Critical Review of ADOT's
Hot Mix Asphalt Specifications
Final Report 630
Prepared by:
Dale S. Decker, LLC
P.O. Box 369
Eagle, Colorado 81631
December 2008
Prepared for:
Arizona Department of Transportation
in cooperation with
U.S. Department of Transportation
Federal Highway Administration
The contents of this report reflect the views of the authors who are
responsible for the facts and the accuracy of the data presented
herein. The contents do not necessarily reflect the official views or
policies of the Arizona Department of Transportation or the Federal
Highway Administration. This report does not constitute a standard,
specification, or regulation. Trade or manufacturers' names which may
appear herein are cited only because they are considered essential to
the objectives of the report. The U.S. Government and the State of
Arizona do not endorse products or manufacturers.
Technical Report Documentation Page
1. Report No.
FHWA-AZ-08-630
2. Government Accession No.
3. Recipient's Catalog No.
4. Title and Subtitle
CRITICAL REVIEW OF ADOT’S HOT MIX ASPHALT
SPECIFICATIONS
5. Report Date
December 2008
6. Performing Organization Code
7. Author
Dale S. Decker, P.E.
8. Performing Organization Report No.
9. Performing Organization Name and Address
Dale S. Decker, LLC
P.O. Box 369
Eagle, Colorado 81631
10. Work Unit No.
11. Contract or Grant No.
SPR 630
12. Sponsoring Agency Name and Address
ARIZONA DEPARTMENT OF TRANSPORTATION
206 S. 17TH AVENUE
PHOENIX, ARIZONA 85007
13.Type of Report & Period Covered
Project Manager: Christ G. Dimitroplos
14. Sponsoring Agency Code
15. Supplementary Notes
Prepared in cooperation with the U.S. Department of Transportation, Federal Highway
Administration
16. Abstract
The Arizona Department of Transportation (ADOT) has developed specifications and procedures to
ensure the quality of the hot mix asphalt materials purchased by the Department. The document
recording these specifications and procedures is the Standard Specifications for Road and Bridge
Construction. The 2008 Standard Specifications is the reference used throughout this document.
Specifications, however, are constantly changing as technology advances, materials change, and mix
design criteria change. The objectives of this project are to: review the state-of-the-industry in Arizona
with a focus on equipment and technologies currently being used; review ADOT’s construction
operations conformance history reports to identify probable causes of non-conformance; perform a
critical review of the asphaltic concrete sections of the current standard specifications; recommend
asphaltic concrete specification changes; and prepare a report of the activities.
These objectives were met by holding a series of workshops in Arizona with both ADOT and
contractor personnel participating. The workshops gave participants an opportunity to discuss issues and
concerns with details of the existing specifications. Based on this input, a critical review of the existing
specifications was prepared and recommendations for revising the specifications to national state-of-the-practice
were made. In addition, recommendations were made for revisions to ADOT’s construction
operations conformance history reporting system.
17. Key Words
hot mix asphalt specifications, asphaltic
concrete specifications, construction
conformance
18. Distribution Statement
Document is available to the
U.S. public through the
National Technical Information
Service, Springfield, Virginia
22161
23. Registrant's Seal
19. Security Classification
Unclassified
20. Security Classification
Unclassified
21. No. of Pages
35
22. Price
SI* (MODERN METRIC) CONVERSION FACTORS
APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FROM SI UNITS
Symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find Symbol
LENGTH LENGTH
in inches 25.4 millimeters mm mm millimeters 0.039 inches in
ft feet 0.305 meters m m meters 3.28 feet ft
yd yards 0.914 meters m m meters 1.09 yards yd
mi miles 1.61 kilometers km km kilometers 0.621 miles mi
AREA AREA
in2 square inches 645.2 square millimeters mm2 mm2 Square millimeters 0.0016 square inches in2
ft2 square feet 0.093 square meters m2 m2 Square meters 10.764 square feet ft2
yd2 square yards 0.836 square meters m2 m2 Square meters 1.195 square yards yd2
ac acres 0.405 hectares ha ha hectares 2.47 acres ac
mi2 square miles 2.59 square kilometers km2 km2 Square kilometers 0.386 square miles mi2
VOLUME VOLUME
fl oz fluid ounces 29.57 milliliters mL mL milliliters 0.034 fluid ounces fl oz
gal gallons 3.785 liters L L liters 0.264 gallons gal
ft3 cubic feet 0.028 cubic meters m3 m3 Cubic meters 35.315 cubic feet ft3
yd3 cubic yards 0.765 cubic meters m3 m3 Cubic meters 1.308 cubic yards yd3
NOTE: Volumes greater than 1000L shall be shown in m3.
MASS MASS
oz ounces 28.35 grams g g grams 0.035 ounces oz
lb pounds 0.454 kilograms kg kg kilograms 2.205 pounds lb
T short tons (2000lb) 0.907 megagrams
(or “metric ton”)
mg
(or “t”)
mg megagrams
(or “metric ton”)
1.102 short tons (2000lb) T
TEMPERATURE (exact) TEMPERATURE (exact)
ºF Fahrenheit
temperature
5(F-32)/9
or (F-32)/1.8
Celsius temperature ºC ºC Celsius temperature 1.8C + 32 Fahrenheit
temperature
ºF
ILLUMINATION ILLUMINATION
fc foot candles 10.76 lux lx lx lux 0.0929 foot-candles fc
fl foot-Lamberts 3.426 candela/m2 cd/m2 cd/m2 candela/m2 0.2919 foot-Lamberts fl
FORCE AND PRESSURE OR STRESS FORCE AND PRESSURE OR STRESS
lbf poundforce 4.45 newtons N N newtons 0.225 poundforce lbf
lbf/in2 poundforce per
square inch
6.89 kilopascals kPa kPa kilopascals 0.145 poundforce per
square inch
lbf/in2
SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380
TABLE OF CONTENTS
Executive Summary .................................................................................................1
I. Introduction .....................................................................................................3
II. Commentary on Conformance Reports...........................................................5
III. Commentary on Section 403 – Asphaltic Concrete Hot Plant Requirements.9
IV. Commentary on Section XXDG – Dense Graded Asphaltic Concrete.........12
V. Commentary on Section XXGG – Gap Graded Asphaltic Concrete ............20
VI. Commentary on Section XXACFC – Asphaltic Concrete Friction Course ..24
VII. Commentary on Section XXMISC ��� Miscellaneous Paving ........................28
VIII. Proposal for Section XXMAT – Materials for Asphaltic Concrete ..............30
IX. Proposal for Section XXWMA – Warm Mix Asphalt .................................30
X. Future Work ..................................................................................................30
XI. Concluding Remarks .....................................................................................30
References..............................................................................................................31
Acknowledgements
This project was guided by a technical advisory committee (TAC). The TAC provided
valuable insight for the project. A listing of the TAC members is presented below:
Project ID: SPR 630
Project Name: A Critical Review of Hot Mix Asphalt Specifications
Sponsor—Champion—Technical Advisory Committee members
NAME ORGANIZATION
Sponsor: Julie Kliewer
ADOT Phoenix Construction
Champion:
Amanda McGennis
Associated General Contractors of
America – Arizona Chapter
TECHNICAL ADVISORY COMMITTEE
NAME ORGANIZATION
Jim Delton ADOT Materials Group
Paul Burch ADOT Materials Group
Scott Weinland ADOT Materials Group
Chad Auker ADOT Regional Materials
Julie Gadsby ADOT Phoenix Construction
Bill Humphrey ADOT Phoenix Construction
James Carusone Salt River Materials Group
Bob McGennis Holly Asphalt Co.
Jon Epps Granite Construction
Adrian Green Vulcan Materials
Brian Gallimore Markham Contracting
Tom Kennedy FNF Construction
Thomas Deitering FHWA
Sharon Gordon FHWA
1
EXECUTIVE SUMMARY
The Arizona Department of Transportation (ADOT) has developed specifications and
procedures to ensure the quality of the hot mix asphalt materials that it purchases. The
document recording these specifications and procedures is Standard Specifications for
Road and Bridge Construction. Specifications, however, are constantly changing as
technology advances, as materials change and as changes in mix design criteria are
accepted. The objectives of this project are to:
• Review the state of the industry in Arizona, with a focus on equipment and
technologies currently being used;
• Review ADOT’s construction operations conformance history reports to identify
probable causes of non-conformance;
• Perform a critical review of ADOT Standard Specification Sections 403, 406, 407,
409, 411, 413, 414, 415, 416, and 417;
• Recommend asphaltic concrete specification changes; and
• Prepare a report of the activities.
The project began with the formation of a Technical Advisory Committee (TAC). The
TAC elected to develop a series of one-day workshops at various locations in Arizona to
solicit feedback from key stakeholders who are using the ADOT Specifications. To
obtain unbiased comments, the workshops were held with two different audiences — one
for agency personnel and another for contractor personnel. The workshops were held in
Tucson, Phoenix, and Flagstaff during October 2007, with an open invitation to each of
the stakeholder groups. Dale Decker served as facilitator for the workshops, with Rita
Leahy and Amanda McGennis serving as recorders.
This report provides the Principal Investigator’s (PI) recommendations based on review
of the workshop comments, input from the TAC and personal experience.
At the workshops, Section 403 was reviewed in detail and Section 416 was used as a
template for a detailed review of the remaining sections. Most of the comments on 416
also were applicable to other asphaltic concrete sections. Key questions asked of each
participant were:
• Is the specification fair?
• Is the specification reasonable?
• Is the specification enforceable?
The key objective of the workshops was to challenge the participants regarding the total
number of specifications in use by ADOT for asphaltic concrete. The current ADOT
specifications have nine unique specification sections, plus other online stored
specifications for asphaltic concrete. The workshop team recorded key comments and
issues made at the workshops for subsequent evaluation.
The workshops provided significant guidance on issues in the specifications that both
ADOT and the contractors believed were important and needed to be addressed. Based on
the input received and detailed review of the specifications, a commentary on the
2
specifications was prepared. The commentary is provided in bullet form for ease of
reference. The bullets address a specific recommendation on a section/paragraph of the
existing standard specification. Each bullet is therefore an individual recommendation on
the particular specification.
Key recommendations that resulted from the specification review are:
• The number of asphaltic concrete specification sections should be reduced from
nine to four as follows:
o Dense Graded Asphaltic Concrete
o Gap Graded Asphaltic Concrete
o Asphaltic Concrete Friction Course
o Miscellaneous Asphaltic Concrete Paving
• A statewide asphaltic concrete plant certification program should be developed
based on either the Arizona Rock Products Association (ARPA) or National
Asphalt Pavement Association (NAPA) models.
• A stand-alone asphaltic concrete materials section should be developed rather
than having a materials section in each of the asphaltic concrete specification
sections.
• The specifications should be updated to national asphaltic concrete industry state-of-
the-practice.
• The revised specifications should include a section for Warm Mix Asphalt.
A review of the ADOT construction operations conformance reporting (CR) system was
conducted. The CR process reportedly includes a site review by experienced and
knowledgeable engineers and senior technicians who specialize in the products they are
inspecting. One of the products of the site review is a conformance history report. A
conformance questionnaire was created by a team of specialists consisting of designers,
engineers, inspectors, contractors, suppliers, and manufacturers who have extensive
knowledge of the products’ requirements.
Some key issues that were identified from the review of the conformance reports are:
• The conformance report concept is valid but the process needs to be updated
and streamlined.
• This process should be renamed construction process audit.
• Product attribute reports that are generated by the inspectors need to be
revised to be useful for quality improvement.
• The inspection check list of questions needs to be revised to remove
subjectivity from the process.
• Plant and field operations should be separated in the questionnaire.
• Feedback to the contractor from the audit should be provided.
Based on this project, the next step is to use the commentary recommendations to make
the appropriate and approved changes to the ADOT Standard Specifications. This
revision process should be a collaborative effort between ADOT personnel and
Association of General Contractors (AGC) members.
3
I. INTRODUCTION
ADOT has developed specifications and procedures to ensure the quality of the
hot mix asphalt materials purchased by the department. The document recording
these specifications and procedures is the Standard Specifications for Road and
Bridge Construction. Specifications, however, are constantly changing as
technology advances, materials change, and mix design criteria change. The
objectives of this project are to:
• Review the state of the industry in Arizona with a focus on equipment
and technologies currently being used;
• Review ADOT’s construction operations conformance history reports
to identify probable causes of nonconformance;
• Perform a critical review of Sections 403, 406, 407, 409, 411, 413,
414, 415, 416, and 417 of the current standard specifications;
• Recommend asphaltic concrete specification changes; and
• Prepare a report of the activities.
The review for this project will utilize the 2008 Edition of the Standard
Specifications. The project began with the formation of a TAC. The TAC initially
met 19 July 2007. The TAC elected to develop a series of one-day workshops at
various locations in Arizona to solicit feedback from key stakeholders who are
using the ADOT Specifications. In order to obtain unbiased comments, the
workshops were held with two different audiences — one was for agency
personnel and another for contractor personnel. The workshops were held in
Tucson, Phoenix, and Flagstaff during October 2007, with an open invitation to
each of the stakeholder groups. Dale Decker served as facilitator for the
workshops, with Rita Leahy and Amanda McGennis serving as recorders.
At the workshops, Section 403 was reviewed in detail and Section 416 was used
as a template for reviewing the remaining sections. Most of the comments on 416
also were applicable to other asphaltic concrete sections. Key questions asked of
each participant were:
• Is the specification fair?
• Is the specification reasonable?
• Is the specification enforceable?
A key issue raised at the workshops was to challenge the participants regarding
the total number of specifications in use by ADOT for asphaltic concrete. The
current ADOT specifications have nine unique specification sections plus other
online stored specifications for asphaltic concrete.
The workshop team recorded key comments and issues for subsequent evaluation.
Issues raised on mix design and pay factors at the workshops were recorded,
although the issues were generally outside the scope of the project.
4
This report provides recommendations based on review of the workshop
comments, input from the TAC, and personal experience of the PI. This report is
divided into the following commentary sections:
• Commentary on Conformance Reports;
• Commentary on Section 403 on Hot Plant Requirements;
• Commentary on Section on Dense Graded Asphaltic Concrete;
• Commentary on Section on Gap Graded Asphaltic Concrete;
• Commentary on Section on Asphaltic Concrete Friction Course;
• Commentary on Section on Miscellaneous Paving;
• Proposal for Section on Materials for Asphaltic Concrete;
• Proposal for Section on Warm Mix Asphalt;
• Description of Future Work; and
• Concluding Remarks.
The commentary is provided in bullet form for ease of reference. The bullets
address a recommendation on a specific section/paragraph of the existing standard
specification. Each bullet is an individual recommendation.
5
II. COMMENTARY ON CONFORMANCE REPORTS
The current specification referenced throughout this report is the Arizona Department of
Transportation Standard Specifications for Road and Bridge Construction (2008).
Conformance Reports
ADOT’s Construction Operations Group operates a project review process. This process
reportedly includes a site review by experienced and knowledgeable engineers and senior
technicians who specialize in the products they are inspecting. It was reported that the
conformance questionnaire was created by a team of specialists consisting of designers,
engineers, inspectors, contractors, suppliers, and manufacturers who have extensive
knowledge of the products’ requirements. ADOT currently has five independent
reviewers who perform these inspections. The independent reviewers are expected to
perform a minimum of one review per organizational unit (ORG) statewide, including
consultants. This process would typically be considered a construction audit.
Apparently the field offices are free to share the conformance reports with the contractor.
However, at the TAC meeting, contractor representatives were not aware the
conformance reports existed. The conformance reports should be shared with the
contractor so that areas needing improvement could be addressed.
During the site visit, the inspector completes a product attribute report. Since the report is
an audit process, either the condition under review is satisfied or it is not. Close enough is
not an acceptable response for an audit. Product attribute reports (PAR) are completed for
the following topics: Asphaltic Concrete Friction Course (A-R); Asphaltic Concrete –
End Product; Asphalt Drum Plant; Asphaltic Concrete (406); Asphaltic Concrete (EP)
SHRP; Asphalt Rubber Blending and Hot Mix Plant; and Bituminous Tack Coat. The
questions in the report vary from safety issues about access steps at the plant to
cleanliness of the pavement prior to paving to the number of roller passes.
One of the products of the site review is a conformance history report. This report
provides an overview of the conformance to ADOT specifications for specific issues.
Task 2 of this project required a review and commentary on the conformance history
reports. This section of the report addresses that issue. The following comments are
presented for consideration:
• The concept for an independent assurance review of construction operations is
excellent. The objective is to improve the quality of pavement construction
throughout Arizona. The process has been in place for several years within
ADOT. As with any review system, each year improvements are made to obtain
better information from the review process.
• The conformance reports (CR) reviewed for this effort were from 1 January 2005
to 22 October 2007. These were provided by Guillermo Silva of ADOT.
6
• The documents reviewed were the PAR and the conformance report by product.
The PAR���s are a list of questions that are completed by the inspector.
• The weighting for the specific question in the PAR should be reviewed. As an
example in the asphalt rubber blending and hot mix plant PAR, the first question
is regarding adequate and safe stairways for material sampling. While this is
important, it is given a weight of 8, while later in the report the weighting for
proper bin loading is a 2. For a PAR, the weighting should be more heavily
focused on what it takes to get a good product. This observation leads to the
conclusion that separate conformance reports should be prepared for safety and
product quality.
• There are many not applicable (N/A) responses in the CR’s. These responses
confound the review and could skew the analysis of the information. If the
response to the question is N/A, it is likely that the wrong question is being asked
for the specific project. For example, in the asphalt drum plant PAR, one of the
questions is “Are the platform truck scales certified?” Eight responses were N/A.
If an asphalt drum plant is being inspected, the scales should be calibrated or the
plant should not be operating. Another example is “Are the trucks equipped with
tarps or covers?” In both of these examples, N/A seems to be an inappropriate
response. Another example is in the Asphalt Rubber-Asphalt Concrete Friction
Course (A-R), the second question is regarding the cleanliness of the trench.
There were two “Yes” responses, zero “No” responses, and 18 “N/A” responses,
giving a 100 percent conformance (percent conformance is the percentage “Yes”
divided by the total of “Yes” and “No”). There are dozens of such examples. For
an independent assurance (IA) audit, it is recommended that the questions be
revised to accommodate either a yes or no response. Separating field and plant
issues in the PAR may help resolve this issue as well.
• Many questions require the inspector to subjectively evaluate the contractor’s
operations. As an example, in the asphalt drum plant PAR, one of the questions is
“Are the stockpiles managed effectively to prevent contamination and
segregation?” This type of question should be revised to ensure a consistent
response by the inspector. More specific questions might be: Are the stockpiles
separated either by space or by bulkheads? — Is the loader operator retrieving
material from the stockpile in a manner to avoid segregation? — Are the
stockpiles managed to ensure uniformity of moisture content of the aggregate
delivered to the plant?
• Some questions are extremely difficult to answer for the inspector. For example,
in the ACFC (A-R) PAR, one of the questions is “Follow up compactor is
operating as close as possible behind the breakdown rollers?” The determination
of the position of the roller is dependent on many mix and environmental factors.
How does the inspector determine “as close as possible” to evaluate the
contractor?
7
• Some of the PAR’s have a category of “other” with responses of either “No�� or
“N/A”. It is appropriate for the inspector to have a comment section, but a
category of “other” does not appear to be of much value in an IA audit.
• There are a disturbing number of items that have very low conformance
percentages. This situation could be indicative of poor performance on the part of
the field personnel or inappropriate questions being asked by the inspector, or
both. An abbreviated list of low-conformance items includes:
o An approved mix design was not available. This could indicate that the
technician simply did not have it in his/her possession, but it could also
mean that there was not an approved mix design for the job. A copy of the
approved mix design must be on the site as a part of the audit process.
o Tarps not being used for hauling. Best practice includes the use of tarps on
the trucks. However, ADOT does not currently require the use of tarps.
This CR requirement is therefore misleading.
o Proper loading of the haul trucks. New verbiage in Section 403 addresses
this issue.
o Approved release agents not being used. For AR, it was as low as 17
percent conformance.
o Poor stockpile management is a pervasive issue. Specific questions should
be devised to evaluate stockpile management.
o Lack of certificates of compliance/analysis for mineral admixture, asphalt
binder, or tack coat. It is possible that the certificate exists, but the
inspector simply did not have a copy.
o Documentation of rolling pattern and number of coverages. These are
items that the inspector should document.
• The PAR questions include both plant and field operations in the same report.
Field and plant operations should be separated to ensure consistency of the audit.
• It is interesting to note that the two CR’s with the highest percentage conformance
are for AC (SHRP) and AC (End Product) with 73.4 and 74.7 percent
respectively. A possible explanation is that the SHRP product is not used
extensively throughout the state (estimated at 25 percent overall). As a result, the
contractor may be placing greater attention to detail on the SHRP and End
Product applications, as both specifications put greater responsibility on the
contractor.
Based on review of the CR’s, the following recommendations are made:
• This audit process could provide significant input to ADOT on how to improve
both the construction process and the standard specifications. However, the
system needs to be revamped. The revamping should include both how the audit
is performed and how the results are used to improve construction processes in
Arizona. This revision effort should be a cooperative activity between ADOT and
AGC members.
8
• A thorough review of the questions used by the inspectors needs to be conducted
by a team of ADOT and contractor personnel. Particularly, the questions need to
be focused for a “Yes” or “No” response. “N/A” is not helpful in determining
issues that need to be addressed. Including a “Comments” section is an excellent
way to record additional information.
• Inspector questions need to be written so that there is as little room for
subjectivity as possible. An independent assurance audit must be a black and
white issue — either the condition under review exists or it does not.
• Because of the vast range of topics, it is recommended to change the title of the
CR to Construction Process Audit.
• Field and plant operations should be separated to ensure consistency of the audit
and a completely separate audit should be conducted for safety issues.
• Questions should be focused on getting as consistent a response as possible,
regardless of the inspector on the site.
• Feedback from the CR should be provided promptly to the ADOT personnel on
the project and the contractor.
9
III. COMMENTARY ON SECTION 403 –
ASPHALTIC CONCRETE HOT PLANT REQUIREMENTS
Asphaltic concrete hot plant requirements have previously been moved from individual
asphaltic concrete specification sections into this stand-alone section. The following
comments address recommended changes to the existing specification:
• Verifying that the plant has the capability of producing a quality product is
critical. Historically verification has been done by ADOT. Given the budget and
personnel requirements for plant inspection, the responsibility for maintaining
proper plant production is being placed on the mix producer.
Arizona Rock Products Association (ARPA) recognized this issue many years ago
and instituted the ARPA certification of hot mix asphalt production facilities plan.
The company applying for the certification must be a member of ARPA. The
certification inspection must be performed by a professional engineer. The ARPA
program needs to be updated to reflect current plant production technology.
The National Asphalt Pavement Association (NAPA) has developed a plant
quality commendation program. The NAPA program is a self-assessment by the
mix producer but does require endorsements from product users. The NAPA
program has a broad scope of inspection items. Given the move within the
asphaltic concrete industry for increased emphasis on end-product performance,
inclusion of the NAPA program in an ADOT specification would be viable. The
producer does not need to be a member of NAPA to participate in the program.
The ARPA and NAPA programs are examples of different approaches to
achieving the same goal. Both the ARPA and NAPA programs offer a mechanism
to review plant production to ensure that quality products can be produced. The
ARPA program has an advantage that the review/inspection is performed by a PE
in the area in which the plant operates. The disadvantages of the ARPA program
are that the plan needs to be updated to reflect current technology with improved
detail to the inspection and that the producer must be a member of ARPA. The
NAPA program is in its infancy, although it is modeled after the very successful
Diamond Achievement program that NAPA has had in place for many years.
It is noted that both programs provide only a snapshot of production operations.
The mix producer must be committed to quality production and to keeping the
plant operating at a level to achieve quality mix. Coupled with the CR’s
previously discussed, both ADOT and the mix producer will have some assurance
that the plant can produce a product meeting specified requirements.
It is recommended that a certification program be required for all asphaltic
concrete producers on ADOT projects. The program should enable ADOT to use
a local supplier in a rural area for a small quantity of mix, but for larger jobs, the
mix producer would have to meet the production certification requirements.
Modifying the ARPA program and using a local PE to perform the inspections
10
would provide a local appeal to the process. Some provision should be made for
producers who are not ARPA members.
Although the certification requirement is not in the true spirit of a performance
specification, it does provide a minimum assurance that the plant used for ADOT
projects has the capability of producing quality mix. ADOT needs to review the
project size and/or tonnage limit for the asphaltic concrete supplier to be required
to have certification.
• A mass flow meter should be required on all continuous asphaltic concrete plants.
This recommendation came from both the workshops and the TAC.
• The current specification requires the addition of lime or cement into the asphaltic
concrete to enhance stripping resistance. In the laboratory, it has been shown that
the addition of lime and/or cement dramatically improves stripping resistance. It
is, however, difficult to confirm the addition of lime or cement into the mix at the
plant.
The Federal Highway Administration (FHWA) has developed an infrared
procedure to detect the presence of lime. It is described by FHWA as “an
extremely rapid method, yielding qualitative or semi-quantitative results" that
requires little preparation of the sample (Arnold et al. 2005). This procedure was
reviewed as part of this project. The test developed has a high degree of
repeatability. However, the test must be done in an analytical chemistry
laboratory and is therefore not applicable to a construction materials field
laboratory. There is no experience with using this procedure as a process control
tool. The FHWA procedure is not recommended at this time for process control.
Since there is not a procedure that has been rigorously evaluated, it is
recommended that current practices continue to determine the presence of lime.
• The current specification requires “The moisture content of the combined mineral
aggregate shall be a minimum of three percent by weight of the aggregate during
the mixing process.” The purpose of the moisture in the mineral aggregate is to
activate the reaction for the lime to bond to the aggregate, thereby minimizing the
mineral admixture that becomes airborne during production. There is no current
method to verify that moisture addition satisfies the specification requirement of
three percent.
Since there is not an accepted procedure, it is recommended that current practices
continue to determine the percentage of moisture added.
• The current specification requires the mix producer to “provide daily
documentation of the proportion of each individual component incorporated into
the mix.” The specification should be clarified to indicate that the report is for one
shift of production. In addition, the specification requires “a copy of the
pyrometer reading shall be provided to the Engineer daily.” Participants in the
11
workshops indicated frustration at the timeliness of delivery for these reports that
are required by the standard specifications. Delay of the reports slows down the
required approval process.
Based on these comments and discussion in the TAC, it is recommended that a
penalty be assessed to the mix producer if reports are not submitted to ADOT as
required. Failure of the contractor to submit the reports within the specified time
frame would result in a penalty as described in Subsection 3.2 of ADOT Bidding
Schedule Item 9240170 – Contractor Quality Control.
• A new paragraph should be added to Section 403 on the issue of hauling units for
asphaltic concrete. Example verbiage is as follows:
o The asphaltic concrete shall be transported to the work site in hauling units
previously cleaned of all foreign material. The contents of each load shall
be completely covered with suitable material of sufficient size to protect it
from the weather and contamination. Each unit shall have convenient
access from ground level to insert a thermometer for the inspector to
determine mix temperature.
o The inside surface of all hauling units shall be treated with an approved
release agent that will not contaminate or alter the characteristics of the
asphaltic concrete. Petroleum derivatives such as fuel oil or diesel shall
not be permitted.
o Asphaltic concrete shall be loaded into the hauling unit in a manner that
ensures segregation will be minimized. Asphaltic concrete industry best
practice recommends using a three-drop loading for end dump trucks and
a five-drop system for belly dumps, with the truck changing position
between drops to ensure uniform product delivery into the truck (TRB
2000, 100-102).
• Add a new paragraph on calibration:
o “Measuring devices on the asphaltic concrete plant shall be calibrated after
any extended shut down, when the plant is relocated and at least once each
year thereafter. All measuring devices, meters, dispensers, test weights,
and other measuring devices shall be inspected, tested, and certified to be
in proper operating condition by competent testing agencies approved by
the Engineer. Certificates of inspection shall be posted in a prominent
place in the plant and a copy shall be promptly submitted to the Engineer.”
o NOTE: This could be incorporated into the plant certification program.
• The ADOT Construction Operations conformance report system could be used as
an audit for the plant certification process.
• One consistent message heard at all the workshops was to ensure consistency in
specification enforcement. Both non-enforcement and inconsistent enforcement
are equally contrary to the objectives of a well-written specification.
12
IV. COMMENTARY ON SECTION XXDG –
DENSE GRADED ASPHALTIC CONCRETE
A new Section XXDG of the specifications should be developed as a combination of old
sections 406, 416 and 417. The new section will be focused on all dense graded mixes.
The following bullets identify the changes recommended:
• Paragraphs 406-1, 416-1 and 417-1 are identical except for the last sentence of
417-1. It is recommended that 417-1 wording be maintained for Section XXDG
on Dense Graded Asphaltic Concrete.
o “The type of asphaltic concrete mix shall be specified in the Special
Provisions” is the sentence in Section 417 that is not in the others.
• The only difference between Section 406-2 and 416-2 is that the latter includes a
1/2” mix size. The table from Section 416-2 should be used in the Section XXDG
on Dense Graded Asphaltic Concrete except that the columns “Without
Admixture” should be deleted as ADOT requires mineral admixture in all mixes.
This table should be labeled Asphaltic Concrete Mix Design Criteria - Marshall.
• Table 417-1 presents mix design criteria for the Superpave (SHRP) mix design
method. This table should remain in the Section XXDG with an adjustment to the
title. The new title of the table should be Asphaltic Concrete Mix Design – SHRP.
If SHRP is fully implemented in Arizona in the future, the Marshall table can be
omitted from the specifications.
• A requirement for dust to bitumen ratio is currently included in the project Special
Provisions. It is recommended that ADOT review this approach to determine if it
would be more appropriate to have the dust to bitumen ratio requirements in the
standard specifications rather than the special provisions.
• Table 417-2 should remain in the new section and be titled Mix Design Grading
Limits for SHRP Mixes. The two columns for mix “Without Admixture” should
be deleted since ADOT requires mineral admixture in all mixes.
• The Materials Sections of all three specifications should be removed and placed in
a stand-alone section. For the most part, the information presented in all
Materials Sections is the same. Minor modifications will be necessary to
accommodate Marshall vs. SHRP mix design procedures.
It is noted that the TAC recommended that the materials requirements remain a
part of each individual specification. The PI does not agree with this
recommendation for the following reasons. With all the material requirements in
the same specification section, easy reference is provided to the user. The
producer will be able to more easily identify adjustments that may be made in
production from one product to another. Many DOT standard specifications have
materials as a separate section in order to reduce repetition in the individual
13
specifications. This concept was used by ADOT to create a new Section 403 on
Plant Requirements and has worked well. ADOT has also used this approach for
bituminous materials.
• The TAC recommended that the Mix Design section for each product remain with
the individual specification section due to the diversity of mix types and specific
mix design requirements for the different types of mixes.
• All references to the materials paragraphs will need to be changed to XXMAT
references.
• The Mix Design Criteria Tables for Sections 406, 416, and 417, Subsections 2
have specification requirements for absorbed asphalt. The Mineral Aggregate
Tables for Sections 406, 416, and 417, Subsections 3 have specification
requirements for combined water absorption. These requirements are intended to
limit the use of highly absorptive aggregates in asphaltic concrete. The
specification requirements for both water and asphalt absorption are redundant. It
is recommended that historical material test results for both properties be
reviewed in detail to determine if one of the specification requirements could be
omitted. If both tests always eliminate potentially problematic aggregates, it is not
necessary to have both specification requirements. The water absorption test is
much easier to perform in the laboratory.
• The text from Section 406-3.01 for mineral aggregate should be used for Section
XXMAT on asphaltic concrete materials. Sections 416-3.01 and 417-3.01 contain
additional verbiage, but Section 406-3.01 contains the essential items to ensure
that the aggregate is of adequate quality.
o It is highlighted that Section 406 requires 85/92 percent (two/one fractured
faces). The 45 percent uncompacted void content is recommended for all
mixes.
• Aggregate processing may occur many months or years in advance of mix
production. It is therefore necessary to have testing performed on the individual
aggregate products during the crushing operation as required in Section 1001-
4.02. For mixture evaluation, aggregate tests are performed on the combined
gradation.
• The mineral aggregate specification should be rewritten to universally permit
reclaimed asphalt pavement (RAP) in all mixes. As a first step, 15-20 percent
RAP could be used as a specification requirement. Higher percentages of RAP
could be allowed as experience is gained with the introduction, with the caveat
that the volumetric properties of the mix must be met. Ownership of the millings
should go to the contractor to ensure that RAP is used in the most cost effective
manner.
o Inclusion of RAP can be accomplished by rewording Paragraphs 2 and 3
of 406-3.01 as follows:
14
“Coarse Mineral aggregate shall consist of crushed gravel, crushed
rock, reclaimed asphalt pavement (RAP), or other approved inert
material…”
“Fine mineral aggregate shall be obtained from crushed gravel,
crushed rock or reclaimed asphalt pavement (RAP)…”
o Because ADOT pays for asphalt cement as a separate item, it will be
necessary to develop a fair and reasonable approach to account for the
asphalt cement in the RAP product. Both the contractor and the agency
should realize benefits if the RAP addition is to be successful. It is
recommended that ADOT and AGC work cooperatively to develop a
process to be used. It is noted that the FHWA Expert Task Group on RAP
is addressing this issue and is planning to develop a recommendation.
• The text in Paragraph 406-3.02, 416-3.02, and 417-3.02 on mineral admixture
should be moved to Section XXMAT on Materials with the following change:
o It was noted at the workshops that a discrepancy exists in the payment of
the mineral admixture specification. Paragraph 416-3.02 requires 1 percent
mineral admixture but allows up to 2 percent if necessary to meet moisture
susceptibility requirements. However, it was reported by some workshop
participants that the contractor is paid for 1 percent, regardless of the
amount used. In Paragraph 416-8, the statement is made that “Mineral
admixture will be measured by the ton for the mineral admixture actually
used in accordance with Subsection 416-6” (it is noted that this reference
should be to 403-3.02). These requirements are in conflict with each other.
It is recommended that this be reworded to pay the contractor for the
mineral admixture necessary to achieve the moisture susceptibility
requirements of the mix design. It was verified to the PI by ADOT
personnel that the policy is that the contractor is paid for the amount of
mineral admixture used provided the mix design demonstrates a required
amount. This minimizes the possibility that the contractor might use
excess mineral admixture to achieve volumetric properties of the mixture.
The following verbiage is suggested:
“Mineral admixture will be required. The amount used shall be
determined by laboratory testing to demonstrate the quantity of
mineral admixture required in order to meet the mix design criteria
for Wet Strength and Index of Retained Strength. A maximum of
2.0 percent admixture will be permitted. The exact amount of
admixture required shall be specified in the mix design.”
The remainder of this subparagraph can be used as written in the
current specification.
• Paragraphs 406-3.03, 416-3.03, and 417-3.03 – Bituminous Material – should be
moved to Section XXMAT on Asphaltic Concrete Materials. The text in all of
these sections is the same.
15
• Paragraph 406-4, 416-4, and 417-4 on Mix Design should all be moved to Section
XXMAT on Asphaltic Concrete Materials. The text in all of these sections is the
same.
• It was noted in the workshops that all mix requirements may not be noted both in
the Special Provisions and on the plans. In order for the mix designer to know all
the requirements, all special requirements for the mix should be on both the
Special Provisions and the Plans. Coordination with other groups within ADOT
should be done to ensure this occurs.
• Sections 406-5, 416-5, and 417-5 have the same text for Contractor Quality
Control. This text should be used in Section XXDG on Dense Graded Asphaltic
Concrete.
• Sections 406-6, 416-6, and 417-6 have the same text for Construction
Requirements. This text, with the recommended changes in the following bullets,
should be used in the Section XXDG on Dense Graded Asphaltic Concrete. It is
recommended that the new section be divided into subsections with possible titles
of Mixture Production, Mixture Placement, Joint Construction, and Sampling.
This arrangement would facilitate referencing specific subsections of the section.
• Concerns were expressed at the workshops about the rumble strip being on the
longitudinal joint. Section 416-6 of the current specification clearly states that
“any longitudinal joint (should be) approximately one foot away from the travel
lane side of the rumble strip.” There is no ambiguity in what is currently in the
specification. No change is recommended.
• Add a new sentence at the end of the first paragraph:
o “Hauling units for asphaltic concrete shall meet the requirements in
Section 403.”
• After the paragraph that begins “The temperature of asphaltic concrete…”, the
following paragraph should be added:
o “Asphaltic concrete delivered to the screed unit shall be a free flowing,
homogeneous mass in which there is no segregation, crusts, lumps or
migration of the bituminous material.”
• In the paragraph that begins “Before asphaltic concrete is placed…” the text from
current Section 415 should be added to the end of the paragraph as follows:
o “…cleaned of objectionable material” and tacked with asphalt cement in
accordance with the requirements of Section 404 of the specifications.
The cleaning of the surface, the tacking of the surface, and the amount
and grade of asphalt cement used shall be as directed by and
acceptable to the Engineer.
16
• The current specification contains the following statement: “Longitudinal joints of
each course shall be staggered a minimum of one foot with relation to the
longitudinal joint of any immediate underlying course.” This sentence should be
deleted and replaced with the following:
o “Both longitudinal and transverse joints in successive courses shall be
staggered so that one is not above the other. Transverse joints shall be
staggered by the length of the paver except where precluded by pavement
geometrics. Longitudinal joints shall be staggered a minimum of 12 in.”
• The current specification contains the following statement: “Joints shall be
formed by a slope shoe or hot-lapped and shall result in an even, uniform
surface.” This sentence should be deleted and replaced with the following
information:
o “Longitudinal joints shall be constructed to provide a continuous bond
between the joint surfaces. After placement and finishing of the new
asphaltic concrete, both sides of the joint shall be dense and the joint shall
be well sealed. Acceptable longitudinal joint construction procedures
include unconfined edge joints, a tapered joint with or without a notch, a
cutback joint or use of an edge compactor. Other methods may be
approved by the Engineer based on local experience.”
Additional information on joint construction may be found in
Quality Improvement Series 121 (Brock and Skinner 1997),
published by the National Asphalt Pavement Association.
• The current specification provides only one option for construction of a transverse
joint — a cutback joint. Discussions at the workshops indicate that the cutback
joint is rarely used. The paragraph “Before a surface course is placed…” should
be deleted and replaced with the following information:
“Transverse joints shall be constructed to provide a continuous
bond between the joint surfaces. After placement and finishing of
the new asphaltic concrete, both sides of the joint shall be dense
and the joint shall be well sealed. Acceptable transverse joint
construction procedures include a bulkhead butt joint, a feathered
joint, a papered joint or a cutback joint. Other methods may be
approved by the Engineer based on local experience. The surface
in the area of the joint shall conform to the requirements
hereinafter specified for surface tolerances when tested with the
straightedge placed across the joint. The contractor shall have a 10-
foot straight edge on site at all times during paving for this
purpose.”
Additional information on joint construction may be found in
Quality Improvement Series 121, published by the National
Asphalt Pavement Association.
17
• The current specification states: “A light coat of bituminous material shall be
applied as directed to edges or vertical surfaces against which asphaltic concrete
is to be placed.” This sentence should be replaced with the following:
“Tack coat shall be applied as directed by the Engineer to all edges
or vertical surfaces against which asphaltic concrete is to be
placed. Tack coat for edges and vertical surfaces is considered an
incidental item to the asphaltic concrete placement.��
• The current specification states “The moisture content of the asphaltic concrete
immediately behind the paver shall not exceed 0.5 percent.” Based on comments
from workshop participants, this requirement is rarely verified. The typical
specification for the asphaltic concrete industry throughout the country would
have the moisture content requirement at the plant. A 0.5 percent moisture content
at the paver would allow substantially more moisture at the plant, depending on
the haul time and type of mix.
• Paragraphs 406-7.01, 416-7.01, and 417-7.01 are all identical. The text can be
used as currently written for Section XXDG.
• Paragraphs 406-7.02, 416-7.02, and 417-7.02 are the same except for the
requirement of uncompacted void content in 416. The current 416 standard
requires the uncompacted void content only for Special Mix. Both 406 and 417
specify uncompacted void content for all mixes. It is recommended that
uncompacted void content be specified for all mixes and the text from 406-7.02 or
417-7.02 be used in Section XXDG.
• Paragraphs 416-7.03 and 417-7.03 contain the same text. This paragraph is blank
in 406. The material spread is a surrogate for yield of mix placed on the
pavement. This is an important measurement tool during construction. It is
recommended that this requirement be a part of Section XXDG with the following
modification. It is recommended that the bulk density value used for the
calculation be the running average of current production bulk density values
rather than a mix design value. By using a current bulk density value, the
calculation will be more accurate, fair, and reasonable.
• The text in Paragraphs 406-7.04, 416-7.04, and 417-7.04 is the same except for
the last two paragraphs and the table of Upper and Lower Limits. It is
recommended to use the existing text for Section XXDG except for the last two
paragraphs which should be revised to read:
o “The target values for gradation, asphalt cement content and effective
voids are given in the contractor’s mix design. The Upper Limits (UL) and
Lower Limits (LL) of acceptable production of each of the measured
characteristics for mixes designed using the Marshall mix design
procedure are as follows:”
Replicate the table from 406-7.04/416-7.04
18
o “The target values for gradation, asphalt cement content and effective
voids are given in the contractor’s mix design. The Upper Limits (UL) and
Lower Limits (LL) of acceptable production of each of the measured
characteristics for mixes designed using the SHRP mix design procedure
are as follows:”
Replicate table from 417-7.04
o “The Engineer will determine the PT of each measured characteristic in
accordance with Subsection XXX-X.XX and utilizing the appropriate
table, will determine pay factors for each measured characteristic.”
• The third paragraph of 416-7.04 should be revised to mandate the use of a
computerized mass flow meter. The specification should read as follows: “A
computerized mass flow meter shall be used to determine asphalt cement addition
to the mix. Documentation of its calibration…”
o It is noted that a calibration procedure should be developed.
• Paragraphs 406-7.05, 416-7.05, and 417-7.05 contain the same text. Part (A) of all
sections references courses 1-1/2 inches or less in nominal thickness. Part (A) is a
method specification that instructs the contractor what equipment to use and the
number of coverages to make with the roller. The TAC recommended maintaining
the <1-1/2” section of the specification. However, upon detailed review, it is
recommended that Part (A) be deleted in its entirety. Part (A) does not coordinate
with ADOT’s move to performance and/or end result specifications in many
elements of the construction process. Part (A) places all the risk for the mix on
ADOT because it is a method specification.
• Part (B) of the respective sections should be retained for Section XXDG with the
following additions/changes:
o The titles from (A) and (B) will be deleted. The paragraph heading should
be Compaction.
o Delete the second paragraph that begins “All edges shall be rolled with a
pneumatic tired compactor…” This requirement results in equipment
ranging from a garden roller to a dump truck on the edge of the pavement.
The improvement in density and/or sealing of the joint is questionable. In
addition, it is possible to damage the pavement edge in the process of this
angled rolling. Comments at the workshops indicate that the requirement
is not routinely performed or enforced.
• In the fourth paragraph of 416-7.05(B) (page 397), there is a discussion about
core sampling of the asphaltic concrete. Reference is made to the ADOT Testing
Manual, Arizona Test Method 104, Section 3. This test method should be revised
to provide specific detail regarding the cutting and handling of the cores.
• Paragraph 406-7.06, 416-7.06, and 417-7.06 contain the same text. The text can
be used as currently written for Section XXDG.
19
• Paragraphs 406-8, 416-8, and 417-8 contain the same text. The text can be used as
currently written for Section XXDG.
• Paragraphs 406-9, 416-9, and 417-9 contain the same text except for
subparagraph (A). 406 does not include the Spread Lot Pay Factor requirements.
If on a specific project ADOT chooses to not use the Spread Lot Pay Factor, it can
be eliminated in the Special Provisions rather than maintaining a completely
separate specification to address a relatively uncommon occurrence. It is
recommended that the text from either 416 or 417 be used in Section XXDG. It is
noted that this project was not focused on pay factors, so this paragraph was not
reviewed in technical detail.
20
V. COMMENTARY ON SECTION XXGG –
GAP GRADED ASPHALTIC CONCRETE
This new section is a combination of old Sections 413 and 415. Reportedly Section 413 is
no longer being specified. The new Section will be XXGG – Gap Graded Asphaltic
Concrete.
• The TAC recommended using the term “Gap Graded” although Sections 413 and
415 deal specifically with Asphalt Rubber products. Using the title “Gap Graded”
provides an opportunity to include SMA specifications at a later date.
• Paragraphs 413-1 and 415-1 are very similar in content. It is recommended that
the text from 415-1 be used for the new specification.
• Paragraphs 413-2 and 415-2 describe the required mix design process for Gap
Graded Asphaltic Concrete. Except for the effective voids range, the information
in both sections is essentially the same. The tighter voids range listed in 415 is
the preferred design range. Table 415-1 will be re-titled “Asphaltic Concrete Mix
Design Criteria – Gap Graded”.
• All references to materials paragraphs will need to be changed to XXMAT
references.
• Tables 413-2 and 415-1 include the same gradation requirements. The column for
mix “Without Admixture” should be deleted as ADOT requires mineral admixture
in all mixes. The gradation requirements should be moved into the mineral
aggregate subparagraph of Section XXMAT.
• Paragraphs 413-3 and 415-3 should be moved into the Section XXMAT on
materials and identified as aggregates for GGAC.
• Paragraphs 413-3.02 and 415-3.03 are the same. Use the existing text for the
Section XXMAT.
• It was noted at the workshops that a discrepancy exists in the payment of the
mineral admixture specification. Paragraph 415-3.03 requires 1 percent mineral
admixture. However, in Paragraph 415-8, the statement is made that “Mineral
admixture will be measured by the ton for the mineral admixture actually used in
accordance with Subsection 415-6” (it is noted that this reference should be to
403-2). These requirements are in conflict with each other. It was reported at the
TAC meeting that AR mixes always use 1 percent lime. In the specification, a
specific requirement for AR mixes can be identified if desired. However, if this
specification is to be flexible enough to include SMA in the future, the issue of
moisture susceptibility should be addressed in a more specific manner. It is
recommended that this subparagraph be reworded to pay the contractor for the
21
mineral admixture necessary to achieve the moisture susceptibility requirements
of the mix design. The following is suggested:
o “Mineral admixture will be required. The amount used shall be determined
by laboratory testing to demonstrate the quantity of mineral admixture
required in order to meet the mix design criteria for Wet Strength and
Index of Retained Strength. A maximum of 2.0 percent admixture will be
permitted. The exact amount of admixture required shall be specified in
the mix design.”
It is noted that appropriate protocols for ARAC testing and criteria
need to be established in order for this to be implemented.
o The remainder of this subparagraph can be used as written in the current
specification.
• Paragraphs 413-3.03 and 415-3.04 are the same except that 413-3.03 requires the
percent of asphalt-rubber in the mix to be specified by the engineer. It is
recommended that the text from 415-3.04 be used in the Section XXGG.
• Paragraphs 413-3.04 and 415-3.05 contain the same text. The text can be used as
currently written for the Section XXGG.
• The text in Paragraph 415-5 should be used in Section XXGG on Gap Graded
Asphaltic Concrete.
• Add a new sentence at the end of the first paragraph in Paragraph 415-6:
o “Hauling units for asphaltic concrete shall meet the requirements in
Section 403.”
• Paragraph 415-6 of the current specification contains the following statement:
“Longitudinal joints of each course shall be staggered a minimum of one foot
with relation to the longitudinal joint of any immediate underlying course.” This
sentence should be deleted and replaced with the following:
o “Both longitudinal and transverse joints in successive courses shall be
staggered so that one is not above the other. Transverse joints shall be
staggered by the length of the paver. Longitudinal joints shall be staggered
a minimum of 12 in.��
• Paragraph 415-6 of the current specification contains the following statement:
“Joints shall be formed by a slope shoe or hot-lapped and shall result in an even,
uniform surface.” This sentence should be deleted and replaced with the
following:
o “Longitudinal joints shall be constructed to provide a continuous bond
between the old and new surfaces. After placement and finishing of the
new asphaltic concrete, both sides of the joint shall be dense and the joint
shall be well sealed. Acceptable longitudinal joint construction procedures
include unconfined edge joints, a tapered joint with or without a notch, a
22
cutback joint or use of an edge compactor. Other methods may be
approved by the Engineer based on local experience.”
• Paragraph 415-6 of the current specification provides only one option for
construction of a transverse joint – a cutback joint. Discussions at the workshops
indicate that the cutback joint is rarely used. The paragraph “Before a surface
course is placed…” should be deleted and replaced with the following:
o “Transverse joints shall be constructed to provide a continuous bond
between the old and new surfaces. After placement and finishing of the
new asphaltic concrete, both sides of the joint shall be dense and the joint
shall be well sealed. Acceptable transverse joint construction procedures
include a bulkhead butt joint, a feathered joint, a papered joint or a
cutback joint. Other methods may be approved by the Engineer based on
local experience. The surface in the area of the joint shall conform to the
requirements hereinafter specified for surface tolerances when tested with
the straightedge placed across the joint. The contractor shall have a 10-
foot straight edge on site at all times during paving for this purpose.”
• Paragraph 415-6 of the current specification states: “A light coat of bituminous
material shall be applied as directed to edges or vertical surfaces against which
asphaltic concrete is to be placed.” This sentence should be replaced with the
following:
o “Tack coat shall be applied as directed by the Engineer to all edges or
vertical surfaces against which asphaltic concrete is to be placed.”
• Paragraph 415-6 of the current specification states “The moisture content of the
asphaltic concrete immediately behind the paver shall not exceed 0.5 percent.”
Based on comments from workshop participants, this requirement is rarely
verified. The typical specification for the asphaltic concrete industry throughout
the country would have the moisture content requirement verified at the plant. A
0.5 percent moisture content at the paver would allow substantially more moisture
at the plant, depending on the haul time and type of mix.
• Paragraph 415-7.01 of the current specification can be used as written in Section
XXGG.
• Paragraph 415-7.02 of the current specification can be used as written in Section
XXGG.
• Paragraph 415-7.03 discusses Material Spread. The material spread is a surrogate
for yield of mix placed on the pavement. This is an important measurement tool
during construction. It is recommended that this paragraph be a part of Section
XXGG with the following modification. It is recommended that the bulk density
value used for the calculation be the running average of current production bulk
density values rather than a mix design value. By using a reasonably current bulk
density value, the calculation will be more accurate, fair, and reasonable.
23
• Paragraph 415-7.04 of the current specification can be used as written in Section
XXGG.
• Paragraph 415-7.05 of the current specification can be used as written in Section
XXGG.
• Paragraph 415-7.06 of the current specification can be used as written in Section
XXGG.
The text in Paragraph 415-9 is recommended to be used in Section XXGG. It is
noted that this project was not focused on pay factors so this paragraph was not
reviewed in technical detail.
24
VI. COMMENTARY ON SECTION XXACFC –
ASPHALTIC CONCRETE FRICTION COURSE
This is a combination of current Sections 407, 411, and 414. The new section will be
XXACFC – Asphaltic Concrete Friction Course.
• Sections 407 and 414 are identical except for the type of binder used and
associated specification requirements. As such, this commentary will address the
use of Section 414 with appropriate adjustments to account for use of both
asphalt-rubber binder and neat asphalt binder. It was reported that the vast
majority of ADOT friction courses are placed under Section 414 of the standard
specifications.
• Section 411 is a method specification for ACFC, used infrequently for small
tonnage jobs. It is recommended that Section 411 be deleted in its entirety. If
ADOT has a small project that requires such an application, the specification
changes can be handled through Special Provisions or stored specifications.
• It is recommended that the text in Section 414-1 be used for Section XXACFC. It
is recommended that the paragraphs be modified as follows:
o 414-1 Description
“Asphaltic Concrete Friction Course shall consist of furnishing all
materials, mixing at a plant, hauling and placing a mixture of an
aggregate material, mineral admixture, and a bituminous material
to form a pavement course or to be used for other specified
purposes, in accordance with the details shown on the project plans
and the requirements of these specifications, and as directed by the
Engineer.”
o 414-1.01 Asphaltic Concrete Friction Course (Asphalt-Rubber)
“The bituminous material for Asphalt-Rubber mixtures shall be
asphalt-rubber conforming to the requirements of Section 1009-
2.01 (A).”
“The contractor shall be responsible for all adjustments to its
equipment necessary to properly accommodate the use of asphalt-rubber
as a bituminous material.”
o 414-1.02 Asphaltic Concrete Friction Course
“The bituminous material for mixtures with conventional asphalt
cement shall be Performance Grade PG XX-XX asphalt cement
conforming to the requirements of Section 1005.”
• Paragraph 414-2 text can be used as currently written with the following
modification:
o The second sentence should read: “The allowable range of percent
absorbed bituminous material shall be 0-1.0, when tested in accordance
with Arizona Test Method 806.”
25
• Paragraph 414-3 should be moved to Section XXMAT (See Section VIII) with the
following changes:
o The first sentence “There is no Department-furnished source of mineral
aggregate.” should be deleted.
o The second sentence should be modified to read:
“The contractor shall provide a source in accordance with the
requirements of Sections 106 and 1001 of the specifications.”
o The mix design grading limits in Table 414-1 should be used in the
revised specification. The grading in Section 414 is slightly coarser than
for Section 407 but as such will provide a better friction course. The
column for mix “Without Admixture” should be deleted as ADOT
requires mineral admixture in all mixes.
• Paragraph 414-3.03 Bituminous Material should be reorganized as follows:
o 414-3.03 General
The percent of bituminous material used shall be based on the
weight of total mix (asphalt binder, mineral aggregate and mineral
admixture).
The percent of bituminous material to be used will be determined
by the mix design or may be specified by the Engineer.
o 414-3.03.01 Asphaltic Concrete Friction Course (Asphalt-Rubber)
Bituminous material shall be asphalt-rubber conforming to the
requirements of Section 1009-2.01 (A).of the specifications. The
type of asphalt-rubber shall be as shown in the Special Provisions.
The crumb rubber additive shall be CRA Type B conforming to the
requirements of Section 1009-2.01 (B).
In no case shall the asphalt-rubber be diluted with extender oil,
kerosene, or other solvents. Any asphalt-rubber so contaminated
will be rejected.
Any kerosene or other solvents used in the cleaning of equipment
shall be purged from the system prior to any subsequent use of that
equipment.
o 414-3.03.02 Asphaltic Concrete Friction Course
Asphalt cement shall be an asphalt binder performance grade PG
XX-XX, conforming to the requirements of Section 1005.
• Paragraphs 414-6.01, 414-6.02, and 414-6.03 (all pertaining to Acceptance of
Materials) can be duplicated in their entirety in Section XXMAT with the
following modification:
o Paragraph 414-6.03 (B) should have a new title of: Bituminous Material
Content. The word “asphalt-rubber” in the third sentence of the first
paragraph should be changed to “Bituminous Material”.
• Paragraphs 414-7.01, 414-7.02, and 414-7.03 can be duplicated in their entirety in
Section XXACFC.
26
• In Paragraph 414-7.04(A) add the following sentence after the first sentence of
the first paragraph of the General Requirements:
o “Hauling units for asphaltic concrete shall meet the requirements in
Section 403.”
• In Paragraph 414-7.04(A) (1) there is a discussion of Placement Dates and
Weather Requirements. The TAC recommended retaining these requirements.
• Paragraph 414-7.04(A)(2) should be revised as follows:
o “Asphaltic concrete delivered to the screed unit shall be a free flowing,
homogeneous mass in which there is no segregation, crusts, lumps or
migration of the bituminous material. Should any one or more of these
conditions be evident in the material delivered to the screed unit, the
contractor will institute one or more of the following procedures:
(a) Cover the haul units with tarpaulins;
(b) Discharge material directly into the paver using an end-dump
truck;
(c) Incorporate a material transfer vehicle into the paving train; or
(d)Reduce the haul distance from the plant to the laydown site.
“Should these efforts not eliminate the condition, the Engineer will order
the work to be stopped until conditions are conducive to the delivery of
the asphaltic concrete in the condition as described above. Other measures
proposed by the contractor which will deliver asphaltic concrete meeting
the above requirements will be considered by the Engineer.”
• Paragraphs 414-7.04(B), (C), and (D) and 414-7.06 (A), (B), and (C) are method
specifications for asphaltic concrete placement. Such specifications place an
undue amount of risk on ADOT if there is a problem with the pavement. By
directing the contractor in the means and methods of placing the material, ADOT
has little recourse when and if a problem occurs.
However, there is currently no technology available to adequately determine the
quality of the ACFC mix at the time of placement other than asphalt content and
gradation. Some agencies use a field permeability test but the variability of the
test is very high. Therefore, the method requirements as currently written
represent the state-of-the-practice for placement of ACFC type mixes.
• Paragraph 414-7.05 can be duplicated in its entirety for Section XXACFC.
• Paragraph 414-7.06 can be duplicated in its entirety for Section XXACFC.
• Paragraph 414-7.07 can be duplicated in its entirety for Section XXACFC.
• Paragraph 414-7.08 can be duplicated in its entirety for Section XXACFC.
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• Paragraph 414-7.09 can be duplicated in its entirety for Section XXACFC.
• In Paragraph 414-8, the follow modifications should be made:
o The first sentence should be changed as follows:
“Asphaltic concrete will be measured by the ton for the mixture
actually used, which will include the weight of mineral aggregate,
mineral admixture and bituminous material.”
o The second paragraph should be changed as follows
“Bituminous material will be measured by the ton.”
o The third paragraph should be changed as follows:
“If asphalt-rubber is used as the bituminous material, the weight of
the asphalt-rubber material…”
• In the second paragraph of Paragraph 414-9, the following changes are
recommended:
o In the first sentence:
“Payment for the bituminous material will be made by the ton.”
o Add a new second sentence:
“For mixes with asphalt-rubber, payment for the asphalt-rubber
will include asphalt cement and crumb rubber.”
o The remainder of the second paragraph can be used as currently written.
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VII. COMMENTARY ON SECTION XXMISC –
ASPHALTIC CONCRETE FOR MISCELLANEOUS PAVING
This is a revision of current Section 409. The new Section will be XXMISC.
• The TAC recommended that this Section be kept separate from XXDG. However,
on detailed review, it is recommended that this section be included in XXDG.
Generally the application for Section 409 is for temporary roadways that may
carry very heavy traffic for several months. Most of the materials properties are
the same. If the XXDG specification were used for these applications, the
following modifications should be made for the Miscellaneous Applications:
o The VMA and air voids criteria should be the same as for dense graded
mixes for the miscellaneous application.
o For temporary applications, the requirement to meet index of retained
strength criterion may be waived by the Engineer.
o Instead of having a compaction method specification, Section 416 could
be used with a change in the volumetric criteria for miscellaneous
applications. The target volumetric properties could be adjusted to
recognize the temporary nature of the application.
The remainder of this commentary is written as if 409 will remain a free-standing
section of the specification.
• Paragraph 409-2 on Materials should be moved to the new Section XXMAT with
the following changes:
• Paragraph 409-2.03 requires 2 percent mineral admixture but allows a minimum
of 1 percent if necessary to meet moisture susceptibility requirements. Currently
the contractor is paid by the ton for mix produced under the 409 specification. If
the specification remains in use only for temporary applications, it may not be
necessary to include the mineral admixture. This matter will need to be reviewed
by ADOT personnel. The subparagraph can be used as written in the current
specification.
• Paragraph 409-2.04 can be duplicated in its entirety for Section XXMISC.
• Paragraph 409-3.01 can be duplicated in its entirety for Section XXMISC with the
following exceptions.
o The paragraph that begins with “The moisture content…” shall be
reworded as follows:
“The moisture content of the asphaltic concrete at the paver shall
not exceed 0.5 percent.”
o The paragraph that begins with “Asphaltic concrete immediately
behind…” shall be reworded as follows:
“Asphaltic concrete immediately behind the laydown machine
shall be a minimum of 275 degrees F.”
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• Paragraph 409-3.02 describes compaction processes to be used. This is a method
specification. As previously discussed, it is recommended that the compaction be
completed in the same manner as with Section 416 but with different acceptance
criteria.
• Paragraphs 409-3.03, 409-4, and 409-5 can be duplicated in their entirety for
Section XXMISC if the ADOT chooses to maintain Section 409.
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VIII. PROPOSAL FOR SECTION XXMAT –
MATERIALS FOR ASPHALTIC CONCRETE
• The new stand-alone Section XXMAT on Materials should have the following
subsections:
o Mineral Aggregate
o Mineral Admixture
o Bituminous Material
Each of these subsections will have the specific product quality requirements for
the different mix types with the changes recommended previously. By having all
the material specifications in one section, the producer can easily see what the
differences are between products. The user also has easier access to the
specifications necessary for mix production.
IX. PROPOSAL FOR SECTION XXWMA – WARM MIX ASPHALT
Warm Mix Asphalt is anticipated to be a significant element of the future asphaltic
concrete industry. It is recommended that a section of the revised specification be
assigned for this topic. Future efforts within the industry will determine the contents of
the section.
X. FUTURE WORK
Review of the Conformance Reports indicated that revision of the reports is appropriate
in order to have the reports reflect current industry practice. The PAR questions need to
be revised to ensure consistency in the inspection process. It is recommended that a joint
ADOT/contractor workshop discuss the scope and objectives of the conformance reports.
These reports can provide value to both ADOT and to the contractor.
A significant effort will be required to incorporate the recommended specification
changes into the ADOT Standard Specifications. This effort can be accomplished through
a combination of ADOT, contractor and/or consultant activities.
XI. CONCLUDING REMARKS
Project SPR630 was developed to provide a critical review of ADOT’s Hot Mix Asphalt
Specifications. The effort has identified ADOT Standard Specification changes
recommended from the agency and industry workshops held in October 2007 and from
the experience of the project PI. The recommendations in the report represent the state-of-
the-practice in the asphalt industry in the United States. It is, however, recognized that
some of the recommendations may not be applicable to the Arizona experience. It is
therefore recommended that new ideas be verified within the confines of the Arizona
asphaltic concrete community.
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REFERENCES
Arnold, Terry S., Muriel Rozario-Ranasinghe and Jack Youtcheff. 2005. "Determination of
Lime in Hot Mix Asphalt." Paper prepared for poster session at the 2006 Annual Meeting
of the Transportation Research Board.
Brock, J. Don and Tom Skinner. 1997. Longitudinal Joints: Problems and Solutions.
Quality Improvement Series 121. Lanham, MD : National Asphalt Pavement Association
Transportation Research Board (TRB). 2000. Hot Mix Asphalt Paving Handbook. Federal
Aviation Administration Advisory circular AC150/5370-14 (Supplement). Washington,
DC: Transportation Research Board, et al.
