02 - Aggregate Gradation - Memphis - Aggregate Gradation.pdfCurve. CIVL 3137 30 Dense-Graded...
Transcript of 02 - Aggregate Gradation - Memphis - Aggregate Gradation.pdfCurve. CIVL 3137 30 Dense-Graded...
Aggregate Gradation
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Important Properties
Hardness (resistance to wear)Durability (resistance to weathering)
Shape and surface texture
Relative density and absorptionGradation
Deleterious substancesCrushing strength
Soft and lightweight particlesChemical stability
Gradation Analysis
A gradation analysis (or sieve analysis) is a procedureused to assess the particle size distribution (gradation)of a granular material by allowing the material topass through a series of sieves of progressivelysmaller mesh size and weighing the amount ofmaterial that is stopped by each sieve as a fraction ofthe whole mass. The size distribution is often ofcritical importance to the way the material performsin use.
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Gradation Analysis
percent coarseror
percent retained
percent fineror
percent passing
Percentagesare calculatedby mass
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Gradation Chart
0
20
40
60
80
100
Perc
ent
Pass
ing
Total mass percent passing each sieve
100 10 1 0.1 0.01
Opening Size (mm)
(typically used for soil)
4.75
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Gradation Chart
0
20
40
60
80
100
Perc
ent
Pass
ing
Total mass percent passing each sieve
0.01 0.1 1 10 100
Opening Size (mm)
(typically used for aggregate)
4.75
Sieve Shakers
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Mary Ann Shaker
Screen Shakers
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Gilson Shaker
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Sieve Sizes Used in Construction
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Sieve Sizes Used in Construction
Openings vary bya factor of two
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Gradation Chart
0
20
40
60
80
100
0.010.1110100
Perc
ent
Pass
ing
(%)
Opening Size (mm)
1½" ¾" 3/8" 4 8 16 30 50 100 200
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Gradation Example
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Gradation Example
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Typical Aggregate Gradations
Open-graded aggregate
Gap-graded aggregate
Uniformly graded aggregate
Dense-graded aggregate
All of the particles are approximately the same size
Very little fine aggregate thus lots of void space between particles
Very little aggregate in the medium size range
Lots of different particle sizes thus very little void space
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Uniformly Graded Aggregate
0
20
40
60
80
100
0.010.1110100
Perc
ent
Pass
ing
Opening Size (mm)
1½" ¾" 3/8" 4 8 16 30 50 100 200
“clear”gravel
uniformsand
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Uniformly Graded Aggregate
Narrow range of sizesGrain-to-grain contactHigh void contentHigh permeabilityLow stabilityDifficult to compact
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Open-Graded Aggregate
0
20
40
60
80
100
0.010.1110100
Perc
ent
Pass
ing
Opening Size (mm)
1½" ¾" 3/8" 4 8 16 30 50 100 200
Opengradedgravel
Opengradedsand
Few finesFew fines
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Open-Graded Aggregate
Decent range of sizesVery few fine particlesGrain-to-grain contactHigh void contentHigh permeabilityHigh stability Difficult to compact
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Gap-Graded Aggregate
0
20
40
60
80
100
0.010.1110100
Perc
ent
Pass
ing
Opening Size (mm)
1½" ¾" 3/8" 4 8 16 30 50 100 200
Opengradedgravel
Opengradedsand
Gapgradedblend
Missingsizes
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Gap-Graded Aggregate
Wide range of sizesMissing middle sizesNo grain-to-grain contactModerate void contentModerate permeabilityLow stability Easy to compact
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Dense-Graded Aggregate
0
20
40
60
80
100
0.010.1110100
Perc
ent
Pass
ing
Opening Size (mm)
1½" ¾" 3/8" 4 8 16 30 50 100 200
Densegradedgravel
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Dense-Graded Aggregate
Wide range of sizesGrain-to-grain contactLow void contentLow permeabilityHigh stabilityDifficult to compact
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Fuller’s Curve
Fuller, W.B. and Thompson, S.E. “The laws of proportioning concrete," Transactions of the ASCE, v. 159, 1907.
0.50i
idpD
pi = percent passing ith sievedi = opening size of ith sieveD = maximum particle size
Produces the highest density and lowest void content
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Aggregate gradation curves: (a) maximum density gradations for 37.5 and4.75 mm sizes based on the Fuller relationship; (b) a uniform aggregate;(c) a gap-graded aggregate; (d) screenings.
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FHWA Maximum Density Curve
In 1962 FHWA published a modified version of Fuller’s equation with a different exponent.
0.450.50
ii
dpD
pi = percent passing ith sievedi = opening size of ith sieveD = maximum particle size
Produces the highest density and lowest void content
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Maximum density curves on Federal Highway Administration 0.45 power gradation chart.
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Dense-Graded Aggregate
0
20
40
60
80
100
0.010.1110100
Perc
ent
Pass
ing
Opening Size (mm)
1½" ¾" 3/8" 4 8 16 30 50 100 200
TDOT 411-D
MaximumDensityCurve
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Dense-Graded Aggregate
0
20
40
60
80
100
0 1 2 3 4 5
Perc
ent
Pass
ing
Opening Size (mm) Raised to the 0.45 Power
200
TDOT 411-D
1/2" 5/8"
MaximumDensity
Curve