Laboratory for the Certification of Asphalt Technicians C -2020.pdf•A factor that must be taken into account when considering asphalt mixture behavior is the volumetric proportions

Laboratory for the Certification of Asphalt Technicians

(LabCAT)

Level C - Volumetrics, Gyratory, Stability & Lottman

2020 Presentation Manual

In cooperation with the Colorado Asphalt Pavement Association,the Colorado Department of Transportation, and the

Federal Highway Administration

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Asphalt Mixtures (Based on the Asphalt Institute SP 2)

Asphalt is a paving material that consists of asphalt binder and mineral aggregate.

Binder

- glues aggregate particles into a dense mass

- waterproofs the mixture

• Mineral Aggregate

- acts as a stone framework to impart strength & toughness

Performance of the mixture both by the properties of the individual components and their combined reaction in the mixture.

Asphalt Binder Behavior (Based on the Asphalt Institute SP-2)

Three binder characteristics are important in performance of mixture:

- Temperature Susceptibility

- asphalt is stiffer at colder temperatures

- temperature must be specified or test results cannot be effectively interpreted

- Viscoelasticity

- it simultaneously displays both viscous and elastic characteristics.

- high temperatures – viscous like motor oil

- very low temperatures – elastic solid, rebounding to it’s original shape

- at intermediate temperatures found in most pavements, has both characteristics.

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Binder - Asphalt Mixtures (Based on the Asphalt Institute SP-2)

• The characteristics of asphalt cement (binder)

under varying temperatures, rates of loading, and

stages of aging determine its ability to perform as

a binder in the pavement mixture (SP 2).

• Hence, it is obvious the importance of performing

the volumetrics testing procedures within the

specified PG Binder temperatures and time

constraints to obtain accurate and comparable

results.

Binder - Aging

• - Aging

• - asphalt is chemically organic & reacts with oxygen from the environment – oxidation

• Oxidation changes the structure & composition of the asphalt molecules, causing it to become more brittle

• Oxidation occurs more rapidly at higher temperatures

• - Another term is “age hardening”, and occurs during asphalt mixture production and when asphalt cement is heated to facilitate mixing and compaction (Asphalt Institute SP-2)

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Coating Aggregate with PG graded Asphalt Binder

Glues the aggregate mass together.

Protects aggregate from absorbing moisture and stripping.

Mineral Aggregate Behavior(Asphalt Institute SP 2)

• Natural Aggregates

• Processed Aggregates

• Synthetic Aggregate

• Reclaimed Asphalt Pavement

• Aggregate must provide enough shear strength to

resist repeated load applications.

• Aggregate shear strength is critically important in

HMA because it provides the mixture’s primary

rutting resistance.

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• Shear strength is primarily dependent on the resistance to movement, or internal friction, provided by the aggregates.

• Cubical, rough-textured aggregates provide more resistance than rounded, smooth-textured aggregates.

• Cubical aggregate particles tend to lock together, resulting in a stronger mass of material, creating internal friction.


• Internal friction is accomplished by specifying a

certain percentage of aggregates with crushed

faces - Processed Aggregates.

• Processed Aggregates provide the interlocking

characteristics that result in internal friction.

• Any aggregate that has been processed through

a crusher and has at least two fractured faces

(CDOT).

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• Synthetic aggregate is any material that is not mined or quarried and is often an industrial by-product, such as blast furnace slag.

• Occasionally, a synthetic aggregate will be included to enhance a particular performance characteristic of an asphalt mixture.

• An example would be, a lightweight expanded clay or shale is occasionally used as a component to improve the skid resistance properties of asphalt mixtures.


• Reclaimed Asphalt Pavement – existing

pavement is removed and reprocessed to

produce new asphalt. RAP is an important

source of aggregate.

• Economical.

• Recycling of existing material is environmentally

friendly.

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Asphalt Mixture Behavior(Asphalt Institute SP 2)

• While the individual properties of asphalt mixture components are important, asphalt mixture behavior is best explained by considering asphalt cement (binder) and mineral aggregate acting together.

• There are three primary asphalt distress types that engineers try to avoid: permanent deformation, fatigue cracking and low temperature cracking.

• These are the distresses analyzed in Superpave.

Superpave Mixture Design(Asphalt Institute SP-2)

• Superpave Gyratory Compactor (SGC)

• Compacts specimens at specified temperatures (PG Binder) and specified design gyrations (based on expected traffic loads).

• Can provide information about the compactability of a mixture by capturing data during compaction.

• Used to design mixtures that do not exhibit tender mix behavior and mixes that do not densify to dangerously low air void contents under traffic action.

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Volumetrics?

• A factor that must be taken into account when considering asphalt mixture behavior is the volumetric proportions of asphalt binder and aggregate components, or more simply, asphalt mixture volumetrics.

• The volumetric properties of a compacted paving mixture provide some indication of the mixture’s probable pavement service performance

(Asphalt Institute SP 2)

Volumetric Properties of a compacted paving mixture are…

• Air Voids (Va)

• Voids in the Mineral Aggregate (VMA)

• Which includes the effective asphalt content (Pbe) and air voids (Va) of the compacted mixture.

• Voids filled with asphalt (VFA) (effective asphalt)

• Another important factor

• Binder Absorption


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Definition of Air Voids (Va)

• The total volume of the small pockets of air

between the coated aggregate particles

throughout a compacted paving mixture,

expressed as percent of the bulk volume of the

compacted paving mixture.


Definition of Voids in the Mineral Aggregate (VMA)

• Is the volume of inter-granular void space

between the aggregate particles of a compacted

paving mixture that includes the air voids and the

effective binder (asphalt) content, expressed as a

percent of the total volume of the sample.


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Definition of Effective Asphalt Content (Pbe)

• The effective binder (asphalt) content, Pbe, of a

paving mixture is the total (asphalt) binder content

minus the quantity of asphalt lost by absorption

into the aggregate particles. It is the portion of

the total (asphalt) binder that remains as a coating

on the outside of the aggregate particles, and is

the (asphalt) binder content that governs the

performance of an asphalt mixture.


Definition of Voids Filled with Asphalt (VFA)

• The percentage portion of the volume of inter-

granular void space between the aggregate

particles that is occupied by the effective binder

(asphalt). It is expressed as the ratio of (VMA-

Va) to VMA.


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Superpave Volumetrics

• The Superpave mix design procedures require the calculation of VMA values for compacted paving mixtures in terms of the aggregate’s bulk specific gravity, Gsb.

• The effective specific gravity, Gse, should be the basis for calculating the air voids in the compacted asphalt paving mixture.

• (Asphalt Institute SP 2)

CP 48 Determination of Voids in the Mineral Aggregate (VMA)

• 1.1 Voids in the mineral aggregate (VMA) are the void spaces between the aggregate particles of the compacted mix. This void space includes the air voids and effective asphalt content.

• Calculation:

VMA = 100-(Gmb * Ps/ Gsb)

(Notice that two values, the Gmb & Gsb are from physical tests that are run. The Gsb is run on the aggregate proposed to be used in the mix design. If aggregate changes significantly during production, this test would need to be run again for an accurate VMA to be calculated. VMA is a specification & therefore a pay factor.)

Gsb = Bulk SpG of aggregate

Gmb = Bulk SpG of compacted mix (CP 44)

Ps = Aggregate, percent by total weight of mix

Gsb = GP P P

P

G

P

G

P

G

n

n

n

=+ +

+ +

1 2

1

1

2

2

...

...

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VMA calculation continued

• Refer to 3.3 in CP 48 if the RAP content in mix is less

than 20%.The effective SpG of the aggregate contained in

the RAP should be used for the RAP fraction in the

calculation for total Gsb on previous slide.Effective SpG

(Gse) of aggregate excludes the voids filled with asphalt.

• A Gsb value of 2.38 shall be used for hydrated lime.

• Report each VMA to the nearest 0.01% and the average

of three to the nearest 0.1%.

• Refer to the Asphalt Institute MS-4 publication for more

detailed information.

Superpave Volumetrics

• Air voids, VMA and VFA are volume quantities, and therefore cannot be weighed, a paving mixture must first be designed or analyzed on a volume basis.

• For design purposes, this volume approach can easily be changed over to a mass basis to provide a job-mix formula (JMF).


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Balancing Binder and Aggregate

• Volumetric Analysis

• Air Voids

• Voids in Mineral Aggregate (VMA)

• Voids Filled with Asphalt (VFA)

• Binder Absorption

The Key = Specific Gravity

1 cc

Stone Specific Gravity = wt of stone/vol of stone = 2.650wt of water/vol of water

Stone2.65 grams

Water1.00 grams

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Adding Material Volumes

AirAir

Binder

Aggregate

Binder

Aggregate

Rocks Have Three Specific Gravities

Vsb

Vse

Vsa

VMA

Air

Effective Asphalt

Absorbed Asphalt

Absorbed Water

Aggregate

Which rock specific gravity is used for calculating VMA??

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Rock Specific Gravities

• Vsb – Volume of aggregate by Bulk SG, includes

permeable & impermeable voids.

• Vse – Volume of aggregate by Effective SG,

excluding VFA.

(Effective SG = volume of permeable material

excluding voids permeable to asphalt - VFA).

• Vsa – Volume of impermeable aggregate.

Rock Specific Gravities

• The specific gravities of the aggregates used in an asphalt mix have a substantial effect upon the calculated amount of air voids and the VMA in the compacted mixture.

• The actual specific gravity of the aggregates in the mixture depends upon the degree to which the aggregate absorbs asphalt.

• Air voids & VMA are volumetric measurements based on physical tests performed on the aggregates, such as specific gravity & absorption. Therefore, accurate calculations for air voids & VMA depend on knowing the aggregates are remaining reasonably consistent to the mix design values.

(Asphalt Institute Handbook MS 4)

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Taken from Asphalt Institute SP 2 Manual

0.45 Power Chart

• In the design of Superpave mix designs, the 0.45 Power Chart is used. CDOT defines the maximum density gradation line as a straight line passing from the origin to one sieve size larger than the nominal maximum aggregate size.

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Caution Zone• The “Caution Zone”. With increased crushed fines

in HMA mixtures, only caution needs to be taken when crossing this zone

• Generally recommended that the gradation not pass through this area when using natural fines

• Gradations that pass through this zone can result in tender mix behavior, which is manifested by compaction problems.

• Can cause reduced resistance to permanent deformation (rutting)

• Can cause inadequate VMA to allow room for sufficient asphalt for durability.

• Can cause sensitive to asphalt content & can then easily become plastic with even minor variations in the asphalt content.

• Many gradations passing through the caution zone perform satisfactorily.

Designing the Aggregate Structure

• Filling Gaps with

Smaller and Smaller

Aggregate =

Dense Grading.

• Leaving Gaps in the Aggregate

Structure =

Gap Grading

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Graphing the Sieves

200 30 4 3/8 1/2 3/4

Sieve Size % Passing 3/4 in 100 1/2 in. 93 3/8 in. 70 No. 4 45 No. 30 20 N0. 200 6

% Passing

0

100

50

Dense Graded

Gap Graded

Sieve Size

Sieve Size % Passing

¾ in. 100

½ in. 90

3/8 in. 20

No. 4 18

No. 30 15

No. 200 6

Too Dense=No Room for AC=Low VMA

100

50

0No. 200 No. 8 1 in. 75m 2.36 mm 25 mm

1.5"

1"3/4"

Aggregates graded on the0.45 Power linesshould have thelowest VMA

Sieves0.45

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VMA and VFA

• Minimum VMA (desirable) can be a difficult

mix design property to achieve.

• The goal is to furnish enough space for the

binder to provide adequate adhesion to bind

the aggregate particles, but without bleeding

when the temperatures rise and the binder

expands.

• Main effect of VFA criteria is to limit

maximum levels of VMA, and subsequently,

maximum levels of binder content.

The Superpave System

100

50

0

No. 200 No. 8 1 in. 75m 2.36 mm 25 mm

Sieves0.45

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Weight VolumeGmb = 2.329

AggregateGsb = 2.705

(Bulk)Gse = 2.731

(Effective)

BinderGb = 1.015

Pb = 5% by Mix

Absorbed Binder

Absorbed Water

Air

W mb

=2.329

(from Lab)

Vmb = 1

Va = Vmb- (Vb +Vse)1 – (.114+.810) = .076

Vb = Wb/Gb.116/1.015 = .114

Vba = Vsb -Vse

.818 - .810 = .008

Vbe = Vb – Vba.114 - .008 = .106

VMA = Vbe + Va.106 + .076 = .182

Vsb = Wmb / Gsb2.213 / 2.705 = .818

Vse =Ws/Gse2.213/2.731=.810

Wb

2.329 X .05= .116

Vmm

Vb + Vse

.114 + .810 = .924

Components of Weight and Volume

Ws =

Wmb X (100 - % Binder)2.329 X .95 = 2.213

Questions ??????

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GYRATORY COMPACTION BY THE

SUPERPAVE METHOD

CP L 5115

OVERVIEW OF CP 5115

• This standard covers the compaction of 100 mm diameter and 150 mm diameter test specimens of an asphalt mixture, using a Superpave gyratory compactor. It also covers the monitoring of specimen density during compaction.

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SUPERPAVE DESIGN GYRATORYCOMPACTIVE EFFORT

Design ESAL’s Compaction Parameters

N init N des N max

0.3 6 50 75

0.3 to 3 7 75 115

3 to 30 8 100 160

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GYRATORY

A SHRP approved electromechanical Superpavecompactor that restrains the molds from revolving during compaction, applies & maintains the specified pressure, tilts specimen mold at specified angle and gyrates specimen mold to compact specimen to desired number of gyrations.

Pine AFG1 & AFG2 SUPERPAVE Gyratory.

Troxler 4140 & 4141 SUPERPAVE Gyratory.

• As per 3.1, this standard is used to prepare specimens for determining the mechanical properties of asphalt.

• Specimens simulate the density, aggregate orientation, and structural characteristics obtained in the actual roadway when proper construction procedures are used in the placement of the paving mix, including monitoring temperatures.

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PINE AFG2 GYRATORY

Pine 100mm Mold

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Compactor

Control Panel

Extractor

Troxler 150 mm

Mold

Troxler 100 mm Mold

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SPECIMEN MOLDINGram pressure600 kPa (+/-18)

150 mm mold

30 gyrationsper minute(+/-.5)

1.25 (+/-.02) deg

100 mm mold (Colorado)

(CDOT)External

Angle

SPECIMEN MOLDING

FMM now requires that an angle of 1.16 +/- 0.02 degrees for 150mm molds be applied and measured internally to the

mold assembly.

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PREPARATION OF APPARATUS

• Verify (Per the manufacturer)

• Angle (Normally 6 months or 480 hrs)

• Rotation (Not specified)

• Load (Normally 6 months or 480 hrs)

• Height (Daily)

• Lubrication

• Height Measurement (LVDT)

HOW THE MIX COMPACTS

89 %, max

95.5%

96.5%

Ninit Ndes Nmax

98%, max

Log Gyrations

%MaxTheorSp Gr

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EFFECT OF ASPHALT ON COMPACTION

89 %, max

95.5%

96.5%

Ninit Ndes Nmax

98%, max

Log Gyrations

%MaxTheorSp Gr

4.0 %

5.0 %

6.0 %

MIXTURE PREPARATION

• Lab produced mix

• CDOT-Mix and condition per CP-L 5115

• Proper weight of mixture (CDOT, 100 mm Molds)

Number of Gyrations Multiplier

50 470 X Gmm

75 474 X Gmm

100 478 X Gmm

125 482 X Gmm

SMA 470 X Gmm

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MIXTURE PREPARATION (CONTINUED

• 150 mm molds – 1670 X Gmm.

• To make weight adjustments for Lottman see CP-L 5109.

• To make height adjustments for Lottman see CP-L 5109 & CP-L 5115.

• Specimen heights should be 63.5mm +/- 5mm for 100mm diameter specimens and 100+/- 5mm for 150mm diameter specimens.

MIXTURE PREPARATION

• Heat to compaction temperature

• Based on binder type & viscosity

-Table 2 from CP-L 5115

SuperPave Binder grade Lab Mixing Temperature

Lab Compaction Temperature

PG 58-28 310° F (154° C) 280° F (138° C)

PG 58-34 310° F (154° C) 280° F (138° C)

PG 64-22 325° F (163° C) 300° F (149° C)

PG 64-28* 325° F (163° C) 300° F (149° C)

PG 70-28 325 F (163 C) 300 F (149 C)

PG 76-28 325° F (163° C) 300° F (149° C)

>/= 15 min &

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MIXTURE PREPARATION

• Mold and base heated minimum 60 min and 15 min after each use.

• A minimum of three volumetric specimen’s per field sample shall be compacted. Mixture sample should be at compaction temperature for at least 15 minutes before compaction takes place.

COMPACTION PROCEDURE FOR TROXLER AND PINE

• Remove mold from oven.

• (Place on non metallic surface).

• Place paper disk in bottom.

• Place funnel on mold.

• Remove material from oven.

• Mix, no segregation.

• Place in mold in one lift.

• Level mix.

• Place paper disk on top.

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• Place mold into compactor.

• Start the gyration process within a maximum of 60 seconds from the time the asphalt mixture was removed from the oven.

• After the required gyrations, remove the mold from compactor.

• Extract the “puck” from the mold, removing the top and bottom papers.

• Allow specimen to cool.

COMPACTION PROCEDURE THE TROXLER COMPACTOR

Compaction Procedure for the Pine Gyratory

• Properly seat mold into compaction chamber.

• Lock down mold with handles.

• Place the top into gyratory and turn to lock in to place.

• Press start key.

• After specified number of gyrations have been applied, remove the gyratory top.

• Push the Ram Up key to extrude the specimen with the built-in extruder.

• Carefully slide the specimen off the mold base onto cooling surface.

• Push Ram Down key to properly PARK the machine in Home position before opening the door.

• Remove mold and place base back into mold.

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Questions??????

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Standard Method of Test forResistance to Deformation of Asphalt

Mixtures by Means of Hveem Apparatus

CDOT CP -L 5106AASHTO T 246

Purpose:

• For the determination of the resistance to deformation of compacted Asphalt mixtures by measuring the lateral pressure developed from applying a vertical load by means of the Hveem Stabilometer

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Summary

• The Hveem stabilometer is a triaxial testing device which registers the horizontal pressure developed by a compacted test specimen as a vertical load is applied.

• Test specimens shall be 100 mm in diameter.

• Test specimens shall have a height of 63.5 ± 5 mm as per CP L 5115.

• Test specimens shall be compacted with a Superpave Gyratory Compactor .

Apparatus

• Hveem Stabilometer.• Adjustable base.• Solid wall metal follower (100.30 ± 0.25mm).• Calibration cylinder (100.00 ± 0.13mm).• Oven Capable of maintaining 60° ± 3° C

(140+/- 5’F).

• Compression machine minimum capacity of 10,000 lbf.

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Procedure

• Stabilometer adjustment (calibration). • Test procedure.

Stabilometer Calibration

• Heat follower, base and calibration cylinder:• 140 ± 5°F (60 ± 3° C)• 1 hour minimum

• Place stabilometer on base.

• Measure distance, 89 mm (3.5 in) base to bottom of upper tapered ring.

• Insert follower, turn pressure gauge to ~20 psi.

• Allow oil temperature to stabilize.

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Stabilometer Calibration (continued)

• Remove the follower,

• Immediately insert the calibration cylinder.

• Set pressure gauge to ~100psi.

• Watch the gauge and allow oil temperature to stabilize.

Stabilometer Calibration (continued)

• As soon as the oil pressure stabilizes:• Set horizontal pressure to 100 (lower just below 100

& back up to 100).

• Quickly set turns indicator to 3 or 4 (can use 0).• Turn the handle slowly to decrease pressure gauge

from 100 in exactly 2 turns while observing the displacement gauge.

• Observe the pressure on the psi gauge.• If not at 5 ± 0.5 psi, adjust air, appendix of CP-L

5106 gives suggestions on how to adjust the air.

• Repeat procedure until you can increase the horizontal pressure from 5 psi to 100 psi by turning the pump handle at the approximate rate of two (2) turns per second.

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Stabilometer Calibration

Once a week or so check that air bubbles are not present in the bladder. Once again, there are different methods for accomplishing this.

Approximately once per month, once the stabilometer is calibrated, with the calibration cylinder still inserted & the gauge pressure set at 5 PSI, verify that the exposed piston length is 2.8 +/- 0.2 “.

Add or remove oil as necessary

Performing the Test

• Test specimens shall be heated in a 140 ± 5F (60 ±3C) oven.

• 2 to 24 hours for forced draft air ovens.• 3 to 24 hours for non-forced draft air ovens.

• Place talcum powder on the curved portion of the specimen or on the rubber membrane.

• Pre-heated specimen placed into stabilometer.• Place the heated follower onto specimen.

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Test Continued

• Turn pump clock wise until the horizontal pressure is ~ 5 psi.

• Place stabilometer onto testing machine.

• Verify the set horizontal pressure (Ph) is at exactly 5 psi, but not over 5psi. (If over 5psi, go below 5 and then back to 5psi).

• Start vertical movement of press at 0.05 in./min. (1.3 mm/min.)

• Record gauge readings (pH) at 5000.• Immediately reduce load to 1000 lbf.

Test (continued)

• Adjust the horizontal pressure to 5psi by lowering pressure below 5 (but not lower than 1) and then back up to exactly 5psi.

• Set turns indicator to 2 or 3 (Zero).• Turn handle at a rate of two (2) turns

per second to increase the pressure from 5 to 100 psi.

• Record the number of turns (D) required to reach 100 psi.

• Calculate the stability.

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Stability Calculations

SPh D

Pv Ph

=

−+

22 2

0 222

.

*.

This chart can be found in the CP-L 5106 procedure

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Video of Stabilometer/CDOT Air Adjustment Procedure

Questions???

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Standard Method of Test for

Resistance of Compacted Asphalt Mixture to Moisture

Induced Damage

CDOT CP-L 5109

Summary

• Evaluate the effects of saturation and accelerated water conditioning of compacted Asphalt mixtures in the laboratory

• Mixture design

• Plant produced material

• This procedure measures the resistance of asphalt mixtures to the detrimental effects of water.

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Apparatus• Compactor

• Vacuum container

• Bulk Sp G Equipment – CP 44 (T 166)

• Freezer

• Plastic Film and Bags

• Mix Design purposes - Aluminum Pans (CDOT 40-100 sq. in.)

• Forced Draft Ovens

• Testing Machine Rate (0.2 in/min)

• Steel Loading Strips (0.5” wide)

Mixture Design Specimen Prep• Mix heated aggregate and binder together

• Place in steel or aluminum pan, 40-100 sq in & approx. 1 -3” deep.

• Cool at room temp for 2 ± 0.5 h

• Cured in oven @ 140 ± 5F (60 ± 1C) for 16 - 24 hrs air must circulate under pans

• Placed in oven set at compaction temperature for the binder for 2.5 +/- 0.5 hrs. (new)

• This short term aging procedure is used for laboratory mixed samples only

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Specimen Molding

• Heat at compaction temperature according to CP-L5115 (Prep. of samples by SGC)

• Compact specimens to 7 ± 1.0% air voids

• Do not begin testing until specimens have cooled to room temperature (after compaction).

Specimen Molding

Height or Weight Adjustments

• Height

• Using the same sample mass as the volumetric specimens adjust the height per the formula in CP-L 5109, Section 6.3.1 to acquire more air voids.

• (Ave. Bulk SpG @ N(des) x Ave. Ht. @ N(des)

• (0.925 x Rice)

• Weight

• Using the formula in CP-L 5109, 6.4, adjust the weight of the material used and compact to the same height as the volumetric specimens to acquire more air voids

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Evaluation and Grouping

• Determine Max. SG of mixture (Gmm)

• Determine specimen heights CP-L 5115 & average of three

• Determine Bulk SG CP 44 of compacted specimens & average of three (Gmb)

• Determine air voids of each specimen (Va)

• Va=100 x (1-(Gmb/Gmm))

Grouping• Determine Dry Subset and Wet Subset (3 Specimens

each group)

• The two subsets should be grouped so that the average air voids between the two subsets are approximately equal.

• Use developed programs or

• Dry set - use highest & lowest air voids plus one mid range air void specimen

• Wet set – mid range

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Preconditioning - Dry Subset

• Store in incubator (77+/- 1F) or at room temp until testing then bring to 77’ F.

• A 25 ± .5 C (77 ± 1F) water bath, may be used providing a method for keeping the specimens DRY is used.

• Another method is placing the specimen in a 77 degree oven until testing.

• Specimens must be at 77 +/- 1F for 3.5 +/- 0.5 hrs until testing

• Determine indirect tensile strength (PEAK or Max Load) of each specimen at 77 degrees +/- 1 degree at a constant rate of 0.2 inches per minute

Conditioning – Wet Subset CDOT

• Place specimen in vacuum container in such a way that water flows under specimen and is covered with at least 1” of water. (can set specimen on side with 1” water covering).

• Vacuum at 28 ± 2mm Hg for 5 ± 0.25 min (begin time when applied vacuum reaches the specified level)

• let the sample remain in the water for a short time after the vacuum is released (greater than 5 seconds)

• Remove specimen and place in bulk tank to determine the weight in water (saturated state) and then the SSD weight (saturated state) (saturate weights are used for calculations for the % swell & the level of saturation)

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Conditioning - Wet Subset CDOT

• Submerge for 1 sec. back in bulk tank

• Wrap in plastic wrap

• Place in plastic bag and seal

• Place in freezer @ -2.5F +/- 7.5 F for minimum for 16 hrs.

Conditioning - Wet Subset

• Place into 140 ± ± 1.0 bath for 24 ± 1h. Remove the bag/plastic film ASAP after the sample has been place into the 140° water bath

• Place into 77 ± 1F (25.0 ± 0.5C) for 3.5 +/- 0.5 hrs.

• 15 minutes to get water back to 25 ± 0.5 C

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Testing

• At time of testing remove each specimen from 77 degree water bath and…

• Place specimen between two ½” steel loading strips in frame, so that load is applied along the diameter of specimen.

• Apply constant loading rate of 0.2 in./min

• Record maximum compressive strength

• Calculate tensile strength (PEAK or MAX Load)

Saturation Calculation

Bsat = ssd mass after saturation

A = dry massB = ssd mass before saturationC = immersed mass before saturation

Gmm = maximum specific gravity%S = percent saturation

%SB A

(B C)[A

G (B C)]

Xsat

mm

=−

− −−

1

100

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Calculate Tensile Strength (St) and Tensile Strength Ratio (TSR)

St1 = average tensile strength (dry)St2 = average tensile strength (wet)

TSR = Tensile Strength Retained 3.1416t = thickness 2.5 “

D = diameter 3.937 in. (100mm)D = diameter 5.906 in. (150mm)

Video of Lottman Procedure

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Questions????

THE END

THANK YOU

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Level C

Standard Practice for Mixture Conditioning of Hot Mix Asphalt (HMA)AASHTO Designation: R 30-02 (2015)1

SCOPE

This standard practice describes procedures for mixture conditioning of compacted and uncompactedhot mix asphalt (HMA). Three types of conditioning are described: (1) mixture conditioning forvolumetric mixture design; (2) short-term conditioning for mixture mechanical property testing (both ofwhich simulate the precompaction phase of the construction process); and (3) long-term conditioningfor mixture mechanical property testing to simulate the aging that occurs over the service life of apavement. The procedures for long-term conditioning for mixture mechanical property testing arepreceded by the procedure for short-term conditioning for mixture mechanical property testing.

This standard practice may involve hazardous materials, operations, and equipment. This standard doesnot purport to address all of the safety problems associated with its use. It is the responsibility of theuser of this standard to establish appropriate safety and health practices and determine the applicabilityof regulatory limitations prior to use.

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1.1.

1.2.

REFERENCED DOCUMENTS

AASHTO Standards:

PP 3, Preparing Hot Mix Asphalt (HMA) Specimens by Means of the Rolling Wheel Compactor2T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of theSuperpave Gyratory CompactorT 316, Viscosity Determination of Asphalt Binder Using Rotational Viscometer

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2.1.

SUMMARY OF PRACTICE

For mixture conditioning for volumetric mixture design, a mixture of aggregate and binder isconditioned in a forced-draft oven for 2 h at the mixture’s specified compaction temperature. For short-term mixture conditioning for mechanical property testing, a mixture of aggregate and binder isconditioned in a forced-draft oven for 4 h at 135°C. For long-term mixture conditioning for mechanicalproperty testing, a compacted mixture of aggregate and binder is conditioned in a forced-draft oven for5 days at 85°C.

3.

SIGNIFICANCE AND USE

The properties and performance of HMA can be more accurately predicted by using conditioned testsamples. The mixture conditioning for the volumetric mixture design procedure is designed to allow forbinder absorption during the mixture design. The short-term mixture conditioning for the mechanicalproperty testing procedure is designed to simulate the plant-mixing and construction effects on themixture. The long-term mixture conditioning for the mechanical property testing procedure is designedto simulate the aging the compacted mixture will undergo during 7 to 10 years of service.

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APPARATUS

Oven—A forced-draft oven, thermostatically controlled, capable of maintaining any desired temperaturesetting from room temperature to 176°C within ±3°C.

Thermometers—Thermometers having a range from 50 to 260°C and readable to 1°C.

Miscellaneous—A metal pan for heating aggregates, a shallow metal pan for heating uncompactedHMA, a metal spatula or spoon, timer, and gloves for handling hot equipment.

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5.1.

5.2.

5.3.

HAZARDS

This standard involves the handling of hot binder, aggregate, and HMA, which can cause severe burns ifallowed to contact skin. Follow standard safety precautions to avoid burns.

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6.1.

MIXTURE CONDITIONING PROCEDURES

Mixture Conditioning for Volumetric Mixture Design:

The mixture conditioning for the volumetric mixture design procedure applies to laboratory- prepared,loose mixture only. No mixture conditioning is required when conducting quality control or qualityassurance testing on plant-produced mixture.

Note 1—The agency may identify the need to condition plant-produced mixture to be morerepresentative of field conditions, particularly where absorptive aggregates are used.

Place the mixture in a pan, and spread it to an even thickness ranging between 25 and 50 mm. Placethe mixture and pan in a forced-draft oven for 2 h ± 5 min at a temperature equal to the mixture’scompaction temperature ±3°C. The compaction temperature range of a HMA mixture is defined as therange of temperatures where the unaged binder has a kinematic viscosity of 280 ± 30 mm2/s(approximately 0.28 ± 0.03 Pa·s) measured in accordance with T 316 (Note 2). The target compactiontemperature is generally the midpoint of this range.

Note 2—Modified binders may not adhere to the equiviscosity requirements noted. The agency shouldconsider the manufacturer’s recommendations when establishing the mixing and compactiontemperatures for modified binders. Practically, the mixing temperature should not exceed 165°C andthe compaction temperature should not be lower than 115°C.

Stir the mixture after 60 ± 5 min to maintain uniform conditioning.

After 2 h ± 5 min, remove the mixture from the forced-draft oven. The conditioned mixture is nowready for compaction or testing.

Short-Term Conditioning for Mixture Mechanical Property Testing:

The short-term conditioning for the mixture mechanical property testing procedure applies tolaboratory-prepared, loose mix only.

Place the mixture in a pan, and spread it to an even thickness ranging between 25 and 50 mm. Placethe mixture and pan in the conditioning oven for 4 h ± 5 min at a temperature of 135 ± 3°C.

Stir the mixture every 60 ± 5 min to maintain uniform conditioning.

After 4 h ± 5 min, remove the mixture from the forced-draft oven. The conditioned mixture is nowready for further conditioning or testing as required.

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7.1.

7.1.1.

7.1.2.

7.1.3.

7.1.4.

7.2.

7.2.1.

7.2.2.

7.2.3.

7.2.4.


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Long-Term Conditioning for Mixture Mechanical Property Testing:

The long-term conditioning for the mixture mechanical property testing procedure applies to laboratory-prepared mixtures that have been subjected to the short-term conditioning for the mixture mechanicalproperty testing procedure described in Section 7.2, plant-mixed HMA, and compacted roadwayspecimens.

Preparing Specimens from Loose HMA:

Specimens Compacted Using the Superpave Gyratory Compactor:

Compact the specimens in accordance with T 312. Cool the test specimen at room temperature for 16± 1 h.

Note 3—Extrude the specimen from the compaction mold after cooling for 2 to 3 h.

Note 4—Specimen cooling is usually scheduled as an overnight step. Cooling may be accelerated byplacing the specimen in front of a fan.

Specimens Compacted Using the Rolling Wheel Compactor:

Compact the specimens in accordance with PP 3.

Cool the test specimen at room temperature for 16 ± 1 h.

Remove the slab from the mold, and saw or core the required specimens from the slab.

Preparing Compacted Roadway Specimens:

Cool test specimens at room temperature for 16 ± 1 h.

Long-Term Conditioning of Prepared Test Specimens—Place the compacted test specimens in theconditioning oven for 120 ± 0.5 h at a temperature of 85 ± 3°C.

After 120 ± 0.5 h, turn the oven off; open the doors, and allow the test specimen to cool to roomtemperature. Do not touch or remove the specimen until it has cooled to room temperature.

Note 5—Cooling to room temperature will take approximately 16 h.

After cooling to room temperature, remove the test specimen from the oven. The long-term-conditionedspecimen is now ready for testing as required.

REPORT

Report the binder grade, binder content (nearest 0.1 percent), and the aggregate type and gradation, ifapplicable.

Report the following mixture conditioning information for the volumetric mixture design conditions, ifapplicable:

Mixture conditioning temperature in laboratory (compaction temperature, nearest 1°C);

Mixture conditioning duration in laboratory (nearest minute); and

Laboratory compaction temperature (nearest 1°C).

Report the following short-term conditioning information for the mixture mechanical property testingconditions, if applicable:

Short-term mixture conditioning temperature in laboratory (nearest 1°C);

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8.1.

8.2.

8.2.1.

8.2.2.

8.2.3.

8.3.

8.3.1.


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1 This standard is based on SHRP Product 1031.

2 PP 3-94 was last printed in the May 2002 edition of the AASHTO Provisional Standards.

Short-term mixture conditioning duration in laboratory (nearest minute); and

Laboratory compaction temperature (nearest 1°C).

Report the following long-term conditioning information for the mixture mechanical property testingconditions, if applicable:

Laboratory compaction temperature (nearest 1°C);

Long-term mixture conditioning temperature in laboratory (nearest 1°C); and

Long-term mixture conditioning duration in laboratory (nearest 5 min).

KEYWORDS

Conditioning; hot mix asphalt; long-term conditioning; short-term conditioning.

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9.1.


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Standard Method of Test for Resistance to Deformation and Cohesionof Hot Mix Asphalt (HMA) by Means of Hveem Apparatus

AASHTO Designation: T 246-10 (2015)1,2

ASTM Designation: D1560-09

SCOPE

These methods cover the determination of (1) the resistance to deformation of compacted HMAmixtures by measuring the lateral pressure developed from applying a vertical load by means of theHveem stabilometer; and (2) the cohesion of compacted bituminous mixtures by measuring the forcesrequired to break or bend the sample as a cantilever beam by means of the Hveem cohesiometer.3

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1.1.


AASHTO Standards:

T 247, Preparation of Test Specimens of Hot Mix Asphalt (HMA) by Means of California KneadingCompactorT 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of theSuperpave Gyratory Compactor

2.

2.1.

RESISTANCE TO DEFORMATION

APPARATUS

Stabilometer—The Hveem stabilometer (Figures 1 and 2) is a triaxial testing device consistingessentially of a rubber sleeve within a metal cylinder containing a liquid that registers the horizontalpressure developed by a compacted test specimen as a vertical load is applied.

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3.1.

Standard Method of Test for Resistance to Deformation and Cohesion of... http://hm.digital.transportation.org/HM/Part_II_Tests/Bituminous_Materi...

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Figure 1—Hveem Stabilometer


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Figure 2—Diagrammatic Sketch of the Hveem Stabilometer (not to scale)

Testing Machine—A compression testing machine having a minimum capacity of 44.5 kN (10,000 lbf).Figure 3 shows the assembly of the stabilometer in a testing machine. The 222-kN (50,000-lbf) capacitycompression testing machine specified in T 247 is normally used to perform the stabilometer test.


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Figure 3—Hveem Stabilometer Mounted in the Testing Machine

Test Specimen Push-Out Device—A lever device, attached to the press, to push the specimen out of themold (see Figure 4). Other acceptable apparatus may be used.

Figure 4—Detailed Drawings of the Test Specimen Push-Out Device

Oven—An oven capable of maintaining a temperature of 60 ± 3°C (140 ± 5°F).

Calibration Cylinder—A hollow metal cylinder, 101.6 ± 0.13 mm (4 ± 0.005 in.) in outside diameter by140 ± 25 mm (51/2 ± 1 in.) high (for calibration purposes).

Rubber Bulb—For introducing air into the stabilometer.

Follower—One solid wall metal follower, 101.2 mm (3.985 in.) in diameter by 140 mm (51/2 in.) high(see Figures 5 and 6).


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Figure 5—Specimen Follower


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Figure 6—Detail Drawing of the Specimen Follower

TEST SPECIMENS

Size of Specimens—Test specimens shall be 102 mm (4 in.) in diameter. The height of the testspecimens should be 64 ± 3 mm (2.5 ± 0.1 in.). However, if this height cannot be obtained, thestabilometer value shall be corrected as indicated by Figure 7.

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4.1.


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Figure 7—Chart for Correcting Stabilometer Values to Specimen Height of 2.5 in. (64 mm)

Compaction of Specimens—Test specimens shall be formed and compacted in accordance with T 247;or compacted into a 4-in. diameter mold using a Superpave gyratory compactor, a gyratory shearcompactor, or other type of compactor.

Note 1—Specimens compacted by different means may not have similar stabilometer or cohesiometervalues.

ADJUSTMENT OF STABILOMETER

Adjust the stabilometer base so that the distance from the bottom of the upper tapered ring (Figure 1)to the top of the base is 89 mm (3.5 in.).

Adjust the amount of air in the air cell so that when the liquid pressure is increased from 34.5 to 689kPa (5 to 100 psi) by turning the pump handle at the approximate rate of two turns per second, theturns indicator will indicate 2.00 ± 0.05 turns with the metal calibration cylinder in the stabilometerchamber.

With the stabilometer and stage base in position on the platen, adjust the testing machine so that theload will be applied at the rate of 1.3 mm (0.05 in.)/min.

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5.1.

5.2.

5.3.

PROCEDURE

Bring the specimen to a temperature of 60 ± 3°C (140 ± 5°F).

Note 2—Bring the specimen to room temperature in the case where it is desired to test with whatevermoisture may be present in the mixture.

Transfer the compacted specimen from the mold to the stabilometer by means of the push-out devicedescribed in Section 2.3. Make sure that the specimen goes into the stabilometer straight, with thetamped end up, and that it is firmly seated level on the base. Place the 140-mm (51/2-in.) follower ontop of the specimen and turn the displacement pump until a horizontal pressure of exactly 34.5 kPa (5psi) is recorded on the stabilometer gauge. If the testing machine has a spherically seated type ofupper head, the locking shims used during the fabrication of the test specimen must be removed priorto performing the stabilometer test. Start the vertical movement of the press (speed of 1.3 mm (0.05in.)/min) and record the stabilometer gauge readings when the vertical load is 2.23, 4.45, 8.90, 13.4,17.8, 22.3, and 26.7 kN (500, 1000, 2000, 3000, 4000, 5000, and 6000 lbf). Stop the verticalmovement of the press when the total load reaches 26.7 kN (6000 lbf). Immediately reduce the verticalload to 4.45 kN (1000 lbf) and then adjust the horizontal pressure to 34.5 kPa (5 psi). This will result ina further reduction of the vertical load in less than 4.45 kN (1000 lbf). This is normal and nocompensation need be made. Measure the number of turns of the pump handle required to raise thehorizontal pressure from 34.5 to 689 kPa (5 to 100 psi) with the specimen in place. Turn the pumphandle at approximately two turns per second when applying this pressure. The number of turnsmeasured is the displacement reading, D. In measuring the displacement, the vertical load will increaseand at times exceed 4.45 kN (1000 lbf). As before, these changes in load are characteristic and noadjustment or compensation is required.

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6.1.

6.2.

CALCULATIONS

Determine the stabilometer value of the specimen as follows:

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7.1.


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(1)

where:

S = stabilometer value;

Ph = horizontal pressure, for corresponding Pv in kPa (or psi);

D = displacement on specimen; and

Pv = vertical pressure (typically 2800 kPa (400 psi)).

REPORT

The report shall include the following:

Stabilometer value,

Test temperature, and

Bitumen content.

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8.1.

8.1.1.

8.1.2.

8.1.3.

COHESIONNote 3—Cohesion testing is optional and is not required to determine Hveem Stability.

APPARATUS

Cohesiometer—A Hveem cohesiometer, as shown in Figures 8 and 9.4

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9.1.


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Figure 8—Hveem Cohesiometer


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Figure 9—Detailed Drawing of the Hveem Cohesiometer

Steel Shot—2000 g of steel shot, size No. 10, all passing a 2-mm (No. 10) sieve and retained on a 1.4-mm (No. 14) sieve.

Oven—An oven capable of maintaining a temperature of 60 ± 1°C (140 ± 2°F).4

Balance—A balance having a capacity of 5 kg and sensitive to 1 g or less.

Note 4—Other materials may be used, provided a rate of loading is achieved which is equivalent tothat obtained when using steel shot.

TEST SPECIMENS

Preparation of Specimen—The test specimen will normally be the compacted specimen used aftercompletion of the stabilometer test. If the sample is taken from a compressed pavement slab by meansother than coring, it should be cut to size with a suitable saw.

Size of Specimens—The cohesiometer is designed to test specimens up to 127 mm (5 in.) in width andfrom 25 mm (1 in.) to 76 mm (3 in.) high.

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10.1.

10.2.

PROCEDURE

Place the specimen to be tested in the oven and allow to stand until the temperature is 60 ± 1°C (140± 2°F) throughout (this normally will require a minimum of 2 h).

Preheat the cohesiometer to 60 ± 1°C (140 ± 2°F). Clamp the test specimen firmly in thecohesiometer, being certain that it is well centered with the top plates parallel with the surface of thespecimen. Tighten the clamp nuts until snug using the fingers only. Delay starting the test until thetemperature within the cohesiometer cabinet returns to 60 ± 1°C (140 ± 2°F). Allow the shot to flowinto the receiver at the end of the lever arm at a rate of flow of 1800 ± 20 g/min. Stop the flow of shotwhen the specimen breaks or when the lever arm deflects 13 mm (1/2 in.) from the horizontal, if thatoccurs before the specimen breaks. Determine and record the mass of shot to the nearest gram.

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11.1.

11.2.

CALCULATIONS

Calculate the cohesiometer values as follows:

U.S. Customary Units:

(2)

Metric Units:

(3)

where:

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12.1.


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1 Except for the allowable tolerances of the calibration cylinder in Section 3.5, this method is the same as ASTMD1560-09.

2 Minor editorial revisions have been made at the discretion of the authors responsible for standards on proportioningof asphalt-aggregate mixtures (technical section 2d).

3 A more detailed description of the procedures for performing the tests is available on request from the CaliforniaDivision of Highways, Transportation Laboratory, 5900 Folsom Blvd., Sacramento, CA 95819. Also available is aprocedure containing details regarding the operation and calibration of the stabilometer and the replacement of thestabilometer diaphragm.

4 Detailed working drawings of the apparatus illustrated in Figure 9 are available at nominal cost from the AmericanSociety for Testing and Materials, 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959. Request Adjunct No.12-415600-10.

C = cohesiometer value, g/25 mm (1 in.) of width corrected to 76-mm (3-in.) height;

L = weight of shot, g;

W = diameter, or width of specimen, cm (or in.); and

H = height of specimen, cm (or in.).

REPORT

The report shall include the following:

Cohesiometer value,

Test temperature, and

Bitumen content.

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13.1.

13.1.1.

13.1.2.

13.1.3.

KEYWORDS

Bituminous mixtures; cantilever beam; Hveem stabilometer; lateral pressure.

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14.1.


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Standard Method of Test for Resistance of Compacted AsphaltMixtures to Moisture-Induced Damage

AASHTO Designation: T 283-141

SCOPE

This method covers preparation of specimens and the measurement of the change of diametral tensilestrength resulting from the effects of water saturation and accelerated water conditioning, with afreeze–thaw cycle, of compacted asphalt mixtures. The results may be used to predict long-termstripping susceptibility of the asphalt mixture and evaluate liquid antistripping additives that are addedto the asphalt binder or pulverulent solids, such as hydrated lime or portland cement, which are addedto the mineral aggregate.

The values stated in SI units are to be regarded as the standard.

This standard may involve hazardous materials, operations, and equipment. This standard does notpurport to address all of the safety concerns, if any, associated with its use. It is the responsibility ofthe user of this standard to establish appropriate safety and health practices and determine theapplicability of regulatory limitations prior to use.

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1.1.

1.2.

1.3.


AASHTO Standards:

R 47, Reducing Samples of Hot Mix Asphalt (HMA) to Testing SizeT 166, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-DrySpecimensT 167, Compressive Strength of Hot Mix AsphaltT 168, Sampling Bituminous Paving MixturesT 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Hot Mix Asphalt (HMA)T 245, Resistance to Plastic Flow of Asphalt Mixtures Using Marshall ApparatusT 247, Preparation of Test Specimens of Hot Mix Asphalt (HMA) by Means of California KneadingCompactorT 269, Percent Air Voids in Compacted Dense and Open Asphalt MixturesT 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of theSuperpave Gyratory Compactor

ASTM Standards:

D979/D979M, Standard Practice for Sampling Bituminous Paving MixturesD3387, Standard Test Method for Compaction and Shear Properties of Bituminous Mixtures by Meansof the U.S. Corps of Engineers Gyratory Testing Machine (GTM)D3549/D3549M, Standard Test Method for Thickness or Height of Compacted Bituminous PavingMixture Specimens

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2.1.

2.2.


As noted in the scope, this method is intended to evaluate the effects of saturation and accelerated

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3.1.

Standard Method of Test for Resistance of Compacted Asphalt Mixtures ... http://hm.digital.transportation.org/HM/Part_II_Tests/Bituminous_Materi...

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water conditioning, with a freeze–thaw cycle, of compacted asphalt mixtures. This method can be usedto test: (a) asphalt mixtures in conjunction with mixture design testing (lab-mixed, lab-compacted); (b)asphalt mixtures produced at mixing plants (field-mixed, lab-compacted); and (c) asphalt mixture coresobtained from completed pavements of any age (field-mixed, field-compacted).

Numerical indices of retained indirect-tensile properties are obtained by comparing the properties oflaboratory specimens subjected to moisture and freeze–thaw conditioning with the similar properties ofdry specimens.

SUMMARY OF METHOD

Test specimens for each set of mix conditions, such as those prepared with untreated asphalt binder,asphalt binder treated with antistripping agent, or aggregate treated with lime, are prepared. Each setof specimens is divided into subsets. One subset is tested in dry condition for indirect-tensile strength.The other subset is subjected to vacuum saturation and a freeze cycle, followed by a warm-watersoaking cycle, before being tested for indirect-tensile strength. Numerical indices of retained indirect-tensile strength properties are calculated from the test data obtained by the two subsets: dry andconditioned.

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4.1.

APPARATUS

Equipment for preparing and compacting specimens from one of the following: T 167, T 245, T 247, T312, or ASTM D3387.

Equipment for determining the theoretical maximum specific gravity (Gmm) of the asphalt mixture fromT 209.

Balance and water bath from T 166.

Water bath capable of maintaining a temperature of 60 ± 1°C (140 ± 2°F).

Freezer maintained at –18 ± 3°C (0 ± 5°F).

A supply of plastic film for wrapping specimens; heavy-duty, leakproof plastic bags to enclose thesaturated specimens; and masking tape.

10-mL graduated cylinder.

Pans having a surface area of 48 400 to 129 000 mm2 (75 to 200 in.2) in the bottom and a depth ofapproximately 25 mm (1 in.).

Forced-draft oven, thermostatically controlled, capable of maintaining any desired temperature settingfrom room temperature to 176°C (350°F) within ±3°C (±5°F).

Loading jack and ring dynamometer from T 245, or a mechanical or hydraulic testing machine from T167, to provide a range of accurately controllable rates of vertical deformation, including 50 mm/min (2in./min).

Steel loading strips with a concave surface having a radius of curvature equal to the nominal radius ofthe test specimen. For specimens 100 mm (4 in.) in diameter, the loading strips shall be 12.7 mm (0.5in.) wide, and for specimens 150 mm (6 in.) in diameter, the loading strips shall be 19.05 mm (0.75 in.)wide. The length of the loading strips shall exceed the thickness of the specimens. The edges of theloading strips shall be rounded to the appropriate radius of curvature by grinding.

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5.1.

5.2.

5.3.

5.4.

5.5.

5.6.

5.7.

5.8.

5.9.

5.10.

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PREPARATION OF LABORATORY-MIXED, LABORATORY-COMPACTEDSPECIMENS

Make at least six specimens for each test, half to be tested dry and the other half to be tested afterpartial saturation and moisture conditioning with a freeze–thaw cycle (Note 1).

Note 1—It is recommended that two additional specimens for the set be prepared. These specimenscan then be used to establish compaction procedures as given in Section 6.5 or 7.4 and the vacuumsaturation technique as given in Section 10.3.

Specimens 100 mm (4 in.) in diameter by 63.5 ± 2.5 mm (2.5 ± 0.1 in.) thick, or 150 mm (6 in.) indiameter by 95 ± 5 mm (3.75 ± 0.20 in.) thick are used. Specimens 150 mm (6 in.) in diameter by 95± 5 mm (3.75 ± 0.20 in.) thick should be used if aggregate larger than 25 mm (1 in.) is present in themixture.

Prepare mixtures in batches large enough to make at least three specimens or, alternatively, prepare abatch large enough to just make one specimen at a time. If preparing a multispecimen batch, split thebatch into single-specimen quantities before placing in the oven.

After mixing, the mixture shall be placed in a pan having a surface area of 48 400 to 129 000 mm2 (75to 200 in.2) in the bottom and a depth of approximately 25 mm (1 in.) and cooled at room temperaturefor 2 ± 0.5 h. Then the mixture shall be placed in a 60 ± 3°C (140 ± 5°F) oven for 16 ± 1 h for curing.The pans should be placed on spacers to allow air circulation under the pan if the shelves are notperforated.

After curing, place the mixture in an oven for 2 h ± 10 min at the compaction temperature ±3°C (5°F)prior to compaction. Compact the specimens according to one of the following methods: T 167, T 245,T 247, T 312, or ASTM D3387. The mixture shall be compacted to 7.0 ± 0.5 percent air voids. This levelof voids can be obtained by adjusting the number of blows in T 245; adjusting foot pressure, number oftamps, leveling load, or some combination in T 247; or adjusting the number of revolutions in T 312 orASTM D3387. The exact procedure must be determined experimentally for each mixture beforecompacting the specimens for each set (Note 2).

Note 2—Due to the elevated void content and potential instability of the specimens, ensure that eachspecimen is adequately cool and stable prior to removal from the mold.

After removal from the molds, the specimens shall be stored for 24 ± 3 h at room temperature.

6.

6.1.

6.2.

6.3.

6.4.

6.5.

6.6.

PREPARATION OF FIELD-MIXED, LABORATORY-COMPACTED SPECIMENS

Make at least six specimens for each test, half to be tested dry and the other half to be tested afterpartial saturation and moisture conditioning with a freeze–thaw cycle (Note 1).

Specimens 100 mm (4 in.) in diameter by 63.5 ± 2.5 mm (2.5 ± 0.1 in.) thick, or 150 mm (6 in.) indiameter by 95 ± 5 mm (3.75 ± 0.20 in.) thick are used. Specimens 150 mm (6 in.) in diameter by 95± 5 mm (3.75 ± 0.20 in.) thick should be used if aggregate larger than 25 mm (1 in.) is present in themixture.

Field-mixed asphalt mixtures shall be sampled in accordance with ASTM D979/D979M.

No loose-mix curing as described in Section 6.4 shall be performed on the field-mixed samples. Aftersampling, divide the sample to obtain the desired size in accordance with R 47. Next, place the mixturein an oven until it reaches the compaction temperature ±3°C (5°F). Then compact the specimenaccording to one of the following methods: T 167, T 245, T 247, T 312, or ASTM D3387. The mixtureshall be compacted to 7.0 ± 0.5 percent air voids. This level of voids can be obtained by adjusting thenumber of blows in T 245; adjusting foot pressure, number of tamps, leveling load, or some

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7.2.

7.3.

7.4.


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combination in T 247; or adjusting the number of revolutions in T 312 or ASTM D3387. The exactprocedure must be determined experimentally for each mixture before compacting the specimens foreach set (Note 2).

After removal from the molds, the specimens shall be stored for 24 ± 3 h at room temperature.

PREPARATION OF FIELD-MIXED, FIELD-COMPACTED SPECIMENS (CORES)

Select locations on the completed pavement to be sampled, and obtain cores. When testing pavementlayers with a thickness less than or equal to 63.5 mm (2.5 in.), use 100-mm (4-in.) diameter cores.Otherwise, use either 100-mm (4-in.) or 150-mm (6-in.) diameter cores. The number of cores shall beat least six for each set of mix conditions.

Separate the core layers as necessary by sawing them or by other suitable means, and store the layersto be tested at room temperature until they are dry.

No loose-mix curing (Section 6.4) or compacted-mix curing (Section 6.6) shall be performed on thefield-mixed, field-compacted specimens (cores).

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8.1.

8.2.

8.3.

EVALUATION AND GROUPING OF SPECIMENS

After curing, heating, or drying mixture samples or cores for the theoretical maximum specific gravity(Gmm) test as described in Sections 6.4 and 6.5, Section 7.4, or Section 8.2 as appropriate, determinethe Gmm of those samples by T 209.

Determine each specimen thickness (t) in accordance with ASTM D3549/D3549M.

Record each specimen diameter (D) as defined in Section 6.2, 7.2, or 8.1, as appropriate.

Determine each bulk specific gravity (Gmb) by Method A of T 166. Express the volume (E) of thespecimens, or the saturated, surface-dry mass minus the mass in water, in cubic centimeters.

Calculate the percentage of air voids (Pa) in accordance with T 269.

Separate the specimens into two subsets, of at least three specimens each, so that the average airvoids of the two subsets are approximately equal.

For those specimens to be subjected to vacuum saturation, a freeze cycle and a warm-water soakingcycle, calculate the volume of air voids (Va) in cubic centimeters using the following equation:

(1)

where:

Va = volume of air voids, cm3;

Pa = air voids, percent; and

9.

9.1.

9.2.

9.3.

9.4.

9.5.

9.6.

9.7.


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E = volume of the specimen, cm3.

Note 3—A data sheet that is convenient for use with this test method is shown as Table 1.

PRECONDITIONING OF TEST SPECIMENS

One subset will be tested dry, and the other will be partially vacuum saturated, subjected to freezing,and soaked in warm water before testing.

The dry subset will be stored at room temperature as described in Section 6.6 or Section 7.5, asappropriate. At the end of the curing period from Section 6.6 or 7.5, as appropriate, the specimens shallbe wrapped with plastic or placed in a heavy-duty, leakproof plastic bag. The specimens shall then beplaced in a 25 ± 0.5°C (77 ± 1°F) water bath for 2 h ± 10 min with a minimum 25 mm (1 in.) of waterabove their surface. Then test the specimens as described in Section 11.

The other subset shall be conditioned as follows:

Place the specimen in the vacuum container supported a minimum of 25 mm (1 in.) above thecontainer bottom by a perforated spacer. Fill the container with potable water at room temperature sothat the specimens have at least 25 mm (1 in.) of water above their surface. Apply a vacuum of 13 to67 kPa absolute pressure (10 to 26 in.Hg partial pressure) for a short time (approximately 5 to 10 min).Remove the vacuum and leave the specimen submerged in water for a short time (approximately 5 to10 min).

Note 4—The time required for some specimens to achieve the correct degree of saturation (between70 and 80 percent) may be less than 5 min. In addition, some specimens may require the use of anabsolute pressure of greater than 67 kPa (26 in.Hg partial pressure) or less than 13 kPa (10 in.Hgpartial pressure).

Determine the mass of the saturated, surface-dry specimen after partial vacuum saturation (Bʹ) byMethod A of T 166.

Calculate the volume of absorbed water (Jʹ) in cubic centimeters by use of the following equation:

(2)

where:

Jʹ = volume of absorbed water, cm3;

Bʹ = mass of the saturated, surface-dry specimen after partial vacuum saturation, g; and

A = mass of the dry specimen in air, g (Section 9.4).

Determine the degree of saturation (Sʹ) by comparing the volume of absorbed water (Jʹ) with thevolume of air voids (Va) from Section 9.6 using the following equation:

10.

10.1.

10.2.

10.3.

10.3.1.

10.3.2.

10.3.3.

10.3.4.


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(3)

where:

Sʹ = degree of saturation, percent.

If the degree of saturation is between 70 and 80 percent, proceed to Section 10.3.7.

If the degree of saturation is less than 70 percent, repeat the procedure beginning with Section 10.3.1using more vacuum and/or time. If the degree of saturation is more than 80 percent, the specimen hasbeen damaged and must be discarded. In this case, repeat the procedure on the next specimenbeginning with Section 10.3.1 using less vacuum and/or time.

Cover each of the vacuum-saturated specimens tightly with a plastic film (Saran Wrap® brand orequivalent). Place each wrapped specimen in a plastic bag containing 10 ± 0. 5 mL of water and sealthe bag. Place the plastic bags containing the specimens in a freezer at a temperature of –18 ± 3°C (0± 5°F) for a minimum of 16 h. Remove the specimens from the freezer.

Place the specimens in a bath containing potable water at 60 ± 1°C (140 ± 2°F) for 24 ± 1 h. Thespecimens should have a minimum of 25 mm (1 in.) of water above their surface. As soon as possibleafter placement in the water bath, remove the plastic bag and film from each specimen.

After 24 ± 1 h in the 60 ± 1°C (140 ± 2°F) water bath, remove the specimens and place them in awater bath at 25 ± 0.5°C (77 ± 1°F) for 2 h ± 10 min. The specimens should have a minimum of 25mm (1 in.) of water above their surface. It may be necessary to add ice to the water bath to preventthe water temperature from rising above 25°C (77°F). Not more than 15 min should be required for thewater bath to reach 25 ± 0.5°C (77 ± 1°F). Remove the specimens from the water bath, and test themas described in Section 11.

TESTING

Determine the indirect-tensile strength of dry and conditioned specimens at 25 ± 0.5°C (77 ± 1°F).

Remove the specimen from 25 ± 0.5°C (77 ± 1°F) water bath, and determine the thickness (tʹ) byASTM D3549. Place it between the steel loading strips and then place the specimen and loading stripsbetween the two bearing plates in the testing machine. Care must be taken so that the load will beapplied along the diameter of the specimen. Apply the load to the specimen, by means of the constantrate of movement of the testing machine head, at 50 mm/min (2 in./min).

Record the maximum compressive strength noted on the testing machine, and continue loading until avertical crack appears. Remove the specimen from the machine, and pull it apart at the crack. Inspectthe interior surface for evidence of cracked or broken aggregate; visually estimate the approximatedegree of moisture damage on a scale from “0” to “5” (with “5” being the most stripped), and recordthe observations in Table 1.

Table 1—Moisture Damage Laboratory Data Sheet (Nonmandatory Information)

11.

11.1.

11.1.1.

11.1.2.


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CALCULATIONS

Calculate the tensile strength as follows:

SI units:

(4)

where:

St = tensile strength, kPa;

P = maximum load, N;

t = specimen thickness, mm; and

D = specimen diameter, mm.

U.S. Customary units:

12.

12.1.


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(5)

where:

St = tensile strength, psi;

P = maximum load, lbf;

t = specimen thickness, in.; and

D = specimen diameter, in.

Express the numerical index of resistance of asphalt mixtures to the detrimental effect of water as theratio of the original strength that is retained after the moisture and freeze–thaw conditioning. Calculatethe tensile strength ratio to two decimal places as follows:

(6)

where:

S1 = average tensile strength of the dry subset, kPa (psi); and

S2 = average tensile strength of the conditioned subset, kPa (psi).

REPORT

Report the following information:

Number of specimens in each subset;

Average air voids of each subset;

Tensile strength of each specimen in each subset;

Tensile strength ratio;

Results of visually estimated moisture damage observed when the specimen fractures; and

Results of observations of cracked or broken aggregate.

13.

13.1.

13.1.1.

13.1.2.

13.1.3.

13.1.4.

13.1.5.

13.1.6.

KEYWORDS14.14.1.


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1 Minor editorial revisions have been made at the discretion of the authors responsible for standards on proportioningof asphalt-aggregate mixtures (technical section 2d).

Accelerated water conditioning; diametral tensile strength; freeze–thaw cycle; liquid antistrippingadditives; long-term stripping; portland cement; pulverulent solids; water saturation.


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Standard Method of Test for Preparing and Determining the Densityof Asphalt Mixture Specimens by Means of the Superpave Gyratory

CompactorAASHTO Designation: T 312-15

SCOPE

This standard covers the compaction of cylindrical specimens of asphalt mixtures using the Superpavegyratory compactor.

This standard may involve hazardous materials, operations, and equipment. This standard does notpurport to address all of the safety concerns associated with its use. It is the responsibility of the userof this standard to establish appropriate safety and health practices and determine the applicability ofregulatory limitations prior to use.

1.

1.1.

1.2.


AASHTO Standards:

M 231, Weighing Devices Used in the Testing of MaterialsR 30, Mixture Conditioning of Hot Mix Asphalt (HMA)R 35, Superpave Volumetric Design for Asphalt MixturesR 47, Reducing Samples of Hot Mix Asphalt (HMA) to Testing SizeT 166, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-DrySpecimensT 168, Sampling Bituminous Paving MixturesT 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Hot Mix Asphalt (HMA)T 275, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Paraffin-CoatedSpecimensT 316, Viscosity Determination of Asphalt Binder Using Rotational ViscometerT 344, Evaluation of Superpave Gyratory Compactor (SGC) Internal Angle of Gyration Using SimulatedLoading

Other Standards:

ANSI/ASME B89.1.6, Measurement of Qualified Plain Internal Diameters for Use as Master Rings andRing GagesANSI/ASME B89.4.19, Performance Evaluation of Laser-Based Spherical Coordinate MeasurementSystemsASME B46.1, Surface Texture (Surface Roughness, Waviness, and Lay)

2.

2.1.

2.2.


This standard is used to prepare specimens for determining the mechanical and volumetric properties ofasphalt mixtures. The specimens simulate the density, aggregate orientation, and structuralcharacteristics obtained in the actual roadway when proper construction procedure is used in theplacement of the paving mix.

3.

3.1.

Standard Method of Test for Preparing and Determining the Density of ... http://hm.digital.transportation.org/HM/Part_II_Tests/Bituminous_Materi...

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This test method may be used to monitor the density of test specimens during their preparation. It mayalso be used for field control of an asphalt mixture production process.

APPARATUS

Superpave Gyratory Compactor—An electrohydraulic or electromechanical compactor with a ram andram heads as described in Section 4.3. The axis of the ram shall be perpendicular to the platen of thecompactor. The ram shall apply and maintain a pressure of 600 ± 18 kPa perpendicular to thecylindrical axis of the specimen during compaction (Note 1). The compactor shall tilt the specimenmolds at an average internal angle of 20.2 ± 0.35 mrad (1.16 ± 0.02 degrees), determined inaccordance with T 344. The compactor shall gyrate the specimen molds at a rate of 30.0 ± 0.5gyrations per minute throughout compaction.

Note 1—This stress calculates to 10 600 ± 310 N total force for 150-mm specimens.

Specimen Height Measurement and Recording Device—When specimen density is to be monitoredduring compaction, a means shall be provided to continuously measure and record the height of thespecimen to the nearest 0.1 mm during compaction once per gyration.

The system may include a connected printer capable of printing test information, such as specimenheight per gyration. In addition to a printer, the system may include a computer and suitable softwarefor data acquisition and reporting.

Specimen Molds—Specimen molds shall have steel walls that are at least 7.5 mm thick and arehardened to at least a Rockwell hardness of C48. The initial inside finish of the molds shall have a rootmean square (rms) of 1.60 μm or smoother when measured in accordance with ASME B46.1 (see Note2). New molds shall be manufactured to have an inside diameter of 149.90 to 150.00 mm. The insidediameter of in-service molds shall not exceed 150.2 mm. Molds shall be at least 250 mm in length. Theinside diameter and length of the molds shall be measured in accordance with Annex A.

Note 2—One source of supply for a surface comparator, which is used to verify the rms value of 1.60μm, is GAR Electroforming, Danbury, Connecticut.

Ram Heads and End Plates—Ram heads and end plates shall be fabricated from steel with a minimumRockwell hardness of C48. The ram heads shall stay perpendicular to their axis. The platen side of eachend plate shall be flat and parallel to its face. All ram and end plate faces (the sides presented to thespecimen) shall be flat to meet the smoothness requirement in Section 4.2 and shall have a diameter of149.50 to 149.75 mm.

Thermometers—Armored, glass, or dial-type thermometers with metal stems for determining thetemperature of aggregates, binder, and HMA between 10 and 232°C.

Balance—A balance meeting the requirements of M 231, Class G 5, for determining the mass ofaggregates, binder, and asphalt mixtures.

Oven—An oven, thermostatically controlled to ±3°C, for heating aggregates, binder, asphalt mixtures,and equipment as required. The oven shall be capable of maintaining the temperature required formixture conditioning in accordance with R 30.

Miscellaneous—Flat-bottom metal pans for heating aggregates, scoop for batching aggregates,containers (grill-type tins, beakers, containers for heating asphalt), large mixing spoon or small trowel,large spatula, gloves for handling hot equipment, paper disks, mechanical mixer (optional), lubricating

4.

4.1.

4.1.1.

4.1.2.

The loading system, ram, and pressure indicator shall be capable of providing and measuring a constantvertical pressure of 600 ± 60 kPa during the first five gyrations, and 600 ± 18 kPa during the remainderof the compaction period.

4.1.3.

4.2.

4.3.

4.4.

4.5.

4.6.

4.7.


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materials recommended by the compactor manufacturer.

Maintenance—In addition to routine maintenance recommended by the manufacturer, check theSuperpave gyratory compactor’s mechanical components for wear, and perform repair, asrecommended by the manufacturer.

HAZARDS

Use standard safety precautions and protective clothing when handling hot materials and preparing testspecimens.

5.

5.1.

STANDARDIZATION

Items requiring periodic verification of calibration include the ram pressure, angle of gyration, gyrationfrequency, LVDT (or other means used to continuously record the specimen height), and oventemperature. Verification of the mold and platen dimensions and the inside finish of the mold are alsorequired. When the computer and software options are used, periodically verify the data-processingsystem output using a procedure designed for such purposes. Verification of calibration, systemstandardization, and quality checks may be performed by the manufacturer, other agencies providingsuch services, or in-house personnel. Frequency of verification shall follow the manufacturer’srecommendations.

The angle of gyration refers to the internal angle (the tilt of the mold with respect to the end platesurface within the gyratory mold). The calibration of the internal angle of gyration shall be verified inaccordance with T 344.

6.

6.1.

6.2.

PREPARATION OF APPARATUS

Immediately prior to the time when the asphalt mixture is ready for placement in the mold, turn on themain power for the compactor for the manufacturer’s required warm-up period.

Verify the machine settings are correct for angle, pressure, and number of gyrations.

Lubricate any bearing surfaces as needed per the manufacturer’s instructions.

When specimen height is to be monitored, the following additional item of preparation is required.Immediately prior to the time when the asphalt mixture is ready for placement in the mold, turn on thedevice for measuring and recording the height of the specimen, and verify the readout is in the properunits, mm, and the recording device is ready. Prepare the computer, if used, to record the height data,and enter the header information for the specimen.

7.

7.1.

7.2.

7.3.

7.4.

HMA MIXTURE PREPARATION

Laboratory Prepared:

Weigh the appropriate aggregate fractions into a separate pan, and combine them to the desired batchweight. The batch weight will vary based on the ultimate disposition of the test specimens. If a targetair void level is desired, as would be the case for Superpave mix analysis and performance specimens,batch weights will be adjusted to create a given density in a known volume. If the specimens are to be

8.

8.1.

8.1.1.


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used for the determination of volumetric properties, the batch weights will be adjusted to result in acompacted specimen having dimensions of 150 mm in diameter and 115 μ 5 mm in height at thedesired number of gyrations.

Note 3—It may be necessary to produce a trial specimen to achieve this height requirement. Generally,4500 to 4700 g of aggregate are required to achieve this height for aggregates with combined bulkspecific gravities of 2.550 to 2.700, respectively.

Place the aggregate and binder container in the oven, and heat them to the required mixingtemperature.

The mixing temperature range is defined as the range of temperatures where the unaged binder has aviscosity of 0.17 ± 0.02 Pa·s when measured in accordance with T 316.

Note 4—Modified asphalts may not adhere to the equiviscosity requirements noted, and themanufacturer’s recommendations should be used to determine mixing and compaction temperatures.

Charge the mixing bowl with the heated aggregate from one pan and dry-mix thoroughly. Form a craterin the dry-blended aggregate, and weigh the required amount of binder into the mix. Immediatelyinitiate mixing.

Mix the aggregate and binder as quickly and thoroughly as possible to yield an asphalt mixture having auniform distribution of binder. As an option, mechanical mixing may be used.

After completing the mixture preparation, perform the required mixture conditioning in accordance withR 30.

Place the compaction mold(s) and base plate(s) in an oven at the required compaction temperature fora minimum of 30 min prior to the estimated beginning of compaction (during the time the mixture isbeing conditioned in accordance with R 30).

Following the mixture conditioning period specified in R 30, if the mixture is at the compactiontemperature, proceed immediately with the compaction procedure as outlined in Section 9. If thecompaction temperature is different from the mixture conditioning temperature used in accordance withR 30, place the mix in another oven at the compaction temperature for a brief time (maximum of 30min) to achieve the required temperature.

The compaction temperature is the midpoint of the range of temperatures where the unaged binder hasa viscosity of 0.28 ± 0.03 Pa·s when measured in accordance with T 316. (See Note 4.)

Plant Produced:

Place the compaction mold(s) and base plates(s) in an oven at the required compaction temperature(see Section 8.1.7.1).

Obtain the sample in accordance with T 168.

Reduce the sample in accordance with R 47.

Place the sample into a pan to a uniform thickness.

Bring the HMA to the compaction temperature range by careful, uniform heating in an ovenimmediately prior to molding.

COMPACTION PROCEDURE

When the compaction temperature is achieved, remove the heated mold, base plate, and upper plate (ifrequired) from the oven. Place the base plate and a paper disk in the bottom of the mold.

9.

9.1.


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Place the mixture into the mold in one lift. Care should be taken to avoid segregation in the mold. Afterall the mix is in the mold, level the mix, and place another paper disk and upper plate (if required) ontop of the leveled material.

Load the charged mold into the compactor, and center the loading ram.

Apply a pressure of 600 ± 18 kPa on the specimen.

Apply a 20.2 ± 0.35 mrad (1.16 ± 0.02 degrees) average internal angle to the

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