1. Pavement Design Guidance
This is an introduction to pavement design for State Aid designated roadways. The information contained in this presentation is current as of May If you have questions or desire clarification of information contained in this presentation, please contact the State Aid Pavement Engineer.

2. Outline Pavement Design guidance Pavement Design
Pavement Design resources and links

3. Pavement Design guidance

4. Pavement Design guidance
Pavement Types
Flexible (Hot-Mix Asphalt – HMA) Pavement Design
Standard Design
Low-Volume Design
Rigid (Portland Cement Concrete – PCC) Pavement Design
Aggregate Surface (Gravel) Road Design
There are essentially three types of pavements to design; flexible which are commonly referred to as hot mixed asphalt pavements or HMA, rigid pavements which are constructed of Portland cement concrete and referred to as PCC pavements, and aggregate surfaced roadways referred to as gravel roads.
The most common roadway pavement in Minnesota Cities and Counties is an asphalt pavement. The design of an asphalt pavement varies depending on type and volume of traffic it needs to carry. Standard asphalt pavements are designed using the following guidance:
For low-volume roadways (less than 1,000 AADT – Average Annual Daily Traffic), standard design parameters are changed to reflect the known fact that these pavements fail because of age and related environmental effects rather than traffic loading. Low-volume roadway pavements typically fail as a result of oxidation of the near surface binder oil. This results in the pavement becoming brittle and cracking allowing moisture into the pavement structure. As a result, the base and subsoils are weakened subjecting the pavement to frost heave action causing accelerated pavement deterioration.
Certain regions within Minnesota have traditionally constructed PCC (rigid) pavements. In recent years with the advancement of PCC overlays over asphalt pavements (whitetopping), these regions have expanded. Design tools and options have been developed and improved by MnDOT and others to assist in design of rigid pavements. These methods have been incorporated into the MnDOT design manuals and tools are available on the State Aid and MnDOT Pavement Design web sites.
Lastly, Minnesota counties still maintain a large network of aggregate surfaced (gravel) roads. State Aid has looked into providing recommendations to assist counties in specifying and producing better quality aggregate surfacing materials and maintenance methods to achieve better performing gravel roads.

5. Standard Pavement Design
State Aid Rules
State Aid Operations Chapter 8820, sections to , requires all pavements to be designed meeting minimum structural design strengths.
Ten Ton
Staged Ten Ton
Nine Ton
Seven Ton
State Aid has rules which help provide standardized pavement designs between agencies across the state of Minnesota. These can be found in State Aid Operations Chapter 8820 sections to Currently most roadways in Minnesota are designed to carry ten ton (20,000 lb.) axle weights. However, there are provisions that allow for a staged ten ton design, nine ton and seven ton designs.

6. Standard Pavement Design (continued)
Ten Ton Pavement Design
Rural divided roadways and roadways having projected AADT of 1,500 or more must be designed to the ten ton standard.
Staged Ten Ton Pavement Design
Ten ton pavement design is recommended for all new or reconstructed pavements and suburban undivided roadways having a projected AADT of 150 to 1,499. It is permissible to design a nine ton pavement with intent to increase it to a ten ton capacity at a later date. This is referred to as “Staged Ten Ton Design”. The geometric typical sections of the original nine ton pavement design must be constructed to accommodate the future ten ton design typical section.

7. Standard Pavement Design (continued)
Seven and Nine Ton Pavement Design
Rules allow for design of seven and nine ton strength roadways.
Minimum nine ton pavement design is permissible within municipal corporate limits.
Minimum seven ton pavement design is permissible for Natural Preservation Routes.

8. Flexible Pavement Design
Most roadways in Minnesota are designed as flexible hot mix asphalt (HMA) pavements. There are three standard design methods available for HMA pavements. These are covered in this presentation.
State Aid Flexible Pavement Design Charts using Soil Factor
Flexible Pavement Design, R-value Method
MnPAVE Flexible

9. Low-volume Roadway Flexible Pavement Design
It is recognized certain low-volume roads designed to minimum standards fail because of environmental factors including oxidation, freeze-thaw action, thermal cracking, etc. A memo was issued by State Aid in February of 2015 to address inquiries from city and county engineers about designing asphalt mixtures for low-volume paved roadways.

10. Rigid Pavement Design
Rigid pavements of Portland Cement Concrete (PCC) consist of either new PCC pavements or concrete overlays. There are two types of concrete overlays; PCC pavement placed on existing PCC pavement (concrete overlay) and PCC pavement placed on an asphalt pavement (whitetopping). Concrete overlays can be designed as either bonded or unbonded.
Chapter 5 of the MnDOT Pavement Design Manual should be consulted for design of PCC pavements.

11. Aggregate Surfaced Road Design
Good aggregate surfacing is key to good performance of the driving surface.
State Aid has reviewed several aggregate surfacing design guides and recommends using the Gravel Roads Maintenance and Design Manual developed by South Dakota Local Transportation Assistance Program or SD LTAP (November 2000) for design of these roadways.

12. Pavement Design

13. Pavement Design Types of Pavement Design Flexible Pavement Design
Standard Design
Low-Volume Roadway Design
Rigid Pavement Design
Aggregate Surface Road Design
The following slides present design procedures for the three types of pavements, HMA, PCC and aggregate surfaced designed in Minnesota.

14. Pavement Design (continued)
When preparing to design a pavement two pieces of information are required:
Estimated traffic loading over the design life of the pavement
Traffic loading is calculated from the Average Annual Daily Traffic (AADT) and reported as Equivalent Single Axle Loads (ESAL’s). The State Aid ESAL Calculator can be used to calculate 10 ton ESAL’s. Flexible (HMA) pavements and PCC pavement overlays are typically designed for a 20 year life while rigid (PCC) pavements are designed for a year life.
Soil subgrade strength
Soil strength is defined as either Soil Factor (SF) or R-value.
In order to prepare a pavement design, one needs to know what the expected traffic load will be and what the subgrade soil strength is. The pavement section is designed to carry and support the estimated traffic load over the subgrade soil. A pavement is designed to carry a defined traffic loading over a specified design life. In our case, 20 years for flexible pavements or concrete overlays on asphalt and 35 years for rigid pavements.

15. Where do I find traffic data?
Go to MnDOT website
Under “Topics A to Z” search for “Traffic Counts”
Click here!
Then click here!
“T” for “Traffic Counts”
Traffic Data can be found on the MnDOT web site for all counties and cities in Minnesota. Go to the MnDOT web site and click on “Topics A to Z” and select “T’ for Traffic Counts.
MnDOT website -

16. Where do I find traffic data? (continued)
Then click here!
“T” for “Traffic Counts”
Scroll down to:
Click here!
After selecting “T”, scroll down to “Traffic Counts”.
Where do I find traffic data? (continued)

17. Where do I find traffic data? (continued)
Click on appropriate item
The page that opens lists several options to select from. Click on the appropriate item (out state Municipality Maps, Twin Cities Metro Maps or County Maps) that you need.
Where do I find traffic data? (continued)

18. Equivalent Single Axle Load
ESAL Calculator
State Aid
Equivalent Single Axle Load
10 Ton ESAL Calculator
The State Aid ESAL Calculator is an excel spread sheet which allows the user to input the type of roadway pavement being designed along with actual historical AADT counts. This can then be analyzed using default heavy commercial traffic percentages based on historical traffic information from around the state (LRRB 2010 Research Report) or the user can define the expected heavy commercial traffic values if there are known special localized conditions. An example of this may be a new manufacturing or distribution center with a larger than average percentage of truck traffic. The calculator provides 10 ton ESAL values for both flexible and rigid pavement designs.

19. ESAL Calculator (continued)
MnDOT vehicle type classification scheme
MnDOT Vehicle Type and Classification show the various vehicles that use the roadways. Each of these vehicles has a unique tire and axle configuration which affects the way its weight is distributed on the pavement. This in turn affects the ESAL calculation.

20. State Aid 10 Ton ESAL Traffic Forecast Calculator
Click here!
Scroll down and Click here!
The ESAL calculator was created to help make ESAL calculations for pavement design easy and uniform for local agencies. To find the ESAL Calculator, go to the State Aid web page, click on the “Pavement” tab, scroll down to “pavement Design Tools” and click on “ESAL Calculator. The form shown on the right will pop up.
State Aid website -
State Aid 10 Ton ESAL Traffic Forecast Calculator

21. State Aid 10 Ton ESAL Traffic Forecast Calculator (continued)
ESAL calculator consists of two worksheets:
Default Traffic Values
User Defined Traffic Values
The ESAL Calculator has been set up to use default values based on a joint research project by the Local Road Research Board and MnDOT Research Services. This project was entitled “Update of Vehicle Classification for County Road Pavement Design”. It was published in April of As an option, a second worksheet was developed to allow the user to define the expected vehicle class percentages so non-typical traffic loadings can be addressed in the pavement design.

22. ESAL Calculator (continued)
“Default Traffic Values” page Incorporates heavy commercial traffic percentages in the ESAL calculation from Report
The default Vehicle Class percentages change for each of the rural and urban AADT ranges (0 – 300, 301 – 750, 751 – 1500, >1500).

23. Soil Strength and R-value
How is soil strength obtained or determined?
Soil Factor
From historic county design records each county has this defined.
R-value
Actual through testing a soil sample.
Geotechnical consultant can estimate from field exploration involving soil borings.
Estimate from chart based on known soil type(s) within project limits.
Soil strength parameters can be either conservatively estimated based on previous historic design records or more accurately defined by hiring a geotechnical consultant who can perform soil borings to explore the subsurface soil conditions and lab testing of obtained soil samples.

24. Soil Strength and R-value (continued)
You may select from this table the Soil Factor or R-value appropriate for the soil conditions in your area that will support the new pavement section.
Soil Strength and R-value (continued)

25. Flexible Pavement Design
Standard Design
State Aid Flexible Pavement Design Charts
R-value Method
MnPAVE-Flexible
Low-volume Roadway Design
State Aid Low-volume Roadway Design Memo
Having both traffic loading (ESAL’s) and soil strength values (SF or R-value), the designer can now prepare a pavement design. As previously noted there are three design options available for designing flexible pavement sections. State Aid Design Charts, R-value Design and MnPAVE Flexible.

26. Pavement Design Charts (using Soil Factor)
Ultimate 10 ton Staged Pavement Design
7 and 9 ton Pavement Design
7 ton Natural Preservation Routes Pavement Design

27. Pavement Design Charts (using Soil Factor) (continued)
The design charts don’t use ESAL’s to calculate the design section, but rely on the actual Heavy Commercial Average Daily Traffic (HCADT). The GE indicated in the table is for a nine ton design. As noted in foot note 1, for Ten Ton Staged Design you will need to determine the ten to ESAL,s and associated required GE to assure the final designed nine ton pavement section will accommodate a future ten ton pavement section. This can be accomplished using the R-value Design worksheet or chart.
Pavement Design Charts (using Soil Factor) (continued)

28. Pavement Design Charts (using Soil Factor) (continued)
Municipalities have an allowance for nine ton pavement designs which are shown in this chart.
Pavement Design Charts (using Soil Factor) (continued)

29. Pavement Design Charts (using Soil Factor) (continued)
As noted, this chart is for use in designing seven ton pavements for those roadways designated as Natural Preservation Routes.
Pavement Design Charts (using Soil Factor) (continued)

30. Flexible Pavement Design (Standard)
Flexible Pavement Design R-value Method
The R-value method of flexible pavement design is the most commonly used by local agencies. There is an R-value design chart and Excel worksheet. These are one and the same method, just expressed differently. The Excel spread sheet is preferred as it provides the plan reviewer within State Aid a print out of the pavement design assumptions and parameters as well as an easy check of the design.

31. Flexible Pavement Design (Standard)
MnDOT developed MnPAVE-Flexible which is a Mechanistic – Empirical (ME) design method which brings environmental affects into the pavement design process. Output can be printed for easy documentation of the pavement design. The program predicts pavement life in years in terms of pavement fatigue and rutting failure.
MnPAVE

32. Flexible Pavement Design (Low-volume)
Low-volume Roadway Flexible Pavement Design
(February 2015 Design Memo)
In response to local agencies asking about pavement design for low-volume roadways, the above memo was issued to provide design guidance for those roads more likely to fail because of age than traffic loading. The following slide provides adjustments to pavement design parameters which should provide additional life for these types of pavements.

33. Flexible Pavement Design (Low-volume) (continued)
Low-volume Flexible Pavement Design
Should only be considered for roads with <1,000 AADT and less than average heavy truck traffic.
Use aggregate size “A” (-1/2”, SP 9.5) for the final lift.
RAP is recommended to be used in the asphalt mixture.
Use traffic level 2 for mix design.
Specify wearing course with 3.0 percent design air voids.
Recommended asphalt binders:
PG (“B Oil”) for asphalt pavement overlays.
PG (“C Oil”) for new asphalt pavements.

34. Flexible Pavement Mix Design Criteria
Asphalt Mix Design Criteria
MnDOT Specification 2360
Guidance is available:
MnDOT Bituminous Engineering under Design
Design Criteria
Binder Guidelines
It is necessary that the designer develop the asphalt mix designation code(s) for each pavement design. The designer needs to select the appropriate aggregate size, traffic level and binder for design of the pavement asphalt mixture. Guidance on selecting the appropriate Mix Design Criteria is found on the MnDOT Bituminous Office website under “Design”.
MnDOT Bituminous Engineering under Design -
Design Criteria -
Binder Guidelines -

35. Rigid Pavement Design ACPA StreetPave
This PCC pavement design software was developed by the American Concrete Paving Association for design of rigid pavements.
Technical Memorandum-SA-03 Authorizes the use of this design software for local agencies in Minnesota.
Chapter 5 PCC Pavements of the MnDOT Pavement Design Manual should be consulted for design of PCC pavements. It can be found at:

36. Rigid Pavement Design (continued)
MnPAVE-Rigid
This PCC pavement design software was developed by MnDOT for design of rigid pavements.
MnDOT developed MnPAVE-Rigid which is a Mechanistic – Empirical (ME) design method which brings environmental affects into the pavement design process. Output can be printed for easy documentation of the pavement design.

37. Rigid Pavement Design (continued)
BCOA-Bonded Concrete Over Asphalt (BCOA) – ME Design Guide
This document guides the user through the design of a bonded concrete overlay placed on top of an existing asphalt pavement.
BCOA – ME Design Guide -

38. Rigid Pavement Design (continued)
Unbonded Overlay Design
This is an Excel worksheet developed by MnDOT
This design procedure is used for design of a PCC pavement overlay placed on an existing asphalt pavement. The designer should refer to the current MnDOT Pavement Design Manual, Chapter 5 – PCC Pavements for design guidance, methods and assistance.

39. Aggregate Surface Road Design
Appendix A: Gravel Road Thickness Design Methods
Gravel Road Design Manual
This manual is the recommended source for design and maintenance of gravel roads for Minnesota’s local agencies. It is located at:

40. Aggregate Surface Road Design (continued)
MnDOT Standard Specifications for Standard Construction
3138 AGGREGATE FOR SURFACE AND BASE COURSES
D Surfacing Aggregates Class 1 or Class 2
This is the MnDOT Standard Specification for surfacing aggregates. It is found in the MnDOT Standard Specifications for Construction.

41. Aggregate Surface Road Design (continued)
MnDOT Standard Specifications for Construction
3138.2D Surfacing Aggregates
Surfacing aggregate shall have:
Clay content = 3 percent minimum
Plasticity Index = 5 – 12 OR
Bitumen content ≥ 1 percent OR
Material is composed of at least 25 percent recycled material
Aggregate surfacing requires binder (clay fines or bitumen) to hold larger particles in place. Without this, the larger aggregate tends to stay loose on the driving surface and is easily kicked off the roadway by the traffic.

42. Pavement Design resources and links

43. Contacts MnDOT and State Aid Pavement Contacts
Joel Ulring, State Aid Pavement Engineer,
Tim Andersen, MnDOT Pavement Design Engineer,
John Garrity, MnDOT Bituminous Engineer,
Maria Masten, MnDOT Concrete Engineer,
Joel Ulring –
Tim Andersen -
John Garrity -
Maria Masten -

44. Resources and links MnDOT and State Aid Resources
State Aid Rules Chapter 8820
MnDOT PG Binder Guidelines-MSCR
2360 Mix Designation Number Examples
MnDOT Technical Memorandums
The above resources are available to assist you in designing pavements in accordance with MnDOT and State Aid Standards.
State Aid Rules Chapter
MnDOT PG Binder Guidelines-MSCR -
2360 Mix Designation Number Examples -
MnDOT Technical Memorandums -

45. Resources and links (continued)
Specifications and Special Provisions:
2301 Concrete Pavement
2360 Plant Mixed Asphalt Pavement
Special Provisions – SP2016
Manuals:
State Aid
MnDOT Pavement Design
MnDOT Grading and Base
MnDOT Geotechnical
MnDOT Concrete
All manuals
2301 Concrete Pavement -
2360 Plant Mixed Asphalt Pavement -
Special Provisions – SP
State Aid Manual -
MnDOT Pavement Design -
MnDOT Grading and Base -
MnDOT Geotechnical -
MnDOT Concrete -
All manuals -

46. Resources and links (continued)
MnDOT and State Aid Links
State Aid Pavement
MnDOT Bituminous
MnDOT Concrete
MnDOT Pavement Design
MnDOT Grading & Base
State Aid Pavement -
MnDOT Bituminous -
MnDOT Concrete -
MnDOT Pavement Design -
MnDOT Grading and Base -

47. Resources and links (continued)
Research:
Local Road Research Board
MnDOT Research Services
MnLTAP
MnRoad
National Center for Asphalt Technology
Other partner links:
Concrete Pavement Association of Minnesota
Minnesota Asphalt Pavement Association
American Concrete Pavement Association
Asphalt Recycling & Reclaiming Association
Pavement Interactive
FHWA Pavements
Local Road Research Board -
MnDOT Research Services -
MnLTAP -
MnRoad -
National Center for Asphalt Technology -
Concrete Pavement Association of Minnesota -
Minnesota Asphalt Pavement Association -
American Concrete Pavement Association -
Asphalt Recycling & Reclaiming Association -
Pavement Interactive -
FHWA Pavements -

48. Questions?
Joel Ulring