ROAD AGGREGATES 01

PAVEMENT MATERIALS PAVEMENT MATERIALS ENGINEERINGENGINEERING

(CE-862) (CE-862) Lec-10

Fall Semester 2016

Dr. Arshad [email protected] , Office Room#111, Tel:

05190854163, Cell: 03419756251

National Institute of Transportation (NIT)

School of Civil & Environmental Engineering (SCEE)

National University of Science and Technology (NUST)

NUST Campus, Sector H-12, Islamabad

ROAD AGGREGATES ROAD AGGREGATES (Cont..)(Cont..)

http://en.wikipedia.org/wiki/File:10mm-aggregate.jpg

http://en.wikipedia.org/wiki/File:20mm-aggregate.jpg

AGGREGATE CHARACTERIZATIONAGGREGATE CHARACTERIZATION

Aggregate Physical PropertiesMaximum Aggregate SizeGradationOther Aggregate Properties

Toughness and Abrasion Resistance Specific Gravity Particle Shape and Surface Texture Durability and Soundness Cleanliness and Deleterious Materials

AGGREGATE CHARACTERIZATIONAGGREGATE CHARACTERIZATION

Maximum Aggregate SizeMaximum size

The smallest sieve through which 100 percent of the aggregate particles pass.

Nominal maximum size The largest sieve that retains some of the

aggregate particles but generally not more than 10 percent by weight.

Aggregate Size DefinitionsAggregate 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

10010010010090907272656548483636222215159944

100100999989897272656548483636222215159944

AGGREGATE GRADATIONAGGREGATE GRADATION

Use 0.45 Power Gradation Chart

Blend Size Definitions◦maximum size◦nominal maximum size

Gradation Limits◦control points◦ restricted zone

Example: Example:

4.75 mm sieve plots at (4.75)4.75 mm sieve plots at (4.75)0.450.45 = 2.02 = 2.02

Sieve Size (mm) Raised to 0.45 PowerSieve Size (mm) Raised to 0.45 Power

00

2020

4040

6060

8080

100100

00 11 22 33 44

Percent PassingPercent Passing

0.45 Power Grading Chart0.45 Power Grading Chart

0.45 Power Grading Chart0.45 Power Grading Chart

0 .075 .3 .6 1.18 2.36 4.75 9.5 12.5 19.00 .075 .3 .6 1.18 2.36 4.75 9.5 12.5 19.0


00

2020

4040

6060

8080

100100

maximum density linemaximum density line


maxmaxsizesize

Aggregate Gradation

0.45 POWER CURVES

Calculation of the Max Density Calculation of the Max Density CurveCurve

n

DdP

where P = % finer than the sieve d = aggregate size being considered D = maximum aggregate size being used n = parameter which equals 0.45—represents the maximum particle packing

100100

00 .075.075 .3.3 2.36 2.36 4.75 4.75 9.59.5 12.5 19.012.5 19.0


control pointcontrol point

restricted zonerestricted zone

max density linemax density line

maxmaxsizesize

nomnommaxmaxsizesize


Superpave Aggregate Superpave Aggregate GradationGradation

100100

00 .075.075.3.3 2.36 2.36 12.5 12.5 19.019.0


Design Aggregate StructureDesign Aggregate Structure


Superpave Mix Size Superpave Mix Size DesignationsDesignations

SuperpaveSuperpave Nom Max SizeNom Max Size Max Size Max SizeDesignationDesignation (mm) (mm) (mm) (mm) 37.5 mm37.5 mm 37.5 37.5 50 50 25 mm25 mm 25 25 37.5 37.5 19 mm19 mm 19 19 25 25 12.5 mm12.5 mm 12.5 12.5 19 19 9.5 mm9.5 mm 9.5 9.5 12.5 12.5

GRADATIONS* Considerations:

- Max. size < 1/2 AC lift thickness- Larger max size

+ Increases strength

+ Improves skid resistance

+ Increases volume and surface area of agg which decreases required AC content

+ Improves rut resistance+ Increases problem with segregation of particles

- Smaller max size + Reduces segregation + Reduces road noise + Decreases tire wear

TARGET GRADATIONTARGET GRADATION

Acceptable gradation band specifiedMix design selects a job mix formula (JMF) which falls

within band and meets design criteriaSuperpave

◦ 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

BLENDING STOCKPILESBLENDING STOCKPILES

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

p = Aa + Bb + Cc + ….

where:p = percent of material passing given sieve sizeA, B, C, .. = percent passing given sieve for

each agg.a, b, c, … = decimal fraction of A, B, C, … to be

used

BLENDING STOCKPILESBLENDING STOCKPILES

Plot individual gradationsPlot specification limitsCan be used for initial

assessmentCan blend be made from available

materials?Identification of critical sievesEst. trial proportions

TRIAL AND ERROR STEPSTRIAL AND ERROR STEPS

Select critical sieves in blendDetermine initial proportions

which will meet critical sievesCheck calc. blend against

specificationAdjust if necessary and repeat

above steps

Blended Aggregate Specific Blended Aggregate Specific GravitiesGravities

Once the percentages of the stockpiles have been established, the combined aggregate specific gravities can also be calculated

COMBINED SPECIFIC COMBINED SPECIFIC GRAVITIESGRAVITIES

G = 1

P1 + P2 + ……. Pn

100 G1 100 G2 100 Gn

BLENDING OF AGGREGATESBLENDING OF AGGREGATES

Reasons for BlendingObtain desirable gradationSingle natural or quarried material

not enoughEconomical to combine natural and

process materials


Agg. #2Agg. #1Blend Target

Material

%Passing

%Passing

% UsedU.S. Sieve %

Batch%

Batch

No. 4No. 8

No. 16No. 30No. 50

No. 100No. 200

3/8 “903073100

1001001008847322410

100



Material

%Passing

%Passing

% UsedU.S. Sieve %

Batch%

Batch

No. 4No. 8

No. 16No. 30No. 50

No. 100No. 200

3/8 “45153.51.50.500

1001001008847322410

100

50 %50 %

First Try(remember trial & error)

903073100

5090 * 0.5 = 4530 * 0.5 = 157 * 0.5 = 3.53 * 0.5 = 1.51 * 0.5 = 0.50 * 0.5 = 500 * 0.5 = 0

100 * 0.5 = 5080 - 10065 - 10040 - 8020 - 657 - 403 - 202 - 10

100



Material

%Passing

%Passing

% UsedU.S. Sieve %

Batch%

Batch

No. 4No. 8

No. 16No. 30No. 50

No. 100No. 200

3/8 “80 - 10065 - 10040 - 8020 - 657 - 403 - 202 - 10

10045153.51.50.500

100505044

23.516125

50

50 %50 %

903073100

509565

47.525

16.5125

1001001008847322410

100



Material

%Passing

%Passing

% UsedU.S. Sieve %

Batch%

Batch

No. 4No. 8

No. 16No. 30No. 50

No. 100No. 200

3/8 “80 - 10065 - 10040 - 8020 - 657 - 403 - 202 - 10

10045153.51.50.500

100505044

23.516125

50

50 %50 %

903073100

509565

47.525

16.5125

1001001008847322410

100Let’s Tryand get

a little closerto the middle of

the target values.



Material

%Passing

%Passing

% UsedU.S. Sieve %

Batch%

Batch

No. 4No. 8

No. 16No. 30No. 50

No. 100No. 200

3/8 “80 - 10065 - 10040 - 8020 - 657 - 403 - 202 - 10

100279

2.10.90.300

1007070

61.632.922.416.8

7

70

70 %30 %

903073100

309779

63.733.822.716.8

7

1001001008847322410

100

Other Aggregate PropertiesOther Aggregate Properties

Aggregate Crushing ValueAggregate Impact ValueLos Angeles AbrasionSoundnessSand Equivalent

AGGREGATE CRUSHING VALUEAGGREGATE CRUSHING VALUE

• Metal measure• Tamping rodBelow mentioned are its specifications:• Three sizes 75mm dia for 1/8 to 1/4 Size aggregate, 150mm dia for 3/8 to 3/4 Size aggregate 300mm dia for 1in to 2in size aggregate

The aggregate crushing value indicates the ability of an aggregate to resist crushing. The lower the figure the stronger the aggregate, i.e. the greater its ability to resist crushing.

AGGREGATE CRUSHING VALUE

Aggregate passing IS sieve 12.5 mm and retained on 10 mm sieve is generally used.

Oven dried aggregates are filled in the measuring cylinder of 11.5cm dia. & 18.0cm height in 3 equal layers, each layer being subjected to 25 tamps with a tamping rod of 16mm dia and 45 to 60mm long.


The crushing test apparatus consist of a 15cm dia open ended heavy steel cylinder, plunger and a base plate.

Compression testing machine a load of 40 tonnes is applied in 10 min. crushed aggregate Sieved through 2.36 mm sieve.

Agg crushing value > 35 weak for pavement.

Agg crushing value < 10 exceptionally strong.

For majority of aggregates the impact value and crushing value are numerically similar.

Rock group Crushing value Impact valueBasalt 14 15 Granite 20 19Lime stone 24 23 Quartzite 16 21


AGGREGATE IMPACT VALUE

A base, which helps in supporting the columns to form a rigid framework around the quick release trigger mechanism for ensuring the effective free fall of the hammer during test. The hammer is offered with locking arrangement and the free fall can be easily adjusted through the 380+ 5mm. cylindrical cup, with the metal measure 75 mm dia x 50 mm high and tamping rod.

Satisfactory resistance to crushing under roller during construction. Adequate resistance to surface abrasion under traffic.

IMPACT VALUE Due to traffic loads the road stones are subjected

to impact. IS sieves 12.5 mm,10 mm & 2.36 mm. Cylindrical steel cup of dia 10.2 cm & depth 5

cm. Metal hammer of weight 13.5 to 14 kg. Height of

fall 38 cm. Cylindrical measure with internal dia 7.5 cm & depth 5 cm.

Metal tamping of 1 cm dia.23 cm long.< 10 % exceptionally strong.10 - 20 % strong.20 - 30 % satisfactory. > 35 % weak.

ELONGATION & FLAKINESS INDEXELONGATION & FLAKINESS INDEX

When the length is more than 1.8 of the mean dimension, then the aggregate particles are considered elongated.The aggregate particles are to be flaky, if the thickness is less than the 0.6 of their mean dimension.

LOS ANGELES ABRASION TESTStart with fraction retained on No. 12

sieve

Sample submerged in magnesium or sodium sulfate—causes salt crystals to form in the aggregate pores

SOUNDNESSSOUNDNESS TESTTEST

SAND EQUIVALENTSAND EQUIVALENT

SE = (Height of Sand/Height of Clay)100

This is a test to determine the amount of clay in fine aggregate.Aggregate passing a No. 4 sieve is agitated in a water-filled transparent cylinder. Liquid is water and flocculating agent. After settling, the sand separates from the flocculated clay. Measure each.

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