1997 U.S. Hot Mix Asphalt Conference and Superpave Workshop

By Phil Arena, FHWA Louisiana Division

The following is a summary of information obtained at the U.S. Hot Mix Asphalt Conference recently held in Phoenix, Arizona. The conference focused on the latest products and processes affecting the quality and performance of asphalt pavements. The conference included a Superpave Product Fair and a full day Superpave Workshop. There were close to 500 registrants for the conference which indicated the interest in the design and construction of hot mix pavements, primarily the Superpave process.

The conference was three and one half days and touched upon construction issues, superpave workshop and hot mix construction. A copy of the agenda is attached. Summaries of the presentations are as follows:

Moderator for the first session was Mike Acott of the National Asphalt Pavement Association and welcomed everyone to Phoenix.

Wednesday, October 29, 1997
General Session

Larry Bonine - Arizona Department of Transportation

In his opening address he indicated that if a process is measured and documented it will normally lead to improvements. He spoke of the increasing changes going on in the highway industry. The private sector has embraced AQuality@, but the public sector needs to wake up to serving their customers.

John Spangler - Milestone Contractors - Contractor Perspective on Achieving Quality in Construction -

• Customer focus - The reason for quality is to serve the public. How can we better serve the public? The customer wants the best roads that can be provided.
  
  • The customer wants the roads to last a long time.
  • Little rehabilitation
  • They want to be kept informed
  • Safe
    
  The customer is aware when quality work is done.
  

• Partnering - contractors are using it within their own company, with equipment manufacturers, aggregate producers, employees etc. Milestone Contractors has participated in A+B+ warranty projects and the customer took notice that the projects were being expedited. Arizona and Indiana both believe strongly in partnering.
  

  In 1995 The Committee on Asphalt Resurfacing Technology was created through partnering with the national Asphalt Paving Association (NAPA). Some of the issues addressed were:
  

  • Laboratory accelerated pavement performance testing
  • Hot Mix mixtures for the year 2000
  • Updated recycling technology
  • Methods and equipment to improve construction
  • User delay costs
  • High surface friction courses
    

• Technology Research
  
  • SHRP has caused Indiana contractors to look at their operations and procedures.
  • Warranty pavements helped contractor learn more about technology and help them realize they needed to know more about their product.
  • Contractors need to have a research line item in their budget to help them perform some research and consequently learn more about their operation. The question was asked how many contractors in the audience had a research line item in their budget. Only four responded.
    

• Change
  

  Contractors must think about the future and realize changes are being made. The State of Indiana has a design build project which is new to the contractors and the state. They both need to focus on change for the future.
  

• The SHRP program has caused industry to look at their products.
  
  
  • Polymers result in higher temperatures, even 25E F doubles the rate of oxidation
  • Fumes consist of 70 -80 % vapor and 20 % smoke
  • Astec has pavers with fume extractors on the pavers and on material transfer vehicles
  • The higher temperatures needed to get compaction produces more oxygen and more fumes. The fume extractors were accomplished through partnering with other equipment manufacturers, OSHA, NAPA, NIOSH etc. It is not known whether or not these fumes are hazardous but they can cause headaches and with the fume extractors the problem is taken care of.

• Joints should last as long as the pavement. Good joints require the following:
  
  • Steer a straight line
  • Approximate overlap should be 2 - 3/4" - do not lute
  • Keep segregation from occurring
  • Auger material all the way to the edge of the joint, use auger
  • extension if needed.
  • Maintain sufficient material for lay down
  • Roll from the hot side, 6" on the cold side

Dean Testa - Kansas Department of Transportation - How to Prevent Segregation

• Segregation solutions will not work on all projects. A joint task force was formed in 1995. In 1997 a NCHRP 9-11 report entitled A Segregation Causes and Cures for Hot Mix Asphalt A came out. There are five types of segregation.
  
  • Truck-ends - segregation on both sides
  • Centerline segregation
  • Joint edge segregation
  • End of truck - one side
  • Random segregation

• Longitudinal density will identify truck segregation. AS@ curve gradation mixes will segregate more readily than straight line gradation curves. Bowed curves will not segregate as much.

• Segregation may be prevented by making adjustments in the:
  
  • Stockpiles
  • Plant
  • Paver - move the material as a mass
  • Keep paver moving
  • The MTV can help to prevent segregation

Dr. Ray Brown - National Center for Asphalt Technology - How to Identify and Measure Segregation

• Segregations needs to be prevented and must be able to be quantified and measured.
  • It can be identified visually but will not be seen if segregation is occurring at the bottom of the layer. Visual is subjective but not good enough.
  • Non-destructive ways:
    • nuclear density
    • change in asphalt content
  • Destructive ways:
    • Cores - A.C. content will decrease
    • Gradation - 10% change on the No.4 and No. 8 sieve is considered max. allowed.
    • Density - Could measure permeability - however, there is no good tests to measure permeability

Chuck Deahl - Compaction America - Bomag/Hypac - Compaction: State-of-the-Practice

• Need for compaction
  • mix confinement
  • correct mix temperature
  • time available for compaction
  • lift thickness - Florida uses 4 times nominal max. size, use today is normally 3 times max. nominal size. You need enough material to rearrange particles for compaction.
  • MTV will give more consistency in compaction

• Gyratory compaction in the laboratory is more like field compaction.
  

• Nuclear densities on coarse graded textures- dust with sand under the nuclear gage for best results.
  

• Rolling:
  
  • vibratory - 285E - 300EF
  • ender zone - 240E - 200EF
  • final rolling - 170E - 150EF
  • if a pneumatic roller is used it should be capable of 85 -95 contact pressures. Pneumatic rollers are not recommended for polymer modified asphalts due to pick-up on the rubber tires. Michelin has produced a tire that will not cause pick-up. It will be tested the summer of 1998.
  • vibratory rollers should bump the paver at approximately 300EF on SMA mixes and possibly modified binders for superpave mixes. The recommended frequency of the roller should be such to produce 10 impacts per foot. Vibrations per minute can be measured with a hand-held tachometer ($500). Some of the newer model rollers will give the speed, vpm and impacts per foot.
  • longitudinal joint compactor wheels for the edge of the mat is difficult to use and not recommended.
  
  

• The speed of the paver should depend on the production rate at the plant, also the roller will have to be able to keep up to achieve compaction. Production is usually limited by the roller production. The following balance must be made:
  
  • haul time
  • number of trucks
  • roller production (most important) you need to get as many rollers
  • necessary to do the job.
    

Panel Discussion

Chuck Deahl

• There is equipment coming out with temperature-on-the-run rollers.
• Density-on-the-run has not fully been developed in the U.S.
• Do not use a vibratory roller in a vibratory mode for finish rolling. You may run the risk of rippling the pavement even at lower temperatures.
  

Tender Zone-

There was a great deal of discussion about what was called the tender zone on superpave projects. The tender zone was described as the zone when the temperature of the mat was in the range of 250E F to 185E F (this can vary) after initial rolling with the vibratory roller. Some persons in the audience wanted to know if it could be avoided or taken care of in the design. It was mentioned by Jay Hensley, of The Asphalt Institute, that this phenomena was nothing new and has been going on for years before superpave. I (Phil Arena) agree with Jay on this issue and even though it was not part of the conference I would like to try and explain in the following paragraph my opinion of why I think we have a tender zone:

When the mix is first laid on the roadway from the paver the temperature may be approximately 300E F. Usually the vibrating screed on the paver will compact a mix to approximately 85 % compaction. Therefore, when the vibratory roller makes its initial pass in a vibratory mode the compactive effort is in a downward direction with little resistance by the mix due to the high temperature and low initial density. As the vibratory roller continues to roll, the density of the mat goes up to a point where you have aggregate interlock and now resistance to the roller in a upward direction. At this point the mix may still be in the temperature range of 250 to 185E F which is still high enough that the mix is in a plastic condition and will continue to try and move under the roller. At this point the vibratory roller is usually running in a static mode ( vibrators shut off) which acts as a normal steel wheel roller. If rolling is continued at these temperatures the steel wheel roller will cause the mix to roll forward at the surface resulting in what is referred to as check cracks. The reason this occurs is that the resistance at the bottom of the mix is high enough with the compaction achieved and the fact that the bottom of the mix is confined there is no more downward movement at this point. However, the mix being still hot and plastic takes the least path of resistance which is at the surface where it is not confined and so the mix tends to move upward when rolled with the steel wheel roller. Once the mix adequately cools below approximately 185E F ( this temperature will vary with various mixes) the asphalt viscosity has risen substantially at the lower temperature in which the mix is no longer in a plastic state giving adequate confining pressure at the surface and thereby allowing the steel roller to roll in a static position without the tenderness experienced when the mix temperature was higher.

This reaction is not new at all, I have seen this on many occasions. Once the vibratory roller has made its required number of passes in a vibratory mode, rolling should cease until the temperature is such that tenderness is not experienced. At that point the static steel wheel roller may be used to eliminate roller marks or just complete finish rolling.

Thursday, October 30, 1997

Superpave Workshop

George Way & Julie Nodes - Arizona Department of Transportation - Arizona DOT's Experience with Superpave

• Arizona is a strong supporter of SHRP. They are the 5th most active SHRP State. Arizona has a Superpave Team since the Summer of 1993. Arizona went to the PG Grading system for asphalt binders in January , 1997.
  

• Arizona DOT has eight superpave test projects. Some of the facts mentioned are as follows:
  
  • All superpave sections are performing well

  • Arizona does not follow the superpave process as written
    1. Increased VMA by 0.50 %
    2. Design for 5 % air voids
    3. Sand equivalent - min. 55%
    4. Crushed faces - min. 85% two crushed faces
    5. No VFA requirement
    6. Dust to asphalt ratio - 0.6 to 1.2 low volume - 0.8 to 1.2 high volume
    7. Curing or aging period - 2 hours
    8. Modified Lottman includes freeze thaw cycle - tensile strength ratio (TSR) 70%
    9. Compaction requirement - 93% Rice gravity

  • Incentives and disincentives are used based on mix properties

  • Experienced a big change in their gradation when going to a superpave process. Their normal mix had 40% passing a No. 80 sieve the superpave mix had only 23 % passing.

  • Arizona uses a rubberized open graded friction course as the surface course on all of their superpave designed projects. They do not use the superpave process to design open graded friction courses.

  • End result specification - ADOT does not do verification checks- just paper checks

  • All of Arizona's superpave projects are doing well to date. Rutting was not more than 0.25" maximum.

  • Has not had any compaction problems- keep rollers close behind paver
    

Bob Erdman - Maricopa County - Maricopa County's Experience with Superpave

• Maricopa County uses a PG 70-10 binder in their superpave mixes

• Had three questions:
  • Should the gradation go through the restricted zone?
  • Is their a correlation between the Marshall and the Gyratory?
  • What is a good compaction requirement?
    

• Some of the county roads showed rutting at the stop bar at intersections - typical
  

• The rutted mixes went through the restricted zone. Those that did not go through the restricted zone did not appear to rut at the stop signs.
  

Tom Burkett - City of Glendale's Experience with Superpave

* Glendale has constructed 70,000 tons of superpave mix and is happy with the mixes thus far.

Mike Worischek - Staker Paving and Construction Co. - Contractor's Experience with Superpave - Utah

• Utah built 20 superpave projects in 1997. In 1998 all binders and mixtures will be superpave.
  

• Some of Utah's superpave requirements are as follows:
  • VMA - 14.5 % for a 19 mm nominal size aggregate
  • Georgia Wheel Rut Tester - 3.5 mm max.
  • Lottman Test - 80 % TSR
  • Flat & Elongated particles (3 to 1) - 20 % max. - to reduce to 15% max. Would require the aggregate manufacturers to purchase a new impact crusher for approximately $200K
  • Mat thicknesses at 1 2" presented some compaction problems- mats at 2 2" had no compaction problems
    

• Industry acceptance is the biggest problem with superpave implementation. Need to get industry involved so they know what is required.
  
  • Adequate number of consultant laboratory testing
  • Availability of testing and inspection personnel
  • Certification of personnel
  • Training and testing of personnel
    

Ron Sines - New York Department of Transportation - Agency's Experience with Superpave

• New York had rutting problems in the 1980's
  

• Why New York was successful with superpave:
  
  • Executive management and upper management buy-in
  • Consistent message to the hot mix industry
  • Lead State responsibility
  • Formal implementation
  • 1996 - 11 full superpave projects
  • 1997 - 20 % of all projects will be superpave
  • 1998 - 50% of all projects will be superpave
  • 1999 - 100% superpave projects
    

• New York is trying to determine what percentage of projects fall into what ESAL categories. Currently using the following:
  
  • PG 70-22 binder grade
  • < 3 million ESAL's
  • use 19 mm nominal size aggregate and PG 70-22
  • < 10 million ESAL's
  • raise binder one PG grading.
  • > 3 million ESAL's use judgement to bump PG grade at signalized intersections or grades of 4% or more
    

• Mixture Design
  
  • Contractors design mixes
  • Gradation typically below the restricted zone
  • Lab verification of mix designs
  • Required plant verification, plant trials, field sections
  • QA/QC production monitoring
    

• Construction
  
  • Requires in-place compaction monitoring
  • Increased compactive effort is required
  • There is a trend toward heavier rollers
  • Problems- intermediate tenderness (tender zone), segregation, permeability
    

• Concerns with the Superpave System
  
  • N_des for high and low volumes - impact on municipalities
  • VMA - Do we need an upper limit?
  • Aggregate consensus properties
  • Depth from surface transition
  • Constructibility of mixes - segregation - permeability
    

• New York is pleased with their superpave projects
  

Ken Murphy - Anderson Colombia Co., Inc., Lake City Florida - Contractors Experience with Superpave - Florida

• Anderson Colombia has performed approximately 75 % of the superpave work in Florida
  

• Typical Pavement Design
  
  • 4.5" mill
  • 0.5" asphalt rubber membrane
  • 3.0" 19 mm base course
  • 1.5" binder course
  • 0.75" surface mix
  • Biggest problem meeting the minimum VMA - mixes have to be gap
  • graded to meet
  • Florida uses 20% RAP
  • Granite - coarse aggregate - Limestone - fine aggregate
  • Sample curing - 2 hours- viscosity increases 2 times for batch plant mixing and 1 2 times for drum mixing - hardening will affect volumetrics - recommend a force draft oven at the plant and cure to some viscosity
    

• Construction
  
  • Florida has had compaction problems - Compaction more difficult than standard mixes

    % of Max. Sp. Gr.	% Pay
    95+	105
    94 - 95	100
    93 - 94	95
    < 93	Run permeability if <100 x10-5 cm/sec
    	Remove and replace - Can obtain higher density with greater lift thicknesses

    
    
    

    Aggregate Nominal Size	Lift Thickness
    9.5 mm	1 2 - 2 A
    12.5 mm	2 - 3"
    19.0 mm	3 - 3 2"

  • Rolling Pattern Used
    • 4 coverages @ 300E F - vibratory
    • Tender Zone 240 -250E F
    • 4 coverages @ 160 - 180 E F - static 12 ton steel roller
      

  • Florida uses a permeability test which requires less than 100 x 10^-5 cm/sec

  • Florida uses a joint maker under screed which provides more material under the screed at the joint and helps get a better joint and higher density at the joint.
    

Jim Gee - Arkansas Highway and Transportation Department - Arkansas Experience with Superpave

• 1995 Arkansas went to PG binders and constructed the first superpave pilot project.

  By Nov. 1997 Arkansas has 30 or 40 superpave projects. To date 1.7 million tons of superpave mix have been constructed. Expects full implementation in 1998.
  

• The nominal aggregate size and the tonnage used is as follows:
  

  - 37.5 mm    425,000 tons
  
     25 mm       675,000 tons
  
     19 mm        690,000 tons 
  
  

• The PG binders used in Arkansas are as follows:

  - PG 64-22 <10 million ESALS
  
    PG 70-22 > 10 million ESALS
  
    PG 76-22 > 30 million ESALS & Interstates ( modified
  requires approx. 3 % polymer)
  
  

• 13 contractors have now obtained gyratory compactors both Pine & Troxler.
  • 1997 DOT purchased 13 Pines & 13 Troxlers
  • 1998 DOT expects to purchase 12 more gyratories
    

• All designs are made by the contractor and verified by the Arkansas DOT - 52 designs submitted - 29 accepted

• Mix Design
  • VMA with the existing aggregate sources in Arkansas can be made
  • 60 % of the time, the other 40 % requires the need to import aggregates. VMA versus field acceptance needs review. VMA - " 1% for 100% pay for field VMA.
  • natural sands - 10 -15 %
  • All designs are below the restricted zone
  • If the mix on a given lot goes within the restricted zone from field the DOT will allow the contractor to adjust to get it back to the specification requirements outside of the zone.
  • Arkansas follows the SHRP requirements for superpave.
  • The number of gyrations to be used for the design mix are listed
  • on the plans.
  • Acceptance testing 5 tests/lot divided into 4 sublots, contractor-
  • 1 test /sublot for control.
    

• Compaction
  • More compactive effort is needed in the field than on previous mixes.
  • Rollers should be kept directly behind the paver.
  • Projects constructed have no rutting after 2 years, one project flushed and two showed high permeability.
  • Permeability - 1 2 A overlay - is the relationship between density.
  • AHTD has put high emphasis on superpave and it has paid off in success.
    

Panel

• Arizona and Florida both use 0.5" rubberized open graded friction courses that are not superpave mixes.
  

• Arizona is willing to gamble with lower asphalt contents to eliminate rutting.
  

• Permeability - Is it a concern? It just may be on some projects were intermittent problems have occurred. If concerned, it should be checked.
  

Jon Epps - University of Nevada, Reno - Update on WesTrack

• Rutting has occurred in the top lift only

• Some fatigue cracking has occurred

• No low temperature cracking

• No water sensitivity

• Baghouse fines make the mix more conducive to rutting at high asphalt contents

• Fine mixes have outperformed coarse in both rutting and fatigue

• Coarse graded mixes appear to be more sensitive to binder grade & stiffness
  

John D'Angelo - Federal Highway Administration, Washington D.C.- Superpave Specifications

• What will be different with superpave?
  
  • Materials

  • Binders:
    • PG binder classification for asphalt cements
    • Modifiers needed in the asphalt to meet higher PG grades
      

  • Aggregates:
    • Aggregates specified by ESALS - new consensus tests on aggregates
    • Coarse aggregate angularity - fractured faces
    • Fine aggregate angularity
    • Flat and Elongated particles
      

  • Mixtures
    • Coarse mix is now defined by the % passing the No.4 and not by top size
    • Coarse mixes will tougher to compact
    • Any contractor who places these mixes without a control strip is taking a chance.
    • Lift thickness is critical - 3 to 4 times nominal aggregate size.
    • Volumetric controls as opposed to asphalt content and gradation
      

Ed Harrigan - National Cooperative Research Program - Research Activities to Improve Superpave

• NCHRP 9-7 - Implement QA/QC for SHRP Superpave

• Control Points
  • Binder
  • Aggregates
  • Plant mix
  • lay down
    

Charlie Pryor - National Stone Association, Washington D.C. - Aggregate Issues for Superpave Implementation

• NSA has 120,000 people in industry, 4,000 quarries
  

• Some concerns with superpave mix specifications
  • A plant tends to produce gradations right along a 0.45 power curve, by specifying a restricted zone we are costing aggregate producers money. There are some who claim that some mixes that fall inside the restricted zone do well.
  • Superpave should not specify VMA for an aggregate size, the issue is too complex
  • Fine graded mixes are less sensitive to percent AC.
  • Which sieve should be used for flat and elongated, No. 4 or 3/8 A (AASHTO)
  • Specifications should be based on performance data.
    

• Restricted zone is designed to prevent sanded mixes, tender mixes to prevent rutting. Also it is known that by staying out of the restricted zone you can more easily achieve VMA.
  

• Fine aggregate specific gravity can influence fine angularity results
  

• Flat and elongated particles- study in the U.S. indicates 10 % failing @ a 5 to 1 ratio (plus No. 4 material), 25 % failing @ a 3 to 1 ratio.
  • Maryland uses -
    • 10% 5 to 1 ratio
    • 20% 3 to 1 ratio
    • 15 % on combined materials at the plant
  • impact crushers result in better crushed material, but also produce more waste fines.
    

• Material availability for superpave mixes
  • No. 57, 8's, sand,
  • -7's, 8's, sand
  • 56's, 7's, 8's, sand
    

• Superpave will result in more fines from the industry - conducting research for use of fines.
  

April Swanson - Amoco Oil Company - Update on Superpave Binder Issues

• It was emphasized that even though superpave specifications and equipment are not perfect, they are better than what we had.
  

• Superpave has forced suppliers to take a closer look at their own quality control.
  

• In the case of rutting, correct the mix first and then correct the PG binder specification if necessary.
  

• Superpave has done a great job with low temperature control, reducing thermal cracking.
  

• Superpave has not adequately addressed fatigue cracking ( tests have poor precision) - issue really is film thickness, mix and temperature of the mix.
  

• Mixing and compaction temperatures should be obtained from the supplier for laboratory designs. Field mixing and compaction temperatures will come from experience in the field.
  

Matt Witczak - University of Maryland, College Park, MD - Superpave: The Search for a Simple Strength

• The University of Maryland has a five year study as follows:
  • Phase I - Study the SHRP models ( Level II and III sophisticated prediction models)

    The present models have problems that need to be corrected.

  • Phase II - Enhance the models

    Phase II objective

    • Modify asphalt concrete characterization
    • Develop a simple strength test to be used with superpave

  • Can one single test be developed to account for:
    • Permanent deformation
    • Fatigue fracture
    • Thermal cracking
    • Water sensitivity/ susceptibility

    Probably not says Witczak. But a strength tests of some kind to go along with the Level I mix design is desirable and has an 18 month completion date.
    

• The test of the mixes may possibly be correlated with performance using the ALF, even if the test itself is empirical. Some possibilities mentioned are as follows:
  • triaxial testing
  • repeated load tests
  • shear testing
  • GTM device
  • direct shear
  • simple shear
  • static creep
  • lateral pressure response
  • rut depth tester
    

• A questionnaire was passed out to the audience to be filled out concerning their thoughts on the type of tests that should looked at, the cost of equipment and the time to run the tests.
  

Don Steinke - Federal Highway Administration, Washington D.C.- How is Superpave Doing?

• Encouraged everyone to get a copy of NCHRP report 9-7 for a
• guide on good QA/QC procedures.
• More than half the states are using binder specifications in 1997
• More than 3/4 of the states plan on using the superpave mix design by 2000.
• Superpave projects: 100 in 1996, 325 in 1997
• Coarse aggregate mixtures- may have to cut down VMA requirements
• Compaction- not any harder to achieve, but must pay attention to detail and do the best job possible.
• Permeability - must improve field density to reduce permeability
• NHI course, Superpave for the Generalists Engineer & Highway Staff
• FHWA has developed a pamphlet, Directory of Superpave Resources.
  

Friday, October 31, 1997

Controlling HMA Construction

Training and Certification Programs

Rich Wolters - Minnesota Asphalt Paving Association

• Acceptance
  • mix design
  • field verification
  • process control
    

• Control
  • contractor does mix design in the lab.
  • contractor verifies it in the field
  • contractor performs control tests during production
    

• Certification - show student what to do and let him do it.
  • Level I - tester (introductory class)
  • Level II - decision personnel
  • Written test - gives good gage of effectiveness - may have oral exam. for people who are not comfortable taking tests.
  • Laboratory performance tests
    

John Roland - Virginia Asphalt Association

• Asphalt Plant - technicians and VDOT
  • Asphalt Field - min. One certified inspector per paving crew & VDOT inspectors
  • Aggregate plant- Aggregate shipped under the VDOT certification program
  • Nuclear - required for base stone and asphalt compaction gage operations
    

• Superpave Certification Program
  • Mix design - intense 3 days hands on superpave mix design school
  • Asphalt aggregates (new) - 1 2 day school for aggregate and asphalt producers technicians ( 2 classroom, 2 lab.)
  • Binder - PG binders tested & accepted on certification from binder suppliers

    A certified inspector also gets a hat with an emblem on it indicating that he is certified along with a certification card for his wallet.
    
    

• All new construction to be superpave in 1998. Fully implement superpave by 2000.
  

Jim Huddleston - Asphalt Pavement Association of Oregon

• 1993 - Quality improvement committee
• 1995 - Certified asphalt technicians
• 1996 - Roadway materials certification
  

• Certified Asphalt Tech. I - lab person, quality control
• Certified Asphalt Tech. II - make adjustments on mix
• Certified mix design technician - performs mix design
  

• Program delivery - by asphalt industry/ODOT. 1997 released request for proposal to deliver program
  • Asphalt & concrete associations had a joint venture - 5 year contract
  • Industry will provide facility, instructors and materials
  • ODOT will keep cost down, keep hands on design participation, will be involved about 50 % on exams.
    

• Training Program Materials
  • Test Procedures
  • AASHTO
  • NAQTC
  • Specifications
  • ODOT
  • Other
    

• Facilities
  • Field trailers will be use inside a warehouse with one wall cut out to see in.
  • Exam. - 2 written, 2 practical
  • It will be on proper techniques and reasonable results
    

Dick Root - Chicago Testing Lab. - Density Measurements

• Max. Specific Gravity of the Mix
  • Don't put bleeder valve on vacuum pump
  • May have to verify vibrating table don't assume it is better than hand shaking
  • Should use dry back results
    

• Roadway core density test
  • If water pickup is 2% of the volume - 10 gms of water between air wt. and saturated surface dry wt.- test not valid.
    

• Nuclear Density Gage
  • fill surface voids with sand
  • Calibrate gage with cores approximately (20)if it is to be used for field densities
  • reasonable compaction requirements are 92 % of Max .Theo. - 94 and 95 % is too high.
    

Larry Scofield - Arizona Department of Transportation - Measuring Smoothness

• Why do it?
  • insure quality and conform to specifications
  • ride comfort
  • verification of design inputs (serviceability is measured by
  • ride)
    

• What is it?
  • vibration
  • wave length of profile
  • vertical movements
  • whatever we agree on
    

• What is involved?
  • roadway surface
  • vehicle speed
  • vehicle suspension
    

• Complexity:
  • type of equipment
  • statistics
    

• Todays equipment:
  • profilographs
  • profilometers (more accurate than profilographs)
  • walking
  • light weight
  • high speed (van)
    

• International Roughness Index (IRI) - is now the world standard