NCAUPG Meeting Minutes
January 27 - 28, 1999

P.O. Box 2382
West Lafayette, IN 47906
Telephone:  (765) 463-2317 x226
Fax:  (765) 497-2402

North Central Region Asphalt User/Producer Group
Meeting Minutes

January 27 - 28, 1999
Kansas City Airport Hilton Hotel
Kansas City, MO

Moderator Tom Cackler, Co-Chair, NCAUPG, Iowa DOT

Introduction

Tom Cackler, Co-Chair, Division of Product Development, Iowa DOT called the meeting to order at 1:00 PM. This was followed by a welcome by Garry Chegwidden, Division Engineer, Materials from the Missouri DOT. Tom Cackler thanked Missouri for hosting the meeting and special thanks to Ken Archuleta, FHWA Regional Office, for making all the arrangements for the meeting. A special thank you to Ken Archuleta, FHWA Kansas City, MO, Tom Bryan, FHWA, Olympia Fields, IL, Ray Hogrefe, Jebro, and Garry Chegwidden, Missouri DOT for putting together the Technician Workshop which preceded this meeting. In 1998 25% of projects in the Iowa DOT were Superpave. Our transition to Superpave will be complete in the year 2000. The program today has a focus on construction related issues contractors and agencies have experienced with implementing Superpave. We hope that you will find the presentations to be helpful and enjoyable.

National Superpave Update John D’Angelo, FHWA

The ability to safely and efficiently move people and goods is key to our nation’s economic health. To ensure that our highways will continue to operate safely and efficiently, the federal; and state highway agencies have set out to develop and support a viable, coordinated asphalt technology program that emphasizes the Superpave system. The goal of the nation’s Superpave program is to provide the highway agencies with the necessary tools to design customized asphalt mixes geared to specific traffic loads and climatic conditions. Superpave specifications and procedures help produce a durable, user-responsive, cost-effective highway pavement system.

Since 1991, as part of the nation’s Superpave program, the Federal Highway Administration (FHWA) has led an aggressive, well-coordinated program of activities to further the implementation of the Superpave mix design system initially developed under the Strategic Highway Research Program (SHRP). Those implementation activities were funded by dedicated funds in the 1991 Inter-modal Surface Transportation Efficiency Act.

The Transportation Equity Act of the 21st Century passed earlier this year not only does not include any specific funding for Superpave implementation, but also dramatically cuts the amount of funds available to FHWA for research and development. FHWA estimates that it can commit $ 1.3 million for Superpave implementation this year, and possibly even less in 2000. In contrast, FHWA obligated $ 11 million for Superpave implementation in 1997 alone.

FHWA will continue to support Superpave implementation activities with its limited budget, but many of the activities that had previously been funded by FHWA will need to be financially supported elsewhere, if they are to be continued. (For an overview of FHWA’s planned Superpave 1999 expenditures and requested NCHRP support, see Table 1 in the Appendix.

The Superpave work plan’s ultimate goal is to provide a fully performance-based system for hot-mix asphalt pavements. The Superpave work plan presented here identifies and defines the specific activities that are necessary to fully implement the Superpave system. It is important to recognize that the Superpave system must be considered as a whole - the asphalt mixture design cannot be optimized without considering traffic, pavement structure, and the environment in which the material will be used. The benefits of combining a mix design and structural design cannot be realized if the specification and construction process cannot produce the design. In effect, the Superpave work plan emphasizes that new and improved tools can be put into practice only by having a coordinated, focused program.

The Superpave work plan is composed of 20 problem statements that describe the scope of work, give background on what each project addresses, explain the product and benefit of the research, and outline the expected costs. This work plan is intended to permit integration of performance-based design into every element of asphalt pavement development and delivery. It is delineated into the areas of binder and mixture selection and design, pavement modeling, and design, and performance specifications and construction procedures. Figure 1 illustrates the Superpave program by describing the specific goal areas that each of the problem statement address, and ultimately how they contribute to full implementation of the Superpave system. In addition, the pavement modeling and design area projects are illustrated in Figure 2 on page 28. ??? These particular projects (page 11,16, 17, 19 and 20) are intricately related and need to be performed in the time sequence indicated.

To help explain how the various Superpave projects described in the work plan advance the research that was performed under SHRP and subsequently FHWA, Table 1 describes the Superpave problem statements in the context of how these activities address the continuing need to optimize the Superpave system. Table 1 depicts the Superpave activities as they relate to refining procedures, filling gaps in current technology, and technology transfer activities that focus on technical assistance and training. These are all critical activities that propose a program of ongoing and planned development, delivery, and deployment. The result of these activities will provide the best products and guidance to the engineer, technician and the road builder. Ultimately, this unified approach will achieve the goal of providing the user a more durable, better performing, and more cost-effective asphalt pavement system. If funding for these projects is not secured, the nation’s investment in the Superpave system to date will be jeopardized.

AASHTO Update Rick Smutzer, INDOT

Rick Smutzer, Chief of Materials and Tests with the Indiana DOT gave an update on what is going on at AASHTO Sub-committee on Materials (SCOM). Rick works closely with Rick Harvey of Wyoming DOT who is the Chair of the AASHTO SCOM. Rick talked about the update on Technical Section 2C. The standard specifications for T-168-96 are identical to ASTM 979-96 (Sampling Bituminous Paving Mixtures) with some exceptions. The provisional specifications which are currently being balloted for are 1) Modification of the " LTTP Bind " software; 2) MP-2 Volumetric Design Update, clarification and simplification; 3) Mixture Conditioning changes based on NCHRP 9-9 Data; 4) Apparatus change to address use of modified binders; 5) Compaction to N-Design, instead of compaction to N-Max with backcalculation; 6) Change PP 28 to be compatible with the MP 2.

John D’Angelo FHWA presented information on changes to Superpave as shown in the following four tables. These are being balloted by AASHTO so they are subject to change and are not FINAL.

Table 1 – Binder Selection on the Basis of Traffic Speed and Traffic Level

Design ESAL’s 1

(million)

Adjustment to Binder PG Grade 5

Traffic Load Rate

Standing 2

Slow 3

Standard 4

< 0.3

-(6)

-

-

0.30 to < 3

2

1

-

3 to < 10

2

1

-

10 to < 30

2

1

-(6)

> 30

2

1

1

  1. Design ESAL’s are the anticipated project traffic level expected on the design lane over a 20-year period. Regardless of the actual design life of the roadway determine the design ESAL’s for 20 years and choose the appropriate N design level.
  2. Standing traffic – where the average traffic speed is less than 20 km/h.
  3. Slow traffic – where the average traffic speed ranges from 20 to 70 km/h.
  4. Standard traffic – where the average traffic speed is greater than 70 km/h.
  5. Increase the high temperature grade by the number of grade equivalents indicated (1 grade equivalent to 6 degrees C.). Use the low temperature grade as determined in Section 5.
  6. Consideration should be given to increasing the high temperature grade by 1 grade equivalent.

Note 4 – Practically, performance graded binders stiffer than PG 82-XX should be avoided. In cases where the required adjustment to the high temperature binder grade would result in a grade higher than PG 82, consideration should be given to specifying a PG 82-XX and increasing the design ESALs by one level (e.g., 10 to <30 million). (14)

Table 2 – Aggregate Gradation Control Points

 

Nominal Maximum Aggregate Size – Control Point (Percent Passing)

37.5mm

25.0mm

19.0mm

12.5mm

9.5mm

Sieve Size

Min.

Max.

Min.

Max.

Min.

Max.

Min.

Max.

Min.

Max.

50.0mm

100

--

--

--

--

--

--

--

--

--

37.5mm

90

100

100

--

--

--

--

--

--

--

25.0mm

--

90

90

100

100

--

--

--

--

--

19.0mm

--

--

--

90

90

100

100

--

--

--

12.5mm

--

--

--

--

--

90

90

100

100

--

9.5mm

--

--

--

--

--

--

--

90

90

100

4.75mm

--

--

--

--

--

--

--

--

--

90

2.35mm

15

41

19

45

23

49

28

58

32

67

0.075mm

0

6

1

7

2

8

2

10

2

10

Table 3 – Boundaries of Aggregate Restricted Zone

Sieve Size Within Restricted Zone

Minimum and Maximum Boundaries of Sieve Size for Maximum Aggregate Size

( Minimum and Maximum)

37.5mm

25.0mm

19.0mm

12.5mm

9.5mm

Min.

Max.

Min.

Max.

Min.

Max.

Min.

Max.

Min.

Max.

0.300mm

10.0

10.0

11.4

11.4

13.7

13.7

15.5

15.5

18.7

18.7

.600mm

11.7

15.7

13.6

17.6

16.7

20.7

19.1

23.1

23.5

27.5

1.18mm

15.5

21.5

18.1

24.1

22.3

28.3

25.6

31.6

31.6

37.6

2.36mm

23.3

27.3

26.8

30.8

34.6

34.6

39.1

39.1

47.2

47.2

4.75mm

34.7

34.7

39.5

39.5

--

--

--

--

--

--

Table 4 – Superpave Aggregate Consensus Property Requirements

Design ESAL’s 1

(million)

Coarse Aggregate Angularity

(percent), minimum

Uncompacted Void Content

Of Fine Aggregate

(Percent), minimum

Sand

Equivalent

(Percent),

minimum

Flat and

Elongated 3

(Percent), maximum

< 100mm

> 100mm

< 100mm

> 100mm

< 0.3

55/ -

- / -

- .

-

40

--

0.3 to < 3

75/ -

50/ -

40

40

40

 

10

3 to < 10

85/ 80 (2)

60/ -

45

40

45

10< 30

95/ 90

80/ 75

45

40

45

> 30

100/100

100/100

45

45

50

    1. Design ESAL’s are the anticipated project traffic level expected on the design lane over a 20-year period. Regardless of the actual design life of the roadway, determine the design ESAL’s for 20-years, and choose the appropriate N design level.
    2. 85/ 80 denotes that 85 % of the coarse aggregate has one fractured face and 80 % has two or more fractured faces.
    3. Criterion based on 5:1 maximum-to-minimum ratio

Note 5 - If less than a 25% of the layer is within 100 mm of the surface, the layer may be considered to be below 100 mm for mixture design purposes. (15)

 

The NCNRP report on 409m has been accepted. The joint AASHTO task force will review 409, the Construction and Materials Subcommittees will be involved.

There will be " white paper " on implementation. We would like everyone’s input on this. Some of the functions and responsibilities of the highway agency are verify the Superpave mix design; inspect plants; monitor control of the operations; and acceptance. The functions and responsibilities of the contractor are: formulation of the Superpave mix design designs; and, process control of the plant operations. The Flow of the Superpave QC Plan is: Establish a laboratory trial mix formula {LTMF) design; verify the LTMF two weeks prior to start-up; verify field LTMF two days prior to start-up; certify the asphalt cement; producer to place the mix and establish control charts; and continue to monitor the QC process.

The contractor and the highway agency shall each test the following properties for each 100 ton sub-lots (the first 500 tons will be broken down into 100 ton sub-lots): 1) The gradation of the cold-feed aggregate; 2) The asphalt content and the combined aggregate gradation (AASHTO T 165); 3) The maximum specific gravity of the HMA (AASHTO T 209); 4) The gyratory compaction curve for the N max (AASHTO Standard Method TP 4); 5) The bulk specific gravity (AASHTO T 166, SSD Method at N design Gyrations (AASHTO Standard Method TP 4); 6) The air void content ( percent V a) at N initial, N design, and N maximum gyrations ( AASHTO Standard Method TP 4); 7) The voids in the mineral aggregate ( percent VMA) and the voids filled with asphalt ( percent VVFA) at N design gyrations (AASHTO Standard Method TP 4) ; and 8) The slope of the gyratory compaction curve.

Superpave quality acceptance:

Agency responsibilities: Verify mix design for conformance to Superpave specifications; Review contractor laboratory mix verification (two weeks before construction); Randomly sample contractor plant verification (two days before construction); Accept/ certify asphalt binder; continue with QA based on specified sub-lots.

Some of the key items in the 409 report are;

  1. The quality control plan must address production and placement;
  2. The contract documents shall control over the QC plan;
  3. All charts and records documenting the QC plan will become agency property upon completion of the work;
  4. The contractor will complete the laboratory trial mix formula;
  5. The contractor will conduct the plant verification of the laboratory mix with the agency approval;
  6. The QC plan is based on the concept of continuous sampling of the HMA at the plant;
  7. The production charts shall have warning and action control limits;
  8. The contractor shall develop a QC plan for their compaction control of the HMA placed on the roadway;
  9. The minimum compaction will be 93% of the maximum theoretical density (MTD) and the maximum compaction will be 98% of the MTD;
  10. Corrective action shall be taken by the contractor (when necessary) to control the in-place compaction process;
  11. The compaction control charts shall also have warning and action control limits; and;
  12. Acceptance is based on the percent within the specification limits.

The 409 report is available for your review. The determination of compaction temperature for the PG grades should be obtained from a fact sheet from the manufacturer of the asphalt binder. A contractor felt that it would be an unrealistic expectation to require the contractor to have the verification of the trial mix done two days prior to plant production. Indiana allows the contractor to adjust the design mix formula to the job mix formula during the first production lot or from the contractors’ library of previously acceptable mix designs.

NC Superpave Update Jan Olek, NCSC

Jan Olek, Superpave Center Director, gave us an update on their activities. NCSC has five employees, Becky McDaniel, Technical Director; Lynn Warble, Communications; Steve Bowman, Technician who works on testing; and Hamid Soleymani, Post Doctoral Research Associate who is working on the RAP study and the NCHRP study. Another Post Doctoral Research Associate will be hired soon. Two graduate students have also been working on various research projects.

NCSC has a newsletter, website, provides training and conducts research. The five Superpave Centers have pooled their resources to produce a centralized newsletter. NCSC is the coordinator and publisher. Eight pages are devoted to information of national interest and four pages to regional news. A winter/spring edition will be published in March; a spring/ summer edition will be published in July, and a fall edition will be published in November, 1999.

The NCSC website was implemented two years ago and it is updated with new information regularly. The url is: http://ce.ecn.purdue.edu/~SPAVE/.   The NCSC telephone number is 765/463-2317;  fax number is 765/497-2402.

NCSC provides training on Superpave Binder, Superpave Volumetric Mix Design, and Volumetric Mix Design for Iowa with a combination of Marshall and Superpave.  They also provide NHI Training courses on; Superpave for Local Governments; Superpave for Senior Managers; and Superpave for the Generalist Engineer.

NCSC's Research projects currently are; NCHRP 9-12; Ohio State; Pooled Funds Study; Regional RAP Study; and a National Pooled Funds study.

The NCHRP study on incorporating RAP into Superpave will be completed in the summer of 1999. The Ohio State study is on rutting. They are comparing 12 different aggregates using Superpave performance tests. All testing is complete; the project ends January 31, 1999. The pooled funds study is looking at FAA and using a battery of tests to find a better test. They are also collecting data from other studies. The regional RAP study covers using RAP under Superpave specifications using local materials. The national pooled funds study is looking at volumetric parameters such as air voids, VMA, FAA, restricted zone, accelerated pavement testing and simple shear testing.

The Center's base funding comes from the states and provinces. Other funding comes from FHWA, pooled fund studies and industry. The newsletter does not generate income, but   some of the publication and editing costs are recovered from the other centers. There are also possibilities for funding from FHWA. They are currently out the details of accepting funding from industry with the university administration.

There are four major areas the NCSC is involved with:

1. Communications -  website, newsletter
2. Research
3. Training
4. Implementation with industry.

Industry is an area that has not yet been developed. The original thought was that the NCSC  would be cooperating with industry on a daily basis but not  many calls for assistance have come from industry. Other Superpave Centers have had the same reaction. The Superpave Centers are interested in looking at  research topics in conjunction with industry. The participating states and provinces in the NCSC are Illinois; Indiana; Iowa; Kansas; Manitoba; Michigan; Minnesota; Missouri; Nebraska and Wisconsin.

 

Research on RAP in Superpave Becky McDaniel, NCSC

Rebecca McDaniel summarized the status of National Cooperative Highway Research Project (NCHRP) 9-12, Incorporation of Reclaimed Asphalt Pavement (RAP) in the Superave System, which is being conducted by the North Central Superpave Center and the Asphalt Institute. The first priority of the project is to address the issue of whether RAP is a black rock or whether some blending occurs between the hardened RAP binder and the added virgin binder. In this study, that will be evaluated by analyzing three different mixture cases corresponding to different states of binder blending. Case represents no blending and is simulated by mixing virgin and extracted RAP aggregates with only the virgin binder. Case B is a real life case where RAP with its binder coating intact is added to virgin aggregate and virgin binder. Case C represents total blending and is simulated by mixing virgin and extracted RAP aggregate with blended binder; the blended binder consists of recovered RAP binder that is physically blended with virgin binder prior to adding to the aggregates. In all three cases, the source (RAP or virgin) and gradation of the aggregate is held constant. If no blending occurs, Case B properties should be similar in mixture properties to Case A. If blending occurs, Case B properties should approach Case C. McDaniel then showed data from one medium stiffness RAP, incorporated at two addition rates (10 and 40%), mixed with two virgin binders (PG64-22 and PG58-28). The data so far shows that at least partial blending occurs, since Case A is significantly different from Case B and C. Following the black rock study, the project will go on to analyze the effects of RAP on binder and mixture properties and to develop detailed guidelines for laboratory and field technicians working with RAP in Superpave. The project will be completed this summer. A companion regional pooled funds project will continue this research focusing on typical regional materials.

Certification, Reciprocity, among States and Provinces
Laird Weishahn, Nebraska DOR

Laird Wieshahn made a review of the highlights that each state or province need to have included in their Technician Certification Plan (TCP). The benefits gained by an "agreement" between the agencies were presented to the group. It was pointed out that when agencies TCP required something in addition to the "basic test procedures" identified in the Region Technician Certification Program that the agency needed to the different requirements.

The North Central Region Technician Certification Plan is does not tell the agencies what their TCP should include, but it does suggest what to include. Surely each state understands the need for a TCP in their state. Now identify what it is and get on with it.

Maybe this Cooperative Agreement should have an Appendix where each agency could include their TCP program and all their updates to it. This would give other agencies or individuals an idea of what the additional requirements will be when applying for certification in another agency.

Summary Report on Asphalt Technicians Workshop
Ray Hogrefe, Jebro

A group of questions were developed from a query of states in advance of the workshop. Previous workshop concerns were lab test equipment and operation problems. Participants at this workshop were more concerned with application of tests to Superpave mix production, meaning of test results, and AMRL certification issues. A panel with John Hinrichsen, IADOT, and Chuck Paugh, FHWA, assisted with the discussion.

There are concerns with stopping at N des during the mix design process. Why change? There are problems with handling a tender specimen. Mixes have passed at N des but fail at back calculations from M max. What happens if the mix fails N max?

Some fracturing of aggregates is occurring in coarse designs. Use of greater lift thickness and attention to frequency and amplitude of vibratory rollers can help.

In the application of LTPP temperature algorithms for PG grade selection, you need to understand the relationships of traffic, axle loadings and reliability.

Moisture content in the mix can be a [problem with compaction. Some states are controlling mix moisture with <0.5% moisture not considered a problem,

The lack of AASHTO guidelines on batching and mixing loose mix samples in the lab caused much discussion. Particularly with modified asphalts, use supplier/ manufacturer recommendations. Temperature based on viscosity can be up to 50 degrees C. to high.

John Hinrichsen, IADOT, presented a study on correlation between different SGC’s using contractor furnished equipment and conducted in their central lab. There were many concerns that could impact quality control and quality assurance management.

Gale King, Koch Materials, presentation at the end of the technician workshop on modified binders referenced numerous papers. NCHRP 9-10 finds that the current MP-1 specification does not adequately measure the fatigue characteristics of a modified binder. A mix strength test is needed. NCAT is evaluating the Asphalt Paving Analyzer as a strength stripping test. According to Mr. King, the Lead States acknowledge an interim use of PG+ specification where states have good experience with polymer modified asphalt as a means to avoid "fooling the tests".

Feedback is to be made to AMRL, AASHTO, and the TWHG’s on concerns discussed at this workshop. Attendees feel another workshop would be productive in a year. Care should be taken to avoid confusion in registration flyers and agendas for future Technician Workshops, NCAUPG annual meetings and the NCSC Steering Committee meetings.

Industry Update
Charles H. Van Deusen P.E., Consulting Engineer

Mr. Van Deuesen reported on a Superpave contractor survey conducted by the National Asphalt Pavement Association (NAPA) and the State Asphalt Pavement Association Executives (SAPAE) in 1998. The objective was to develop a broad overview of the Superpave successes/ problems from the contractor’s perspective. Twenty-five states were involved with 110 projects and 4.5 million tons of hot-mix asphalt (HMA). There were about a ¼ low, ¼ medium and ½ high volume traffic loadings. The projects were on rural/urban two lane and multi-lane pavements. About 25% was base , 25% leveling and 50% surfacing. 12.5 mm was the predominant size material.

On the binder side they found huge differences in the product by the asphalt suppliers. Different grades were used in the base and the surface mixes. There were PG graded asphalt as well as PG + grades of asphalt. In other words many states were supplying asphalt with supplemental specifications. The usual suppliers could also provide the PG grades. There were 12 different grades used on these projects. The grades ranged from PG grade 52-28 to 82-22, with the predominant grade being 64-22. The Thickness of the lifts ranged from 1 and a half to 4 inches in thickness. The max aggregate size went from 9.5 mm to37.5 mm. Most lift thickness’ were up to three time’s nominal size.

50% of the mix used an anti-strip additive( 60% liquid). The compaction temperature was as recommended by the supplier.

The contractors used their regular suppliers of aggregate which were readily available using conventional crushing at a possible higher cost for material.

Some of the changes to the aggregate were: more clean materials; more manufactured sand; and more splitting of sizes. The blend of the aggregates were coarser along with the need for a clean intermediate size for mix design. 70% of the mixes were designed to go below the restricted zone. 65% were not allowed to go through the restricted zone, however, some states allowed to go through the restricted zone if they pass volumetrics.

Some 70% had no problem designing around the restricted zone. There is a very small window. About half used the "S" shaped compaction curve. It was easier to achieve VMA on the fine side of the gradation band. Most contractors had to work through many trial mix designs to come up with a final design. Natural fines improve the workability of the mix. All manufactured sand makes for a very harsh mix. 60% of the contractors used RAP in their mixes.

50%of the contractors had to reduce natural sand in their mixes. 40% had to eliminate the natural sand. Some DOT's did not allow RAP in their Superpave mixes. The volumetrics and the supply of RAP limited the amount of RAP in the mixes. Some states allowed up to 50% in their base mixes although the typical range was 20-30%. In the surface they allowed up top 30%, however, the typical was 10to 30%.

The contractor designed 80% of the mixes. This is up from 65% in the last survey. The gyratory compactor is performing well. 90% of the contractors owned at least one. 60% reported using a two-hour cure. 70% use no aging in production.

Superpave does not eliminate the need for good mix design practices.

The problems in mix design were in achieving the proper volumetrics. The challenges were getting the proper aggregate specific gravity, low or inconsistent voids, use of more manufactured sands, the need for intermediate sizes and the steep learning curve (homework) to achieve a satisfactory mixture.

As far as plant operation goes, 90% reported no changes. The number of bins averaged six. 50% reported using higher mix temperatures with about 25% ranging between 275 to 300 F; 40% 300 to 325 F; and 35% reporting 325 to 359 F. The higher temperature will cause a lot of problems. The material going out the stack at 350 degrees is much different than that going out with a 300 degree mix. The workers could be adversely affected with the higher mix temperatures around the paver. This is not conducive to a good workplace. There is no need for these high temperatures.

The aggregates are more cubical and are harder to compact. There is more need for additional binder storage (tanks, lines, etc.). Splitting the coarse aggregates requires more bins and related equipment. You are constantly making small changes to your operations to keep the volumetrics where we want them to be. There is more wear and tear on the equipment due to the coarser aggregate going through the plant and the paver. There is more noise at the plant as the aggregate goes through the plant.

Some of the overall comments were; Using the best management practices are critical, along with changes for commercial work such as using a PG 58-28 on a low volume parking lot created scuffing, going to a PG 64-22 got away from scuffing. We don’t think there will be a long-term durability problem. Attention to details such as stockpile management, mate4rials delivery, increases in the number of mixes has forced better plant staff cooperation. This has been a great thing for the plant team. This has forced the involvement of the loader opera5tor, the truckers, the plant operator etc. This has brought good teamwork to the plant operations.

Some of the contractors reported that handwork was more difficult due to the coarser nature of the mix (80%). 30% reported more difficulty with the longitudinal joints, although 70 % reported no segregation. Good paving practices critical!

To get proper compaction, it required increasing the number of roller passes and keeping the roller closer to the paver. The big question was where to position the second roller. This was different for each mix. Again more wear and tear on the rollers as well. Two-thirds of the contractors noted tenderness in the mix. The temperature zone ranged from 140-260 F. They stayed off the mix in the tender zone. They used vibratory compaction equipment above the zone, used pneumatics in the zone. They had more problems with tenderness in mixes with the "S" shaped compaction curve. Tenderness problems varied with the mix and the time of day. It was worse with thin lifts and was sensitive the particle size. 85% said that density was consistently achieved. 55% reported that the mixes cooled faster. This was due to the coarser mix, the temperature distribution in the aggregate and the harder binder. Some felt that fines "insulate" the mix better. Some overall comments on compaction of Superpave mixes is that they are not as forgiving; overall they are harder to compact; and require more attention from the roller operators. Overlays on PCC are different than on HMA. They need to use temperature guns religiously.

A summary of comments on Superpave are: "Superpave is a big deal for a lot of people, but QC/QA is more of a challenge and a better change"; " QC is the best thing that has happened to us"; "Superpave is a chance to differentiate HMA form the competition"; " Superpave is an exciting pain in the butt";" All the Superpave horror stories didn’t come true". On quality control, all states are using Rice Density one or two tests per day. The most common density specification is 92%. Two-thirds are using the ignition oven for the percent asphalt binder. 96% ran VMA on the plant produced HMA, although 60% did not use that as a pay factor. 85% said that the appearance of the pavement was the same or better than before. It’s appearance is more open and more consistent. 90% of the contracts specified smoothness in the specifications. 60% said they had some difficulty in achieving. 60% used the profilograph and 22% used the profilometer. The thin lifts were hard to make smooth. The smoothness depends on the mixture.

The QC personnel liked the Superpave mixtures. They thought that there were too many samples taken and they required too much material.

In summary, regarding Materials and Mix Design , we possibly need a change in the binder content; coarser, cleaner aggregates with less natural sand; design below the restricted zone; the contractor should do the mix design; and we will continue to struggle with the volumetric properties.

Plant Operations: Good paving practices are critical; Handwork is more difficult, mix may cool more quickly; although there was no problem with segregation.

Compaction: More effort is needed for compaction; need to be aware of how the mix/thickness/roller location/ tender zone inter-relate to one another. Attention to the details is important so that compaction density is consistently achieved. It is hard to do , but not impossible.

In general, the implementation of Superpave has been successful with positive construction results. The main issues are:

Volumetric Properties
|Compaction
Attention to detail

Modified Binder Update
Hussain Bahia, U of WI

There are at least 17 generic modifiers used to modify asphalt. Modified binders looked at in the study ranged from PG82-22 to PG 58-40.

Bahia first looked at storage stability, primarily phase separation and thermal degradation. The LAST is supposed to address this problem. Also looked at were fillers which make "trick" the specifications, and the PAT rest should limit/eliminate the use of such modifiers. The LAST test needs to be run at high and intermediate temperatures.

Next Bahia tried to address the effect of the traffic speed, traffic volume and pavement structure. Traffic speed can be addressed by testing at multiple frequencies to determine the effect of traffic speed on the binder. The traffic volume can be addressed in a fatigue test (proposed modifications to the PAV DSR test ate supposed to address this). The effect of the strength of a pavement structure can be addressed by testing at different strain levels.

Some modifiers lose strength rather quickly as strain increases. Certain modifiers may actually hurt the performance of the binder.

The temperature at which the PAVDSR is run will vary depending on whether or not you are in a freeze/thaw zone. Approximately 2/3 of the US is in a freeze/thaw zone. this includes ND, SD, MN, IA, NE, MO, and KS. In freeze/thaw areas, the PAV DSR is to be run at 6 degrees C and for all PG grades.

To address the effect of cooling rate on the cold temperature performance of a binder, Bahia recommends testing the BBR at the actual temperature (for example –28 for a PG 58-28) and 6 degrees C. above the temperature. Through time/temperature superposition, you can determine the effect of cooling rate on the performance of a binder, although I am not sure how they do this.

With the changes Dr. Bahia is proposing, he feels there should be no need for "PS+" specifications or grade bumping to account for traffic. The modifications to the test procedures to account for traffic speed, traffic volume, pavement structure, and cooling rate should account for this.

Dr. Bahia said there needs to be much more work to determine the test criteria. He feels that the changes he is proposing will be validated before it becomes a specification,

Construction Issues and Solutions/Agency and Contractor Experience/Superpave

Minnesota Dave Martini, MNDOT, District 7

Mankato        Larry Nurri, Southern Minnesota Construction (SMC)

6/9/99

General Scope

The general scope of this project was to mill four inches of the inplace bituminous surface and replace it with four inches of a Superpave mixture. Along with this work there was widening for the addition of left turn lanes, culvert extensions, culvert replacements, and curb and gutter replacement. To accomplish this work, the project was divided into four stages of construction.

Bituminous Quantities

Three different mix types made up the bituminous quantities for this project. Approximately 19,000 metric tons of a low volume mixture was used for shoulder construction, approximately 44,000 metric tons of a medium volume mixture was used for base construction, and approximately 70,000 metric tons of Superpave was used for the mainline paving.

Test Strips

Prior to mainline paving, two 500-ton test strips were paved to check mix properties. In addition, a test strip was paved between stages one and two of the construction to check mix design changes that had been made.

Fumes

Almost immediately, the paving crew started to notice problems with the fumes from the PG 58-34 asphalt that was being used. The problem was to the point that the paving crew started wearing respirators. A change in anti-strip agents seemed to help with this issue. Prior to stage two of construction, there was a change from the PG 58-34 to a PG 64-28 asphalt. This change seemed to reduce the fume problem and the paving crew was able to stop wearing respirators.

Compaction

Compaction of the Superpave mix was difficult from the beginning of this project. Early efforts to address the problem focussed on rolling patterns with little success. To make the mix more compactable, some mix design changes were made. These mix designs changes involved going from 100%-crushed material to the addition of 10% natural sand. With this change and constant monitoring of the rolling patterns with the nuclear gage, density was achieved.

Conclusions

Southern Minnesota Construction worked very hard to solve the problems that were encountered with the Superpave mixture used on these project. This hard work was the key to the success of the project. Attention to mat temperature and constant monitoring of the rolling patterns was the key to achieving density. This project was a learning experience for everyone involved because the Superpave mixture that was used acted very differently from the mixes used in the past.

Ohio Gary Ferguson, Sharp Testing Services

6/9/99

Iowa Michael Heitzman, IADOT and
         Barry Meldrem, Norris Asphalt Paving

Agency Perspective

Iowa’s Superpave implementation plan is well underway. During 1998 construction, 25 percent of the HMA placed used Superpave mix design technology. In 1999, 50 percent is scheduled to apply Superpave. And in 2000, Iowa will fully implement Superpave on the State system. We are currently developing the implementation plan for the local application of Superpave with full implementation targeted for 2002. The problems we are experiencing involve consistency of the aggregate sources (varying specific gravities) and achieving acceptable compaction (aggregate crushing on thin lifts).

Two projects discussed in more detail were research on the application of Superpave by local agencies and a laboratory investigation of different gyratory compactors.

Iowa Highway Research Board Project TR-414 was developed in early 1997 and involves the monitoring of construction and performance impacts from the use of Superpave on low volume roads. The eight projects selected were constructed in 1997 and 1998. A number of projects encountered poor sub-grade conditions. Most projects successfully used locally available aggregate sources in the mix. The cost of applying Superpave criteria to the mix design showed comparable values to normal Marshall design mixes. Generally, when mix designs were modified, the increased aggregate costs were offset be reductions in AC content. A formal report of the research findings is being prepared.

The Iowa DOT Central Lab recently completed a study of gyratory compactors from four different manufacturers. SHRP correlation protocol was followed and very consistent results were received. Preliminary findings showed that not all units initiated at the same level of compaction (n ini). Most deviations between the results were attributed to some cause. While the results do not appear to be statistically different, there does appear to be consistent differences between the four units tested. Similar evaluations are needed. A report of the findings will be prepared for TRB 2000.

Contractor Perspective

Superpave has been a significant change for the contractors in Iowa, but there have not been any major problems with implementing the new system. The Superpave system requires more time to prepare the mix designs and demands more attention to detail. Some companies have had problems with the combination of vibratory and pneumatic rollers.

Kansas Wade Culwell, Kansas APA

Wade Culwell; PE worked for the Kansas DOT for 32 years before taking the Assistant Director position with the Kansas Asphalt pavement Association under Jim Jones, Director. Wade was the District Engineer on the SHRP LTPP SPS l Asphalt Pavement Study in Southern Kansas. We have five major asphalt contractors with considerable experience with Superpave. These five contractors responded to the guideline questions and the responses are very similar. The contractor’s are:

Ritchie Paving - Witchita, KS
Venture Corp. – Great Bend, KS
Hamm Companies – Perry, KS
Shears Construction L.P. – Hutchinson, KS
Shilling Construction, Inc. – Manhattan, KS

Responses:

Question One: How have the changes in aggregates and asphalt affected production and laydown of asphalt pavement?
Answer: It has slowed production up to 20%. It takes more compactive effort and handwork is more difficult.

Question Two: How have you changed your aggregate production or purchase of aggregate?
Answer: Yes it has changed. It requires more clean durable material and crushed fines. Usually requires more producers (sources) to obtain the mix required.

Question Three: How have these changes affected the cost of materials in the final mix?
Answer: Costs are up, local aggregates are unsuitable requiring linger hauls. Asphalt hauls are also longer.

Question Four: How has the use of manufactured sands affected the production and cost of the mixture?
Answer: Increased the costs and slowed the production because of high moisture content also increasing costs.

Question Five: Have you had problems correlating your gyratory compactor with others or agency gyratory compactors?
Answer: No problems experienced to date.

Question Six: How about correlating different manufacture compactors?
Answer: Not yet.

Question Seven: Did you have trouble getting voids, VMA, etc.?
Answer: Yes, fluctuations in the field, requires many changes.

Question Eight: Please includes any performance measurements if you have them.
Answer: NA

Question Nine: Did you experience problems getting density of the mixture behind the paver? If so, how did you solve the problem?
Answer: Yes, but solved problem with more quality control of compactive effort. Requires more training of roller operators.

Overall there is a concern that the increased costs for Superpave and QC/QA will make HMA less competitive with the concrete pavements. Density behind the paver requires more effort. You have to be flexible and have a wider range of rollers available. Things are a lot different than conventional mixes. Trained personnel are difficult to find . Finding and handling of materials has its growing pains. Just getting there requires more personnel costs.

Kansas Rodney Maag, Kansas DOT

Rodney Maag gave us an agency perspective on Superpave. Kansas change ordered seven Marshall design projects to QC/QA Superpave projects. This was to provide the contactors and KDOT experience with Superpave. KDOT is implementing QC/QA and Superpave on the same projects. The first letting of a Superpave project was June, 1997. This project contained over 400,000 tons of Superpave mix. It is believed to be the third largest tonnage 1997 Superpave project.

Starting in October 1997, all major projects have been QC/QA Superpave projects. In 1998, 16 projects were let and they contained over 1.5 million tons of Superpave hot mix. This was approximately on half of the 1998 tonnage let by KDOT. Five 1R (thin maintenance overlay) projects were let in November and December 1998. The goal for the fall 1999 lettings is to have all 1R projects with over 20,000 tons Superpave. A few small projects may not be full Superpave projects. Training of personnel has been implemented. This is the third year of QC/QA Superpave training at Kansas State University. The contractors and KDOT employees both attend the same classes.

Mix problems have been encountered with using soft limestones from eastern Kansas. VMA and dust to binder ratio have been critical items. VMA is dropping 1 to 2 percent through the hot mix plant. Some limestones are being washed at the quarries before being hauled to the Superpave projects. Western Kansas, with only one quarry in an area over 200 miles by 250 miles has a definite aggregate supply problem. Crushed aggregates from Colorado, New Mexico, Oklahoma and Texas quarries have sometimes been used in the Superpave mixes. Another concern is the new software for selecting PG binders. The new criteria calls for –22 degrees C. in the southern part of Kansas and –28 in the northern part. Transverse cracking is a major problem with the existing bituminous pavements and the use of -22 degrees C. is questioned. Water permeability of some 19 mm Superpave mixes has been a problem.

Missouri Jim Campbell, MODOT

Introduction

Jim Campbell is the Field Materials Director for the Missouri Department for Transportation. To date, eleven Superpave projects have been constructed in Missouri. Their goal was to have projects in each of their districts by now, but budgeting and other problems have prevented all areas from being covered.

VMA

From the outset of Superpave, achieving the required VMA has been difficult. Missouri typically has what are considered soft (LA greater than 30) limestones and dolomites. At this time we have not been able to design a fine graded Superpave mixture. All of pour designs have been coarse graded (below the restricted zone). Most mixtures we have designed have required that a harder, more durable aggregate be added to the blend. The northern and western areas of the state are the most deficient in durable aggregates.

We have not changed from the procedures used in the past for purchasing mineral aggregate in Superpave blends. The hot mix asphalt contractor is the "prime" contractor and he makes his deal with the aggregate producer. That’s been the situation for a long time in Missouri. We have noticed no appreciable change in costs for the respective mixes of Superpave when compared to the older conventional mixes.

Contractor Design

As a part of our implementation of a QC/QA specification, we required our contractors to submit complete Superpave mix designs for the 1998 construction season. This was a first for Missouri. Traditionally, the contractors have submitted designs based on past experiences that were tested and approved in our Central Laboratory. In 19988, the contractors were required to submit samples of the mixture components for MODOT to verify the design in our laboratory.

Verification of Mix Design

The first contractor that sent in a design for verification had designed the mixture on a different brand of gyratory than we use in our lab. After a series of tests and passing samples around, it was determined that the compactive effort of the gyratories were not the same. The difference in bulk specific gravities of the specimens generally ranged from 0.030 to 0.050 on all of the projects. The difference was not resolved on the first project until the contractor designed mixtures for the job on the same gyratory that was used for field verification of the mixtures.

VMA Loss

In addition to the difficulties in attaining VMA during design, loss of VMA in production due to the generation of fines has been a problem. All of the projects constructed to date have had to make adjustments to the mix design to achieve VMA. A portion of the baghouse fines were wasted on all projects constructed in 1998 in order to maintain an acceptable VMA level.

Contractors to this point did not know how much was actually being returned from the baghouse. The plant personnel on one project said, "little was being returned" so all of the baghouse collection was diverted to the mixture. They estimated over 13 tons of material; was removed from the baghouse in a 250-ton test strip. A non-uniform rate of return for baghouse fines has also generated variability.

Compaction

Compaction of the mixture has been a problem with almost all of the projects so far. Our specifications called for compaction to be 92-95% of the theoretical maximum specific gravity of the mixture. Many of the projects had averages between 90% and 92%. We have made some minor adjustments to our specifications and continue to encourage the contractors to train their personnel for consistent rolling patterns. We think as experience is gained with placement of Superpave mixtures that compaction will improve.

Tenderness

Nationwide there has been some concern with tenderness in Superpave mixtures. One of our first projects constructed had tenderness in both 12.5 mm and 19.0 mm mixtures. Since that time, only one other project has exhibited signs of tenderness in the mixture. We think limiting the amount of gravel in our mixtures can minimize this problem in the future. We also hope to limit this by educating lay down people in the tendencies of some asphalt binders to be plastic during certain temperature ranges.

Summary

Overall, we feel our Superpave projects have been successful and continue to look for ways to improve our specifications and new processes created by the implementation of QC/QA. At this time, all projects are being constructed under a Pilot Phase. We look forward to full implementation of our QC/QA specifications in the year 2000. Twenty to 25 new projects are anticipated to be constructed in 1999 with Superpave mixtures.

Comments to the NCAUPG Tom Bryan, FHWA

Capturing Credible Data and It’s Use

A. Where Are We? - The data used for pavement assessment in use by owners to date has been "blind" or "nearly blind" data. That is, performance evaluations have been based on the observed condition of the pavement in service and an assumption made that the basis of design has been satisfied. This thinking may have been developed along the following lines:

1. What is designed, produced in the lab, and produced at the project is the same and will meet anticipated service life estimates.

2. The specifications reflect the design assumptions and requirements.

3. If the materials specified are met on the project, material handling, processing, and construction procedures have little impact on the material characteristics and capabilities, whether a single material or combinations of materials are involved. These concerns will be accounted for in the activities performed under the contract to provide specified materials.

4. The language of the contract assures that the design and specification requirements will be met. Anything not meeting these requirements is not incorporated into the end product.

5. Testing and inspection by all parties to the contract will assure that the contract requirements are met to provide the designed and specified product.

6. The influence of "outside considerations" such as construction expediency, seasonal demands for completion, sufficient resources available to provide contract satisfaction, and borderline materials use are irrelevant. The contract has identified that the product will meet the contract requirements and therefore this will be accomplished.

7. There is a known tie between material characteristics or combined material products and final product performance. "Reduced payment" provisions of the contract will take this tie into account.

B. What’s The Bottom Line? - The primary consideration for project administration has been generally based on satisfactory "completion of the contract" which is a budgetary orientation. This boils down to

1) the contract was completed on time (or thereabouts),
2) within budget (or thereabouts), and
3) in reasonable conformity with the approved plans and specifications.

To be fair, it’s a long time between construction and reconstruction or replacement and the need for additional projects must be satisfied by a system, which has been mandated to perform with ever reducing manpower resources. Also, changes in product loading (traffic) and the environment where the product is to function within the projects are not controllable items.

There is a reasonable window of service life that can be anticipated due to past history, given the design used for the product. This window is X to Y years plus or minus Z years under L loads/conditions. If X is not satisfied forensic investigations may be ordered to find out why. The control of X years to determine the characteristics of what was built as a forensic tool takes on the aspects of using a least common denominator.

In short, we don’t fully know the characteristics of what we have built, but the performance results are used to project fiscal commitments and future project/product design requirements.

TECHNICIAN TRAINING/CERTIFICATION and UNIFORM TEST METHODS

A. Technician Training/Certification - Under the provisions of Quality Control - Quality Assurance (QC/QA) contracting procedures, the assumptions of items three through seven above are now shared responsibilities. Test results from both the buyer (owner) and seller are used for contract compliance decisions during construction and whether or not performance anticipations will be realized. If informed decisions are to be made on the part of the buyer and seller the test results used in the decision-making must be credible.

Inherent variability in the process of sampling material, the test method itself and variability of the material being sampled and tested may cause test result differences. If informed decisions are to be made by the buyer (do I know what I’m paying for?) and the seller (do I know what I have produced?) both parties have a considerable financial stake in credible sampling and testing done by the technicians, whether "theirs" or "ours". If the results of the tests can be questioned due to the credibility of the technician sampling and testing, any further use of the test data is pointless from the prospective of both the buyer and seller. The objective is to identify the variation in the material or product, without further clouding due to sampling and testing issues. The test results of the seller’s technician must be credible for use in quality control, process adjustment, and inclusion as part of the quality assurance evaluation. The results of the buyer’s technician must be credible for use in product or material payment decisions for value received.

If the credibility question arises, considerable resources on the part of both the buyer and seller are often expended in an arena of discussion that begins with diverse positions based on opinion. That is, whose test truly shows the characteristics of the product tested and who incurs the expense of payment or correction? If there is no resolution to this discussion, dispute resolution procedures and re-testing is done by one or both parties (or a third party) often using a series of tests to establish comparison of test result averages.

B. Uniform Test Methods - A given for combined test result use under QC/QA contracting procedures, is that the buyer and seller use the same sampling and test methods. This is a means of assuring the comparison of apples with apples and not oranges, by avoiding a mix of different variables into the process. There may also be a need to use the same brand of testing equipment for the same reason. Technician training and demonstrated competency in the performance of the test methods to be used is essential. Once again, as stated above, the objective is to measure the variation in the material or product (the basic subject of the contract) to the best possible so informed decisions can be made by both buyer and seller. Both the buyer and seller must reach agreement on the test methods used, or have them identified in the contract.

We are currently in the middle of a design and testing change explosion under the Superpave experience. There are new and better testing tools, design tools, and specifications being placed in use as the conversion to Superpave takes place. The new testing methods have created an atmosphere of uncertainty for both the buyer and seller as we proceed from past empirical judgments into the engineered product arena. The changes are both a blessing and a chore to the practitioners. The chores will be handled, and are being solved as use of Superpave design and control spreads throughout our community.

The blessing is that we now have the capability of measuring engineering properties of more of the components of the asphalt mix and performance estimates than we had before and the opportunity to match engineering properties with performance through data capture of the test results using electronic data processing. If, however, there is a proliferation of test method tweaks reminiscent of the Marshall procedure days, we will lose the opportunity for progress and improvement by losing a measuring stick of known length uniformly applied by all.

Use of MY way of testing and MY way of training and certifying test technicians may yield pride of authorship and the convenience of doing things in OUR system the way we always have done (never changing has comfort index benefits but we need to address the concern with "rutting" in our processes as well as our product). In several states around the country and within our own organization, when states openly and honestly sat down to compare supposed differences between MY test methods and YOURS; they found the "differences" to be semantic or irrelevant.

The value of the data obtained through uniform test method application across the North Central Asphalt User Producer Group (NCAUPG) is in the increase in informed use of the tools that Superpave has offered to us. Uniform training in a common test method will also yield benefits to both buyer and seller through provision of a common base of experience that all can use in tying down the cause and effect of material use to performance.

Through the AASHTO Subcommittees on Materials and Construction and industry, there are activities underway to develop a Technician Training and Certification Guide for technicians in the areas of soils, aggregates, bituminous and concrete. This guide includes the test methods previously developed within the NCAUPG for consideration three years ago by Rich Wolters and Jerry Huber. There was a consensus that the work done by Rich and Jerry was a desirable way to go but we have not moved any further than the consensus other than in KS, IA, MO, and NE.

Work has been done through a Midwest task group, including representation of states, industry, suppliers and the FHWA from the Midwest, the west, and east, to develop a training manual covering the Superpave and associative test methods geared toward the technician in language and guidance in the performance of AASHTO test methods that are included in the above guide underway and reflect previous NCAUPG initiated work by Rich and Jerry. This manual is to be available soon. Similar training material has been developed for the Western and Northeastern states as they move toward a common uniform test method application and reap the benefits of common data available for use in construction and design.

SO WHAT? WHAT’S IN IT FOR ME?

All the tools for use of technician training and certification programs that will include uniform test methods are soon to be available. If you have an ongoing program of training and certification that covers buyer, seller, supplier and consultant forces necessary for Superpave, there is still the question of test method uniformity and data comparison.

A fair question was raised concerning the presentation on the NCAUPG implementation of technician training and certification program use and uniform test method use. The question was "Is this a crusade for a dream? Is there a need or just a desire?"

At this time there is a need. See the previous assumptions under "Capturing Credible Data and It’s Use". If we are to make the historic assumptions shown somewhat reliable, we need to take positive steps to provide the tools and information to make them achievable. Each assumption is based on good information or data from our experiences and we haven’t developed a good bank of information and data yet for Superpave. We can if we want. The benefits will depend on the uniformity of the data and that will depend on a program proficient in establishing the credibility of the personnel that supply the data. Common test methods use and common training foundations will provide the tools. It still remains up to us to use the tools effectively. Agreed, there’s no such thing as a free lunch, but there is much that can and should be done to improve our knowledge base and improve our product. Individually this can be addressed by each state, but only as long as there are resources available to address the concerns in each state. Acting through the NCAUPG as a group, the accomplishments that can be realized should come cheaper than independent efforts.

Comments to NCAUPG:

Tom Bryan, Materials Engr.- FHWA (MRC) 2/21/99
NCAUPG Meeting January 27-28, 1999, Kansas City, MO

NEXT NCAUPG MEETING

The next meeting of the NCAUPG will be in Kansas City, at the Airport Hilton on the 19th and 20th of January, 2000. It will start at 1:00PM on Wednesday and adjourn at noon on Thursday, the 20th.

Meeting adjourned at 11:45 Thursday, January 28,1999. If you have any additions or corrections to these minutes, please contact me:

Richard C. Ingberg, PE Tel/Fax 651-429-2955
Secretary, NCAUPG
2185 Regent Drive
White Bear Lake, MN 55110-4335

North Central Asphalt User 3-6099

APPENDIX

Return to NCAUPG Annual Meeting Minutes


NCAUPG Meeting Minutes January 1999
E-mail your comments to: ncsc@ecn.purdue.edu