Transcript
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
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Coarse Aggregate Angularity
• Historical
• Currently used or recommended
• Advanced topics
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Coarse Agg. Angularity
• Traditional and Newly Recommended
• Particle Index
• Flat and elongated
• Percent crushed faces
• Uncompacted voids
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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
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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
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Flat and Elongated Particles
Max : min
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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
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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
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Nord Jaws
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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
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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
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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)
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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
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Uncompacted Voids in Coarse Aggregate
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Uncompacted Voids in Coarse Aggregate
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Uncompacted Voids in Coarse Aggregate
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R2 = 0.8638
R2 = 0.8743
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0 10 20 30 40
% Flat or Elongated (3:1)
Un
com
pac
ted
Vo
ids,
% (
Co
arse
A
gg
.)
Gravel Stone
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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
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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
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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
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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
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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
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10
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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
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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
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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
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Micro Deval Abrasion Test
Small steel balls
Aggregate in water
Steel jar
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Micro Deval Abrasion Test
Step 5: Calculate loss
%Loss = (Orig. wt – Dry wt. after) x 100 Orig. wt
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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
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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
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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
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Gyratory Compactor
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Soundness
• Evaluates coarse aggregate resistance to weathering (freeze/thaw)
• Most common methods
• Sodium or magnesium sulfate
• AASHTO T104
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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.
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Soundness Test MethodAASHTO T104
• Aggregates prepared for soaking and drying
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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
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Soundness Test MethodAASHTO T104
• Aggregate rinsed at the end of the test
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Soundness Test MethodAASHTO T104
• The rinse water is checked to determine when salts are removed
• Water is not cloudy when tested
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Soundness Test MethodAASHTO T104
• Oven dry after rinsing
• Conduct sieve analysis to determine change in gradation
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Soundness AASHTO T104
Before After
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Soundness
• Advanced Topics
• Aggregate Durability Index
• ASTM C88 (AASHTO T210)
• Soundness by freezing and thawing
• AASHTO T103
• Canadian Freeze/Thaw Test
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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
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Aggregate Durability Index ASTM D3744
• Step 1: Washed and dried aggregate agitated in mechanical washing vessel for 10 min.
(photo to be added)
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Aggregate Durability Index ASTM D3744
• Step 2: Wash water and minus 0.075 mm fines collected and mixed with stock calcium chloride solution
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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
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Freezing and Thawing (AASHTO T103)
• Aggregate washed, dried, and separated into individual fractions
• 3 methods for saturation
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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
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QUESTIONS?
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