Asphalt Concrete Mix Design and Field Control (T 5040.27)

AASHTO
M-226

U.S. Department of Transportation
Federal Highway Administration

TECHNICAL ADVISORY

ASPHALT CONCRETE MIX DESIGN AND FIELD CONTROL

T 5040.27
March 10, 1988

Par.

Purpose
Cancellation
Background
Materials
Mix Design
Plant Operations
Laydown and Compaction
Miscellaneous

PURPOSE. To set forth guidance and recommendations relating to asphalt concrete paving, covering the areas of materials selection, mixture design, and mixture production and placement. The procedures and practices outlined in the Technical Advisory (TA) are directed primarily towards developing quality asphalt concrete pavements for high-type facilities. The TA can also be used as a general guide for low-volume facilities.
CANCELLATION. Federal Highway Administration (FHWA) Technical Advisory T 5040.24, Bituminous Mix Design and Field Control, dated August 22, 1985, is canceled.
BACKGROUND
1. Over one-half of the Interstate System and 70 percent of all highways are paved with hot-mix asphalt concrete. Asphalt concrete is probably the largest single highway program investment today and there is no evidence that this will change in the near future. However, there is evidence that the number of premature distresses in the nation's recently constructed asphalt pavements is increasing. Heavier truck axle weights, increased tire pressures, and inadequate drainage are some of the factors leading to the increase in premature distress. The FHWA has been concerned with the deterioration in quality of asphalt concrete pavements for many years and in 1987 a special FHWA Ad Hoc Task Force studied two of the most common distresses existing today and subsequently issued a report titled "Asphalt Pavement Rutting and Stripping." The report contained both short-term and long-term recommendations for improving the quality of asphalt pavements.
2. With the variables of environment, component materials, and traffic loadings found throughout the United States, it is not surprising that there are many State-to-State or regional variations of design and construction requirements. No one set of specifications can achieve the same results in all States because of the factors mentioned above. However, there are many things that States can do to improve their current mix design and field control procedures to ensure that quality asphalt pavements will be constructed. This TA incorporates many of the FHWA Task Force recommendations and presents the current state-of-the-art in materials, mix design, plant operation, laydown and compaction, and other areas relating to quality hot-mix asphalt pavements.

MATERIALS

Aggregate is the granular material used in asphalt concrete mixtures which make up 90-95 percent of the mixture weight and provides most of the load bearing characteristics of the mix. Therefore, the quality andphysical properties of the aggregates are critical to the pavement performance. The following is recommended:

Asphalt grade and characteristics are critical to the performance of the asphalt pavement. The following is recommended:

(1) Grade(s) of asphalt cement used in hot-mix paving should be selected based on climatic conditions and past performance.

(2) It is recommended that asphalt cement be accepted on certification by the supplier (along with the testing results) and State project verification samples. Acceptance procedures should provide information on the physical properties of the asphalt in a timely manner.

(3) The physical properties of asphalt cement that are most important to hot-mix paving are shown below. Each State should obtain this information (by central laboratory or supplier tests) and should have specification requirement(s) for each property except specific gravity.

(a) Penetration 77° F

(b) Viscosity 140° F

(d) Ductility/Temperature

(e) Specific Gravity

(f) Solubility

(g)Thin Film Oven (TFO)/Rolling TFO; Loss on Heating

(h) Residue Ductility

(i) Residue Viscosity

(j)Low temperature cracking is related to the physical properties of the asphalt and may beincreased by the presence of wax in the asphalt. The low temperature ductility test at 39.2° F (4° C) can indicate where this may be a problem. The test is performed at a pull speed of 1 cm/min. Typical specification requirements are:

AASHTO
M-226
Table 2

AC 2.5 50 + cm

AC 5 25 + cm

AC 10 15 + cm

AC 20 5 + cm

(4) The temperature viscosity curves or absolute and kinematic viscosity information should be available at the mixing plant for each shipment of asphalt cement. This can identify a change in asphalt viscosity which necessitates a new mix design. Each State should provide temperature/viscosity information on the asphalt used in the laboratory mix design to the projects. Differences in the viscosity (as well as the penetration) of the asphalt from the asphalt used in the mix design may indicate the necessity to redesign the mix (Attachment 2).

MIX DESIGN

Asphalt concrete mixes should be designed to meet the necessary criteria based on type of roadway, traffic volumes, intended use, i.e., overlay on rigid or flexible pavements, and the season of the year the construction would be performed. Each State's mix design criteria should be as follows.

PROPERTY
HEAVY TRAFFIC DESIGN
(>1,000,000 ESAL*)
MEDIUM TRAFFIC DESIGN
(10,000 - 1,000,000 ESAL)
LIGHT TRAFFIC DESIGN
(<10,000 ESAL)

Marshall

Compaction Blows
75 50 35

Stability (min.)
1,500 750 500

Flow
8-16 8-18 8-20

Hveem

Stability (min.)
37 35 30

Swell
0.030 in. 0.030 in. 0.030 in.

Void Analysis

Air Voids
3-5 3-5 3-5

* Equivalent Single Axle Load

MINIMUM PERCENT VOIDS IN MINERAL AGGREGATE (VMA)

Nominal Maximum Particle Size, USA Standard Sieve Designation Minimum Voids in Mineral Aggregate Percent

No. 16 23.5

No. 8 21

No. 4 18

3/8 in. 16

½ in. 15

3/4 in. 14

1 in. 13

1 ½ in. 12

2 in. 11.5

2 ½ in. 11

Standard mix design procedures (Marshall, Hveem) have been developed and adopted by AASHTO, however, some States have modified these procedures for their own use. Any modification from the standard procedure should be supported by correlation testing for reasonable conformity to the design values obtained using the standard mix design procedures.
Stripping in the asphalt pavements is not a new phenomenon, although the attention to it has intensified in recent years. Moisture susceptibility testing should be a part of every State's mix design procedure. The "Effect of Zero on Compacted Bituminous Mixtures" (immersion compression test) (AASHTO T-165) and "Resistance of Compacted Bituminous Mixture to Moisture Induced Damage" (AASHTO T-283) are currently the only stripping test procedures which have been adopted by AASHTO. The AASHTO T-283, commonly known as the LottmanTest, requires that the test specimens be compacted so as to have an air void content of 7 ± 1 percent, while AASHTO T-165 does not. This air void content is what one would expect in the mat after construction compaction. There is considerable research underway on developing better tests for determining moisture damage susceptibility of the aggregate asphalt mixtures. One of the most promising test procedures is that developed by Tunnicliff and Root as reported in the National Cooperative Highway Research Program (NCHRP) Report 274. This test is similar to AASHTO T-283, but it takes less time to perform. In the majority of cases hydrated lime and Portland cement have proven to be the most effective antistripping additives.
The determination of air voids in the laboratory mix is a critical step in designing and controlling asphalt hot-mix. In order to determine air voids, the theoretical maximum density or the maximum specific gravity of the mix must be determined. This can be accomplished by using the "Maximum Specific Gravity of Bituminous Paving Mixtures" (Rice Vacuum Saturation) (AASHTO T-209).
Proper mix design procedures require that each mix be designed using all of the actual ingredient materials including all additives which will be used on the project.
The complete information on the mix design should be sent to the plant. The following information should be included in the mix design report and sent to the plant.
Formal procedures should be established to require that changes to mix designs be approved by the same personnel or office that developed the original mix design.
After startup, the resulting mixture should be tested to verify that it meets all of the design criteria.

PLANT OPERATIONS
1. In order to assure proper operation, an asphalt plant must be calibrated and inspected. Plant approval should be required and should cover each item on the asphalt plant checklist (Attachment 3).
2. To avoid or mitigate unburned fuel oil contamination of the asphalt mixture, the use of propane, butane, natural gas, coal or No. 1 or No. 2 fuel oils is recommended.
3. If the asphalt cement is overheated or otherwise aged excessively, the viscosity of the recovered asphalt will exceed that of the original asphalt by more than four times. However, if the viscosity of the recovered asphalt is less or even equal to the original viscosity, it has probably been contaminated with unburned fuel oil.
4. For drum mixer and screenless batch plants there should be three separate graded stockpiles for surface courses and four for binder and base courses. Each stockpile should contain between 15 to 50 percent by weight of the aggregate size in the mix design. The plus #4 sieveaggregate stockpile should be constructed in lifts not exceeding 3 feet to a maximum height of 12 feet. There should be enough material in the stockpiles for at least 5 days of production. The plant should be equipped with a minimum of four cold feed bins with positive separation.
5. Control testing of gradation and asphalt content should be conducted to assure a quality and consistent mixture. In many States, the contractor or supplier is required to do this testing.
6. Acceptance testing should be conducted for gradation and asphalt content of the final mixture.
7. The plotting of control and acceptance test results for gradation, asphalt content, and density on control charts at the plant provides for easy and effective analysis of test results and plant control.
8. The moisture content of the aggregate must be determined for proper control of drum mixer plants. The asphalt content is determined by the total weight of the material that passes over the weigh bridge with the correction made for moisture. Sufficient aggregate moisture contents need to be performed throughout the day to avoid deviations in the desired asphalt content.
9. Moisture contents of asphalt mixtures is also important. The extraction and nuclear asphalt content gauge procedures will count moisture as asphalt. For this reason, a moisture correction should be made. In addition, high moisture contents in asphalt mixtures can lead to compaction difficulty due to the cooling of the mix caused by evaporation of the moisture. This is particularly important with drum mixer mixes which require moisture for the mixing process. Some States specify a maximum moisture content behind the paver. A recommended maximum moisture content behind the paver is 0.5 percent.
LAYDOWN AND COMPACTION
1. Prior to paving startup, equipment should be checked to assure its suitability and proper function. Projectequipment approval should include the items shown on the project inspection checklist (Attachment 4).
2. Paving startup should begin with a test strip section. This will allow for minor problems to be solved, establishment of roller patterns and number of passes, and will assure that proper placement and compaction can be attained.
3. In order to assure proper placement and compaction, it is essential that the mat be placed hot. Establishment of and compliance with the following items should be included: minimum mix, underlying pavement, and ambient temperatures. Cold weather and early or late season paving should be avoided. The practice of raising the temperature of the mixture to combat the cold conditions should not be permitted, as this will contribute to excessive aging of the asphalt cement.
4. The use of a pneumatic roller in the compaction process is strongly encouraged. When used in the intermediate rolling it will knead and seal the mat surface and aid in preventing the intrusion of surface water into the pavement layers. It will also contribute to the compaction of the mat.
5. Density requirements should be established to result in an air void system in the mat of 6-8 percent immediately after construction. This allows for the inherent additional densification under traffic to an ultimate air void content of about 3-5 percent. Density acceptance specifications should require a percentage of maximum density as determined by AASHTO T-209. A percentage of test strip density or Marshall laboratory density can be used provided each is related to the maximum density. The specified density should be attained before the mat temperature drops below 175° F.
6. Density measurement should be accurate, taken frequently, and the results made available quickly for each day of production. Density should be determined by test cores, or by properly calibrated nuclear test gauges. Specifications should require several tests to be averaged to determine density results for acceptance.
7. Successive hot-mix courses should not be placed while previous layers are wet. To avoid, or minimize the penetration of water into base and binder courses, paving operations should be scheduled so that the surface layer(s) is placed within a reasonable period after these courses are constructed. To the greatest extent possible, construction should be planned to avoid the necessity of leaving layers uncovered during wet seasons of the year.
MISCELLANEOUS
1. Some States have established procedures to accept out-of-specification material and pavement with a reduction in price. These procedures include definition of lot size/ production time, tolerances, and pay factor reductions for ingredient materials, combined mixture properties, pavement density, pavement smoothness, and lift thickness.
2. Prior to the start of production and placement operations, a preplacement conference, including all the paving participants, should be held. This conference would define duties and responsibilities for each phase of the operation as well as problem-solving procedures.
3. During startup it is very effective to have a construction and/or materials specialist at the project site to assist in identifying and solving any problem that develops.
4. Because asphalt hot-mix pavement construction is complex, it requires that each person involved understand his/her function thoroughly. It is also helpful if each person has a basic understanding of each of the many phases involved. It is recommended that States develop or use existing training to address these phases of asphalt paving.

/S/
Ronald E. Heinz
Associate Administrator for
Engineering and Program Development

AGGREGATE GRADATION

It has long been established that gradation of the aggregate is one of the factors that must be carefully considered in the design of asphalt paving mixtures, especially for heavy duty highways. The purpose in establishing and controlling aggregate gradation is to provide sufficient voids in the asphalt aggregate mixture to accommodate the proper asphalt film thickness on each particle and provide the design air void system to allow for thermal expansion of the asphalt within the mix. Minimum voids in the mineral aggregate (VMA) requirements have been established and vary with the top aggregate size.

Traditionally, gradation requirements are so broad that they permit the use of paving mixtures ranging from coarse to fine and to either low or high stability. To further complicate matters, different combinations of sieve sizes are specified to control specific grading ranges. Standardization of sieve sizes and aggregate gradations, which has often been suggested, is not likely to occur because of the practice of using locally available materials to the extent possible.

In the early 1960's, the Bureau of Public Roads introduced a gradation chart (Figure 1) which is especially useful in evaluating aggregate gradations. The chart uses a horizontal scale which represents sieve size openings in microns raised to the 0.45 power and a vertical scale in percent passing. The advantage in using this chart is that, for all practical purposes, all straight lines plotted from the lower left corner of the chart, upward and toward the right to any specific nominal maximum particle size, represent maximum density gradations. The nominal maximum particle sieve size is the largest sieve size listed in the applicable specification upon which any material is permitted to be retained. An example is shown in Figure 2.

The gradations depicted in Figures 3 and 4 are exaggerated to illustrate the points being made. By using the chart, aggregate gradations can be related to maximum density gradation and used to predict if the mixture will be fine or coarse textured as shown in Figure 3.

Soon after the chart was developed, it was used to study gradations of aggregate from several mixtures that had been reported as having unsatisfactory compaction characteristics. These mixtures could not be compacted in the normal manner because they were slow in developing sufficient stability to withstand the weight of the rolling equipment. Such mixtures canbe called "tender mixes." This study identified a consistent gradation pattern in these mixes as is illustrated in Figure 4.

Most notable is the hump in the curve near the #40 sieve and the flat slope between the #40 sieve and the #8 sieve. This indicates a deficiency of material in the #40 to #8 sieve range and an excess of material passing the #40 sieve. Mixtures with an aggregate exhibiting this gradation characteristic are susceptible to being tender, particularly if the fines are composed of natural sand.

As part of the bituminous mix design process, the aggregate gradation should be plotted on the 0.45 power gradation chart.

Figure number is given above each thumbnail graphic (click on graphic to link to larger image).

Figure 1: Gradation Chart Figure 1: Gradation Chart-Link

Figures 2 and 3: 0.45 Power Gradation Charts

Figure 4: 0.45 Power Gradation Chart

ASPHALT VISCOSITY

Each particular asphalt has a unique temperature-viscosity relationship. This relationship is sometimes described as temperature susceptibility. This temperature-viscosity relationship can be plotted on a modified semilog chart as shown on the attached chart. These charts are very useful in determining the optimum mixing and compacting temperature of a particular asphalt. Past research has identified the optimum mixing tempera ture as that corresponding to a viscosity of 170 ± 20 centi stokes, and the optimum compaction temperature as that corre sponding to a viscosity of 280 ± 30 centistokes for laboratory mix design. The optimum mixing temperature should be identified for the asphalt used in the mix design and included in the mix design report which is sent to the production plant.

Prior to the oil embargo, there was a relatively fixed distribu tion system for crude oil. This allowed for a relatively uniform asphalt cement from each refinery. Highway agencies became familiar with the handling and performance characteristics of those asphalt cements. As a result of the embargo, a new vari able distribution system is in place which allows shifting and blending of crude oils resulting in production of asphalt cements with very different temperature viscosity characteristics.

The attached chart will allow plotting the temperature-viscosity curve for the asphalts used in a State or a particular asphalt from a project. If the kinematic viscosity (275° F) of the asphalt being used changes from the kinematic viscosity of theasphalt used in the mix design by a factor of more than about two, a new mix design should be required.

Attachment 2: Asphalt Viscosity Chart

MODEL CHECKLIST FOR

ASPHALT PLANT

COMPANY _______________________________

LOCATION __________________ INSPECTED BY __________ DATE ________

TYPE PLANT AND MANUFACTURER NAME ________________________________

MAXIMUM BATCH ____________________ LBS.

RATED TONS PER HOUR ______________

PROJECT NO. ______________________ COUNTY _______________________

Stockpiles
1. Properly separated.
2. Material segregated.
3. Has contractor submitted and received approval of intended materials sources and job mix formula?
4. Is area clean and properly kept?
General Requirements for all Plants
1. Are tanks for storage of asphalt cement equipped for heating the material under effective and positive control at all times?
2. Are tanks or storage material properly heated?
3. Is a circulating system for the asphalt cement of adequate capacity to provide proper and continuous circulation between storage tank and proportioning units during the entire operating period?
4. Is the discharge end of the asphalt cement circulating pipe kept below the surface of the material in the storage tank?
5. Are all pipe links and fittings steamed, oil jacketed, or otherwise properly insulated to prevent heat loss?
6. Is storage tank capacity such as to ensure continuous operation of the plant and uniform tem perature of the asphalt cement when it is mixed with the aggregate?
7. Are tanks accurately calibrated to 100 gallons (378.5 L) and accessible for measuring the volume of the asphalt cement?
8. Is a sampling outlet provided in the asphalt feed lines?
9. Is a drainage receptacle provided for flushing the outlet prior to sampling?
Antistrip and Other Additive Systems
1. Is antistrip material added at plant site?
2. If antistrip material is added at plant site, does the antistrip system meet specifications?
3. If other approved additives are used, are they handled in accordance with an established proce dure?
Cold Feed System
1. Number of cold bins. ____________
2. Does plant have mechanical or electrical means for uniformly feeding the aggregates into the dryer?
3. Does cold feed have a synchronized proportioning method when blending aggregates from two or more bins?
4. If mineral filler is required, is a separate bin provided?
5. Is the feeder for mineral filler furnished with the feeder drive positively interlocked and syn chronized with the aggregate feeds?
Drier
1. Number of driers. ___________
2. Is a drier of satisfactory design provided?
Dust Collectors and Emission Controls
1. What type dust collector is provided?
2. Can the material collected in the dust collector be wasted or any part or all of the material be returned to the aggregate mixture?
3. Does the plant meet applicable limitations on emissions?
4. Has company received a permit to operate from EPA?
Thermometric Equipment
1. Is a recording pyrometer or armored thermometer located in the asphalt cement feed line near the discharge end at the mixer unit?
2. Is the plant equipped with recording pyrometers, or armored thermometers or other approved thermometric instruments at the discharge end of the drier?
3. Has accuracy of pyrometers or thermometers been checked?
Surge and Storage Bins
1. Is plant equipped with surge or storage bins?
2. What type bin? Surge or storage?
3. Is unit enclosed, insulated, weather proof?
4. Is unit equipped with material level indicator?
5. Is the indicator visible from plant operator or weigh master's station?
6. Does unit have approved thermometric instrument so placed to indicate automatically the temperature of mixture at discharge?
7. Is conveyer system covered and insulated (if necessary) so as to prevent excessive loss of heat during transfer of material from mixing plant to storage bin?
8. Does storage bin have acceptable heating system?
9. Has surge or storage bin received prior evaluation and approval before using?
Safety and Inspection Provisions
1. Are gears, pulleys, chains, sprockets, and other dangerous moving parts thoroughly protected?
2. Is an unobstructed and adequately guarded passage provided and maintained in and around the truck loading space for visual inspection purposes?
3. Does plant have adequate and safe stairways or guarded ladders to plant units such as mixer platforms, control platforms, hot storage bins, asphalt storage tanks, etc. where inspections are required?
4. Is an inspection platform provided with a safe stairway for sampling the asphalt mixture from loaded trucks?
Truck Scales
1. Are scales capable of weighing the entire vehicle at one time?
2. Do scales have digital printing recorder or automatic weight printer?
3. Have scales been checked and certified by a reputable scale company in the presence of an authorized representative of the highway department?
4. Date checked
  Agency Name
5. Is copy of certification available?
6. Remarks
Transportation Equipment
1. Are truck bodies clean, tight, and in good condition?
2. Do trucks have covers to protect material from unfavorable weather conditions?
3. Is soapy water or other approved products available for coating truck bodies to prevent material from sticking? Diesel fuel should not be used.
4. Type of material used.(_________)
Provisions for Testing
1. Does size and location of laboratory comply with specifications?
2. Is laboratory properly equipped?
3. Is laboratory acceptable?
SPECIAL REQUIREMENTS FOR BATCH PLANTS
Weigh Box or Hopper
1. Is weigh box large enough to hold full batch?
2. Does gate close tightly so that material cannot leak into the mixer while a batch is being weighed?
Aggregate Scales
1. Are scales equipped with adjustable pointers or markers for marking the weight of each material to be weighed into the batch?
2. Are ten 50-lb. (22.7 kg) weights available for checking scales?
3. Has accuracy of weights been checked?
4. Have scales been checked and certified by a reputable scales company in the presence of an authorized representative of the highway department?
5. If the plant is equipped with beam type scales, are the scales equipped with a device to indicate at least the last 200 lb. (97 kg) of the required load?
Asphalt Cement Bucket
1. Is bucket large enough to handle a batch in a single weighing so that the asphalt material will not overflow, splash or spill?
2. Is the bucket steamed, or oil-jacketed or equipped with properly insulated electric heating units?
3. Is the bucket equipped to deliver the asphalt material over the full length of the mixer?
Asphalt Cement Scales
1. Have scales been checked and certified by a reputable scale company in the presence of an authorized representative of the highway department?
2. Are scales equipped with a device to indicate at least the last 20 lb. (9.1 kg) of the approaching total load?
Screens
1. Condition of screens.
  (Satisfactory or Unsatisfactory)
2. Do the plant screens have adequate capacity and size range to properly separate all the aggregate into sizes required for proportioning so that they may be recombined consistently?
Hot Bins
1. Number of bins? _____________________
2. Are bins properly partitioned?
3. Are bins equipped with overflow pipes?
4. Will gates cut off quickly and completely?
5. Can samples be obtained from bins?
6. Are bins equipped with device to indicate the position of aggregate at the lower quarter point?
Asphalt Control
1. Are means provided for checking the quantity or rate of flow of asphalt material?
2. Time required to add asphalt material into pugmill.
Mixer Unit for Batch Method
1. Is the plant equipped with an approved twin pugmill batch mixer that will produce a uniform mixture?
2. Can the mixer blades be adjusted to ensure proper and efficient mixing?
3. Are the mixer blades in satisfactory condition?
4. What is the clearance of the mixer blades? (___ in.)
5. Does the mixer gate close tight enough to prevent leakage?
6. Does the mixer discharge the mixture without appreciable segregation?
7. Is the mixer equipped with time lock?
8. Does timer lock the weigh box gate until the mixing cycle is completed?
9. Will timer control dry and wet mixing time?
10. Can timer be set in 5-second intervals throughout the designated mixing cycles?
11. Can timer be locked to prevent tampering?
12. Is a mechanical batch counter installed as part of the timing device?
Automation of Batching
1. If the plant is fully automated, is an automatic weighing, cycling and monitoring system installed as part of the batching equipment?
2. Is the automatic proportioning system capable of weighing the materials within ± 2 percent of the total sum of the batch sizes?
SPECIAL REQUIREMENT FOR DRUM MIXERS
Aggregate Delivery System
1. Number of cold feed bins? __________________
2. Are cold feed bins equipped with devices to indicate when the level of the aggregate in each bin is below the quarter point?
3. Does the cold feed have an automatic shut-off system that activates when any individual feeder is interrupted?
4. Are provisions available for conveniently sampling the full flow of material from each cold feed and the total cold feed?
5. Is the total feed weighed continuously?
6. Are there provisions for automatically correcting the wet aggregate weight to dry aggregate weight?
7. Is the flow of aggregate dry weight displayed digitally in appropriate units of weight and time and totaled?
8. Are means provided for diverting aggregate delivery into trucks, front-end loaders, or other containers for checking accuracy of aggregate delivery system?
9. Is plant equipped with a scalping screen for aggregate prior to entering the conveyor weigh belt?
Asphalt Cement Delivery System
1. Are satisfactory means provided to introduce the proper amount of asphalt material into the mix?
2. Does the delivery system for metering the asphalt material prove accurate within ± 1 percent?
3. Does the asphalt-material delivery interlock with aggregate weight control?
4. Is the asphalt material flow displayed in appropriate units of volume or weight and time and totaled?
5. Can the asphalt material be diverted into distributor trucks or other containers for checking accuracy of delivery systems?
Drum Mixer
1. Is the drum mixer capable of drying and heating the aggregate to the moisture and temperature requirements set forth in the specifications, and capable of producing a uniform mix?
2. Does plant have provisions for diverting mixes at startup and shutdowns or where mixing is not complete or uniform?
Is plant approved for use?

PROJECT INSPECTION CHECKLIST

Compaction of Foundation

Have all courses of the foundation been compacted to required density?

Old Asphalt Pavement

Have all potholes been patched?
Have all necessary patches been made?
Have all loose material and "fat" patches been removed?
Have all depressions been filled and compacted?
Has fog seal been used on surface that has deteriorated from oxidation?
Has an emulsified asphalt slurry seal been applied on old surfaces with extensive cracking?

Rigid Type Pavement

Has pavement been under sealed where necessary?
Has premolded joint material and crack filler been cleaned out?
Have all "fat" patches been removed?
Has badly broken pavement been removed and patched?
Have all depressions been filled and compacted?

Incidental Tools

Do incidental tools comply with specifications?
Are all necessary tools on job before work begins?

The Engineer and the Contractor

Have the engineer and inspectors held a preliminary conference with the appropriate contractor personnel?
Has continuity of operations been planned?
Has the number of pavers to be used been determined?
Have the number and type of rollers to be used been determined?
Has the number of trucks to be used been determined?
Has the width of spread in successive layers been planned?
Is it understood who is to issue and who is to receive instructions?
Have weighing procedures and the number of load tickets to be prepared been determined?
Have procedures for investigation of mix been agreed upon?
Has method of handling traffic been established?

Preparation of Surface

Have all surfaces that will come into contact with the asphalt mix been cleaned and coated with asphalt?
Has a uniform tack coat of correct quantity been applied?

Asphalt Distributor

Does the asphalt distributor comply with specifications?
Are the heaters and pump in good working condition?
Have all gauges and measuring devices such as the bitumeter, tachometer, and measuring stick been calibrated?
Are spray bars and nozzles unclogged and set for proper application of asphalt?

Hauling Equipment

Are truck beds smooth and free from holds and depressions?
Do trucks comply with specifications?
Are trucks equipped with properly attached tarpaulins?
For cold weather or long hauls, are truck beds insulated?
When unloading, do trucks and paver operate together without interference?
Is the method of coating of contact surfaces of truck beds agreed upon?

Paver

Does the paver comply with specifications?
Is the governor on the engine operating properly?
Are the slat feeders, the hopper gates, and spreader screws in good condition and adjustment?
Are the crawlers adjusted properly?
Do the pneumatic tires contain correct and uniform air pressure?
Is the screed heater working properly?
Are the tamper bars free of excessive wear?
Are the tamper bars correctly adjusted for stroke?
Are the tamper bars correctly adjusted for clearance between the back of the bar and the nose of the screed plate?
Are the surfaces of the screed plates true and in good condition?
Are mat thickness and crown controls in good condition and adjustment?
Are screed vibrators in good condition and adjustment?
Is the oscillating screed in proper position with respect to the vibrating compactor?
Is the automatic screed control in adjustment and is the correct sensor attached?

Spreading

Are the required number of pavers on job?
Is the mix of uniform texture?
Is the general appearance of the mix satisfactory?
Is the temperature of the mix uniform and satisfactory?
Does the mix satisfy the spreading requirements?
Has proper paver speed been determined?
Is the surface smoothness tolerance being checked and adhered to?
Is the depth of spread checked frequently?
Has the daily spread been checked?

Rolling

Are the required number of rollers on the job?
Is proper rolling procedure being followed?
Is the proper rolling pattern being followed?
Are joints and edges being rolled properly?

Miscellaneous

Are all surface irregularities being properly corrected?
Is efficient control of traffic being maintained?
Are sufficient samples being taken?
Are samples representative?
Have assistant inspectors been properly instructed?
Are inspection duties properly apportioned among assistants?
Are records complete and up-to-date?
Are safety measures being observed?
Has final cleanup and inspection been made?

FHWA Home | Directives | Technical Advisories | Feedback

United States Department of Transportation - Federal Highway Administration

PROPERTY	HEAVY TRAFFIC DESIGN (>1,000,000 ESAL*)	MEDIUM TRAFFIC DESIGN (10,000 - 1,000,000 ESAL)	LIGHT TRAFFIC DESIGN (<10,000 ESAL)

Marshall

Compaction Blows	75	50	35
Stability (min.)	1,500	750	500
Flow	8-16	8-18	8-20

Hveem

Stability (min.)	37	35	30
Swell	0.030 in.	0.030 in.	0.030 in.

Void Analysis

Air Voids	3-5	3-5	3-5

	Nominal Maximum Particle Size, USA Standard Sieve Designation	Minimum Voids in Mineral Aggregate Percent

	No. 16	23.5
	No. 8	21
	No. 4	18
	3/8 in.	16
	½ in.	15
	3/4 in.	14
	1 in.	13
	1 ½ in.	12
	2 in.	11.5
	2 ½ in.	11