 2 conditions: 1. Preliminary acceptance 2. Final acceptance Completion of remedial, corrective or removal and replacement work of the HIPR
pavement and both conditions of acceptance must be met by the HIPR pavement before the Engineer recommends Contract acceptance of the project
Preliminary Acceptance Within 5 days of the completion of HIPR pavement work you and the Engineer
together visually inspect and evaluate the HIPR pavement surface for raveling, segregation, rutting, humps, depressions, irregularities or surface blemishes.
Thickness Using the density cores, make HIPR Remix thickness measurements under the
procedures in CT 531. Although CT 531 is for PCC layer thickness, the procedure in CT 531 can be used to measure the HIPR Remix thickness. Report thickness results to the Engineer.
Percent of Maximum Theoretical Density
The HIPR Remix must have a density of 92.0-97.0% of maximum theoretical density. For percent of maximum theoretical density 90.0% to 91.9%, or 97.1% to 99.0%, the
Engineer determines a deduction for each test result outside the specifications in compliance with:
Reduced Payment Factors for Percent of Maximum Theoretical Density
HIPR Remix Percent of Maximum
Theoretical Density
Reduced Payment Factor
HIPR Remix Percent of Maximum
Theoretical Density
Reduced Payment Factor
92.0 0.0000 97.0 0.0000 91.9 0.0125 97.1 0.0125 91.8 0.0250 97.2 0.0250 91.7 0.0375 97.3 0.0375 91.6 0.0500 97.4 0.0500 91.5 0.0625 97.5 0.0625 91.4 0.0750 97.6 0.0750 91.3 0.0875 97.7 0.0875 91.2 0.1000 97.8 0.1000 91.1 0.1125 97.9 0.1125 91.0 0.1250 98.0 0.1250 90.9 0.1375 98.1 0.1375 90.8 0.1500 98.2 0.1500 90.7 0.1625 98.3 0.1625 90.6 0.1750 98.4 0.1750 90.5 0.1875 98.5 0.1875 90.4 0.2000 98.6 0.2000 90.3 0.2125 98.7 0.2125 90.2 0.2250 98.8 0.2250 90.1 0.2375 98.9 0.2375 90.0 0.2500 99.0 0.2500
< 90.0 Remove and Replace > 99.0 Remove and Replace
Criteria for Remove and Replace If the percent of maximum theoretical density is less than 90.0% or greater than
99.0%, then remove the HIPR Remix and replace it with Type A HMA, 1/2" gradation, binder type PG 64-28PM, which meets the requirements of Section 39, "Hot Mix Asphalt," of the Standard Specifications.
Final Acceptance The Contractor and the Engineer inspect and evaluate the HIPR pavement not less
than 60 business days after receiving preliminary acceptance and within 90 business days of the completion of the HIPR work for these signs of distress:
Raveling – aggregate separation from binder caused by surface wear. Flushing – bituminous material on pavement surface resulting in a coefficient of
friction less than 0.30, as detemined by method CT 342. Rutting – longitudinal surface depression in wheel path greater than 1/4". Cracking – cracking the HIPR Remix layer 1/8" or greater. Delamination – separation of HIPR Remix from underlying existing pavement. When requested by the Engineer submit your written evaluation of the HIPR Remix
within 10 days of your inspection listing by location the cause of distress, extent effecting service and life of the pavement with your proposal of corrections to minimize further deterioration. List areas which you evaluate as normal wear and tear.
Before requesting final acceptance of the HIPR pavement make corrections to failed areas of HIPR pavement by removing and replacing with HMA (Type A).
The Department withholds from payments an amount equal to 25 percent of the estimated value of the HIPR Remix performed during each progress payment period. The Department includes payment of the withhold on the next progress payment after the Engineer gives you final acceptance.
MEASUREMENT AND PAYMENT
Measurement The contract item for HIPR Remix is measured as the in-place recycled area in square
yards. Payment
The contract price paid per square yard for HIPR Remix as designated in the Engineer's Estimate includes full compensation for furnishing all labor, materials, tools, equipment, and incidentals for doing all the work involved in constructing HIPR Remix, complete in place, as shown on the plans, as specified in these specifications and the special provisions, and as directed by the Engineer.
Full compensation for performing and submitting mix designs and for JITT, inspection, sampling, testing, testing facilities, and preparation and submittal of results, constructing test strips, and remove and replace HIPR as corrective actions required for final acceptance or by the Engineer, is included in the contract price paid per square yard for hot-in-place recycling as designated in the Engineer's Estimate and no additional compensation will be allowed therefor.
