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HMA Pavingfor Inspectors

2020

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Topics of Discussion

Hot Mix Asphalt “HMA” (Section 402)

HMA Series (50, 60, 70, and 80)

Prep

Joint Adhesive

Tack Coat

HMA Paver

HMA Paving Defects

Documentation

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Section 402

Seasonal Limits for Top Course

Upstate – April 15 to October 31

Downstate – April 1 to November 30

Surface Temperature 50°F and rising for layer thickness 1.0 inch or less

45°F and rising for greater than 1.0 - 3.0 inches thick

40°F and rising for layer thickness greater than 3.0 inches

Guidelines for measuring surface temperature

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HMA Series

50 Series – Expressways

60 Series – High Volume Hwy >2000 tons of top

70 Series – High Volume Hwy <2000 tons of top or Low Volume Hwy >2000 tons of top

80 Series – Specified for miscellaneous placements, shoulders, bridge approaches (regardless of the project location), True & Leveling, Shim, 6.3mm etc.

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Methods to Check Density

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HMA Series Compaction

50 Series - Daily Coring

60 Series - Coring for test section and additional coring every 3rd day of mainline placement

70 Series - No coring, construct a test section and monitor density with a nuclear gauge

80 Series – No coring or nuclear gauge; compaction determined by number of roller passes (see Table 402-6)

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50 Series Construct a Test Section (Option 1), or Proceed with Routine

Paving (Option 2) (Contractor’s Choice)

Routine Density Monitoring via Daily Coring Mainline Paving, Ramps >1250 feet

Cores Results Used to Determine Pavement Density Quality Adjustment Factor (QAF) QAF Range 0.60 - 1.05

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60 Series Construct a Test Section - Project Target Density “PTD”

Option 1 (Test Strip Only) or Option 2 (Continue Paving)

Contractor uses a gauge to monitor density every 200 ft

≥96% and ≤103% of PTD

Moving average of last 10 tests ≥98% of PTD

See MP 402-02 for density monitoring using a gauge

Engineer or Inspector checks BR Form 5 times signs off

96% or 103%Average of last 10 98%

200 ft

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60 Series Compaction

Additional Cores for Density Verification One set of 4 cores every 3rd day of

mainline paving Cores Assigned QAF Applied to

Mainline tonnage only. Maximum QAF = 1.0

Multiple Paving SitesNew Test Section Not RequiredFirst Day of PavingUse Previously Established PTDTake 4 cores over entire day's

placement for PTD verification

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70 Series Compaction

Test section is 1500 ft max in one lane

PTD is the average of highest densities at each of

3 random locations

150 ft 1350 ft

1500 ft

Lane 1

Lane 2

Excluded Area

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70 Series Construct a Test Section and

determine the PTD by “peak” method using a nuclear gauge

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70 Series Compaction Contractor uses a gauge to monitor density Each test location ≥96% and ≤103% of PTD Moving average of last10 tests ≥98% of PTD See MP 402-02 for density monitoring using a

gauge Engineer or Inspector checks BR Form 5 times

signs off

�96% or 103%Average of last 10 98%

200 ft

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80 Series Compaction

This method is used for

6.3 HMA

Small Placements

Bridge Approaches, Culvert Replacements, etc.

T&L (where thickness is not specified)

Misc. Paving, i.e., repairs

Number of Passes per Table 402-6

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80 Series CompactionTABLE 402-6 NUMBER OF PASSES1

Pavement Courses

Static Compaction Vibratory Compaction

Steel WheelRollers

PneumaticRollers

VibratoryPasses

StaticPasses

37.5 Base (Each Lift)

8 3 6 4

25 Binder 8 3 6 4

19 Binder 6 3 4 2

12.5 Top 6 3 4 2

9.5 Top 4 3 4 2

Permeable Base2 - - - 2

Vibratory Pass Movement of Roller with Both Drums Vibrating

Static Pass Movement of Roller with Both Drums Not Vibrating

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80 Series Compaction

Check Number of Passes

Engineer may modify if damage occurs Determine Impacts per Foot

VPM / FT PER MINUTE Verify

Spec Requires 12 Minimum Modify roller settings if necessary

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80 Series Table 402-6 includes recommended number of roller

passes

Follow table it is not the contractor’s choice

Requires approved rollers (from approved List)

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Definition of a Roller Pass

Vibratory PassOne vibrating drum passes over a point

Static PassA roller (non-vibrating mode) passes over a point

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80 Series

Where will this method be used?

6.3 HMA paving

Small placements, i.e., bridge approaches, culvert replacements etc

Some T&L paving, repairs

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Inspector Responsibilities

Attend Pre-Pave Meeting

Identify Mix Type

Check Mix Temperature

Check Mat Quality

Check Mat Density

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CIM Paving

Checklist

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Asphalt

Paving CheckList

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Gauge Inspector Certification

Gauge operators must be certified

50, 60, and 70 series specification

Nuclear and non-nuclear gauges

Discuss with Contractor

Pre-construction

Pre-pave

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Binder Grade

Gyration Level

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Identify Mix Type Too many possibilities

Mix codes

Mix Codes are printed on the delivery tickets

Example: 12.F2.2.H.C

TABLE 401-7 DELIVERY TICKET MIX CODINGMix

TypeCode

FrictionCode

Design ESAL Code Mix Type CodePG Binder

TypeCode

9.5 09 F1 <0.3 million 1 HMA H PG 58E-34 A

12.5 12 F2 <30 million 2 WMA W PG 64S-22 B

19.0 19 F3 ≥30 million 3 PG 64V-22 C

25.0 25 F9 PG 64H-22 D

37.5 37 ----- PG 64E-22 E

OTHER G

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The Paving Day

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Inspector Supplies

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Review Plans and Specifications

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Check Equipment

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Tack Coat Tack provides a bond between layers

No tack on permeable base

Prior to tack application, surface must be clean

Must be evenly applied

Must break (brown to black)

Application rate may be adjusted

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Bad Good

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Self Propelled Paving Machine

HMA Flow

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Forces on Screed

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There are two primary forces acting on the paver screed as the paver places the mix.

The first force is the F3 - it varies as the speed of the tractor increases or decreases.

The second force on the screed is the head of the material pushing against the screed

Paver Screed

The speed of the paver needs to remain constant.

If the speed changes the mat thickness changes and this will affect the HMA mat quality

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It takes 5 lengths of the leveling or tow arm to attain 99% of the change in the mat thickness.

A paver with a10 foot tow arm will need to travel 50 feet

before the change in the mat thickness is achieved

Paver Screed Reaction Time

After the desired mat thickness is obtained, there should be no need to make adjustments throughout the day…

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Mix Temperature

Why check temperature?

Helps maintain consistent densities

Check temperature at the hopper

Use either Infra Red gun or dial type thermometers

Insure the Temperature is between 325°F and 250°F ±20°F (To reject trucks, use only dial types)

Should not exceed the maximum of 325°F unless PG Binder is polymer modified

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It is essential to have a continuous operation…

Continuous does not mean the paver never stops…

Quality HMA Pavement…

Continuous refers to the supply of HMA from the plant so that trucks are arriving one at a time instead of in groups.

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After the truck is emptied, the paver can continue placing the mat as long as there is sufficient material in the hopper, i.e. slat conveyors are not visible.

High Quality HMA Pavement…

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Common Problems

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Common Problems

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Safety

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Segregation and Mat Problems

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Pavement Defects

§402-3.07 Compaction

...Upon completion of the HMA placement, there shall be no visible defects in the pavement, such as shallow ruts,

ridges, roller marks, cracking, tearing, segregation,

bleeding, or any other irregularities. Any defects that

become apparent shall be corrected, or the defective

pavement replaced, to the satisfaction of the Engineer,

at no additional cost to the State.

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Quality HMA Pavement

A continuous supply of

HMA also minimizes

segregation of the mix.

Therefore, it is important

not to empty the hopper

If you can see the slat conveyors the hopper is empty…don’t let this happen

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Mat Quality

Bleeding (flushing)

Mix related

Too much asphalt

Too much fines

Construction related

Traffic put on too early

Spilling fuel, etc

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Mat Quality

Segregation

Improper loading at the plants

Broken or missing auger (sometime more than one)

Unnecessary emptying of paver hopper

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Missing Auger Extension• can cause segregation or

irregularities in the mat

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Mat Quality

Pavement tears

Generally associated with Tender Zone

Caused by rollers

Wait for Temperature to drop below the tender zone before finishing the rolling

Tear

GaugeReading

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Mat Quality Bumps

Due to excessive compaction effort

Mat moving

Poor paving practice

Check roller speed

Not to exceed 2 ½ mph

For Vibratory Rollers

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DO NOT WALK ONTOP COURSE!!!!!!!!!!!!!!

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Joint Failures

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Why Do Joints Fail?

Lack of densification

Bad joint construction practice

Lack of enough material at the joint

Lack of bond between hot and cold joints

Bad paving practice, e.g., not a straight line

All these leads to moisture penetration

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Specification Objective

To improve joint performance

Make contractor pay attention

Inspire innovation

Let contractors select the best way to construct joints i.e., Use best construction practice

Use mechanical tools

Cutting a joint with “pizza cutter”

Joint heaters

Use of joint makers

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Joint Core Location

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Joint Adhesive

Provides a sealer between joints

Application of joint adhesive Butt joint - entire vertical face

Wedge joint – entire 1 inch vertical face and 3-4 inches on the wedge.

First Pass

First Pass Second Pass

Second Pass

Joint adhesive

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Documentation

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BR 340 & 341

Filled daily

A copy will be submitted to Engineer at the end of each day

60 Series Compaction

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BR 340 & 341

filled daily

A copy will be submitted to Engineer at the end of the day

70 Series Method

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