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
3Aggregate Coarse Aggregates
Coarse Aggregate Angularity
• Historical
• Currently used or recommended
• Advanced topics
4Aggregate Coarse Aggregates
Coarse Agg. Angularity
• Traditional and Newly Recommended
• Particle Index
• Flat and elongated
• Percent crushed faces
• Uncompacted voids
5Aggregate Coarse Aggregates
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
6Aggregate Coarse Aggregates
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
7Aggregate Coarse Aggregates
Flat and Elongated Particles
Max : min
8Aggregate Coarse Aggregates
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
9Aggregate Coarse Aggregates
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
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Nord Jaws
11Aggregate Coarse Aggregates
Nord Jaws
12Aggregate Coarse Aggregates
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
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Percent Fractured FacesASTM D5821
0% Crushed 2 or More Fractured Faces
14Aggregate Coarse Aggregates
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
15Aggregate Coarse Aggregates
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)
16Aggregate Coarse Aggregates
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
17Aggregate Coarse Aggregates
Uncompacted Voids in Coarse Aggregate
18Aggregate Coarse Aggregates
Uncompacted Voids in Coarse Aggregate
19Aggregate Coarse Aggregates
Uncompacted Voids in Coarse Aggregate
20Aggregate Coarse Aggregates
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
21Aggregate Coarse Aggregates
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
22Aggregate Coarse Aggregates
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
23Aggregate Coarse Aggregates
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
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LA Abrasion
• Step 2: Rotate for 500 revolutions at 30 to 33 rpm’s
25Aggregate Coarse Aggregates
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
26Aggregate Coarse Aggregates
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
27Aggregate Coarse Aggregates
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
28Aggregate Coarse Aggregates
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
29Aggregate Coarse Aggregates
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
30Aggregate Coarse Aggregates
Micro Deval Abrasion Test
Small steel balls
Aggregate in water
Steel jar
31Aggregate Coarse Aggregates
Micro Deval Abrasion Test
Step 5: Calculate loss
%Loss = (Orig. wt – Dry wt. after) x 100 Orig. wt
32Aggregate Coarse Aggregates
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
33Aggregate Coarse Aggregates
Micro Deval Abrasion Test
• 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
34Aggregate Coarse Aggregates
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
35Aggregate Coarse Aggregates
Gyratory Compactor
36Aggregate Coarse Aggregates
Soundness
• Evaluates coarse aggregate resistance to weathering (freeze/thaw)
• Most common methods
• Sodium or magnesium sulfate
• AASHTO T104
37Aggregate Coarse Aggregates
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.
38Aggregate Coarse Aggregates
Soundness Test MethodAASHTO T104
• Aggregates prepared for soaking and drying
39Aggregate Coarse Aggregates
Soundness Test MethodAASHTO T104
• 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
40Aggregate Coarse Aggregates
Soundness Test MethodAASHTO T104
• Aggregate rinsed at the end of the test
41Aggregate Coarse Aggregates
Soundness Test MethodAASHTO T104
• The rinse water is checked to determine when salts are removed
• Water is not cloudy when tested
42Aggregate Coarse Aggregates
Soundness Test MethodAASHTO T104
• Oven dry after rinsing
• Conduct sieve analysis to determine change in gradation
43Aggregate Coarse Aggregates
Soundness AASHTO T104
Before After
44Aggregate Coarse Aggregates
Soundness
• Advanced Topics
• Aggregate Durability Index
• ASTM C88 (AASHTO T210)
• Soundness by freezing and thawing
• AASHTO T103
• Canadian Freeze/Thaw Test
45Aggregate Coarse Aggregates
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
46Aggregate Coarse Aggregates
Aggregate Durability Index ASTM D3744
• Step 1: Washed and dried aggregate agitated in mechanical washing vessel for 10 min.
(photo to be added)
47Aggregate Coarse Aggregates
Aggregate Durability Index ASTM D3744
• Step 2: Wash water and minus 0.075 mm fines collected and mixed with stock calcium chloride solution
48Aggregate Coarse Aggregates
Aggregate Durability Index ASTM D3744
• 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
49Aggregate Coarse Aggregates
Freezing and Thawing (AASHTO T103)
• Aggregate washed, dried, and separated into individual fractions
• 3 methods for saturation
50Aggregate Coarse Aggregates
Freezing and Thawing (AASHTO T103)
• Method A
• Aggregates soaked in water for 24 hr
• Samples remained completely immersed during freezing and thawing
• 50 cycles typical
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Freezing and Thawing (AASHTO T103)
• 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
• 6 cycles typical
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Freezing and Thawing (AASHTO T103)
• Method C
• Same as B except no alcohol is used
• 25 cycles typical
53Aggregate Coarse Aggregates
QUESTIONS?
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