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