1

AGGREGATES

KH4444

ROAD CONSTRUCTION

2

1.1 INTRODUCTION

Natural rocks as outcrops near surface or gravel deposits along river streams

Natural igneous, sedimentary, and metamorphic

Other lightweight (heated clay) and slag

Igneous crystalline, cooling of magma, classified based on grain size or acidity

Sedimentary deposition of rock residue or inorganic remains, classification based on predominant mineral calcareous, siliceous, or argillaceous

Metamorphic rocks subjected to heat an/or pressure >> change mineral structure, generally crystalline in nature

3

1.1 INTRODUCTION cont..

Gravel breakdown of natural rocks in waterways, smooth, rounded >> need to be crushed B4 use

Sands the most resistant final residue of rocks, predominantly quartz, often contain silt or clay >> maybe need to be washed

Slag byproduct of steel, copper or tin, glassy or honeycombed. Good skid resistance but high absorption

Physical properties important, chemical properties to ensure bonding

Important to sample and test on regular basis to ensure properties consistent and meet the specification

4

1.2 AGGREGATE PRODUCTION & SAMPLING

Agg physical characteristic determined by parent rock and production process

The production process in the quarry can significantly improve the quality of the aggregate by eliminating of the weaker rocks and by the

effect of crushing on the particle shape and gradation of the agg.

Inferior rock stripped, wasted tru grizzly

Aggregate processing:

Excavation

Transportation

Crushing

Sizing

Washing*

5

1.2.1 Quarry Operations

Basic purpose to remove sound rock from face via blast, then use crushers, pulverizers, screening to separate into diff. size

Desirable to produce cube shaped not flat or elongated

Operation : remove overburden >> blast (danger) >> transport via truck to feeder >> grizzly (waste > jaw >> screen (stockpile) >> cone >> screen

Primary crusher reduce blasted rock to max size ranging from 8 - 1

Secondary & tertiary reduce to desired size

Stockpiled according to size

6

1.2.1 Quarry Operations

Four mechanical reduction mechanism impacts, attrition, shearing,

compression (refer figure 3-2 to 3-6)

1. Impact sharp, instantaneous impingement of object against another (most crushers)

harder rocks use of more compression crushers than impact.

1. Attrition rubbing between two hard surfaces (hammermill, gyratory, cone)

2. Shear trimming or cleaving action (single roll crusher combine with other mechanisms)

3. Compression use compressive forces between surfaces (jaw)

Select crusher type based on rock type and production req.

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1.2.2 Aggregate Sampling

B4 test, sample must be obtained from source random (QC) or representative (mix design)

Tests are meaningless if improper sampling

Samples taken from stockpile, belts, bins, or truck

Avoid segregated samples (truck, bin) >> best from conveyor

Representative sample - combine random samples truout time/place

Stockpile coarse (bottom edge), climb to mid, take underneath stockpile, taken at several location >> combine >> representative

Reduce sample prior testing via quartering or splitting

***TEST results depends on technique used

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1.2.2 Aggregate Sampling

Why sampling is important?

1. To evaluate the potential quality of a proposed aggregate source.

Does new source meet aggregate specifications?

2. To determine compliance with project specification requirements.

Do current aggregates meet specifications?

9

1.3 AGGREGATE PROPERTIES

Physical properties is primary concern

Physical (density, porosity, strength) and chemical (wetting, adhesion, stripping) are functions of composition and structure of minerals in aggregate

1.3.1 Aggregate Mineralogy Composed of minerals silica, feldspar, ferromagnesian, carbonate

and clay

Mineral composition also affect skid resistance quartz and feldspar

Presence of surface coating and deleterious substance affect bonding and moisture susceptibility

Most important effect of mineralogy its influence on adhesion and moisture damage (carbonate bonds better than siliceous)

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1.4 PHYSICAL PROPERTIES OF AGGREGATES

Classification by size: 1. Coarse Aggregate

Retained on 4.75 mm (No. 4) ASTM D692

Retained on 2.38 mm (No. 8) Asphalt Institute

Retained on 2.00 mm (No. 10) HMA Book

2. Fine Aggregate

Passing on 4.75 mm (No. 4) ASTM D1073

Passing on 2.38 mm (No. 8) Asphalt Institute

3. Mineral Filler

At least 70% passed 75 m ASTM D242

11

For HMA need to be hard/tough/strong, durable/sound, properly graded; consist of cubical, low WA; and have

clean, rough, and hydrophobic surfaces

Suitability for HMA determined by evaluating gradation, cleanliness, toughness, soundness, surface texture,

particle shape, WA, and affinity

Characteristics, significant, tests and specification (T 3-6)

JKR/SPJ/1988 toughness, soundness, shape, WA, polishing, cleanliness, gradation, affinity

12

1.4.1 Toughness/Abrasion Resistance

Agg transmit wheel load tru internal friction >> must be abrasion, polishing, disintegration and crushing

resistant.

Agg undergo all this during manufacturing, placing, construction and service life.

Tests involved ACV, LAAV

ACV 30, LAAV < 40

13

1.4.2 Durability and Soundness

Estimates resistance to weathering (breakdown and

disintegration) Soundness Test

* Simulates freeze/thaw action by successively wetting and

drying aggregate in sodium sulfate or magnesium

sulfate solution

+ One immersion and drying is considered one cycle

* Result is total percent loss over various sieve intervals for

a prescribed number of cycles

+ Max. loss values typically range from 10 to 20% per

5 cycles (depends on aggregate)

14

1.4.3 Particle Shape & Surface Texture

Cubical not flat or elongated shape (angular better interlock and internal friction), rough texture increase bond with AC.

Tests particle index (ms 106 - time consuming), fractured face, EI & FI

JKR/SPJ/1988 specifies material shall be crushed rock, or crushed gravel, or mixture of crushed and natural

aggregates, which is hard, durable

Flaky 30, Fracture face 80%

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1.4.4 Cleanliness & Deleterious Materials

Absence of foreign or deleterious material.

Tests sand equivalent, clay lumps, PI

JKR/SPJ/1988 aggregate shall be . clean and essentially free from clay and any deleterious materials

PI 6

Clean?, deleterious?

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1.4.5 Specific Gravity

Ratio weight of mat. to water of equal volume at 23C, useful in making weight-vol conversion

In metric units, G simply:

G = weight / vol

Four Gs apparent, bulk, effective, bulk impregnated: (F 3-9)

1. Apparent weight / vol solid Dry

2. Bulk weight / overall vol SSD

3. Effective weight / (overall vol asp asorb. pores)

4. Bulk impregnated eff. but immerse in asphalt

Gsb < Gse < Gsa

17

1.4.5 Specific Gravity, cont

G and absorption of coarse & fine

Weighted G, aggregate of various sizes/stockpiles

P1 + P2 + + Pn

G = P1 + P2 + + Pn

G1 + G2 + + Gn

Example 3 -1 and 3 2, pages 114 -117

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1.4.6 Gradation

Distribution of particle sizes expressed as a percentage of total weight (total % passing various sieve sizes)

Determined by sieve analysis

Graphically presented on semi-log graph

3 gradations : well (dense), uniform (single), gap graded (F 3-10)

Gradation affect stiffness, stability, durability, permeability, workability,

fatigue, skid, and moisture damage resistance >> limits on the agg

gradation to be used in HMA

HMA need to have sufficient air voids in grading mix for durability (permits

enough AC to be incorporated) and avoid bleeding and rutting (yet

still have enough air space in mixture)

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1.4.8 Gradation, cont

Two designation for max size

1. Max size smallest sieve tru which 100% particles pass

2. Nominal max size largest sieve retain some agg (

20

Sieve Analysis

To determine gradation dry sieve and washed-sieve

Washed more accurate but dry faster and often used (measured amount passing 75 m lower)

Example 3-3 pg 122

21

Aggregate Blending

Two or more stockpile need to be blended to get max density and desired void for HMA (or meet spec envelope)

Reasons for blending:

1. Obtain desired gradation

2. Single natural or quarried material not enough

3. Economical to combine natural and processed materials

Normally three or more stockpiles plus mineral filler

Most common method for determining proportion trial & error

Example 3-4 and 3-5

Blended aggregate specific gravity

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Questions?

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Igneous Rock

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Sedimentary Rock

25

Metamorphic Rock

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Gravel, Sand, Slag

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Simplified Crusher Set-up

28

Blasting

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Impact (F3-2)

30

Impact and Attrition (F3-4)

Hammermill

31

Shear, Impact and Compression (F3-5)

Single-roll Crusher

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Compression and Impact (F3-6)

Jaw

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Natural sands and gravels 2 sources, underwater and land

1. Underwater sources lakes and river Use barge-mounted dredges, draglines,

scoops, conveyors or pumps

Relatively clean 2. Land sources gravel or sand pits

Use bucket loaders and back hoes

Excavation

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Excavation

35

Crushed stone and rock 1. Rock depths < 50, overburden washed out during

processing

2. Rock depths > 50, remove overburden (soil stripped with bulldozers and scrapers

Blasting required

Excavation

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Excavation

37

Crushing

38

Partially Crushed

River Gravel

River Gravel

Crushed Rock

Crushing

39

Land Transportation

40

Rail Transportation

41

Barge / Water

Transportation

42

Sizing

43

* Prevent segregation and contamination * Good stockpiling = uniform gradations

- Short drop distances - Minimize moving - Don't use "single cone" method - Separate stockpiles

Stockpiling

44

Stockpiling

45

Sampling from Fine

Aggregate Stockpile

Sampling from Stockpile

46

Sampling from Conveyor

47

Splitter

48

Classification based on Surface Charges

F3-7

49

Characteristics & Tests of Aggregate for HMA

Characteristics Test Malaysian Requirement

Hardness/Toughness MS-30, ASTM C131 ACV < 30, LAAV < 40

Soundness AASHTO T104 Loss < 12%

Shape & Texture MS-30 FI < 30, > 80% fracture

Polishing resistance MS-30 PSV > 40

Stripping resistance AASHTO T182 Coated > 95%

SG and WA MS-30 WA < 2%

Gradation and size BS 1377 Minimum & maximum

depends on use & mix

Cleanliness &

deleterious material

BS 1377 Free from dust, clay,

vegetative and organic, and

deleterious substances

PI < 6%

50

Toughness

* Aggregate Crushing Value (MS 30: Part 8: 1995)

Relative measure of the resistance of an aggregate to

crushing under a gradually applied compressive load

Test specimen compacted into steel cylinder

subjected to load applied tru plunger.

Degree of crushing assessed by sieving test and

taken as a measure of aggregate crushing value

(ACV)

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ACV

52

* Los Angeles Abrasion (AASHTO T96, ASTM C131):

Resistance of coarse agg to abrasion and

mechanical degradation during handling,

construction and use

* Aggregate at standard gradation subjected to

damage by rolling with prescribed number of steel

balls in large drum for a given number of rotations

* Result expressed as % changes in original weight

Abrasion Resistance

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LA Abrasion Test

- Approx. 10% loss for extremely hard igneous rocks - Approx. 60% loss for soft limestones and sandstones

54

Soundness

(AASHTO T 104)

55

Soundness

Before After

56

Flakiness & Elongation

57

Flakiness & Elongation (MS 30)

58

* ASHTO T176, ASTM D2419

- Used to estimate the relative proportions of fine agg. and clay-like or plastic fines and dust.

SE = Sand Reading Clay Reading

Sand

Reading

Clay Reading

Flocculating

Solution

Suspended

Clay

Sedimented

Aggregate

x 100

Clay Content

(Sand Equivalent Test)

59

Bottle of Solution on Shelf

Above Top of Cylinder

Hose and

Irrigation Tube

Measurement Rod

60

Marker on Measurement Rod

Top of Suspended Material

Top of Sand Layer

61

Clay Lumps and Friable Particles

ASTM C 142

Clay and friable particles may cause stripping, pitting and affect durability

Normally removed during crushing operation at grizzly or washing

1. Washed and dried a given mass of aggregate

2. Soaks for 24 hrs

3. Rubs each particle

4. Performs washed sieve over several screens

5. Dries the aggregate

6. Report percent loss as % of clay and friable

particles

62

Plasticity Index

ASTM D4318

Difference between LL and PL of material passing 42 m

PI is measure of degree of plasticity of fines, can indirectly indicate amount and type of plastic fines

63

Ratio of the mass to volume of an object to that of water at the same

temperature

G =

Mass Solid

Volume

Mass Water

Volume

Specific Gravity, G

64

Density is the unit weight of a material

lb/ft3 or kg/m3

Unit weight = g w G

gw = 1.000 g/cm3

gw = 1000 kg/m3

gw = 62.4 lb/ft3

Bulk density means sample contains

more than one mass and/or volume

Densities

65

Gsa =

Mass of oven dry agg

Vol of agg

Apparent Specific Gravity

66

Gsb =

Vol of agg, + perm. pores

Vol. of water-perm. pores

Surface Voids

Bulk Specific Gravity

Mass of oven dry agg

67

Gs, eff = Mass oven dry agg

Vol of agg, + perm. pores not absorb. asphalt

Effective Specific Gravity

Surface Voids

Solid Agg.

Particle

Vol. of water-perm. voids

not filled with asphalt

Absorbed asphalt

68

Phase: a change in state (e.g. solid, liquid, gas) Oven dry weight of agg = Ws Unit weight of water, gw = 1 g/cm3

Water

permeable

pores

Aggregate

Solids Vs

Vpp

Vpp - Vap

Vap

Phase Diagram (F 3-9)

Gsa = Ws / (Vs x gw )

Gsb = Ws / (Vs + Vpp) gw

Gse = Ws / (Vs + Vpp -Vap) gw

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Specific Gravity Tests for

Aggregates

Two tests are needed:

1. Coarse aggregate (retained on the 4.75

mm sieve)

2. Fine aggregate (passing the 4.75 mm

sieve)

70

Coarse Aggregate Specific Gravity

ASTM C127

1. Dry aggregate

2. Soak in water for 24 hours

3. Decant water

4. Use pre-dampened towel to get SSD condition

5. Determine mass of SSD aggregate

6. Determine mass under water

7. Dry to constant mass

8. Determine oven dry mass

71

Coarse Aggregate Specific Gravity

72

Coarse Aggregate Specific Gravity

73

Coarse Aggregate Specific Gravity Calculations

Gsb = A / (B - C)

A = mass oven dry

B = mass SSD

C = mass under water

Gsa = A / (A - C)

Water absorption, %

Absorption % = [(B - A) / A] * 100

74

Fine Aggregate Specific Gravity

ASTM C128 1. Dry aggregate

2. Soak in water for 24 hours

3. Spread out and dry to SSD

4. Add 500 g of SSD aggregate to pycnometer of known volume

Pre-filled with some water

5. Add more water and agitate until air bubble have been removed

6. Fill to line and determine the mass of the pycnometer, aggregate and water

7. Empty aggregate into pan and dry to constant mass

8. Determine oven dry mass

75

Fine Aggregate Specific

Gravity

76

Fine Aggregate Specific

Gravity

77

Fine Aggregate Specific

Gravity

78

Fine Aggregate Specific Gravity Calculations

Gsb = A / (B + D - C)

A = mass oven dry

B = mass of pycnometer filled with water

C = mass pycnometer, SSD aggregate and water

D = mass SSD aggregate

Gsa = A / (B + A - C)

Water absorption, %

Absorption % = [(D - A) / A] * 100

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2. Uniformly graded (single size)

Few points of contact Poor interlock (shape dependent) High permeability

1. Well graded (dense) Good interlock Low permeability

3. Gap graded Only limited sizes Good interlock Low permeability

Types of Gradations

80

Aggregate Gradations

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100

Gap-graded

(open)

Well-graded

(dense)

Uniformly graded

(single-size)

81

Aggregate Gradation

Use 0.45 Power Gradation Chart

Blend Size Definitions maximum size

nominal maximum size

Gradation Limits control points

restricted zone

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Example:

5.00 mm sieve plots at (5.00)0.45 = 2.25

Sieve Size (mm) Raised to 0.45 Power

0

20

40

60

80

100

0 1 2 3 4

Percent Passing

0.45 Power Grading Chart

83

0.45 Power Grading Chart Percent Passing

0 .075 .3 .6 1.18 2.36 4.75 9.5 12.5 19.0

Sieve Size (mm) Raised to 0.45 Power

0

20

40

60

80

100

maximum density line

max

size

84

Aggregate Size Definitions

Nominal Maximum Aggregate Size one size larger than the first sieve

to retain more than 10%

Maximum Aggregate Size one size larger than nominal

maximum size

100 100 90 72 65 48 36 22 15 9 4

100 99 89 72 65 48 36 22 15 9 4

85

Gradations Considerations

Considerations: Max. size < 1/2 lift thickness

Larger max size:-

1. Increase strength

2. Improve skid resistance

3. Increase volume and surface area of agg which decreases required AC content

4. Improve rut resistance

5. Increase problem with segregation of particles

Smaller max size:-

1. Reduces segregation

2. Reduces road noise

3. Decreases tire wear

86

Expected Problems

87

T 4.11 Tolerances for Asphaltic Concrete Mixes

JKR/SPJ/1988

Parameter Permissible Variation

(% by weight of total mix)

Bitumen 0.2 %

Fraction of combined agg.

passing 5 mm and larger sieves

5.0 %

Fraction of combined agg.

passing 3.35 mm and 1.18 mm

4.0 %

Fraction of combined agg.

passing 425 m and 150 m

3.0 %

Fraction of combined agg.

passing 75 m sieve

2.0 %

88

100

0 .075 .3 2.36 4.75 9.5 12.5 19.0

Percent Passing

control point

restricted zone

max density line

max

size

nom

max

size

Sieve Size (mm) Raised to 0.45 Power

Restricted Zone

89

Superpave Aggregate Gradation

100

0 .075 .3 2.36 12.5 19.0

Percent Passing

Design Aggregate Structure

Sieve Size (mm) Raised to 0.45 Power

90

Superpave Mix Size

Designations

Superpave Nom Max Size Max Size

Designation (mm) (mm)

37.5 mm 37.5 50

25 mm 25 37.5

19 mm 19 25

12.5 mm 12.5 19

9.5 mm 9.5 12.5

91

Target Gradation

Acceptable gradation band specified

Mix design selects a job mix formula (JMF) which falls within band and meets design criteria

Superpave 5 nominal sizes (37.5, 25, 19, 12.5, and 9.5 mm)

Four sieve sizes used to set upper and lower limits

Staying out of the restricted zone in suggested to minimize problems with natural sands

92

Washed sieve analysis

Part 1 - Washing

1. Dry aggregate and determine mass

2. Wash and decant water through 0.075 mm sieve until water is clear

3. Dry aggregate to a constant mass

Part 2 - Sieving

1. Place dry aggregate in standard stack of sieves

2. Place sieve stack in mechanical shaker

3. Determine mass of aggregate retained on each sieve

Part 3 - Computation

1. Add mass washed into mass passing 0.075 mm

2. Calculate percent passing as usual

93

Washed Sieve

94

Individual Sieve Stack of Sieves

Mechanical Sieve

95

Stack in

Mechanical

Shaker

Mechanical Sieve

96

Blending Stockpiles

Basic formula for combining stockpiles to achieve a target gradation is:

p = Aa + Bb + Cc + .

where:

p = percent of material passing given sieve

size for the combined agg

A, B, C, .. = percent passing given sieve for each agg.

a, b, c, = proportion (decimal fraction) of A, B, C, to be used in blend, a + b + c + = 1.00

97

Blending Stockpiles

1. Plot individual gradations

2. Plot specification limits

3. Can be used for initial assessment Can blend be made from available

materials?

Identification of critical sieves

Estimate trial proportions

Possible outcome (F 3-15)

98

All possible combinations fall between A and B

Gradation B

Control points for

12. 5 nominal max. size

Gradation A

0

10

20

30

40

50

60

70

80

90

100

0.075 0.3 1 .18 4.75 9.5 12.5 19

Sieve Size, mm

Percent Passing, %

99

No poss. combination of A and B will meet spec.

Gradation B Gradation A

Control points for

12. 5 nominal max. size

0

10

20

30

40

50

60

70

80

90

100

0.075 0.3 1 .18 4.75 9.5 12.5 19

Sieve Size, mm

Percent Passing, %

100

All poss. combinations pass through cross-over point

Blends containing more A than B will be closer to A

Gradation A

Gradation B

Control points for

12. 5 nominal max. size

0

10

20

30

40

50

60

70

80

90

100

0.075 0.3 1 .18 4.75 9.5 12.5 19

Sieve Size, mm

Percent Passing, %

101

Trial and Error

Aided by experience and plots of indiv. gradation curves and spec limits

Calculated grading compared with spec adjust until pass

Guided by reasoning, maths, experience

Use of spreadsheet now common

Steps in trial and error:

1. Select critical sieves in blend

2. Determine initial proportions which will meet critical sieves

3. Check calc. blend against specification

4. Adjust if necessary and repeat above steps

102

Blending of Aggregates

Agg. B Agg. A

Blend Target

Material

%

Passing

%

Passing

% Used

U.S. Sieve %

Batch

%

Batch

No. 4

No. 8

No. 16

No. 30

No. 50

No. 100

No. 200

3/8

90

30

7

3

1

0

0

100

100

100

88

47

32

24

10

100

103

Blending of Aggregates

Agg. B Agg. A

Blend Target

Material

%

Passing

%

Passing

% Used

U.S. Sieve %

Batch

%

Batch

No. 4

No. 8

No. 16

No. 30

No. 50

No. 100

No. 200

3/8

45

15

3.5

1.5

0.5

0

0

100

100

100

88

47

32

24

10

100

50 % 50 %

First Try

(remember trial & error)

90

30

7

3

1

0

0

50

90 * 0.5 = 45

30 * 0.5 = 15

7 * 0.5 = 3.5

3 * 0.5 = 1.5

1 * 0.5 = 0.5

0 * 0.5 = 0

0 * 0.5 = 0

100 * 0.5 = 50

80 - 100

65 - 100

40 - 80

20 - 65

7 - 40

3 - 20

2 - 10

100

104

Blending of Aggregates

Agg. B Agg. A

Blend Target

Material

%

Passing

%

Passing

% Used

U.S. Sieve %

Batch

%

Batch

No. 4

No. 8

No. 16

No. 30

No. 50

No. 100

No. 200

3/8

80 - 100

65 - 100

40 - 80

20 - 65

7 - 40

3 - 20

2 - 10

100

45

15

3.5

1.5

0.5

0

0

100

50

50

44

23.5

16

12

5

50

50 % 50 %

90

30

7

3

1

0

0

50

95

65

47.5

25

16.5

12

5

100

100

100

88

47

32

24

10

100

Lets Try

and get

a little closer

to the middle of

the target values.

105

Blending of Aggregates

Agg. B Agg. A

Blend Target

Material

%

Passing

%

Passing

% Used

U.S. Sieve %

Batch

%

Batch

No. 4

No. 8

No. 16

No. 30

No. 50

No. 100

No. 200

3/8

80 - 100

65 - 100

40 - 80

20 - 65

7 - 40

3 - 20

2 - 10

100

27

9

2.1

0.9

0.3

0

0

100

70

70

61.6

32.9

22.4

16.8

7

70

70 % 30 %

90

30

7

3

1

0

0

30

97

79

63.7

33.8

22.7

16.8

7

100

100

100

88

47

32

24

10

100

106

Blended Aggregate Specific

Gravities

Once the percentages of the stockpiles have been established, the combined aggregate

specific gravities can also be calculated

Combined G = 100

P1 + P2 + . Pn

G1 G2 Gn