Block 8 coarse aggregate 13

Aggregate Coarse Aggregates 1

Coarse Aggregates

Senior/GraduateHMA Course

2Aggregate Coarse Aggregates

Deleterious MaterialsASTM C142

• Mass percentage of contaminants such as clay lumps, shale, wood, mica, and coal

• Test

• Wet sieving agg. size fraction over specified sieves

• Mass lost = % contaminants

• Range from 0.2% to 10%, depending upon contaminant


Coarse Aggregate Angularity

• Historical

• Currently used or recommended

• Advanced topics


Coarse Agg. Angularity

• Traditional and Newly Recommended

• Particle Index

• Flat and elongated

• Percent crushed faces

• Uncompacted voids


Particle Index ASTM D3398

• Vol. of voids between packed, uniform-size aggregate particles indicate combined effect of shape, angularity and surface texture

• 203 mm (8 in), 152 mm (6 in), 102 mm (4 in), 76 mm (3 in), and 51 mm (2 in) diameter mold

• Blows on each of three layers 50 mm above surface

• Ia = 1.25 V10 - 0.25 V50 - 32.0

• Particle index increases with angularity

• Ia weighted on basis of % of each fraction


Flat and Elongated Particles

• ASTM D4791

• Flat

• Elongated

• Total flat and elongated

• Superpave

• Flat or Elongated

• Maximum to minimum dimension

• 1:5

• 1:3

• 1:2


Flat and Elongated Particles

Max : min


Semi-Automated Flat and Elongated

• Martin Marietta has developed semi-automated method

Digital Height Caliber

Handle for raising and

lowering foot

Foot and base plate

Computer for data acquisition and

analysis program


Nord Jaws

• Place agg under foot in largest dimension

• Step on foot pedal to enter data

• Rotate agg to least dimension

• Step on foot pedal again to enter least

• Place aggregate particle in appropriate ratio bowl

• Separates agg into 2:1, 3:1, 4:1, and 5:1


Nord Jaws


Nord Jaws


Percent Fractured FacesASTM D5821

• Retained on 4.75 mm (#4)

• Fractured = min 25% of area

• Clean, well-defined edges

• Can specify

• 1 or more fractured faces

• 2 or more fractured faces


Percent Fractured FacesASTM D5821

0% Crushed 2 or More Fractured Faces


Coarse Aggregate AngularityHMA 1995

2 Fractured Faces:13 States with requirementsRange from 30 (all mixes, AZ) to 100 (Surface, IN)

1 Fractured Face:30 States with requirementsRange from 40 (Ohio) to 100 (Utah)

Usually designated for either high quality HMA or wearing courses


Uncompacted VoidsAASHTO TP 56

• Up-scaled version of the fine aggregate angularity test discussed in preceding sections

• Two methods can be used

• Standard gradation (Method A)

• Each sieve size (Method B)


Uncompacted VoidsAASHTO TP 56

• Method APass Retained 19 mm 12.5 m

19 mm 12.5 mm 1,740 -----12.5 mm 9.5 mm 1,090 1,9709.5 mm 4.75 mm 2,170 3,030

• Method B

• Uses 5,000 grams of each fraction, tested individually

• A weighted average is used to combine results


Uncompacted Voids in Coarse Aggregate






R2 = 0.8638

R2 = 0.8743

43

44

45

46

47

48

49

50

51

52

53

0 10 20 30 40

% Flat or Elongated (3:1)

Un

com

pac

ted

Vo

ids,

% (

Co

arse

A

gg

.)

Gravel Stone


Image Analysis

• University of Arkansas

• Aggregate spread on glass plate

• High resolution video camera

• Modern digital imaging hardware, analysis techniques and computer analysis used

• Uses two parameters

• EAPP

• Roughness Index


ToughnessDegradation due to handling, construction, and in-

service

• Traditional or newly recommended

• Los Angeles Abrasion

• Micro-Deval

• Advanced topics

• Aggregate Impact Value

• Aggregate Crushing Value

• Gyratory Compactor


LA AbrasionASTM C131

• Step 1: prepare specific agg gradation

Passing Retained A B C D37.5 mm 25.0 mm 1,250 --- --- ---25.0 mm 19.0 mm 1,250 --- --- ---19.0 mm 12.5 mm 1,250 2,500 --- ---12.5 mm 9.5 mm 1,200 2,500 --- ---9.5 mm 6.3 mm --- --- 2,500 --6.3 mm 4.75 mm --- --- 2,500 ---4.75 mm 2.36 mm --- --- --- 5,000

No. Steel Balls 12 11 8 6


LA Abrasion

• Step 2: Rotate for 500 revolutions at 30 to 33 rpm’s


LA Abrasion (ASTM C131)

• Step 3. Empty cylinder, remove balls, and make preliminary separation of agg on 1.70 mm (No. 12) sieve

Steel balls need to be removed


LA Abrasion (ASTM C131)

• Step 4: Wash material retained on No. 12 sieve, dry to constant weight, and determine dry (cooled) mass

• % Loss = (original wt – final wt) x 100

original wt


0

10

20

30

40

50

60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Agg. Source No.

LA

Ab

rasi

on

Lo

ss,

%

Good

Poor

Good PoorFair

Source 15 had poor performance due to rutting and bleedingThis would not be related to toughness


Micro Deval Abrasion Test• One of two gradations can be used

19.0 to 9.5 mm 3.2 to 4.75 mm Sieve Size Amount AmountPass Retained Retained Retained19.0 16.0 mm 375 g ------16.0 13.2 mm 375 g 375 g13.2 9.5 mm 750 g 750 g 9.5 6.7 mm ------- 375 g 6.7 4.75 mm ------- 375 g


Micro Deval Abrasion Test

Step 1: Dry, weighed sample with 2-L water for 1 hour

Step 2: Sample and water with 5,000 g steel balls into jar; roll at 100 rpms for 2 hours

Step 3: Wash sample and balls out of jar over stacked 4.75 and 1.18 mm sieves

Step 4: Combine material from both sieves and dry to constant mass at 110oC



Small steel balls

Aggregate in water

Steel jar



Step 5: Calculate loss

%Loss = (Orig. wt – Dry wt. after) x 100 Orig. wt


0

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Agg. Source No.

Mic

ro-D

eval

Los

s, %

Good

Fair

Poor

Criteria = 18%

Good PoorFair



• Ontario Ministry of Transportation (MTO) has:

• Standardized equipment

• Reference materials for calibration

• 12% loss for 19 to 9.5 mm

• 14.5% loss for 13.2 to 4.72 mm


Gyratory Compactor

• 0.6 MPa (87 psi), 1.25o angle, 30 rpm/min

• Can be use with just coarse, fine, or blend

• Gradation before and after specified numbers of gyrations

• Differences can be analyzed for given particle sizes

• Research indicates changes in % passing 4.75 mm (No. 4) good indicator


Gyratory Compactor


Soundness

• Evaluates coarse aggregate resistance to weathering (freeze/thaw)

• Most common methods

• Sodium or magnesium sulfate

• AASHTO T104


Soundness Test MethodAASHTO T104

• Repeated immersions in sodium or magnesium sulfate

• Followed by oven drying

• Salts precipitate in permeable voids during drying

• Salt expands and contracts with wet/dry cycling

• Simulates in-service weathering of agg.



• Aggregates prepared for soaking and drying



• Aggregates soaked then transferred to oven to dry

• 1 cycle = one soak + one dry

• 5 cycles to 30 cycles used

• 5 to 10 most common



• Aggregate rinsed at the end of the test



• The rinse water is checked to determine when salts are removed

• Water is not cloudy when tested



• Oven dry after rinsing

• Conduct sieve analysis to determine change in gradation


Soundness AASHTO T104

Before After


Soundness

• Advanced Topics

• Aggregate Durability Index

• ASTM C88 (AASHTO T210)

• Soundness by freezing and thawing

• AASHTO T103

• Canadian Freeze/Thaw Test


Aggregate Durability IndexASTM D3744

• Resistance to producing clay-like fines when aggregates are subjected to mechanical agitation in the presence of water

• Especially suitable for basalt type aggregates containing interstitial montmorillonite


Aggregate Durability Index ASTM D3744

• Step 1: Washed and dried aggregate agitated in mechanical washing vessel for 10 min.

(photo to be added)



• Step 2: Wash water and minus 0.075 mm fines collected and mixed with stock calcium chloride solution



• Step 3: After 20 min of sedimentation, level read and height of level used to calculate the durability index

Dc = 30.3 + 20.8 cot(02.29 + 0.15 H)

Test method provides table of solutions for H in increments of 0.5 mm


Freezing and Thawing (AASHTO T103)

• Aggregate washed, dried, and separated into individual fractions

• 3 methods for saturation



• Method A

• Aggregates soaked in water for 24 hr

• Samples remained completely immersed during freezing and thawing

• 50 cycles typical



• Method B

• Aggregates soaked and subjected to vacuum of not over 25.4 mm (1 in) of mercury

• Penetration of water increased by using 0.5% by mass solution of ethyl alcohol and water

• Sample frozen/thawed in alcohol-water solution




• Method C

• Same as B except no alcohol is used



QUESTIONS?

Block 8 coarse aggregate 13

Documents

minaggregate coarse

aggregate coarse aggregates9

abrasion step

elongated superpave

abrasion astm c131 step

place aggregate particle

utah2 fractured faces

elongated maximum