NCHRP 9-45NCHRP 9-45

Test Methods and Specification Criteriafor Mineral Filler Used in HMANCHRP 9-45

Hussain U. Bahia

University of Wisconsin – Madison

NCAUPG MeetingFebruary 2-3, 2011, Columbus , Ohio

NCHRP 9-45

Research Team – NCHRP Project 9-45

•Results are based on NCHRP Project :– Test Methods and Specification Criteria for Mineral

Filler Used in HMA

•Research Team:– MTE - Gerry Reinke and Erv Dukatz

– UIUC - Imad Al Qadi

– UW-Madison - Ahmed Faheem, Cassie Hintz & Hussain Bahia

NCHRP 9-45

Objectives of the NCHRP Study

(1)Identify or develop test methods for mineral fillerthat characterize its mechanical and chemicaleffects on the performance of :

(a) mastics and

(b) hot mix asphalt (HMA)

(2) Recommend specification criteria for mineralfiller that optimize HMA performance

Project started in 2007, draft final is under review

NCHRP 9-45

Do binders or mastics control HMAperformance?

Stiff particle

In Collaboration with Prof. Rod Lakes UW- Madison

•Fillers & modifiers affect all aspect of masticbehavior

NCHRP 9-45NCHRP 9-45

Fillers’EffectsVary

Problem Statement:Predicting effects of fillers

• Fillers vary in their effects onbitumen properties

• Einstein Model for DilutedComposites (1911):

– ηr = 1 + KEøηr= Viscosity of mastic/ viscosity of (Binder)

KE= Einstein Constant ~2.5

Ø: Filler volume fraction

ηr

Ø Volume conc. of filler

NCHRP 9-45

Basic Concept of Study:Fillers’ Interaction with Binders (Tunnicliff in 1960)

1. Filler2. Asphalt adsorbed layer3. Asphalt layer affected by adsorption

Gradient of stiffening

Important Filler Properties:1.Geometry , and 2.Composition

NCHRP 9-45NCHRP 9-45

Conceptual Model –Binder& Filler Interaction (Faheem et al. 2008 )

0

10

20

30

40

50

0 20 40 60

80

Filler Volume Fraction (%)

G*

rati

o

In this region, filler particlesare separated enough by thefree asphalt volume

Co

nc

en

trate

d

Dilu

ted

1. Initial Stiffening Rate,2. Critical Filler Concentration, 3.Terminal Stiffening Rate

3

2

1 At this concentration the transitionis due to the consumption of “FreeAsphalt”

G* Ratio vs. Filler Volume Fraction

NCHRP 9-45

Important Filler Properties – 1. Geometry

• Fillers’ geometry can be defined by four measurements:

–Size, shape, angularity, & texture.

Last 3 are difficult to measure individually.

–A good indicator of all is (Packing)

–Fractional Voids (also called Rigden Voids)

•Two Secondary : Absorption & Specific Gravity

NCHRP 9-45

Rigden Voids -- Fixed & Free binder

• Rigden voids’ content

– Volume percentage of voids in a dry, compacted filler sample

• Higher Rigden voids leads to higher stiffening of binder

NCHRP 9-45

RIGDEN VOIDS (BS 812, EN 1097-4)

NCHRP 9-45

New Rigden Voids Device by Gilson

NCHRP 9-45

New Device by Instrotek

NCHRP 9-45

Important Filler Properties – 2. Composition

•There appears to be a small number of chemicalcompounds that affect asphalt-filler interactions.

•Two main properties are important:

– Reactivity

Calcium compound.

Water solubility.

– Harmful fines

Active Clay Content.

Organic Content.

NCHRP 9-45

Filler Mineralogical Types Selected

Filler Type

1.Andesite2.Basalt

3.Caliche4.Dolomite5.Granite

6. Limestone1.Hydrated Lime

2.Fly Ash

3.Slag

• Natural Fillers

•Imported Fillers

NCHRP 9-45

Distribution of Rigden VoidsCan be grouped by Mineralogy

25

30

35

40

45

50

Rig

de

nV

oid

s(%

)

Average

NCHRP 9-45

0

10

20

30

40

50

60

70

Filler Type

Composition Variation of Fillers

Al2O3 CaO FeO K2O MgO SiO2

NCHRP 9-45

Asphalt Binders for Producing Mastics

• (a) PG 64-22 with low asphaltenes

– (from a light crude source)

• (b) PG 64-22 with high asphaltenes

– (from a heavy crude source)

• Binder (a) modified with PPA to a PG 76-22

• Binder (a) modified with SBS to a PG 76-22

• All mastics prepared at 1:1 ratio by mass

NCHRP 9-45

Distribution of Volume Fraction@ 1:1 ratio by mass

0.20

0.22

0.24

0.26

0.28

0.30

Vo

lum

eF

rac

tio

n(%

)

± One StandardDeviation (0.01)

Average

NCHRP 9-45

Mastic & Mixture Testingand Analysis of Results

NCHRP 9-45

Mastic Properties Measured

1. Workability measure:

Viscosity: 135°C at 1 – 50 RPM

2. Rutting:

MSCR Jnr, %Recovery, 58°C, 64°C, at 0.1, 3.2,10kPa

3. Fatigue:

G*.Sinδ, and Time Sweep, 25°C and 10Hz

4. Low Temp Cracking:

S, m, at -12°C, Cracking temperature (ABCD)

5. Moisture Damage

Pull Off Test, 24hr moisture conditioning at 60°C

NCHRP 9-45

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

NoFille

r

AN1

BH1

BH2

CA2

DH1

DS2

GH1

GH2

GRQ2

GS1

GS2

LH1

LS2

FAC2

FAF1 FS2

HL2

Visc

osity

(cP)

Filler

Flint Hills

PPA

SBS

Valero

Average

Legend:1st Letter: Filler 2nd / 3rd Letter:A:Andesite FS: Furnace Slag H: HardB: Basalt G: Granite S: Soft

C: Caliches GRQ: Gravel Quartzite 4th/5th Letter:D: Dolomite HL: Hydrated Lime 1: Source 1FA: Fly Ash 2: Source 2

Natural Manufactured

Viscosity at 135 C

NCHRP 9-45

0

5

10

15

20

25

30

35

40

45

50

55

FDH

1

FGH

2

FGS2

FLH

1

PFA

C2

PG

RQ

2

PG

S1

PH

L2

SAN

1

SCA

2

SDS2

SFS2

VB

H2

VC

A2

VG

RQ

2

VG

S1

Nu

mb

er

of

Gyr

atio

ns

to9

2%

Max

imu

mD

en

sity

Mastics

Coarse

Fine

Flint Hills +

PPA PG 70-22

Flint Hills +

SBS PG 70-22Valero

PG 64-22

Flint Hills

PG 64-22

Legend:1st Letter: Binder 2nd Letter: Filler 3rd/4th Letter:

F: Flint Hills A: Andesite FS: Furnace Slag H: HardV: Valero B: Basalt G: Granite S: SoftP: PPA C: Caliches HL: Hydrated Lime 4th/5th Letter:S: SBS D: Dolomite 1: Source 1

FA: Fly Ash 2: Source 2

Filler type can increasecompaction resistance( N92 ) By 100%

NCHRP 9-45

0.01

0.10

1.00

10.00

No

Fille

r

AN1

BH1

BH2

CA2

DH1

DS2

GH1

GH2

GRQ

2

GS1

GS2

LH1

LS2

FAC2

FAF1 FS2

HL2

Jnr(

1/kP

a)

Filler

Flint Hills

PPA

SBS

Valero

Average

Legend:1st Letter: Filler 2nd / 3rd Letter:

A:Andesite FS: Furnace Slag H: HardB: Basalt G: Granite S: Soft

C: Caliches GRQ: Gravel Quartzite 4th/5th Letter:D: Dolomite HL: Hydrated Lime 1: Source 1

FA: Fly Ash 2: Source 2

Natural Manufactured

MSCR test: Effects of fillers on Jnr

Jnr is 10 times lowerDue to type of filler

NCHRP 9-45

0%

10%

20%

30%

40%

50%

60%

70%

No

Fille

r

AN1

BH1

BH2

CA2

DH1

DS2 GH1

GH2

GRQ

2

GS1

GS2

LH1

LS2

FAC2

FAF1 FS2

HL2

%Re

cove

ry

Filler

Flint Hills

PPA

SBS

Valero

Average

Legend:1st Letter: Filler 2nd / 3rd Letter:

A:Andesite FS: Furnace Slag H: HardB: Basalt G: Granite S: Soft

C: Caliches GRQ: Gravel Quartzite 4th/5th Letter:D: Dolomite HL: Hydrated Lime 1: Source 1

FA: Fly Ash 2: Source 2

Natural Manufactured

MSCR - % Recovery @ 3.2 KPa

NCHRP 9-45

Jnr at 58°C and 3.2kPa –Compare effects of modifiers + fillers

0.1

1.0

10.0

Jnr

(1/k

Pa)

PPA

SBS

Valero

Increasing Rigden Voids

PG 64

PG 76

NCHRP 9-45

Prediction of Mastic Jnr

The best fit regression equation at ( 1:1 binder to filler) is:

Mastic Jnr = 1.19 + 0.156 Binder Jnr - 0.0273 Rigden Voids

Predictor Coef SE Coef T P

Constant 1.1934 0.2248 5.31 0.000

Binder Jnr 0.15590 0.02193 7.11 0.000

Rigden Voids -0.0272 0.005632 -4.84 0.000

S = 0.123381 R-Sq = 74.7% R-Sq(adj) = 72.7%

NCHRP 9-45

0

500

1,000

1,500

2,000

2,500

3,000

FDH

1

FFA

C2

FFS2

FGH

2

PCA

2

PDS2

PFA

F1

PLS2

SAN

1

SBH

2

SGR

Q2

SGS2

VG

H1

VG

S1

VH

L2

VLH

1

Flow

Num

ber

Mastics

Coarse

Fine

Flint Hills +

PPA PG 70-22

Flint Hills +

SBS PG 70-22

Valero

PG 64-22

Flint Hills

PG 64-22

Legend:1st Letter: Binder 2nd Letter: Filler 3rd/4th Letter:

F: Flint Hills A: Andesite FS: Furnace Slag H: HardV: Valero B: Basalt G: Granite S: Soft

P: PPA C: Caliches HL: Hydrated Lime 4th/5th Letter:S: SBS D: Dolomite 1: Source 1

FA: Fly Ash 2: Source 2

Mixture Flow Number (FN)

Mix FN canVary by 6 timesDue to filler type

NCHRP 9-45

Effects on Mixture Rutting ResultsMeasured by FN (Coarse Mixtures)

Coarse: Correlation Between Mixture and

Mastic Rutting Indicators

y = -1037.1x + 1379.9

R2 = 0.652

0

200

400

600

800

1000

1200

1400

1600

1800

0.00 0.20 0.40 0.60 0.80 1.00 1.20

Mastic Jnr (1/kPa)

Mix

ture

Flo

wN

um

be

r

NCHRP 9-45

Deriving Mastic Jnr LimitsFor Acceptable Rutting Resistance

• Mixture (FN) Limits derived from NCHRP 9-33 Recommendations:

• Corresponding Mastic Jnr Limits:

Traffic Level (Million ESALs) Minimum Flow Number @ 200kPa< 3 -----------

3 to < 10 53010 to < 30 1,900

≥ 30 7,400

Mixture Gradation Maximum Mastic Jnr at 3.2kPa (1/kPa)

Fine 0.41Coarse 0.62

NCHRP 9-45

Limits on Measured or PredictedMastic Jnr (@ 3.2 Kpa) Propose limits on Mastic Jnr as measured or

predicted. Jnr < 0.5 1/Kpa

Best fit regression analysis:

Jnr (mastic) = 2.05 + 0.166 Binder Jnr - 0.0162 RigdenVoids - 4.67 Volume Fraction

Predictor T P

Constant 5.38 0.000

Binder Jnr 10.71 0.000

Rigden Voids -5.97 0.000

Volume Fraction -3.84 0.000

S = 0.136097 R-Sq = 70.9% R-Sq(adj) = 69.5%

NCHRP 9-45

Effects on Low TemperatureCracking

Measured

1.S, m for mastics

2. Creep Stiffness and Strength for mixtures

NCHRP 9-45

Mastic Stiffness at -12°C

0

100

200

300

400

500

600

700

800

900St

iffn

ess

at-1

2°C

MP

a

Flint Hills

PPA

SBS

Valero

Increasing Rigden Voids

Filler effect is importantBut filler type is (NOT)

NCHRP 9-45

Relative m-value at -12°C

0.6

0.7

0.8

0.9

1.0

1.1

1.2

Re

lati

vem

-val

ue

at-1

2°C Flint Hills

PPA

SBS

Valero

Increasing Rigden Voids

Filler effect is importantBut filler type is (NOT)Binder Modification is most important

NCHRP 9-45

ANOVA Analysis for Mixture Stiffnessat -12 C

Variable F-Value P-Value

Gradation 55.21 0.000

Binder Source 17.34 0.000

Binder Modification 0.35 0.708

Filler Mineralogy 0.37 0.946

R2 = 62.31%•Binder type (source) & aggregate gradation are most important.•Binder modification and fillers are insignificant.•Some fillers may negate or even reverse the effect of the bindermodification ( e.g. PPA binder with soft limestone).

NCHRP 9-45

ANOVA Analysis for Mixture Strengthat -12 C

Variable F-Value P-Value

Gradation 5.84 0.019

Binder Source 1.38 0.246

Binder Modification 5.08 0.010

Filler Mineralogy 1.96 0.065

R2 = 39.80%

Binder modification is the most significant factorwhile filler effects are only marginal.

NCHRP 9-45

So, What ‘s New?

•Measure Rigden Voids

•Measure Specific Gravity

•Change mixture design procedure to include

– Volume fraction of fillers rather than dust to binderratio

– Caution about modifiers and fillers combinations

NCHRP 9-45

Recommended specification criteria formineral fillers that optimize HMA performance

Perform.Indicator

MasticProperty

MasticLimit

Mastic Models

WorkabilityRel. Viscosity

@135ºC<5.00

Mastic Vis. =- 8244 + 4.68Binder Viscosity + 205 Rigden

Voids

RuttingJnr @3.2kPa -58ºC, (1/kPa)

< 0.40 Mastic Jnr = 1.01 + 0.160

Binder Jnr - 0.0230 Rigden Voids

Low TemperatureRelative Stiffness @60 Seconds and

@-12ºCNo Limits

Mastic Stiffness = 145 + 2.32 Binder Low Temp Stiff +4.84 Rigden Voids – 1.71 CaO%

Moisture Damage Pull off strength No Limits No acceptable Model

FatigueG*sin(delta),

Number of Cycles to FailureNo Limits No acceptable Model

• Because of high binder-filler interaction,criteria is based on Mastic testing

NCHRP 9-45

Recommended specification criteria formineral fillers that optimize HMA performance

Perform.Indicator

MasticProperty

MasticLimit

Mastic Models

WorkabilityRel. Viscosity

@135ºC<5.0

Mastic Vis. =- 8244 + 4.68Binder Viscosity + 205 Rigden

Voids

RuttingJnr @3.2kPa -58ºC, (1/kPa)

< 0.40 Mastic Jnr = 1.01 + 0.160

Binder Jnr - 0.0230 Rigden Voids

LowTemperature

Relative Stiffness @60Seconds and @-12ºC

NoLimits

Mastic Stiffness = 145 + 2.32 BinderLow Temp Stiff + 4.84 Rigden Voids

– 1.71 CaO%

MoistureDamage

Pull off strengthNo

LimitsNo acceptable Model

FatigueG*sin(delta),

Number of Cycles toFailure

NoLimits

No acceptable Model

NCHRP 9-45

RIGDEN VOIDS (BS 812, EN 1097-4)

NCHRP 9-45

Acknowledgment

•NCAUPG Organizers

– Dr. McDaniel

•NCHRP

– Dr. Ed Harrigan and the Project Panel

•Asphalt Research Consortium- FHWA. WRI

Bahia@engr.wisc.eduuwmarc.org