Improved Test Methods for Specific Gravity and Absorption ...onlinepubs.trb.org/Onlinepubs/webinars/160218.pdf · Improved Test Methods for Specific Gravity and Absorption of Coarse

Improved Test Methods for Specific Gravity and Absorption of Coarse and Fine Aggregate February 18, 2016

Today’s Presenters

• Moderator Julie Kliewer, Arizona Department of Transportation

• Presenters Randy West, National Center for Asphalt Technology

• Nam Tran, National Center for Asphalt Technology

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Today’s First Presenter

• Randy West National Center for Asphalt Technology

1

Improved Test Methods for Specific Gravity and Absorption of Coarse and Fine Aggregate

Dr. Randy West, P.E. Dr. Nam Tran, P.E. National Center for Asphalt Technology

2

Presentation Outline Research need and objectives Results Task 1: Identify test methods Task 4: Conduct lab evaluation program Task 6: Conduct ruggedness study Task 8: Revise test methods

Recommendations

3

Current Methods and Challenges AASHTO T 85 – Coarse aggregate Visual method of determining SSD condition Subjective, especially for high absorption aggregates

Soak time (15 ~ 19 hours) Inefficient for quality control purposes

SSD Condition

4

Current Methods and Challenges AASHTO T 84 – Fine aggregate Cone & tamp technique of determining SSD cond. Does not work well for some aggregates (angular, high

dust content, and/or highly absorptive)

Soak time (15 ~ 19 hours) Inefficient for quality control purposes

SSD Condition

5

Asphalt Durability Problems? NCAT Newsletter, Spring 2015

6

Objectives Develop test methods with balanced improvements in:

Accuracy, precision, ruggedness Ease of use Time of conditioning and testing Costs of equipment and operation Use for broad range of materials

Determine impacts of changes to test methods on: HMA mix design and PCC proportioning Other aggregate characteristics Technician training and qualification

7

Project Tasks 1. Identify test methods 2. Plan lab evaluation program 3. Interim report 4. Conduct lab evaluation program 5. Plan ruggedness study 6. Conduct ruggedness study 7. Evaluate impacts 8. Revise test methods 9. Final report

8


Recommendations

9

Test Methods for Coarse Aggregate 1. AASHTO T 85 and ASTM C 127 2. AggPlus System using CoreLok Device 3. Rapid AASHTO T 85 with CoreLok 4. SG-5 Specific Gravity and Absorption System 5. Volumetric Immersion using Phunque (funky) Flasks

10

Test Methods for Fine Aggregate 1. AASHTO T 84 and ASTM C 128

Modifications to Determination of SSD Condition Modification to Test Materials

2. SSDrier Device 3. SSDetect System

11

Test Methods for Fine Aggregate 4. AggPlus System using CoreLok Device 5. SG-5 Specific Gravity and Absorption System 6. Volumetric Immersion using Phunque Flasks

12

Test Methods for Combined Aggregate 1. AggPlus System using CoreLok Device 2. SG-5 Specific Gravity and Absorption System 3. Volumetric Immersion using Phunque Flasks

Panel’s Selections Select for Evaluation? ID Test Method Yes No %Yes

Test Selected for Evaluation

I. Test Methods for Determining Specific Gravity and Absorption of Coarse Aggregate I-1 AASHTO T 85 and ASTM C 127 7 2 78 √ I-2 AggPlus System using CoreLok Device 2 7 22 I-3 Rapid AASHTO T 85 with the CoreLok 7 2 78 √ I-4 SG-5 Specific Gravity and Absorption System 7 2 78 √ I-5 Volumetric Immersion using Phunque Flasks 5 4 56

II. Test Methods for Determining Specific Gravity and Absorption of Fine Aggregate II-1 AASHTO T 84 and ASTM C 128 7 2 78 √ II-2 Modifications to Determination of SSD Condition

in AASHTO T 84 / ASTM C 128 2 7 22

II-3 Modification to Materials Tested in AASHTO T 84/ASTM C 128 8 1 87 √

II-4 SSDrier Device 4 5 44 II-5 SSDetect System 9 0 100 √ II-6 AggPlus System using CoreLok Device 2 7 22 II-7 SG-5 Specific Gravity and Absorption System 7 2 78 √ II-8 Volumetric Immersion using Phunque Flasks 8 1 89 √

III. Test Methods for Determining Specific Gravity and Absorption of Combined Aggregate III-1 AggPlus System using CoreLok Device 3 6 37 III-2 SG-5 Specific Gravity and Absorption System 7 2 78 √ III-3 Volumetric Immersion using Phunque Flasks 7 2 78 √

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Recommendations

15

Laboratory Evaluation Program Comparing results, variability and others

Experiment 1 – Preliminary evaluation (more tests, fewer materials)

Experiment 2 – Detailed evaluation (fewer tests, more materials)

Experiment 3 – Modifications to drying and soaking methods in AASHTO T 85 and T84

Experiment 4 – Effect of P200 on AASHTO T 84 results Experiment 5 – Zero-time reading for Phunque method

16

Results of Experiments 1 & 2 Test Method Comments on Accuracy Equipment

Ruggedness Ease of

Use Time Eqmt

Cost Total Operator AASHTO T 85 / ASTM C 127

Current standard Good Manual 3 days 30 min. $100 ~ $600

AASHTO TP 77 (Phunque Flask)

Less accurate results for absorption, Gsb and Gssd, especially for

absorptive aggregate

Fragile in current design

Manual 2 days 2 hrs $500

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Comparing Absorption

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

Elmore Gravel

PS Coarse RC LMS Coarse

BF Slag Coarse

RE Concrete

Abs

orpt

ion

(%)

Test Material

T85

Phunque

19

Comparing Gsb

2.30

2.35

2.40

2.45

2.50

2.55

2.60

2.65

2.70

2.75

Elmore Gravel

PS Coarse RC LMS Coarse

BF Slag Coarse

RE Concrete

Gsb

Test Material

T85

Phunque

20

Results of Experiments 1 & 2 Test Method Comments on Method Equipment

Ruggedness Ease of

Use Time Eqmt

Cost Total Operator AASHTO T 84 / ASTM C 128

Current standards; concerns regarding materials with high P200 content

Good Manual 3 days 1.5 hrs $100 ~ $300

Modified AASHTO T 84 (Removal of P200)

Eliminates effects of P200; requires another test for P200. Similar or better precision as T 84.

Good Manual 3 days 1.5 hrs $100 ~ $300

ASTM D 7172 (SSDetect)

Yields more rational & objective method of determining SSD condition. Specific gravity and absorption results are different than T84.

Good Auto 1 day 1 hr $7,056

AASHTO TP 77 (Phunque Flask)

Yields less accurate measurements of absorption, Gsb and Gssd , especially for absorptive aggregate

Fragile in current design

Manual 2 days 2 hrs $500

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22

Experiment 3: Evaluating Drying Options Drum Split

replicates Sieve

over #4 Wash dust Oven Dry Soak 15

hrs Test Oven Dry Back

Drum Split replicates

Sieve over #4

Wash dust

undried condition

Soak 15 hrs Test Oven Dry

Back


Sieve over #4

Wash dust

Vacuum Dry

Soak 15 hrs Test Vacuum

Dry Back

T85


Sieve over #4

Wash over #200 Oven dry Soak for

15 hrs Test Oven dry back


Sieve over #4

Wash over #200

undried condition

Soak 15 hrs Test Oven Dry

Back


Sieve over #4

Wash over #200

Vacuum Dry

Soak 15 hrs Test Vacuum

Dry Back

T84

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Comparing Absorption, T85 3.

6

1.0

2.0 2.

4

3.9

4.5

1.1

2.2 2.4

4.7

2.5

1.0

1.8 1.9 2.

2

0

1

2

3

4

5

6

7

BF Slag Coarse Elmore Grav PS Coarse RC LMS Coarse RE Concrete

Abso

rptio

n (%

)

Oven DryNatural MoistureCoreDry

More water in permeable voids

Not enough suction to dry water

Undried

24

Comparing Absorption, T84 0.

4

1.8 1.8

3.1

1.7

0.2

2.8

1.0

2.5

1.1

0.3

1.4

1.2

3.4

1.1

0

1

2

3

4

5

6

7

Ark NS BF Slag Fine PS Fine RC LMS Fine TX Sand

Abso

rptio

n (%

)

Oven DryNatural MoistureCoreDryUndried

Undried and CoreDry have less effect on T84

25

Experiment 3: Evaluating Soaking Methods

T85 Drum Split

replicates Sieve

over #4 Wash dust Oven dry Soak 15 hrs Test Oven dry

back


Sieve over #4

Wash dust Oven dry Vacuum soak 5,

10, 15 min. Test Oven dry back


Sieve over #4

Wash over #200 Oven dry Soak 15 hrs Test Oven dry

back


Sieve over #4

Wash over #200 Oven dry Vacuum soak 5,

10, 15 min. Test Oven dry back

T84

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Comparing Soaking Methods, T85 Results Materials P-Value Significance? Grouping Using Tukey’s Method

15-hr Soak 5-min Vac. 10-min Vac. 15-min Vac. Gsa BF Slag Coarse 0.000 Yes A A A B

Elmore Grav 0.001 Yes A B B B PS Coarse 0.148 No A A A A RC LMS Coarse 0.002 Yes A B B B

RE Concrete 0.000 Yes A B B B Gsb BF Slag Coarse 0.605 No A A A A

Elmore Grav 0.517 No A A A A PS Coarse 0.166 No A A A A RC LMS Coarse 0.000 Yes A A A B

RE Concrete 0.088 No A A A A Gssd BF Slag Coarse 0.000 Yes A A A B

Elmore Grav 0.513 No A A A A PS Coarse 0.663 No A A A A RC LMS Coarse 0.004 Yes A A A B

RE Concrete 0.072 No A A A A Abs BF Slag Coarse 0.000 Yes A A A B

Elmore Grav 0.209 No A A A A PS Coarse 0.000 Yes A A B B RC LMS Coarse 0.000 Yes A B B B

RE Concrete 0.006 Yes A B B B

27

Comparing Soaking Methods, T84 Results Materials P-Value Significance? Grouping Using Tukey Method

15-hr Soak 5-min Vac. 10-min Vac. 15-min Vac. Gsa Ark NS 0.396 No A A A A

BF Slag Fine 0.039 Yes A A A B PS Fine 0.033 Yes A A A B RC LMS Fine 0.200 No A A A A

TX Sand 0.498 No A A A A Gsb Ark NS 0.269 No A A A A

BF Slag Fine 0.745 No A A A A PS Fine 0.002 Yes A A A B RC LMS Fine 0.480 No A A A A

TX Sand 0.056 No A A A A Gssd Ark NS 0.361 No A A A A

BF Slag Fine 0.792 No A A A A PS Fine 0.001 Yes A A A B RC LMS Fine 0.517 No A A A A

TX Sand 0.053 No A A A A Abs Ark NS 0.227 No A A A A

BF Slag Fine 0.483 No A A A A PS Fine 0.003 Yes A B B B RC LMS Fine 0.386 No A A A A

TX Sand 0.054 No A A A A

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Findings of Experiment 3 Testing aggregate without initial drying saves up to 4

hours Testing undried aggregate yielded consistent results for low

absorption coarse aggregate, but had inconsistent effects on fine aggregates.

Using vacuum soaking method saves up to 15 hours Vacuum soaking aggregate for 5- or 10-min. yield results

comparable to those of 15-hour soaking method Absorption results can be significantly affected by drying and

soaking method for highly absorptive methods

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Evaluation Plan

Drums Split 36 replicates

Sieve over #4

Wash over #200

Keep +#200 Oven Dry

Drums Sample enough material Oven Dry Dry sieve

over #200 Keep all -#200

Mix NS and RC LMS with P200 + clay to create 12 blends (Table 8)

Soak 15 hours

Test

Step 1: Prepare +#200 samples using Arkansas Natural Sand and RC Limestone

Step 2: Prepare -#200 samples from TX Limestone Fine Aggregate

Step 3: Prepare samples for testing

Step 4: Test samples as follows: •Conduct AASHTO T84 on the 24 blends •Conduct AASHTO T84 on NS and RC LMS materials retained on the No. 200 sieve •Conduct ASTM C110 on the blend of clay and P200 from the Texas limestone •Determine the sand equivalent for P200 material from the Texas limestone

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Comparing Abs for NS Blends

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

100 95 90 80 70 95 95 90 90 80 70 80

0 5 10 20 30 3.75 2.5 7.5 5 15 22.5 10

0 1.25 2.5 5 7.5 10

Abs(

%)

+200

-200

Clay

Differences are insignificant Differences are significant, higher absorption values

32

Comparing Gsb for NS Blends

2.02.12.22.32.42.52.62.72.82.93.0

100 95 90 80 70 95 95 90 90 80 70 80

0 5 10 20 30 3.75 2.5 7.5 5 15 22.5 10

0 1.25 2.5 5 7.5 10

Gsb

+200

-200

Clay

Differences are insignificant Differences are significant

%0.14650.2

)0.5100(400.2100 =

−×

−=VMA

33

Findings of Experiment 4 If P200 does not contain highly absorptive clays,

increasing P200 content does not yield statistically different results

However, if P200 is greater than 10%, testing aggregate with P200 may yield lower absorption due to over-drying

If P200 contains highly absorptive clays, it significantly affects T84 results

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Recommendations

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Ruggedness Study – T85, <2% Abs ID Variable Low

Value High Value

% of Times Significant Gsb Gssd Gsa Abs

A Section 7.2 – Aggregate size +#8 +#4 33 17 17 50

B Section 8.1 – Moisture condition

oven-dried undried 17 0 50 50

C Section 8.1 – Cooling time 0 3 hrs 0 0 0 33

D Section 8.1 – Vac. time 9 min. 11 min. 17 17 0 17

E Section 8.1 – Vacuum pressure

3.3 -3.6kPa

3.8 -4.1kPa 0 0 0 17

F Section 8.4 – Water temperature

21 - 22°C

24 - 25°C 50 50 17 33

G Section 8.5 – Cooling time 0 3 hrs 0 0 50 50

36

Ruggedness Study – T85, >2% Abs ID Variable Low

Value High Value


A Section 7.2 – Aggregate size +#8 +#4 0 0 0 17

B Section 8.1 – Moisture condition

oven-dried undried 0 17 50 50

C Section 8.1 – Cooling time 0 3 hrs 0 33 50 33

D Section 8.1 – Soak time 15 hrs 20 hrs 0 0 0 17

E Section 8.3 – Drying sample dry cloth damp

cloth 33 0 17 33

F Section 8.4 – Water temperature

21 - 22°C

24 - 25°C 17 33 50 50

G Section 8.5 – Cooling time 0 3 hrs 0 0 33 50

37

Ruggedness Study – T84, <2% Abs ID Variable Low

Value High Value


A Section 7.1 – Aggregate size

with P200

without P200 100 83 67 100

B Section 7.1 – Aggregate size dry sieve wash 17 17 0 33

C Section 7.1.1 – Moisture condition

oven-dried

in-situ moisture 0 0 0 17

D Section 7.1.1 – Vacuum time 9 min. 11 min. 67 67 0 67

E Section 7.2.1 – Cone test 25 drops at once

25 drops in 4 sets 50 50 0 17

F Section 8.2 – Agitation mech. agitation manual 17 17 0 33

G Section 8.3 – Cooling time 0 1.5 hrs

(~50°C) 17 33 100 67

38

Ruggedness Study – T84, >2% Abs ID Variable Low

Value High Value


A Section 7.1 – Aggregate size

with P200

without P200 100 100 67 100

B Section 7.1 – Aggregate size dry sieve wash 67 33 17 83

C Section 7.1.1 – Soak type immerse 6% moisture 0 33 17 33

D Section 7.1.1 – Soak time 15 hrs 20 hrs 100 83 17 100

E Section 7.2.1 – Cone test 25 drops at once

25 drops in 4 sets 17 17 0 0

F Section 8.2 – Agitation mech. agitation manual 50 67 33 33

G Section 8.3 – Cooling time 0 1.5 hrs

(~50°C) 67 17 67 83

39

Presentation Outline Research need and objectives Results Task 1: Identifying test methods Task 4: Conducting lab evaluation program Task 6: Conducting ruggedness study Task 8: Revising test methods

Recommendations

40

Recommendations Tests selected

Coarse aggregate: AASHTO T 85 Fine aggregate: AASHTO T 84 & SSDetect

Modifications to AASHTO T 85 Testing coarse aggregate in undried condition could be

considered for aggregate with Abs < 2% If Abs < 2%, vacuum soaking for 10+0.5 min can be used If Abs > 2%, soaking for 15 to 17 hours should be used Bath temperature is 23.0 ± 1ºC instead of 23.0 ± 1.7ºC

41

Recommendations Modifications to AASHTO T 84

Testing fine aggregate without P200 fraction Testing fine aggregate in undried condition If Abs < 2%, vacuum soaking for 10+0.5 min can be used If Abs > 2%, soaking for 15 to 17 hours should be used Fill pycnometer with water at 23.0 ± 1ºC instead of 23.0 ±

1.7ºC Use consistent methods for cone test and eliminating

bubbles from pycnometer

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Thank You