hot mix asphalt technology

WWW.HOTMIX.ORG

VOLUME 15, NUMBER 3

PUBLISHED BY THE NATIONAL ASPHALT PAVEMENT ASSOCIATION

MAY/JUNE 2010

Going GreenTheres More to Being a Green Producer

Than Warm Mix and Recycling

E liminating Delaminationin Asphalt Overlays

The Evolution ofPerpetual Pavements

Tack Coats:Setting the Record Straight

Warm Mix: Where We Are,Where Were Going

Troxler Model 5850 Gyratory Compactor

Trust Troxlerto completely redesign our newest gyratory compactor with improved electronics, a hydraulic motor and software adjustable angle of gyration.

Trust Troxler molds for Asphalt Mix Performance Testing and a Shear Measurement option.

Trust Troxlerto make testing easier with a keypad adjustable angle, the most ergonomic design on the market and USB and serial ports for data storage and downloading.

Trust TROXLERThe Leader in Construction Testing Equipment

gnidneP stnetaP

Troxler Electronic Laboratories, Inc. - Troxler International, Ltd.3008 Cornwal l is Road, P.O. Box 12057, Research Tr iangle Park, NC 27709 - USA

Telephone: 1.919.549.8661 Telefax: 1.919.549.0761 Web: t roxler labs.com

453290_Troxler.indd 1 3/22/10 1:32:10 PM 467468_Heatec.indd 1 2/23/10 7:03:19 PM

AMERICAN MADE MAKING AMERICAN MONEYDEPENDABLE, STRAIGHT-FORWARD PAVERS

Buying American is good, but dont base your buying decision on that alone.

With our pavers you get high-quality, non-segregated mats, simple operation, maintenance, and trouble shooting; and when you have questions or want to order parts, its great to talk direct to the factory.Our customers buy from us because reliability and customer service are most important to them. Why? Because it helps them save time and make money.

ROADTEC an Astec Industries Company800 MANUFACTURERS RD CHATTANOOGA, TN 37405 USA 423.265.0600 FAX 423.267.7104 roadtec.com

Call us or visit our web site today!

ROADTEC: THE AMERICAN WAY TO MUTUAL SUCCESS AND PROFITABILITY.

ROADTEC HIGHWAY CLASS PAVERS: RP-195 10 track paver, RP-190 10 tire paver, RP-175 8 track paver, RP-170 8 tire paver, SP-200 10 spray paver. See roadtec.com for more.

444868_Roadtec.indd 1 8/31/09 11:00:07 PM

..

Shaker decks are a very economical way to filter out oversized aggregate or RAP from getting into your mix. Shaker decks are economical, durable, dependable, rugged and affordable. As a result of their simple construction, there is less to maintain and break down.

Shaker decks are constructed to use common size screen cloths, thereby making it easy to locate the various sizes you need to get your mix done.

Shaker decks can be custom made - such as mounting the motor on a certain side, should you be tight for room.

A custom stand can also be manufactured for your shaker deck. Alternatively, you can have a conveyor line in either stationery or portable configurations manufactured.

Shaker decks come in various sizes. Single decks range from 3' x 5' up to 5' x 10'.

Screen cloths are also available.

The RAPwranglerTM is designed to be powerful, efficient and easy to maintain. It can shred football sized asphalt chunks, down to more suitable gradations for introduction into both stationery and portable drum mix and batch plants. It eliminates off-site pre-crushing of asphalt materials to be recycled. It is powered by either a 30HP or a 50HP TEFC motor, and can be shive belt or direct driven.

The 20" rotor is equipped with 312 replaceable tungsten-tipped milling teeth that shred chunks of asphalt down to 1" at a rate of 250 tons per hour. The rotor spins at a constant 127rpm undermining the material in the 30" x 40" hopper directly above it.

434991_TheAce.indd 1 6/26/09 11:10:32 AM 414412_LakeAsphalt.indd 1 2/9/09 5:29:49 PM

434991_TheAce.indd 1 6/26/09 11:10:32 AM

TLA-X is a warm mix additive providing grade bump to the next higher level with load bearing enhancement and environmental benefi ts.

Lake Asphalt of Trinidad and Tobago (1978) Limited

Head Of ce United States of Amercia Of ceBrighton, La Brea, Trinidad, West Indies Trinidad Asphalt Corporation of America (TACA)Tel: 1.868.648.7572 / 8521 One Gateway Center, Suite #2600Fax 1.868.648.7433 Newark, NJ 07012Web: www.trinidadlakeasphalt.com Tel: 973.622.3423

414412_LakeAsphalt.indd 1 2/9/09 5:29:49 PM

FMI Corporation is the premier investment banking

and management consulting firm serving the world-

wide engineering and construction industry. For

more than 55 years, FMI has built a reputation for

assisting our clients in the creation and realization

of value in their firms.

Company noted has been represented by FMI Corporation

MERGERS & ACQUISITIONS | FINANCIAL ADVISORY SERVICES

Cal l FMI Today for Your Merger and Acquis i t ion Needs

For more information, visit our website at www.fminet.com, or contact: George Reddin at 919.785.9286 / [email protected]

Will Hill at 303.398.7237 / [email protected]

The assets of

and Mirimec Trucking Inc.

have been acquired by

has been acquired by


Selected assets of

Heavy Civil Division


J.C. Compton Company(dba Riverbend Sand & Gravel

Valley Concrete & Gravel and Salem Road & Driveway)


Oldcastle Materials, Inc.

(a U.S. subsidiary of CRH,Dublin, Ireland)

(a Rinker Group Limited company)

Nally & Haydon, LLCand its affiliates

sold its Eastern Kentucky

operations to a subsidiary of

has sold its Gunnison County Colorado

operations to

Oldcastle Materials, Inc.

(a U.S. subsidiary of CRH,Dublin, Ireland)

The stock of

Gibraltar NationalCorporation(a subsidiary of

Triss Corporation)


and

Tom Brook, Inc.

were acquired by

Elmer Larson, LLC


Florida Rock Industries, Inc.

Superior Asphalt & Concrete

Western States AsphaltTranstate AsphaltMid Columbia AsphaltBlue Mountain AsphaltBasin Asphalt



The assets, barging, quarry and constructionaggregates operations of

Jim Smith Contracting

has been acquired by has been acquired by

459062_FMI.indd 1 12/9/09 8:58:22 AM

Hot Mix Asphalt Technology MAY/JUNE 2010 7

Features

13 Book Review: Third Edition of Hot-Mix Asphalt Materials, Mixture Design and Construction

16 Eliminating Delamination in Asphalt Overlays

18 The Evolution of Perpetual Pavements

22 Going All Green: A Contractors Guide to Environmental Stewardship

30 Tack Coats: Setting the Record Straight

34 Unlocking the Potential of Porous Asphalt Pavement

40 Warm Mix: Where We Are, Where Were Going

Column

9 Chairmans Commentary

In Every Issue

11 Industry News

46 On the Road with Pavia Systems A Closer Look at How Warm Mix is Produced

49 Tools for the Trade

50 Calendar of Events

52 Index of Advertisers

54 Advertisers.com

On the cover: APAC Southeast, Inc. in Kissimmee, FL has been a recipient of NAPAs Diamond Achievement Commendation since 2000.

2010 National Officers

CHAIRMANLarry H. Lemon

Haskell Lemon Construction Co.Oklahoma City, Oklahoma

FIRST VICE CHAIRMANKim W. Snyder

Eastern Industries, Inc.Center Valley, Pennsylvania

SECOND VICE CHAIRMANKurt Bechthold

Payne & Dolan, Inc.Waukesha, Wisconsin

THIRD VICE CHAIRMANJohn J. Keating

Oldcastle Materials Grp.-EastLeominster, Massachusetts

SECRETARYWilliam C. Ensor, III

Maryland Paving, Inc.Timonium, Maryland

TREASURERMichael Cote

The Lane Construction CorporationCheshire, Connecticut

NAPA Executive Staff

Mike AcottPresident

Margaret Blain CervarichVice President, Marketing & Public Affairs

Tracie ChristieAssociate Director of Awards & Marketing

R. Gary ForeVice President, Environment,

Health & Safety

Jay HansenVice President, Government Affairs

Kent Hansen, P.E.Director of Engineering

Mike KvachVice President, Product Deployment

Nancy LawlerVice President, Convention & Meetings

Patricia Davitt LongDirector of Communications

Howard Marks, Ph.D., J.D.Director of Regulatory Affairs

David Newcomb, P.E., Ph.D.Vice President, Research & Technology

Carolyn E. WilsonVice President, Finance & Operations

MAY/JUNE 2010 VOLUME 15, NUMBER 3

THE VOICE OF THE ASPHALT PAVEMENT INDUSTRY

C O N T E N T S

Publishers: Mike Acott, NAPA PresidentChris Hodges, Naylor, LLCEditor: Patricia Davitt Long, NAPA Director of CommunicationsManaging Editor: Catherine Jones, Naylor, LLCProject Manager: Tom SchellSales Manager: Tom SchellPublication Director: Paul WalleyAdvertising Sales: Ryan Griffin, Rick Sauers, Jamie Williams, Chris ZabelContributing Writer: Mary Lou Jay

Layout and Design: Emma Law

Advertising Art: Reanne Dawson

Published April 2010/NAP-S0310/9736

National Asphalt Pavement AssociationAll contents copyright NAPA 2010, world rights reserved. 3rd class postage paid at Fargo, ND Subscriptions to HMAT are complimentary to qualified public works officials, pavement consulting engineers, architects, and others involved with paving materials and pavement design, construction and maintenance at U.S. addresses. To receive HMAT, send your request on your agency or company letterhead to the address below. Address all editorial inquiries and correspondence to Editor, HMAT, National Asphalt Pavement Association,5100 Forbes Blvd., Lanham, MD 20706-4407, 301-731-4748, fax: 301-731-4621, e-mail: [email protected], or visit www.hotmix.org. Address advertising insertion orders and inquiries to Naylor, LLC, HMAT Magazine, 5950 Northwest 1st Place, Gainesville, FL 32607-2025, 800-369-6220, 352-332-1252, fax: 352-331-3525, or visit www.naylor.com.

Published by Naylor, LLC., 5950 Northwest 1st Place, Gainesville, FL 32607-2025, 800-369-6220, 352-332-1252, fax: 352-331-3525, www.naylor.com

22

16

49

459062_FMI.indd 1 12/9/09 8:58:22 AM

ROAD AND MINERAL TECHNOLOGIES www.wirtgen-group.com

Track gauge 3 ft. 7 in.mpf 002 ot pu deeps gnivaP

enigne ZTUED lacimonoce dna lufrewoP rated at 60 h.p., with ECO Mode

,deercS 002 BA ELEGV htiw senibmoC paving widths from 20 in. to 10 ft. 6 in.

reppoh lairetam lacirtemmysA sa hcus sboj gnivap seldnah ylisaE

walkways, paths, tracks, etc.

SUPER 700SMALL PAVER

VGELE America, Inc.1445 Shefer Drive Chambersburg, PA 17201 Telephone: 717-264-3200 www.voegele.info

ELECTRICSCREED

HEATING

VGELE SUPER 700THE MOST PRACTICAL SMALL PAVER EVER!

433603_Vogele.indd 1 6/10/09 8:43:02 AM


A Legacy of Which We C an All Be Proud

by Larry Lemon

CHAIRMANS COMMENTARY

As I take the reins as NAPA Chairman for 2010, there is one thing of which I am certain; the greatest asset my

generation of contractors can leave to the next generation is long-lasting asphalt roads that are built as Perpetual Pavement. The legacy that we, as a road building industry, can provide for future generations will be pavements that remain a permanent asset for this nation. Through research and a desire for continuous improvements, the asphalt paving industry has created the technology to produce high-quality pavements that our grandchildren and their grandchildren will be able to use, pavements that are infinitely reclaimable, reusable, and renewable.

Without a doubt, asphalt perpetual pavement is the greatest thing thats happened to the road construction industry. It is the best value for the owner/engineer, and for the American taxpayer. It has transformed the way we engineer and build our roads and has created a new generation of highways that are safer and smoother for the traveling public.

Perpetual Pavements are defined as an asphalt pavement designed and built to last longer than 50 years without requiring major structural rehabilitation or reconstruction, and needing only periodic surface renewal in response to distresses confined to the top of the pavement. This concept was validated by the Asphalt Pavement Alliance (APA)

in 2001 with structural engineering of current asphalt materials and designs. However, our industry has been building long-lasting asphalt pavements since the 1960s, and more than 69 pavements across the nation have already received awards for being built as Perpetual Pavements, since they have been giving their owners long life, with minimum maintenance.

The APA recognized that many well-built, thick asphalt pavements that were categorized as either full-depth or deep-strength have been in service for decades, with only periodic surface rehabilitation to remove defects and improve ride quality. Using these pavements as a model, the APA designed the methodology for a pavement that resists bottom-up fatigue cracking and deep structural rutting. When the structure of a roadway can support the millions of cars and trucks that will be using it, our only needed maintenance will be to renew the surface every 15 or 20 years. What a great benefit our families receive when we are able to renew the driving surface with the latest, safest, anti-skid materials of the day and give the roadway a completely new life. And even better, we can do this in off-peak hours when most of America is asleep, to minimize the inconvenience of our construction. Theres no need for the entire highway to be removed and replaced from the ground up, as with other pavement types. Perpetual pavements are more environmentally

friendly than other pavements because they reduce the amount of material resources over the life of the pavement and recycle any materials removed for the old pavement surface.

This issue of HMAT includes a perpetual pavement synthesis overview that lays out the history of perpetual pavements and the design philosophies that have been shown to provide adequate strength over extended life cycles. Incredibly, these asphalt pavements have endured an unprecedented amount of traffic growth a 580 percent increase in the average daily ton-miles of freight from 1970 to 1998. And, that freight loading continues to increase 2.7 percent per year.

To my mind, the story of perpetual pavements is an example of true leadership in action. It reflects vision and execution and results in a greater good for our society and for generations to come. It is just one of the reasons why Im proud to be an active member of the asphalt industry, and the Chairman of the National Asphalt Pavement Association. My children, and their children, will be better off, both economically and environmentally, because of the asphalt roads we are building today. Thats a legacy of which we can all be proud.

Larry Lemon is the president of Haskell Lemon Construction Co. He is the 2010 Chairman of the National Asphalt Pavement Association.

What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others. Pericles

HMAT

433603_Vogele.indd 1 6/10/09 8:43:02 AM

LETS WORK.In these uncertain times, you need a partner you can rely on. Volvo not only builds high quality road building equipment we back our machines with the most knowledgeable people in the industry. With your experience and our expertise, lets work together to ensure the infrastructure of tomorrow is a resounding success.

Partner with a Volvo dealer near you. Visit volvoce.com/dealer today.

6OLVO#ONSTRUCTION%QUIPMENT

468477_Volvo.indd 1 2/23/10 1:12:55 PM


INDUSTRY NEWS

Global Alliance Fosters New Asphalt Initiatives

The Global Asphalt Pavement Alliance (GAPA), an international group of asphalt pavement associations organized to foster greater international coordination within the industry, held their second meeting in January, immediately following the NAPA Annual Meeting.

Represented were Europe (EAPA), Southern Africa (SABITA), Australia (AAPA), Japan (JRCA), and the United States (NAPA).

Each association gave presentations on the challenges and opportunities in its country and the group formulated some key agreements with regard to industry initiatives.

The Alliance agreed to release a position statement extolling the benefits of warm-mix asphalt, including support for an international warm-mix conference in 2011. The group also agreed to evaluate the UKs carbon calculator, and create a statement on the differences between re-use and recycling to highlight the benefits of asphalt in this regard.

The Alliance elected NAPA President Mike Acott as Chairman of GAPA for 2010-2011.

Roads Fail in Engineers 2009 Infrastructure Report Card

The condition of Americas roads continues to worsen, according to the American Society of Civil Engineers (ASCE). The groups four-year Infrastructure Report Card, issued earlier this year, gave roads a grade of D-.

Roads, transit and aviation were cited by ASCE as having worsened since its 2005 report card, while bridges and most other types of infrastructure were thought to have stayed the same. Joining roads at the D- grade level, the lowest on the 2009 report card, were drinking water, inland waterways, levees and wastewater.

The highest grade on the 2009 report card, a C+, went to solid waste infrastructure.

ASCE said the 2009 report card reflected the need for a five-year investment of $2.2 trillion from all levels of government and the private sector. The group also noted that the cost of needed improvements has increased by more than a half trillion dollars since the 2005 report card.

Biodiesel Passesthe Mining Test

Advocates of biodiesel fuels are touting a new 206-page report by the federal governments Mine Safety Health Administration that gives the alternative fuels high marks for air quality in underground mining tests.

After testing multiple biodiesel blends, MSHA concluded that biodiesel reduces emissions, especially when combined with the use of after-treatment devices on diesel engines. The result is a cleaner and healthier working environment for miners, MSHA states.

Biodiesel is touted as a cleaner burning, renewable fuel, and may be part of a future certification program for green highway contractors. It is made from agricultural co-products, such as soybean oil, other vegetable oils, fats, and recycled cooking oil.

Road Usage Increased in 2009The Federal Highway

Administrations estimate of Vehicle Miles Traveled increased by 1.4 percent in November 2009 compared to November 2008, the latest month reported at press time. Travel for the month was estimated at 236.4 billion vehicle miles, up 3.2 billion vehicle miles from the same period in 2008.

Highway and street usage peaked at 2,789 billion vehicle miles traveled in 2007, then declined to 2,687 VMT in 2008.

Road usage has increased since the end of the first quarter of 2009, though VMT values dropped slightly in October before rising again in November. FHWA projects that VMT will increase 0.3 percent for the year.

DOT Report Targets Construction Inflation

Spending by all levels of government on the nations highways and transit lines has increased substantially in recent years but steep increases in construction costs have eroded the purchasing power of this investment, according to a U.S. Department of Transportation report released earlier this year.

The report, 2008 Status of the Nations Highways, Bridges, and Transit: Conditions and Performance, focused on changes in various indicators from 1997 through 2006.

In nominal dollar terms, combined investment by all levels of government in highway and bridge infrastructure has increased sharply since TEA-21 was enacted, according to the report, AASHTO News reported. Those expenditures jumped 58 percent between 1997 and 2006.

However, capital spending dropped 4.4 percent in constant dollar terms during that timeframe because of construction inflation. The Federal Highway Administrations Composite Bid Price Index shot up 43 percent between 2004 and 2006 due to notable increases in the prices of such materials as steel, asphalt, and cement. HMAT

468477_Volvo.indd 1 2/23/10 1:12:55 PM

Not every mix and application is the same, so your asphalt compactor should be versatileand easy to set up to match performance to ever-changing conditions. If it isnt easy to use,how can it be productive?

Cat Asphalt Compactors get the work done on the breakdown pass, when the mattemperatures are higher and conditions are optimal for compaction. They are comfortableand simple to operate: high amplitude for aggressive compaction, low amplitude for gentlemassaging. They match high paving speeds with high frequency, and low paving speeds withlow frequency. Simple and reliable, with predictable density every time in minimal passes. No complexity and constant tweaking, as there is using non-aggressive compactiontechnologies; no hoping your density numbers will catch up on the intermediate or final pass.

Caterpillar is the market leader because we offer proven technology that makes turning aprofit easier. Isnt that what technology is supposed to do? To get the real story on asphaltcompaction, visit your Cat Dealer today.

www.cat.com

SAFELY HOME. EVERYONE. EVERYDAY. SAFETY.CAT.COM

Versatile Cat Asphalt Compactors use proven technology that is easy to set up for any mix or application.

CAT, CATERPILLAR, their respective logos, Caterpillar Yellow and the POWER EDGE tradedress, as well as corporate and product identity used herein, are trademarks of Caterpillarand may not be used without permission. 2010 Caterpillar All Rights Reserved

AGGRESSIVEWHEN YOUWANT IT,GENTLE WHENYOU NEED IT.

467628_Caterpillar.indd 1 2/24/10 3:59:57 PM


Book ReviewThird Edition of Hot-Mix Asphalt Materials, Mixture Design and Construction (E. R. Brown and N. Tran)

Hot-Mix Asphalt Materials, Mixture Design and Construction was first written in 1991, and the second edition

was prepared in 1996. The third edition of the book was completed in 2009 and is now available from the National Asphalt Pavement Association (NAPA). It has been nearly 13 years since the second edition and many innovations have been developed and implemented in recent years. Prior to the development of the first edition of this book, there was very little comprehensive information available in one location on hot-mix asphalt (HMA). Only a few academic programs at universities throughout the country were available to address HMA technologies and pavement construction practices. In fact, engineers who worked with asphalt pavements received most of their experience on the job, resulting in a trial and error approach that detracted from the quality and cost effectiveness of HMA. The hot-mix asphalt industry has come to rely upon the Hot-Mix Asphalt Materials, Mixture Design and Construction textbook to inform and educate future leaders. The third edition remains dedicated to continuing this work and providing information on all aspects of producing and delivering quality hot-mix asphalt.

In the third edition, the latest HMA technologies are incorporated and general background and basic fundamentals are updated. Chapter 1 provides the background and importance of this all inclusive text book on HMA pavements. Chapter 2 covers the production and classification of asphalt cement. This includes the basics of crude

refining, asphalt classifications and latest technologies in asphalt testing. Chapter 3 is about the production and characteristics of aggregates used in HMA. Basic aggregate mineralogy, crushing and characteristic of quality aggregates and gradation are provided in this chapter. Chapter 4 addresses mix design procedures including Marshall, Hveem and Superpave. The background for development of each method is provided and example mix designs are illustrated. Chapter 5 was completely rewritten to include the most recent technical developments in evaluating the mechanistic engineering properties of asphalt mixtures. Basic empirical tests such as Marshall, Hveem and wheel tracking tests are explained. This chapter also gives insight into tests that identify basic engineering properties of HMA. Resilient modulus, indirect tensile, dynamic modulus, flow number and complex modulus properties are discussed. In addition, the relationships between these tests and predicted field performance are provided. The chapter also provides introductory information on emerging concepts such as creep compliance and dissipated energy determinations. Chapter 6 provides information on the latest equipment and construction techniques for production and field operations required for quality HMA. This includes batch and drum mixers, calibration of plant operations, paver fundamentals, roller basics and density measurement equipment. Chapter 7 addresses issues and requirements of special mixtures and additives. This chapter incorporates new warm-mix technologies and includes stone mastic and recycled mix fundamentals. Chapter 8

gives information on performance measure and distresses associated with HMA. Present serviceability index, construction smoothness requirements and common visual distress present on HMA are discussed in this chapter. Chapter 9 addresses maintenance rehabilitation and reconstruction of HMA. This chapter discusses timing of maintenance procedures and typical application of procedures to preserve HMA pavement or correct deficiencies. The comprehensive coverage of the production, placement, and performance of HMA in the third edition of Hot Mix Asphalt Materials, Mixture Design and Construction is unparalleled.

The asphalt paving industry is a key component of the transportation system. Over 94 percent of all paved roads have asphalt surfaces, with more than 500 million tons of HMA produced each year. The industry is very important to the financial well being of local, state, and national government agencies as areas with good transportation systems have been proven to be more successful in attracting new industry and creating jobs. The third edition of Hot-Mix Asphalt Materials, Mixture Design and Construction provides the new and practicing pavement engineer with the latest information needed to fulfill the promise of delivering high quality HMA pavement to the transportation community.

This review was written by Monte Symons. Mr. Symons is retired from the Federal Highway Administration where he worked for over 30 years in various pavement and materials-related positions. He is currently the Directorof the Airfield Asphalt Pavement Technology Program.

HMAT

Reviewed by: Monte Symons, National Center for Asphalt Technology

467628_Caterpillar.indd 1 2/24/10 3:59:57 PM

WE DONT JUST SELL YOU A PLANT. WE HELP YOU BUILD IT.

If youre looking for more service than a friendly wave goodbye, call ADM at 260-637-5729.

admasphaltplants.com

When purchasing a new asphalt plant, theres a bit of intimidation that goes along with the purchase. ADM didnt just cash the check and wave goodbye. They have been very helpful in setting up our plant and teaching our employees how to operate and maintain it.

Dave Covington, DECCODave Covington, DECCO

422989_ADM.indd 1 3/12/09 8:01:40 PM

WE DONT JUST SELL YOU A PLANT. WE DONT JUST SELL YOU A PLANT. WE HELP YOU BUILD IT.WE HELP YOU BUILD IT.

If youre looking for more service than a friendly If youre looking for more service than a friendly wave goodbye, call ADM at 260-637-5729.wave goodbye, call ADM at 260-637-5729.

admasphaltplants.comadmasphaltplants.com

Asphalt Drum Mixers, Inc.Asphalt Drum Mixers, Inc.

Dave Covington, DECCO

422989_ADM.indd 1 3/12/09 8:01:40 PM

16 Hot Mix Asphalt Technology MAY/JUNE 2010

One of the most avoidable causes of cracking and potholing in surface pavements is the

type of delamination that occurs when the surface lift separates from the pavement structure below it due to insufficient bonding between the layers. Delamination is characterized by crescent-shaped cracks resulting from horizontal forces induced by traffic load. It is most commonly found in pavements subject to the stresses of stop and go traffic, or where vehicles turn frequently. This form of delamination can be prevented with a strong tack coat treatment prior to the placing of the surface course.

The Louisiana Transportation Research Center is breaking new ground in this area with the ongoing study, Optimization of Tack Coat for HMA Placement(National Cooperative Highway Research Program project 9-40). In this work, Louisiana researchers are determining the optimum application methods, equipment type, calibration procedures, application rates, and asphalt binder materials for tack coats. They also will recommend revisions to relevant AASHTO methods and practices related to tack coats. Louay Mohammad, Ph.D., Louisiana State University Civil and Environmental Engineering professor and Manager

Delaminationof the Engineering Materials Characterization Research Facility at the research center is currently spearheading the project as its principal investigator.

Why tack coat?A tack coat provides necessary

bonding between pavement surface layers to make sure they act as a monolithic system to withstand the traffic and environmental loads, explains Dr. Mohammad. Strong tack coat bonding between pavement layers is critical to transfer radial tensile and shear stresses into the entire pavement structure.

Mohammad also stresses that an insufficient bond decreases the pavement bearing capacity and may cause slippage. In addition, insufficient bonding may cause tensile stresses to be concentrated at the bottom of the wearing course. Such concentrated stresses may accelerate fatigue cracking and lead to total pavement failure.

To evaluate the quality of the bond strength of tack coat materials for this NCHRP research, a new test device named the Louisiana Tack Coat Quality Tester has been developed. Researchers evaluated three emulsions (CRS-1, SS-1h, and trackless) as well as PG 64-22 asphalt cement on an existing pavement surface with the Quality Tester. They found that each tack coat material developed its

Eliminating

Louisiana Researchers Evaluate the Importance of Tack CoatBy Skip Paul, P.E.

One of the tell-tale signs of delamination crescent-shaped cracking.

in Asphalt OverlaysDelaminatDelaminat

maximum tensile strength at a different temperature, and that each products softening point had a strong relationship to the temperature at which it exhibits its maximum tensile strength. They concluded that they can conduct the tack coat pull-off test in the field at the softening point.

The research team also developed a direct shear device, known as the Louisiana Interlayer Shear Strength Tester to measure the interface shear strength of cylindrical specimens. The device is designed to fit into any universal testing machine. It has a nearly frictionless linear bearing to maintain vertical travel and can accommodate sensors that measure vertical and horizontal displacements. The Shear Strength Tester can also


Facility. This test site was designed and constructed using conventional tack coat application and paving equipment over an existing asphalt pavement surface.

A preliminary analysis of the results showed that the trackless tack coat produced the highest shear strength at the three application rates, while SS-1 and CRS-1 resulted in the medium and lowest strengths, respectively. The majority of the cases showed a statistically significant difference between clean and dusty conditions. However, no significant difference was found between dry and wet conditions.

Results on the roadwaysDr. Mohammad explains,

Its worth noting that the test method for the measurement of the interface bond strength using the

LISST device developed during this NCHRP project was successfully used in a recent forensic analysis of a distressed pavement. Louisiana researchers also discovered that low interface shear strengths, less than 40 psi, measured between the wearing and binder course, confirmed the potential for future problems.

In summary, to prevent future delamination failures, agencies should ensure the total structural design is sufficient and insist on good tack coat material that must be applied uniformly at sufficient rates to produce minimum shear strength at the interface of the top two layers.

ReferencesMohammad, L.N., Bae, A., Elseifi,

M., Button, J., and Scherocman, J. Development of Pull-Off Test Device and Methodology to Evaluate the Bond Strength of Tack Coat Materials in the Field. Journal of the Transportation Research Board, TRR No. 2126, 2009, pp. 1-11.

Mohammad, L.N., Bae, A., Elseifi, M., Button, J., and Scherocman, J. Interface Shear Strength Characteristics of Emulsified Tack Coats. Journal of the Association of Asphalt Paving Technologists, Vol. 78, 2009, pp. 249-278.

Harold Skip Paul is the Director of the Louisiana Transportation Research Center.

HMAT

apply a constant normal load up to 689 kPa and it accommodates specimens with 100-mm or 150-mm diameters. Researchers used the device to evaluate the interface shear strength of emulsified tack coats under a wide range of testing conditions commonly encountered in field applications. Three types of emulsified tack coats (CRS-1, SS-1h, and trackless) were considered at three application rates, 0.14/m2, 0.28/m2, and 0.70 l/m2. In addition, a no tack coat condition was included in the analysis. The effects of construction conditions such as wet (rainfall) and dusty conditions were also evaluated. Laboratory direct shear tests were performed at 25C. To simulate these test conditions, cores were extracted from a full-scale test site at the Centers Pavement Research

This illustration depicts distress modes at the pavement interface under service conditions.

Researchers tested the interface shear strength of three different tack coats at different application rates. The trackless tack coat produced the highest shear strength at each application rate.


The Evolution of Perpetual Pavements N

APA, through the Asphalt Pavement Alliance (APA), has developed a new technical document

Perpetual Asphalt Pavements: A Synthesis, which can be found on the APA Web site at www.asphaltroads.org .

The concept of Perpetual Pavements was introduced in 2000 by the Asphalt Pavement Alliance (APA). They defined a Perpetual Pavement as an asphalt pavement designed and built to last longer than 50 years without requiring major structural rehabilitation or reconstruction, and needing only periodic surface renewal in response to distresses confined to the top of the pavement. At that time, it was recognized that many well built, thick asphalt pavements that were categorized as either full-depth or deep strength pavements had been in service for decades with only minor periodic surface rehabilitation to remove defects and improve ride quality. The advantages of such pavements include:1. Low life-cycle cost by avoiding

deep pavement repairs or reconstruction,

2. Low user delay costs since minor surface rehabilitation of asphalt pavements only require shor t

work windows that can avoid peak traffic hours, and

3. Low environmental impact by reducing the amount of material resources over the pavements life and recycling any materials removed from the pavement surface.Pavement engineers have been

producing long-lasting asphalt pavements since the 1960s. Research at institutions such as the University of Washington and the University of California has shown that well-constructed and well-designed flexible pavements can perform for extended periods of time. Many of these pavements in the past forty years were the products of full-depth or deep strength asphalt pavement designs, and both have design philosophies that have been shown to provide adequate strength over extended life cycles. It is significant that these pavements have endured an unprecedented amount of traffic growth. For instance, from 1970 to 1998, the FHWA estimates the average daily ton-miles of freight increased by 580 percent, and the average freight loading continues to increase 2.7 percent per year. As the demand on existing pavements in the U.S. increases with probably minimal funding for expansion and rehabilitation, efficient design

By Dave Newcomb, P.E., Ph.D

of new and rehabilitated sections through Perpetual Pavement design will become increasingly important. Congestion on the existing system requires pavements that can be maintained with minimal disruption of traffic.

Full-depth pavements are constructed by placing asphalt pavement on modified or unmodified soil or subgrade material. Deep strength pavements consist of asphalt pavement layers on top of a thin granular base. Both of these design scenarios allow pavement engineers to employ a thinner total pavement section than if a thick granular base were used. By reducing the potential for fatigue cracking and by confining cracking to the upper removable/replaceable layers, many of these pavements have far exceeded their design life of 20 years with minimal rehabilitation; therefore, they are considered to be superior pavements.

Pavements which are either under-designed or poorly constructed exhibit structural distresses, such as fatigue cracking and rutting, before their design life is achieved. The successes seen in the full-depth and deep strength pavements are the result of designing and constructing pavements that

An Overview


resist these detriments to the pavements structure. In recent years, pavement engineers have begun to adopt a methodology of designing pavements to resist bottom-up fatigue cracking and deep structural rutting, the two most devastating pavement distresses, and through this change in thinking the idea of Perpetual Pavements or long-lasting pavements has evolved.

The approach to the design of Perpetual Pavements requires a different strategy than that which has normally been applied to pavement design in the past. Empirical pavement design must rely on relationships between observations of pavement performance, a scale that represents traffic, some gross indicator of material quality such as a structural coefficient, and the thickness of the layers. For a given level of material quality, the thickness of the pavement increases with increasing traffic.

A somewhat unified approach to designing Perpetual Pavements was adopted by a number of experts based on mechanistic-empirical concepts originally proposed by Professor Carl Monismith in the design of the I-710 freeway in California. The premise to this approach was that pavement distresses with deep structural origins could be avoided if pavement responses such as stresses, strains, and deflections could be kept below thresholds where the distresses begin to occur. Thus, an asphalt pavement could be designed for an indefinite structural life by designing for the heaviest vehicles without being overly conservative.

This contrasts to empirical methods that predated the Perpetual Pavement design approach. In those design procedures, greater volumes of heavy vehicles resulted in greater pavement thickness. This was due largely to the way these empirical

Since 2001, the Asphalt Pavement Alliance has given out more than 56 Perpetual Pavement Awards to agencies who have submitted long-lived pavement sections across the country.

A study of Interstate Highways in Kansas by Professor Steve Cross showed that over a 40-year period asphalt pavements cost less than concrete pavements. Perpetual Pavements are economical.

A study of Interstate Highways in Washington State by Professor Joe Mahoney showed that asphalt pavements are as old or older than concrete pavements. Asphalt pavements have a track record of long life.

1 Award2 Awards3 Awards5 Awards6 Awards7 Awards

0

200

400

600

800

1000

0 - 10 11 - 20 21 - 30 31 - 40 41 - 50 51 - 60 61 or More

Age (Years)

Lan

e M

iles

HMA (Lane Miles)

PCCP (Lane Miles)

$3,500,000

$3,000,000

$2,500,000

$2,000,000

$1,500,000

$1,000,000

$500,000

$-0 5 10 15 20 25 30 35 40 45

Pavement Age (Years)

PCCP HMAE

xpen

dit

ure

s p

er 4

-Lan

e M

ile (

$20

01)

7IF>7BJ$7=;+/

6B:G>86G>9:HDCJH

6he]VaiGdVYh#dg\

HDB:I=>CC


PERPETUAL PAVEMENTS continued

methods were developed. For instance, the 1993 American Association of State Highway and Transportation Officials (AASHTO) Guide for the Design of Pavement Structures was based on the results of a road test conducted in the late 1950s and early 1960s. In that two-year study, pavements were subjected to 1 million axle load applications, and failures were monitored over time. The heaviest single axle load used at the Road Test (30,000 lb) applied about 8 million equivalent single axle loads (ESAL) (18,000 lb equivalents) to the thickest asphalt section. Since that time, pavement structures have been designed for heavy traffic volumes that exceed the 8 million ESAL level by 25 times, thus forcing pavement designers to extrapolate the road test results far beyond the conditions for which they were developed. The result of this extrapolation was ever increasing thickness with higher traffic volume, instead of recognizing the pavement thickness at which the heaviest loads could be sustained without additional structure. Thus, the idea of Perpetual Pavements came into existence as much to prevent over-design as to provide a long-life structure.

Since the time of the introduction of Perpetual Pavements in 2000, the some of the important milestones have been: The Asphalt Pavement Alliance

presented 69 Perpetual Pavement awards through 2009.

The International Society for Asphalt Pavements dedicated a special session to Perpetual Pavements in 2002.

Three international conferences have been held on the topic at Auburn University in 2004 and Ohio University in 2006 and 2009.

The Transportation Research Board held a workshop session on Perpetual Pavements in 2001.

The Federation of European Highway and Road Laboratories (FEHRL) has undertaken a series of efforts to define long-life pavements.

Three major national studies on Perpetual Pavements were initiated through the National Cooperative Highway Research Program (NCHRP).

State studies on Perpetual Pavements have been or are currently being conducted in Kansas, Ohio, Wisconsin, Pennsylvania, Oklahoma, Texas, Michigan, New Mexico, Illinois, Washington, and California.

Perpetual Pavement design workshops have been held in Ohio, Kansas, Oregon, Colorado, Texas, Minnesota, Tennessee, Georgia, Hawaii, Wisconsin, Oklahoma, and Indiana.

The National Center for Asphalt Technology (NCAT) Test Track has pavement test sections designed as Perpetual Pavements which are instrumented to validate the design concepts.

Two pavement design computer programs specifically for Perpetual Pavements have been developed at Auburn University.

The concept of the endurance limit has been incorporated in the new American Association of State Highway and Transportation Officials (AASHTO) Mechanistic-Empirical Pavement Design Guide (MEPDG).As research continues on

many different fronts, greater refinements in the design of Perpetual Pavements will improve the structural and economic efficiency. As progress continues to be made even more state departments of transportation and local agencies will consider methods to incorporate the concepts of Perpetual Pavement design into their asset management strategies to more wisely spend their infrastructure funds. HMAT

ASPHALT_ad.indd 1 3/17/10 1:37:12 PM

E. D. Etnyre & Co.www.etnyre.com800-995-2116

email: [email protected]

Asphalt Distributors

ChipSpreaders

Heavy Duty Trailers

Live Bottom Trailers

Asphalt Transports

418121_EDEtnyre.indd 1 2/3/09 8:46:38 PM


Theres more to green asphalt production and paving than simply promoting increased percentages of reclaimed asphalt pavement (RAP) or waste roofing shingles in mixes, or boosting the use of low-emission warm mix

asphalt.Instead, field experience shows that being an

environmentally conscientious producer encompasses the whole of a plants operations, from administration to extraction to production to placement.

Being a green asphalt producer includes, at a minimum, an analysis or audit of the degree to which a plant meets or exceeds federal and state emissions regulations.

But it goes further, to include such considerations as how well the plant suppresses fugitive dust from its roads and noise from its operations; how effectively it shields its operations from its neighbors; whether or not it fuels its burners with recycled oil or uses biodegradable asphalt release agents. It even extends to the field, to how carefully a contractor places tack coats, or cleans equipment at the end of the day.

And it all has nothing to do with climate change. Whether or not you believe that man-made climate change is taking place, maintaining a smaller environmental footprint when producing asphalt and placing pavements can pay dividends both now and in the future.

A smaller environmental footprint will not only make your operation more acceptable to residents and businesses adjoining it, but it will also prepare you to meet coming roadbuilding environmental standards and certification now being modeled after the highly successful Leadership in Energy and Environmental Design (LEED) program aimed at commercial, institutional, government and residential structures.

Its a lot to contemplate in a down market. At the same time, the asphalt industry always has existed in a state of transition, and the trend toward smaller environmental footprints is just one more chapter in the saga.

Going All GreenTheres more to being a Green producer than Warm Mix and recycling. How a comprehensive approach can prepare you for future certification.by Tom Kuennen

Comprehensive ChallengeGreen asphalt begins, but doesnt end, with RAP.

Asphalt pavement reuse and recycling is ubiquitous in this country, said Mike Acott, president, National Asphalt Pavement Association, at a U.S. House Subcommittee on Technology and Innovation hearing last year. Reuse/recycling and other sustainable technologies are so completely integrated into our normal processes that virtually all 300,000 of our workers could be considered green collar workers.

Today, emissions from asphalt plants are low and well controlled, and this has resulted in the Environmental Protection Agency declaring that asphalt plants are not major sources of hazardous air pollutants.

Total emissions from asphalt operations decreased by 97 percent from 1970 to 1999, while production of asphalt pavement material increased by 250 percent, Acott pointed out in his testimony. The industry is proud of its record of environmental stewardship and its proactive position of continuously reducing emissions, including greenhouse gas emissions.

Ecologically friendly asphalt mixes also are enhancing the industrys environmental bona fides. The industry has taken the initiative in demonstrating to road agencies that mixes with significantly larger percentages of RAP are functional, even in friction or surface courses.

Lower-energy warm mixes produce lower levels of emissions both at the plant and in the field, with measurable savings in terms of heat input at the plant. Foamed asphalt mixes produced either at the plant, or in-situ are becoming more and more popular. And porous asphalt pavements provide a means by which storm water may be captured and stored in a stone recharge bed until it percolates into the soils below the pavement. This results in improved water quality and a reduction in surface runoff.

We have used recycled material for years, but now we are stressing moving the bar up and using more recycled products in mixes, said Steve Moyna, project manager, Grimes Asphalt & Paving Corp., Grimes, Iowa. Because


this is governed by the road agencies we contract with, we are promoting the use of more and more recycled materials in our products. We would like to theoretically achieve 100 percent of our RAP into the mix, but we have to bring the specs up to allow use of more recycled products.

But a comprehensive approach to green asphalt production and paving goes beyond plant emissions and controls, and environmentally friendly mixes. It will begin with a look at reduction of energy costs and emissions at every step of production, including drying of aggregate, heating of stored liquid asphalt and hot mix asphalt, and electricity consumption.

Reducing energy consumptionOpportunities for controlling energy consumption are

explored in detail in NAPAs Quality Improvement Series 126 publication, Energy Conservation in Hot-Mix Asphalt Production (2007). Energy costs constitute a significant percentage of the total cost of HMA production, so conserving energy can improve the bottom line for hot-mix producers, author T.J. Young writes.

The publication outlines ways to reduce energy use via reduction of aggregate moisture content, insulation of dryer shells and surfaces, reduction of exit gas and exit material temperatures, use of alternate fuels, use of more efficient hot oil heater designs, use of more effective piping, tank and silo insulation, and use of variable frequency drives on large motors.

Covered stockpiles, which keep moisture out of fine aggregates or RAP (neither of which drain freely) are indicated instead of exterior storage, because drier raw materials require lower heat input.

Just as used oil drained from mobile equipment should be recycled, many asphalt producers benefit from burning low-cost recycled oil in their plants.

We consider ourselves to be a green producer, said Tom Mitana, material resource manager, Pace Construction Co., Inc., St. Louis. Pace has 10 plants in Missouri, including a traveling plant, and Pace places asphalt as well as produces it. We recycle RAP and tear-off shingles, recycle oil for our burner fuel, and place warm mix.

Pace sells used oil from its mobile equipment to a collector. Its collected here in our shop, and then a company takes it and recycles it, Mitana said. They pay us, although it used to be the other way around. Now that things are going green, and there is a demand for recycled oil, they pay us.

In Missouri, Fred Weber, Inc. is using methane gas derived from landfills to reduce the energy costs associated with liquid asphalt and to dry aggregates. Landfill gas (LFG) is generated by the decomposition of organic waste, the company states. Landfill gas typically is composed of approximately 50 percent methane and 50 percent carbon dioxide.

In 1983, we began using landfill gas to heat the oil burner at the North Asphalt plant, Fred Weber said. The success of this innovative effort led to the utilization of LFG as an alternative fuel to heat the rotary dryers at the asphalt plant. The improvements to the system have created an opportunity for the company to optimize the energy potential from landfill gas.

Following improvements in the LFG filtration process, Fred Weber has been able to boost its use of

In January 2010, Granites Utah Cottonwood plant received NAPAs 2009 Ecological Award for a New Asphalt Facility.

GRAN

ITE

CON

STRU

CTIO

N CO

.

Keeping RAP under cover reduces its moisture content, resulting in lower burner fuel costs.

FHW

A

STARTRACK 1313i CRUSHING PLANTCat C10 diesel engine, 400hp, equipped with 36" cross

belt magnet, 51" impact diameter, 50" x 42" inlet opening, (4) New Blow bars, New 48" discharge belt, 11' 6" discharge height, 32" side discharge belt, 9' 9" discharge height, Grizzly heavy duty double deck

screen, quick setup for location change, track mounted.

INCREASE PROFITS BY RECYCLING SHINGLES INTO NEW ASPHALT BY SAVING A/C COST &

MAKE MORE MONEY!ASPHALT SHINGLE GRINDING SERVICE

SHINGLES + RECYCLING = INCREASED PROFITS

RECYCLING & PROCESSING EQUIPMENT, INC.Call Jerry NOW for details and pricing O ce: (765) 472-5500

Fax: (765) 472-4519 Email: [email protected]

NEW & USED IMPACT CRUSHERS JAW CRUSHERS GRINDERS SCREENING PLANTS FOR SALE

MAKE MORE MONEY BY SAVING DISPOSAL, TRANSPORTATION AND NEW AGGREGATE COST BY RECYCLING ON SITE.

2006 RETEK 313i50" x 28" inlet opening, impact track mounted crusher, magnetic, separator, radio remote control, Cat engine.

2005 Keestrack TrackMounted Screening Plant

Heavy Duty 16'/5' punch plate screen, apron feed and radio remote control, superb in all screening

applications, asphalt, concrete, soils, etc.

Extec S-5 Screening PlantExcellent condition, like new 300HRS, track mounted,

radio remote control, main discharge conveyor, triaxle chassis for transport, shredder, vibrating grizzly,

2 side conveyors, 2-deck, 3-way split.

Contract Grinding at Your Site Asphalt Shingles New Rejects Shingle Tear O s

Pricing based per tonWe have been grinding shingles for over

20 years and have processed many thousand tons of shingles for many

major companies across the country.

SHINGLESBEFORE

$HINGLE$AFTER

READ THIS!

Financing & Leasing Available

THINK GREEN, BE GREEN, MAKE MORE GREEN

467553_Recycling.indd 1 3/9/10 5:10:05 PM


the byproduct. The North Asphalt Plant is now able to use more renewable green energy and less natural gas, resulting in a real environmental benefit and a significant cost reduction, the company said.

Plants can reduce their electrical load as well as their fossil fuel consumption. Producers operating automated aggregate plants sometimes can take advantage of lower off-peak electric rates by running the next days production the night before.

Many more producers can take advantage of variable frequency drives as recommended in the NAPA publication Energy Conservation in Hot-Mix Asphalt Production. Variable frequency drives allow conservation of electrical energy on large fan motors by slowing the fan, instead of using dampers to restrict air flow. Todays lower prices for VFDs make them an energy-saving option for the large exhaust fan motors and burner blower motors used in asphalt plants, Young said.

Production of warm-mix asphalt definitely will reduce the energy demand. Paces Mitana told HMAT, Use of warm mix is becoming more and more common in our area, and we see a nice, steady growth in its use.

Auditing Environmental PracticeA comprehensive audit can be conducted to determine

a plant and paving operations green profile or footprint.We are going above and beyond emissions

guidelines, not only with the plant, but with the area around the plant, Grimes Asphalts Moyna told HMAT. Controlling dust, and any material washing off, is an important task. We either water the roads, or use dust control measures on the roads and on the stockpiles. We do it as a good neighbor policy. We also install berming and tree plantings, everything we can to isolate what weve got going from passers-by.

A top-to-bottom plant environmental audit will help asphalt producers get a grasp on where they stand in terms of their greenness. For example, out West, Granite Construction has developed a complete assessment of the environmental impact of various construction, rehabilitation and maintenance operations.

We developed a carbon footprint calculator for RAP, asphalt shingles and warm mix, and looked at it from a holistic standpoint, from taking materials from the ground, to placing them on the roadway, said Christopher Robinette, quality control engineer, Granite Construction, Inc., Sparks, Nev. We have been able to establish the carbon and energy footprint of a typical operation, down to a ton of hot mix. Robinette described the guidance at the January annual meeting of NAPA.

Sometimes the industry can partner with the state regulatory agencies. In 2000-2002, the Colorado

Going all Green continued

Asphalt Pavement Association (CAPA) worked with the Colorado Department of Public Health and Environment to launch a voluntary Compliance Assurance Pilot program, dubbed Compass. The program involved integrating pollution prevention and environmental leadership principles into ongoing compliance efforts, via a partnership between the division and the industry through CAPA.

Compass was a program in which the state provided an inspector to audit our members production facilities, said Tom Peterson, P.E., CAPA executive director. They benchmarked them from a compliance standpoint, and went back a year later to compare. They then went back another year later, and overall, the results were very favorable in terms of the improvements.

The project was undertaken as a joint effort with the environmental agency, not as an adversarial inspection. We worked in partnership to address each others concerns, and in the long run, improve air quality, Peterson said. We were recognized for that, and in 2003 were recognized with the governors Environmental Leadership Award.

While the Colorado Compass partnership lasted just a few years, other states continue to work in partnership with asphalt producers. For example, in Missouri, Fred Weber, Inc. has been involved in the Missouri Environmental Management Partnership (MEMP) with the Missouri Department of Natural Resources (MDNR) since 2008. Thats when the firms North Complex became part of a very select group which recognizes companies for their high level of environmental commitment and performance. MDNR began the program to encourage the development of voluntary Environmental Management Systems (EMS) in all companies to help manage the environmental impact of an organization.

Fred Webers EMS displays a commitment to regulatory compliance, continual improvement through performance-based objectives and periodic review, and evaluation of the performance to ensure the firms

Place tack coats evenly and pave over them before motorists or workers spread tack material outside paving lane.

TOM

KUE

NN

EN

SHINGLES + RECYCLING = INCREASED PROFITS

THINK GREEN, BE GREEN, MAKE MORE GREEN

467553_Recycling.indd 1 3/9/10 5:10:05 PM


Going all Green continued

environmental impact is diminished, and its operations are more sustainable, the firm says.

There are benefits to the contractors involvement. The MEMP program features a single point of contact, or gatekeeper, for communications between MDNR and Fred Weber, Inc.s EMS; expedited reviews of permit applications; flexibility in permitting new control technologies; streamlined reporting; a process for resolving some regulatory violations without formal enforcement action; and forms of public recognition, including the use of the MEMP logo on corporate facilities and in public venues.

Recognizing AchievementTo provide an avenue for continuous improvement

and to assist their members in reaching environmental and other goals, NAPA launched the Diamond Achievement Commendation for Excellence in Asphalt Plant/Site Operations in 1999.

Various NAPA initiatives over the years have addressed aspects of continuous improvement, but the Diamond Achievement is the crown jewel of NAPAs efforts to recognize and encourage excellence in operations at asphalt plants.

This comprehensive process begins with a self-assessment of six aspects of plant/site operations: appearance, operations, environmental practices, safety, permitting and regulatory compliance, and community relations. It also includes verification by an outside third party who is not associated with the company. Nearly 800 plant/sites are current Diamond Achievement recipients.

Green Practice in the FieldA pavers environmental footprint can be reduced

with the right type of equipment, especially the type of engines (Tier III and Tier IV, for example), machine productivity, and the type of fuel used. Biodiesel, derived from soy products, may be a green option to diesel fuel. Use of biofuels in the equipment is one way an operation can be made greener, Paces Mitana said. The trend is that way, everything is going green, and there is no reason asphalt contractors cant do the same.

Engine idling can be limited. Excessive idling contributes to the deterioration of air quality and the production of unnecessary emissions. Idling also wastes fuel and may damage vehicle engines. The City of Dallas requires its contractors to limit idling time to five minutes for work vehicles with a GVW rating equal to or greater than 14,000 lbs.

Care must be taken to keep tack coat material from migrating into side streets, parking lots and even tracked into retail establishments. Usually, the longer a tack coat is exposed, the greater the chance it has of

being tracked. New high-performance, value-added tack coat materials set quickly and preclude tracking.

Use of biodegradable release agents in truck hoppers is an environmentally friendly option. We lean toward these environmentally friendly release agents, Mitana said. We dont allow dump truck beds to be sprayed down with diesel fuel, and one plant has an automated system that sprays the release agent in the bed of each dump truck before it enters the load-out.

Likewise, diesel fuel now is precluded from end-of-day cleanup of tools and screeds; environmentally friendly release agents have taken its place.

We have all but eliminated the use of diesel fuel to clean shovels, rakes and hand equipment around the paver, CAPAs Peterson said. Its been replaced across the board by environmentally friendly release agents, and its a very clear movement in the environmental direction by operations.

An exhaustive listing of road construction environmental best practices is contained in the publication Construction Practices for Environmental Stewardship from AASHTOs Center for Environmental Excellence; it can be found at http://environment.transportation.org/environmental_issues/construct_maint_prac/compendium/manual/4_1.aspx. Also, NAPA has produced 101 Ideas to Reduce Costs and Enhance Revenues, which can be found at the NAPA store on www.hotmix.org.

Why do it?Why should asphalt producers begin focusing now

on greening facilities, operations and management practices?

From a purely pragmatic point of view, because some kind of environmental certification program is probably coming in the months ahead. The rapid spread of LEED certification through the structural sector was driven by architects and corporations, but since then governments, showing leadership for their communities, have gotten on the bandwagon and are demanding LEED certification for their new structures.

That means the states, cities and counties with which asphalt contractors work eventually will probably require green certification for their road projects. Indeed, such a thing may be encouraged in the next U.S. surface transportation bill now being debated in Washington. But beyond pragmatism, it is the right thing to do.

When we reduce our impact on the environment, said NAPA president Mike Acott, we make our industry and our individual businesses more acceptable to our communities. In the long run, thats good for business. HMAT

451596_Wirtgen.indd 1 10/22/09 9:13:59 AM

www.wirtgen-group.com

THE FOUR #1 BRANDS FOR ROAD CONSTRUCTION AND MINERAL PROCESSING FROM A SINGLE SOURCE.

Wirtgen America6030 Dana Way Antioch TN 37013Telephone: 615-501-0600 Fax: 615-501-0691www.wirtgenamerica.com

The market-leading brands Wirtgen, Vgele, Hamm and Kleemann offer strong technologies for road construction and for the mining and processing of mineral raw materials. Wirtgen America provides best-in-class, professional consulting and customer service. We are Close to our customers.

ROAD AND MINERAL TECHNOLOGIES

451596_Wirtgen.indd 1 10/22/09 9:13:59 AM

'RLQJWKH5LJKW7KLQJ67:RRWHQ&RUSRUDWLRQPDLQWDLQVIRFXVRQFRPPLWPHQWWRWKHFXVWRPHUDQGWKHFRPPXQLW\

67:RRWHQIRFXVHVRQVXVWDLQDEOHFRQVWUXFWLRQSUDFWLFHVVLQFHWKHHDUWKSURYLGHVWKHYLWDOUHVRXUFHVQHHGHGWRGRRXUZRUN7KHFRPSDQ\VGHGLFDWLRQWRHQYLURQPHQWDOVWHZDUGVKLSDQGUHVSRQVLELOLW\EHJLQVZLWKIXOOFRPSOLDQFHZLWKDOOIHGHUDOVWDWHDQGORFDOUHJXODWLRQV67:RRWHQVDWWLWXGHWRZDUGVWKHHQYLURQPHQWLVWKHVDPHDVWKRVHDGYRFDWHGWRZDUGHPSOR\HHVDQGFXVWRPHUVWREHFRPPLWWHGFRQVLGHUDWHDQGFRPSDVVLRQDWHUHJDUGOHVVRIWKHVLWXDWLRQ

7KH67:RRWHQ&RUSRUDWLRQUHFHQWO\H[SDQGHGLQWRWKH6RXWKZHVW)ORULGDPDUNHWZLWKZKDWLVSHUKDSVWKHLUJUHHQHVWDVSKDOWSODQWIDFLOLW\ORFDWHGLQWKH)RUW0\HUV1DSOHVDUHD

7KLVDVSKDOWSODQWLVOLNHQRRWKHU7KHVLWHLWVHOIIHDWXUHVH[WHQVLYHWUHHDQGVKUXESODQWLQJVZDWHUFRQVHUYLQJLUULJDWLRQV\VWHPVD)ORULGD%DOG&\SUHVVSUHVHUYHZLWKLQGLJHQRXVSODQWLQJDUHDDQGHYHQDQRQVLWHSUHVHUYHIRUDSRSXODWLRQRIHQGDQJHUHG*RSKHU7RUWRLVH'HGLFDWHGWRUDLVLQJLQGXVWU\VWDQGDUGVRIQRWRQO\HQYLURQPHQWDOVXVWDLQDELOLW\EXWDOVR

ma^:LM>

:][Ymk]Ykh`Ydlak)((j][q[dYZd]$alakYn]jq_gg\$kmklYafYZd]hjg\m[l&L`]affgnYlan]\]ka_fg^l`]9kl][LB@G

468480_Astec.indd 2-3 2/23/10 12:43:52 PM


Tack Coats: By Dan Brown

Applying a tack coat to an existing pavement is such a simple and inexpensive process that its importance

is often overlooked. In many specifications, the tack coat is considered to be an incidental expense, so it is not paid for directly, but is included in the cost of other items in the contract.

The proper application of a tack coat, however, is critical to the performance of an asphalt pavement. When you apply a tack coat correctly, it can significantly improve the bond between the pavement layers, says consulting engineer Jim Scherocman, an experienced expert on the subject. The tack coat can reduce the tendency for the surface layer

to slide on the underlying layer under the force of accelerating or decelerating traffic. And the tack coat may reduce top-down cracking in the surface course layers.

Residual amount of binderScherocman says the application

rate of the tack coat is not nearly as important as the residual amount of asphalt binder the material remaining on the surface after the tack coat has set. The residual amount normally does not cover the entire pavement surface. In the vast majority of paving situations, Scherocman says the tack coat should be distributed over only 90 to 95 percent of the existing surface. That leaves 5 to 10 percent of the surface visible after the tack coat has been applied.

Setting the Record Straight

LEFT. Note that all nozzles are working and are adjusted at the same angle to the spray bar. MIDDLE. Excessive tack coat application can cause a slip plane between the two layers of pavement. RIGHT. This spray bar has major problems; tack coat distribution is totally non-uniform because some nozzles are plugged, others are not set at the right angle.

The amount of desired residual coating is up for debate, says Don Etnyre, sales manager for E.D. Etnyre & Co., a manufacturer of tack application equipment. Some people like to cover 100 percent, and some people like streaks, he says. Scherocman says it depends on the pavement surface.

If the existing pavement surface is porous, you should have 100 percent coverage, says Joe Button, senior research fellow at the Texas Transportation Institute, Texas A&M University, because some of the material will seep into the pores.

Too little tack coat may result in a significant reduction in the strength and durability of the pavement structure, says Scherocman. Too much tack coat


will create a slip plane between the layers and cause the upper pavement to slide on the lower layer.

Type of materialTypically an asphalt emulsion

is used for the tack coat, and it can be a rapid-set or a slow-set material. For the rapid-set emulsions, usually an RS-1, RS-1h, CRS-1 or CRS-1h material is specified. For the slow- set emulsions, the most common grades are SS-1, SS-1h, CSS-1, and CSS-1h. For some high-traffic roadways, the asphalt emulsion may be polymer modified.

In some areas, asphalt binder is used for the tack coat instead of emulsion. In that case, the tack coat material is 100 percent asphalt; usually the grade of binder selected is the same as the grade contained in the asphalt pavement overlay.

Most grades of asphalt emulsion contain approximately 60 to 65 percent asphalt binder, and the remainder is water and emulsifying agent. After the tack coat, or emulsion, has been applied, the water evaporates and the residual asphalt content remains on the surface. For practical purposes, you can assume that an emulsion is two-thirds binder and one-third water.

Tack coats are applied at 0.04 to 0.10 gallons per square yard, says Scherocman. Based on an applied rate of 0.06 gallons of emulsion per square yard, the residual asphalt binder in an undiluted emulsion would be 0.06 X 2/3, or 0.04 gallons per square yard.

If an emulsion is diluted 1:1 with water, then the residual amount of asphalt binder is only one-third of the application rate. So, a diluted

emulsion has to be applied at twice the application rate compared to an undiluted emulsion to achieve the same residual amount on the road. For a diluted emulsion, to achieve a residual amount of 0.04 gal/square yard, it would be necessary to apply 0.12 gal/sq.yd. (0.12 X 1/3 equals 0.04 gal./sq.yd.)

The chart below gives Scherocmans recommended residual application rates for various pavement surfaces:

Recent research, says Scherocman, indicates that you may not need to place a tack coat on a milled asphalt surface. Thats because the roughened surface helps provide a mechanical, shear-resistant bond between the two layers. In that case, you need to make sure the milled surface is very clean, says Button. Sweeping with a rotary broom will not be enough; you need to use pressurized air or water, he says. Merely sweeping will leave debris in the texture of the milled surface.

Common mistakesUniform tack coat application

depends on the size of the nozzles used on the distributor spray bar. Dont make the mistake of applying tack coat with the same nozzles you use for a chip seal, says Scherocman. The nozzles for a chip seal have much larger holes than you need for a tack coat, because application rates for a chip seal are much greater. If you use chip seal nozzles, the holes will be too large, and the emulsion will come out in longitudinal streaks. You will not get uniform coverage.

A chart is usually supplied with each distributor to provide

EXISTING PAVEMENT CONDITION RESIDUAL RATE (GAL./SQ. YD.)New asphalt layers 0.02-0.03Old, oxidized asphalt 0.04-0.06Milled asphalt surface 0.05-0.07Milled PCC surface 0.05-0.07Portland Cement Concrete 0.04-0.06

information on the proper nozzle size to use for different application rates. Dont neglect the pump pressure or the ground speed of the distributor both must match the desired application rate of the tack coat.

Next, you need to make sure that all nozzles on the spray bar are set at the correct angle and are functioning properly. The nozzle opening, or slot, should be set at an angle of approximately 30 degrees to the axis of the spray bar. If all of the nozzles are not set at the same angle, you will not get a uniform application of tack coat.

If the distributor has not been used for some time, it is a good practice to do a trial run on an unused area. In addition, the trial run can be used to judge the uniformity of application and confirm the proper application rate. If you want, you can calibrate the distributor application rate according to ASTM D 2995.

If the existing pavement surface is dusty, Scherocman warns, the application of the tack coat may not provide a bond between the layers of asphalt. It is extremely important to clean the existing surface before the tack coat is applied. It may be necessary to sweep or flush the existing pavement with high-pressure water to remove any dust film.

Pick-up on truck tiresWhen an asphalt emulsion

breaks, the asphalt binder particles separate from the water. When the water has evaporated, which takes place in 15 minutes to two hours, the emulsion has set. Once the emulsion has set, it is ready to have the fresh asphalt placed on it. Between the tack coat emulsion break time and the set time, the tack coat is very sticky and will adhere to the haul truck tires and be carried away.

That obviously defeats the purpose of applying a tack coat in


Tack Coats continued

the first place, says Scherocman. However, the pick-up of the tack coat on truck tires can be reduced by driving over the asphalt emulsion before it has broken. If that cant happen, then the only way to prevent the tack coat pick- up problem is to assure that the coat completely sets before driving the haul trucks on it. That can significantly delay the placement of the asphalt mixture.

The pick-up problem can be minimized by using the following techniques: Minimize the tack coat

application rate; Achieve uniform tack coat

application across the pavement by using the proper nozzle size, nozzle angle, and spray bar height;

Use an asphalt binder for the tack coat;

Apply the tack coat as far ahead of the paver as is feasible, depending on traffic safety requirements.

Research has shown that even a set tack coat material will cut down the friction available to a vehicle tire, especially if the surface is wet. Use caution in placing the tack coat ahead of the paver. If rain is imminent, the amount of tack coat placed ahead should be controlled. And if the tack coat is exposed to traffic, you might apply a light layer of sand to the tack coat.

Getting it RightTo get the best performance

from a tack coat, it is important to understand the basics: Its main purpose is to provide a bond between the existing pavement surface and a new layer of asphalt. The bond reduces the possibility of a sliding failure between the new and the old pavement layers.

The tack coat need not completely cover the underlying surface only 90 to 95 percent of the surface area needs to be covered to achieve a

bond. Too little or too much tack coat material is detrimental to the performance of the pavement.

The residual amount of asphalt binder is of primary importance. When using undiluted emulsions, you should calculate the residual amount of tack coat based on the applied rate times two-thirds (the percentage of binder in the emulsion).

Tips when applying emulsion, Scherocman says, include the following: Make sure all nozzles on the spray

bar are open and fully functioning; All nozzles should be set at the

same angle to the axis of the bar and all the fans should be in the same direction;

The height of the spray bar above the ground should provide for a double or triple overlap of the fans.The proper uniform application of

an asphalt tack coat will contribute greatly to the durability of the new asphalt layers. HMAT

467339_PQ.indd 1 2/16/10 4:45:27 PM

419669_RLPainting.indd 1 2/12/09 9:07:45 PM

FREE ESTIMATE!(800) 962-8415 (937) 968-5526 FAX (937) 968-3733

IF YOU ARE THE KIND OF PERSON THAT WANTS THE JOBDONE RIGHT, CALL US!

PLEASING YOU IS OUR BUSINESS.

Farm Buildings Barns Grain Leg Set-Ups Tanks SilosCorn Cribs Bins Industrial Buildings Concrete Plants

Asphalt Plants Aggregate Plants Stone QuarriesTruck Terminals Steel Structures & Red-Iron

419669_RLPainting.indd 1 2/12/09 9:07:45 PM

Unlocking the Potential of Porous Asphalt PavementWhat every pavement professional should know about the potential and limitations of porous asphalt.By Kirk Landers

Porous asphalt is a concept that essentially makes a pavement into a high-performance retention area for runoff water. It filters the runoff through an open-graded asphalt pavement, then a coarse single-size aggregate

base which serves as a retention area until the water can percolate into the uncompacted native soil below. It optimizes right of way utilization, avoids erosion problems due to water runoff, enhances water quality, and creates a driving surface which virtually eliminates wheel spray and hydroplaning.

While there are additional costs associated with porous pavements, significant savings can be realized by avoiding other stormwater mitigation structures. It has performed admirably in test applications in high load and relatively high traffic count situations.

The use of porous asphalt pavements has expanded as environmental stewardship has become an ever more prominent theme in the design and construction of roads and parking lots. Just how significant porous asphalt will be in the full spectrum of pavement technologies depends upon who you talk to. Most believe it will be an

A steady rain clearly delineates this parking lots wet conventional asphalt from its nearly dry porous asphalt pavement section. Porous asphalt eliminates wheel spray and hydroplaning in addition to enhancing water quality and minimizing erosion.

Porous asphalt pavement is one of the hallmarks of Salem, Oregons Pringle Creek subdivision, one of Americas most advanced green construction projects.Pringle Creek photos: Oregon Asphalt Pavement Association



important specialty pavement, used to deal with special environmental considerations. Some think it could be more widely used than that, because it may outperform conventional pavements in some applications.

Porous pavement basicsAccording to Tom Cahill, P.E., of CH2M Hill, engineers

began using porous asphalt designs back in the 1970s as a way to control runoff water and its effects on everything from soil erosion to water quality. The introduction of non-woven geotextiles in 1979 gave rise to todays designs that combine high-voids asphalt and a high-voids aggregate base to create an in-situ water retention and percolating facility.

The environmental benefits of porous asphalt roadways stem from two basic facts: the structure is effective in filtering impurities from stormwater, including heavy metals; and the in-situ water retention and percolating feature minimize the impact the paved surface has on soil erosion, flooding, and water quality in streams and lakes. In addition, the porous asphalt pavement reduces the amount of space needed for the pavement and management of its runoff water.

In recent years, porous asphalt projects have flourished as pavement engineers have become more confident in the performance and durability of the design principles and materials involved. High profile early projects, such as a Visitor Center parking lot at Walden Pond in Massachusetts, led the way. The Walden Pond lot, created in 1976, is still in service today.

Subsequent projects have tested porous pavements ability to perform under higher loads, from ever larger parking lots, to industrial areas, to residential streets, and even to highway applications.

Out of the parking lotIn recent presentations on porous pavement by the

National Asphalt Pavement Association, presenters agreed that the case for porous asphalt is based on its contributions to water quality, reduced runoff, groundwater recharge, and also its safety virtues (it eliminates puddles, vision-blocking spray, and hydroplaning).

Presenters also agreed that it has limitations. It costs more to build than a conventional pavement, but it can be less expensive than a conventional pavement and a drainage and retention system. It works best on upland soil with good drainage and adequate depth to groundwater and rock.

That leaves thousands of lane miles of potential road and street applications, and untold acres of parking lots as potential applications for porous pavement.

One of porous pavements most knowledgeable advocates is Jim Huddleston, head of the Oregon Asphalt Pavement Association. He recited a long list of successful porous asphalt projects in a presentation titled Not Just for Parking Lots Anymore at the 2009 World of Asphalt, including residential street applications in Portland and

the environmentalist-touted Pringle Creek Community in Salem, Oregon. He also described successful experimental porous pavements installed in high load applications, such as a Portland industrial area, and a busy Chandler, Arizona highway.

Theres no question you can engineer a porous asphalt pavement to handle heavy traffic loads, he told HMAT. It may or may not be adequate for the highest volume Interstates, but it certainly could be deployed in many applications.

One of the examples Huddleston cites of this is a test pavement on U.S. 87 in Chandler, a Phoenix, Arizona suburb. When the Arizona DOT replaced about a mile of pavement in 1985, they used porous asphalt pavement

A key concern in constructing porous asphalt pavements is protecting the open-graded friction course during construction. In this photo of the Pringle Creek (OR) subdivision project, contractors use geotextiles to protect the open-graded asphalt friction course from contamination, and plywood to protect it from scuffing while the asphalt is curing.

Haul trucks plied Pringle Creeks unfinished porous roads during Oregons wet

winter months without causing any damage.


Porous Asphalt Pavement continued

on two lanes going in one direction, and conventional asphalt pavement for the two lanes going in the other direction. The porous pavement lanes served 20 years under growing traffic volumes without a repair before being replaced as part of a larger-scale reconstruction of the highway.

Jim Delton, now the Arizona DOT State Materials Engineer, was the agencys supervising construction engineer on the project.

It was a 20-year pavement design, Delton told HMAT, But the traffic volume on the road quickly exceeded the projections we used for the design. It probably hit our lifetime traffic volume goal in 14 or 15 years. The pavement continued to stand up to traffic well beyond its design life, said Delton. It also handled stormwater with splashless efficiency for its entire life, though Delton noted that after four or five years, the speed with which water drained from the surface was somewhat less impressive than when the pavement was new.

Constructing porous asphalt pavements

Porous asphalt pavements require permeable soils with at least two feet to bedrock and three feet to high water. They are generally not recommended for roads built on fills, or for surface slopes greater than 5 percent. The

classic porous asphalt pavement construction begins with an uncompacted subgrade topped by a non-woven geotextile, then clean, uniformly graded 2-3 inch aggregate (40 percent voids). This coarse aggregate layer may be covered with a uniformly graded layer of half-inch crushed aggregate for enhanced stability, then one or more lifts of open-graded asphalt.

NAPA recommends that the asphalt mix have a minimum of 16 percent air voids to assure good permeability. Their engineers also recommend a minimum 5.75 percent asphalt binder content by weight of total mix to enhance its durability. And they recommend a draindown test threshold of 0.3 percent maximum to make sure the binder doesnt drain down during storage.

The actual construction of a porous pavement involves more planning and care than the construction of a conventional pavement. For example, care must be taken not to compact the subgrade with work-vehicle tires, or to rut the aggregate base. In addition, it is vital to keep mud, dirt, dust and other solids out of the base and the asphalt lifts during construction in order to avoid clogging the voids that are the key to the structures ability to efficiently channel and hold storm water.

For this reason, in NAPAs 2009 webinar on porous paving,

NAPA Director of Engineering Kent Hansen, PE, recommended extra attention to scheduling. In projects like subdivisions, he said, Its important to build the pavement late in the construction process, after the vegetation is established, or to keep sediment controls in place until vegetation has stabilized the adjacent soils.

To avoid compacting the subgrade during general construction, contractors can excavate the bed to a foot or so above the planned elevation so the road can be used by work vehicles. When general construction is completed, the bed can be excavated to the planned elevation, and construction of the porous pavement can begin.

Only tracked machines with soft footprints or backhoes should be used to grade the subgrade, says Hansen.

After the subgrade has been graded, the geotextile is laid. Where the sheets of fabric meet, they should overlap by 16 inches, and at the ends of the project about four feet of excess fabric should be left. This fabric will be pulled over the aggregate course as temporary protection from voids-clogging dust and dirt and other contaminants; it is removed when paving commences.

After drain pipes (if any) are installed, the stone recharge bed is placed. In this process, trucks cannot drive on the fabric, so they

This illustration shows how open graded asphalt and open-graded base aggregate are combined with an uncompacted subgrade and geotextiles to create a pavement that also functions as a water retention and percolating facility.

Figure 1: Typical Porous Pavement Cross Section


dump their loads at the edges of the roadway and track-type machinery spreads and grades the aggregate from there. The coarse aggregate of the recharge bed is typically placed in 8- to 12-inch lifts, and compacted by a roller working in static mode.

An optimal choker course of half-inch clean-washed aggregate covers the recharge bed. Its role is to lock up the coarse aggregates surface to keep the structure stable during paving.

Paving is done with a track-mounted paver. Hansen says care must be taken to limit truck movement on the stone bed since the structure doesnt achieve full stability until the asphalt lift sets up. Explains Hansen, The open-graded aggregate achieves good stability when it is confined, and the final piece of the confinement is the OGFC.

Caltrans recommends placing the open-graded mix at 200 to 250 degrees F. Mix temperature is important, especially with modified

binders which can be difficult to work at lower temperatures. If the paving crew engages in too much handwork or other delays, porosity can be compromised.

After compaction two to four passes with a steel-whe

hot mix asphalt technology

Documents

shaker decks

warm mix

tire paver

track paver

single decks

portable drum mix

spray paver

american way