J W Marriott Desert Springs Resort & Spa, Palm Desert, CA

Link below for more info on the NAPA web site.

http://www.asphaltpavement.org/index.php?option=com_content&task=view&id=672&Itemid=1310

Grand Hyatt Seattle  721 Pine Street  Seattle, WA  98101

Board of Director’s Meeting  11/17/2011 at 1:00pm

Associate Member’s Meeting 11/17/2011 at 3:30pm

General Meeting 11/18/2011 at 8:30am

Awards Banquet 11/18/2011 at 6:00pm

Hotel reservations should be made by following this link:  https://resweb.passkey.com/go/WAPA11

Types of Awards

WSDOT AWARDS & CARL MINOR AWARD

WSDOT awards are selected by WSDOT and nominated by each Region based upon a rating system that includes, among other things, ride, pay factor and project complexity.

CITY AWARDS

City awards, sponsored jointly by WAPA and the American Public Works Association (APWA) are given to the best City paving projects in the State – one east of the Cascades and one west of the Cascades.  They are nominated by Cities and chosen by a special WAPA evaluation committee.

COUNTY AWARDS

County awards, sponsored jointly by WAPA and the Washington Association of County Engineers, are given to the best County paving projects in the State – one east of the Cascades and one west of the Cascades.  They are nominated by Counties and chosen by a special WAPA evaluation committee.

WA ASPHALT PAVEMENT ASSOCIATION COMMERCIAL AWARD

This award sponsored by WAPA, is given to the outstanding paving project for a private owner. Candidates are nominated by WAPA members and the winner is chosen by a special WAPA evaluation committee.

SPECIAL OR INNOVATIVE USE and AIRPORT AWARDS

Special or innovative awards and Airport awards, sponsored by WAPA, are given to outstanding paving projects that demonstrate a special or innovative use of hot mix asphalt.  They are nominated by WAPA members and chosen by a special WAPA evaluation committee.

CARL MINOR AWARD

Awarded to the best asphalt paving project in the State of Washington.  See the winner at the top of the WSDOT Awards page.

• Diamond Paving. Recognizes companies whose paving crews demonstrate best practices that result in excellent product quality and ensure safety through proper training and compliance for supervisors and crew members, and demonstrated use of best practices in paving.
• Diamond Achievement. Recognizes asphalt plants and facilities that operate as good neighbors by maintaining a good appearance, meeting or exceeding all regulatory compliance, safety, and permitting requirements, operate using the latest environmental practices and safety procedures and maintain community relations.
• Diamond Quality. Recognizes companies that produce top quality material through proper practices in quality management, RAP and aggregate handling, asphalt storage, drying and mixing, air quality, truck scales, silos and control rooms.

Congratulations to the Diamond Award Recipients

WAPA strongly encourages all members to participate and achieve Diamond Status to recognize the excellence of our membership and differentiate companies.

The first recorded use of asphalt by humans was by the Sumerians around 3,000 B.C.  Statues from that time period used asphalt as a binding substance for inlaying various shells, precious stones and pearls.  Other common ancient asphalt uses were preservation (for mummies), waterproofing (pitch on ship hulls), and cementing (used to join together bricks in Babylonia).  Around 1500 A.D., the Incas of Peru were using a composition similar to modern bituminous macadam to pave parts of their highway system.  In fact, asphalt is mentioned several times in the Book of Genesis (Baird 2002).

In more modern times, asphalt paving uses first began with foot paths in the 1830s and then progressed to actual asphalt roadways in the 1850s.  The first asphalt roadways in the U.S. appeared in the early 1870s (Abraham 1929).

Roman Roads

The oldest Roman road still in use today, Via Appia (Figure 1), dates back to 312 B.C.  At its height, the Roman road network consisted of over 62,000 miles of roads.   By law, all of the public was entitled to use Roman roads, but the maintenance of the roadway was the responsibility of the inhabitants of the district through which the road ran (the same basic system used in the U.S. today).  Although Roman roads did not use asphalt as a binder, they did often use lime grout and other natural pozzolans as binders.  Figure 2 shows a typical Roman road structure.

Figure 1: Roman Road Surface

Figure 2: Roman Road Structure

Telford Pavements

Skipping forward several thousand years, Telford pavements begin to show likeness to today’s modern HMA pavements.  Thomas Telford (born 1757) served his apprenticeship as a building mason (Smiles 1904).  Because of this, he extended his masonry knowledge to bridge building.  During lean times, he carved grave-stones and other ornamental work (about 1780).  Eventually, Telford became the “Surveyor of Public Works” for the county of Salop (Smiles 1904), thus turning his attention more to roads.  Telford attempted, where possible, to build roads on relatively flat grades (no more than a 1 in 30 slope) in order to reduce the number of horses needed to haul cargo.  Telford’s pavement section was about 14 to 18 inches in depth as shown in Figure 3.  Telford pavements did not use any binding medium to hold the stones together.

Figure 3: Typical Telford Road (after Collins and Hart 1936)

Macadam Pavements

Macadam pavements introduced the use of angular aggregates (Figure 4).  John McAdam (born 1756 and sometimes spelled “Macadam”) observed that most of the “paved” U.K. roads in early the 1800s were composed of rounded gravel (Smiles 1904).  He knew that angular aggregate over a well-compacted subgrade would perform substantially better.  He used a sloped subgrade surface to improve drainage (unlike Telford who used a flat subgrade surface) onto which he placed angular aggregate (hand-broken, maximum size 3 inches) in two layers for a total depth of about 8 inches (Gillette 1906).  On top of this, the wearing course was placed (about 2 inches thick with a maximum aggregate size of 1 inch) (Collins and Hart 1936).  Macadam, who did not use any binding medium to hold the stones together, realized that the layers of broken stone would eventually become bound together by fines generated by traffic. The first macadam pavement in the U.S. was constructed in Maryland in 1823.

Figure 4: Macadam Pavement Core

Figure 5: Typical Macadam Road (after Collins and Hart 1936)

Tar Macadam Pavements

A tar macadam road consists of a basic macadam road with a tar-bound surface.  It appears that the first tar macadam pavement was placed outside of Nottingham (Lincoln Road) in 1848 (Hubbard 1910; Collins and Hart1936).  At that time, such pavements were considered suitable only for light traffic (i.e., not for urban streets).  Coal tar, the binder, had been available in the U.K. from about 1800 as a residue from coal-gas lighting.  Possibly this was one of the earlier efforts to recycle waste materials into a pavement!

As a side note, the term “Tarmac” was a proprietary product in the U.K. in the early 1900s (Hubbard 1910).  Actually it was a plant mixed material, but was applied to the road surface “cold.”  Tarmac consisted of crushed blast furnace slag coated with tar, pitch, portland cement and a resin.  Today the term “tarmac” is generic and generally refers to airport pavements (however, inappropriately).

Sheet Asphalt Pavements

Sheet asphalt placed on a concrete base (foundation) became popular during the mid-1800s with the first one of this type being built in Paris in 1858.  The first such pavement placed in the U.S. was in Newark, New Jersey, in 1870.  Generally, the concrete layer was 4 inches thick for “light” traffic and 6 inches thick for “heavy” traffic (Baker 1903).  The final thickness was based on the weight of the traffic, the strength of the concrete and the soil support.

Bitulithic Pavements

HMA pavement began to take on its modern form around the beginning of the 20th century when Frederick J. Warren was issued patents for a “hot mix” asphalt paving material and process, which he called “bitulithic”.  A typical bitulithic mix contained about 6 percent “bituminous cement” and graded aggregate proportioned for low air voids.  The concept was to produce a mix which could use a more “fluid” binder than was used for sheet asphalt.  Warren received eight patents in 1903.  A review of the associated claims reveals that Warren, in effect, patented HMA, the asphalt binder, the construction of HMA surfaced streets and roads, and the overlay of “old” streets.

In 1910 in Topeka, Kansas, a court ruling stated that HMA mixes containing 0.5 inch maximum size aggregate did not infringe on Warren’s patent (Steele and Himmelman 1986).  Thus, most U.S. hot mix asphalt (HMA) thereafter became oriented to the smaller maximum aggregate sizes.  A typical “Topeka mix” consisted of 30 percent graded crushed rock or gravel (all passing the 0.5 inch sieve), about 58 to 62 percent sand (material passing the No. 10 sieve and retained on the No. 200 sieve), 8 to 12 percent filler (material passing the No. 200 sieve).  This mixture required 7.5 to 9.5 percent asphalt cement.  By 1920, Warren’s original patents had expired in the U.S. (Oglesby and Hewes 1962) but the legacy of the Topeka mix lived on as reflected by the U.S. tendency towards finer mixes.

Dense-Graded Mixes

A dense-graded mix (Figure 1) is a well-graded HMA intended for general use.   When properly designed and constructed, a dense-graded mix is relatively impermeable.  Dense-graded mixes are generally referred to by their nominal maximum aggregate size.  They can further be classified as either fine-graded or coarse-graded.  Fine-graded mixes have more fine and sand sized particles than coarse-graded mixes.  Dense-graded mixes are used extensively in Washington State for all purposes.

Figure 1: Dense-Graded Cores

Stone Matrix Asphalt (SMA)

Stone matrix asphalt (SMA), sometimes called stone mastic asphalt, is a gap-graded HMA originally developed in Europe to maximize rutting resistance and durability (Figure 2 and 3).  The mix goal is to create stone-on-stone contact.  Since aggregates do not deform as much as asphalt binder under load, this stone-on-stone contact greatly reduces rutting.  SMA is generally more expensive than a typical dense-graded HMA because it requires more durable aggregates, higher asphalt content, modified asphalt binder and fibers.  In the right situations it should be cost-effective because of its increased rut resistance and improved durability.  SMA, has been used in the U.S. since about 1990, although it has only been used in Washington State on several pilot projects.

Figure 2: SMA Surface

Figure 3: SMA Lab Sample

Open-Graded Mixes

Unlike dense-graded mixes and SMA, an open-graded HMA mixture is designed to be water permeable.  Open-graded mixes use only crushed stone (or gravel) and a small percentage of manufactured sands.  The two most typical open-graded mixes are:

1. Open-graded friction course (OGFC).  Typically 15 percent air voids and no maximum air voids specified.
2. Asphalt treated permeable bases (ATPB).  Less stringent specifications than OGFC since it is used only under dense-graded HMA, SMA or PCC for drainage.

Figure 5: OGFC Surface

Figure 6: OGFC Lab Samples

WAPA Pavement Note on Open Graded Mixes

Open-graded friction course (OGFC) is not used widely in Washington State because of its susceptibility to studded tire wear.  Tire studs will tend to dislodge aggregate from the mix in the wheelpaths causing a depression typically referred to as studded tire wear. From 2006 through 2009 WSDOT paved three test sections of OGFC to investigate its use as a “quieter pavement” and performance in Washington State. For the most part, these mix designs were taken from Arizona where they have been extensively used. WSDOT information on these test sections can be found here.

Figure 1. Trinidad Lake Asphalt

Figure 2: Petroleum Refinery

“Asphalt cement” refers to asphalt that has been prepared for use in HMA and other paving applications.  This section uses the generic term, “asphalt binder”, to represent the principal binding agent in HMA because “asphalt binder” includes asphalt cement as well as any material added to modify the original asphalt cement properties.

Asphalt Physical Properties

Asphalt can be classified by its chemical composition and physical properties.  The pavement industry typically relies on physical properties for performance characterization.  An asphalt’s physical properties are a direct result of its chemical composition.  Typically, the most important physical properties are:

• Durability.  Durability is a measure of how asphalt binder physical properties change with age (sometimes called age hardening).  In general, as an asphalt binder ages, its viscosity increases and it becomes more stiff and brittle.
• Rheology.  Rheology is the study of deformation and flow of matter.  Deformation and flow of the asphalt binder in HMA is important in HMA pavement performance.  HMA pavements that deform and flow too much may be susceptible to rutting and bleeding, while those that are too stiff may be susceptible to fatigue cracking.
• Safety.  Asphalt cement like most other materials, volatilizes (gives off vapor) when heated.  At extremely high temperatures (well above those experienced in the manufacture and construction of HMA) asphalt cement can release enough vapor to increase the volatile concentration immediately above the asphalt cement to a point where it will ignite (flash) when exposed to a spark or open flame.  This is called the flash point. For safety reasons, the flash point of asphalt cement is tested and controlled.
• Purity.  Asphalt cement, as used in HMA paving, should consist of almost pure bitumen.  Impurities are not active cementing constituents and may be detrimental to asphalt performance.

Slideshow 1: Asphalt Binder Testing Equipment Used with Superpave

Grading Systems

WAPA Pavement Note on Asphalt Binder Grading Systems

Washington State uses the PG system for asphalt binder grading.  Typically the mix type and the PG binder are specified (e.g., 1/2-inch Superpave, PG 64-28).

Asphalt binders are typically categorized by one or more shorthand grading systems according to their physical characteristics.  These systems range from simple to complex and represent an evolution in the ability to characterize asphalt binder.  Today, most States use the Superpave performance grading (PG) system, although brief mention of the older systems is still worthwhile.

Older Grading Systems
The two major historical grading systems used in the U.S. are:

• Penetration grading.  Based on the depth a standard needle will penetrate an asphalt binder sample when placed under a 100 g load for 5 seconds.  The test is simple and easy to perform but it does not measure any fundamental parameter and can only characterize asphalt binder at one temperature (77°F).  Penetration grades are listed as a range of penetration units (one penetration unit = 0.1 mm).  Typical asphalt binders used in the U.S. are 65-70 pen and 85-100 pen.  This system is not used in Washington State.
• Viscosity grading.  Measures penetration (as in penetration grading) but also measures an asphalt binder’s viscosity at 140°F and 275°F.  Testing can be done on virgin (AC) or aged (AR) asphalt binder.  Grades are listed in poises (cm-g-s = dyne-second/cm²) or poises divided by 10.  Typical asphalt binders used in the U.S. are AC-10, AC-20, AC-30, AR-4000 and AR 8000.  Viscosity grading is a better grading system but it does not test low temperature asphalt binder rheology.

Superpave Performance Grading (PG) System
The Superpave PG system was developed as part of the Superpave research effort to more accurately and fully characterize asphalt binders for use in HMA pavements.  The PG system is based on the idea that an HMA asphalt binder’s properties should be related to the conditions under which it is used.  For asphalt binders, this involves expected climatic conditions as well as aging considerations.  Therefore, the PG system uses a common battery of tests (as the older penetration and viscosity grading systems do) but specifies that a particular asphalt binder must pass these tests at specific temperatures that are dependant upon the specific climatic conditions in the area of intended use.  Therefore, a binder used in Northeastern Washington would be different than one used in Western Washington.

Superpave performance grading is reported using two numbers – the first being the average seven-day maximum pavement temperature (in °C) and the second being the minimum pavement design temperature likely to be experienced (in °C). Thus, a PG 58-22 is intended for use where the average seven-day maximum pavement temperature is 58°C and the expected minimum pavement temperature is -22°C.  Notice that these numbers are pavement temperatures and not air temperatures.  WSDOT has analyzed pavement temperatures across the State and come up with two baseline asphalt binder grades (Figure 3).  If no other information is available, these grades should be the default choices for use in HMA.

Figure 3: WSDOT Base PG Grades

Asphalt Binder Modifiers

Some asphalt cements require modification in order to meet specifications.  Asphalt cement modification has been practiced for over 50 years but has received added attention in the past 20 years or so.  There are numerous binder additives available on the market today.  The benefits of modified asphalt cement can only be realized by a judicious selection of the modifier(s); not all modifiers are appropriate for all applications.  In general, asphalt cement should be modified to achieve the following types of improvements (Roberts et al. 1996):

• Lower stiffness (or viscosity) at the high temperatures associated with construction. This facilitates pumping of the liquid asphalt binder as well as mixing and compaction of HMA.
• Higher stiffness at high service temperatures. This will reduce rutting and shoving.
• Lower stiffness and faster relaxation properties at low service temperatures. This will reduce thermal cracking.
• Increased adhesion between the asphalt binder and the aggregate in the presence of moisture. This will reduce the likelihood of stripping.  Figure 4 shows two aggregate samples from the same source after they have been coated with asphalt binder.  The asphalt binder used with the sample on the left contain no anti-stripping modifier, which resulted in almost no aggregate-asphalt binder adhesion.  The asphalt binder used with the sample on the right contains 0.5% (by weight of asphalt binder) of an anti-stripping modifier, which results in good aggregate-asphalt binder adhesion.

Figure 4: Effects of an Antistripping Modifier

Other Forms of Asphalt Used in Paving

Besides asphalt cement, three other forms of asphalt are used prominently in the paving industry:

• Emulsified asphalt.  Emulsified asphalt is a suspension of small asphalt cement globules in water, which is assisted by an emulsifying agent (such as soap).  Emulsions have lower viscosities than neat asphalt and can thus be used in low temperature applications.  After an emulsion is applied the water evaporates away and only the asphalt cement is left.  Emulsions are often used as prime coats and tack coats.
• Cutback asphalt.  A cutback asphalt is a combination of asphalt cement and petroleum solvent.  Like emulsions, cutbacks are used because their viscosity is lower than that of neat asphalt and can thus be used in low temperature applications.  After a cutback is applied the solvent evaporates away and only the asphalt cement is left.  Cutbacks are much less common today because the petroleum solvent is more expensive than water and can be an environmental concern.  Cutbacks are typically used as prime coats and tack coats.
• Foamed asphalt.  Foamed asphalt is formed by combining hot asphalt binder with small amounts of cold water.  When the cold water comes in contact with the hot asphalt binder it turns to steam, which becomes trapped in tiny asphalt binder bubbles.  The result is a thin-film, high volume asphalt foam.  This high volume foam state only lasts for a few minutes, after which the asphalt binder resumes its original properties.  Foamed asphalt can be used as a binder in soil or base course stabilization, and is often used as the stabilizing agent in CIR.

Figure 1: Sand and Gravel

Aggregate Physical Properties

Aggregates can be classified by their mineral, chemical and physical properties.  The pavement industry typically relies on physical properties for performance characterization.  An aggregate’s physical properties are a direct result of its mineral and chemical properties.

Maximum Size

Maximum aggregate size can affect HMA and base/subbase courses in several ways.  In HMA, instability may result from excessively small maximum sizes; and poor workability and/or segregation may result from excessively large maximum sizes (Roberts et al. 1996).  ASTM C 125 defines the maximum aggregate size in one of two ways:

• Maximum size. The largest sieve that retains some of the aggregate particles but generally not more than 10 percent by weight.  Superpave defines nominal maximum aggregate size as “one sieve size larger than the first sieve to retain more than 10 percent of the material” (Roberts et al., 1996).
• Nominal maximum size. The smallest sieve through which 100 percent of the aggregate sample particles pass.  Superpave defines the maximum aggregate size as “one sieve larger than the nominal maximum size” (Roberts et al. 1996).It is important to specify whether “maximum size” or “nominal maximum size” is being referenced.

Gradation

WAPA Pavement Note on Aggregate Gradation

Aggregate is typically crushed to certain size or gradation specifications.  Each crushed gradation is typically stored as a different aggregate stockpile.  While some standard mixes can possibly be met using a single aggregate stockpile (with the possible addition of some blending sand), Superpave mixes often require combinations of up to three or four different stockpiles to meet gradation requirements.

An aggregate’s particle size distribution, or gradation, is one of its most influential characteristics.  In HMA, gradation helps determine almost every important property including stiffness, stability, durability, permeability, workability, fatigue resistance, frictional resistance and resistance to moisture damage (Roberts et al. 1996). Because of this, gradation is a primary concern in HMA mix design and thus most agencies specify allowable aggregate gradations.

Measurement

 Gradation is usually measured by a sieve analysis.  In a sieve analysis, a sample of dry aggregate of known weight is separated through a series of sieves with progressively smaller openings. Once separated, the weight of particles retained on each sieve is measured and compared to the total sample weight.  Particle size distribution is then expressed as a percent retained by weight on each sieve size.  Results are usually expressed in tabular or graphical format.  The typical graph uses the percentage of aggregate by weight passing a certain sieve size on the y-axis and the sieve size raised to the n^th power (n = 0.45 is typically used) as the x-axis units.  The maximum density appears as a straight line from zero to the maximum aggregate size (the exact location of this line is somewhat debatable, but the location shown in Figure 2 is generally accepted).

Typical Gradations (Figure 2)

• Dense or well-graded.  Refers to a gradation that is near maximum density.  The most common HMA mix designs in the U.S. tend to use dense graded aggregate.
• Gap graded.  Refers to a gradation that contains only a small percentage of aggregate particles in the mid-size range.  The curve is flat in the mid-size range.  These mixes can be prone to segregation during placement.
• Open graded.  Refers to a gradation that contains only a small percentage of aggregate particles in the small range. This results in more air voids because there are not enough small particles to fill in the voids between the larger particles.  The curve is flat and near-zero in the small-size range.
• Uniformly graded.  Refers to a gradation that contains most of the particles in a very narrow size range.  In essence, all the particles are the same size.  The curve is steep and only occupies the narrow size range specified.

• 
  Figure 2: Typical Aggregate Gradations

Other Gradation Terms

• Fine aggregate (sometimes just referred to as “fines”).  Defined by AASHTO M 147 as natural or crushed sand passing the No. 10 sieve and mineral particles passing the No. 200 sieve.
• Coarse aggregate.  Defined by AASHTO M 147 as hard, durable particles or fragments of stone, gravel or slag retained on the No. 10 sieve.  Usually coarse aggregate has a toughness and abrasion resistance requirement.
• Fine gradation.  A gradation that, when plotted on the 0.45 power gradation graph, falls mostly above the 0.45 power maximum density line.  The term generally applies to dense graded aggregate.
• Coarse gradation.  A gradation that, when plotted on the 0.45 power gradation graph, falls mostly below the 0.45 power maximum density line.  The term generally applies to dense graded aggregate.
• Mineral filler.  Defined by the Asphalt Institute as a finely divided mineral product at least 65 percent of which will pass through a No. 200 sieve.  Pulverized limestone is the most commonly manufactured mineral filler, although other stone dust, silica, hydrated lime, portland cement and certain natural deposits of finely divided mineral matter are also used (Asphalt Institute 1962).

Other Properties

WAPA Pavement Note on Aggregate Properties

In general, Washington aggregate is tough, abrasion resistant, durable and sound.  While other states such as Mississippi (mostly river rock) or Hawaii (some absorption problems) may have trouble meeting aggregate physical property specifications, Washington usually does not. Aggregate quality is especially good west of the Cascade Mountains.

Other important aggregate physical properties are:

• Toughness and abrasion resistance.  Aggregates should be hard and tough enough to resist crushing, degradation and disintegration from activities such as  manufacturing, stockpiling, production, placing and compaction.
• Durability and soundness.  Aggregates must be resistant to breakdown and disintegration from weathering (wetting/drying) or else they may break apart and cause premature pavement distress.
• Particle shape and surface texture.  Particle shape and surface texture are important for proper compaction, load resistance and workability.  Generally, cubic angular-shaped particles with a rough surface texture are best.
• Specific gravity.  Aggregate specific gravity is useful in making weight-volume conversions and in calculating the void content in compacted HMA (Roberts et al., 1996).
• Cleanliness and deleterious materials.  Aggregates must be relatively clean when used in HMA.  Vegetation, soft particles, clay lumps, excess dust and vegetable matter may affect performance by quickly degrading, which causes a loss of structural support and/or prevents binder-aggregate bonding.