Properties of aggregrate

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PROPERTIES OF AGGREGATES

DR.M.Heeralal

NIT WARANGAL

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TYPES OF AGGREGATES

• Natural aggregates are from

– Igneous Rocks– Sedimentary Rocks– Metamorphic Rocks

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Road Making Aggregates in India

• Basalt - Good for base & Surface

• Granite – Very good for Bituminous courses & WBM

• Lime Stone – Good for base

• Quartzite – Good for base

• Sand Stone – Good for base

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DESIRABLE PROPERTIES OF ROAD AGGREGATES

Desirable Property TestResistance to crushing or strength Crushing test

Resistance to abrasion or hardness Los Angeles abrasion value

Resistance to impact or toughness Aggregate impact test

Good shape factors to avoid too flaky and elongated particles

Combined flakiness and elongation index

Resistance to weathering Soundness test

Good adhesion with bituminous materials Stripping test

Resistance to polishing action under traffic Polished stone value

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Laboratory Tests

Gradation Test In order to have perfect degree of interlocking

between aggregate Strength

I. Aggregate Crushing Test Toughness

I. Aggregate impact Test Hardness – Los Angels’ Test Specific gravity and Water absorption Tests Shape Factors

I. Flakiness TestII. Elongation Test

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GRADATION OF AGGREGATES

Dry sieve analysis is generally suitable for gradation

Maximum size of an aggregate is the mesh size of the smallest sieve through which 100% material will pass.

There are two types of gradation of metalNominal Size MetalGraded size Metal

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Grading requirements for Nominal size CA

Sl. No Nominal Size

100% Aggregate

should pass through

100% aggregate

should retain on

1 75mm 106mm 63mm

2 63mm 90mm 53mm

3 45mm 53mm 26.5mm

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Grade ISize varying from 90mm to 45mm and to be laid for minimum 100mm compacted thick (for Bottom layer only)

Grade IISize varying from 63mm to 45mm and to be laid for both 100 and 75mm thick (For both Bottom and Middle layer)

Grade IIISize Varying from 53mm to 22.4mm and to be laid for 75mm thick (For Top layer)

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GRADING REQUIREMENTS OF COARSE AGGREGATES

Grade Range IS sieve Designation

(mm)

Percent by Weight passing

I 90mm to 45mm 125 100

90 90-100

63 25-60

45 0-15

22.4 0-5

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(mm)


II 63mm to 45mm 90 100

63 90-100

53 25-75

45 0-15

22.4 0-5

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(mm)


III 53mm to 22.4mm 63 100

53 95-100

45 65-90

22.4 0.10

11.2 0-5

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AGGREGATE CRUSHING VALUE TEST

Assess the strength of aggregate. Resistance to crushing under roller

during construction Low ACV - Stronger aggregates High ACV - Soft aggregates

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LOADING NATURE

Gradually applied compressive load

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APPARATUS

Steel Cylinder with open ends of 15.2 cm dia. (Internal) on square base plate plunger with 15.0cm dia. piston.

Cylinder jar of 11.5cm dia. and height 18cm

Steel Tamping rod Balance capacity 3 Kgs.Compressive testing machine of capacity

40 tones @ uniform loading of 4 tones/Minute.

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CRUSHING TEST

Metal Measures and Tamping Rods

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PROCEDUREAggregate passing 12.5 sieve and retained

on 10mm sieveHeated up to a temp.100o C to 110o C for a

period of 4 Hours and cooled to a room temp.Cylindrical jar to be filled by aggregate in 3

layers each layer should be tamped level of the jar by tamping rod.

Weigh the sample nearly equal to 6.5 Kgs.Pour the aggregate in cylinder test apparatus

placed in position on the base plate in three layers.

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Place the cylinder along with plunger under compressive testing machine

Load is applied up to 40 tonnes at the rate of 4 tonnes per minute.

Aggregate including the crushed portion should be sieved on 2.36mm sieve

Weigh the material which passes the sieve.

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CALCULATION

Total weight of dry sample = W1 GramsWeight of the crushed material passing

2.36mm = W2Aggregate crushing value = 100 x W2/W1

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APPARATUS1. Impact Testing Machine2. Measure : Metal Cylinder internal dia 7.5cm and depth 5cm3. Tamping Road4. Sieves : IS sieves 12.5mm,

10mm and 2.36mm5. Balance : Capacity >500gms, up to

0.1gm accuracy6. Oven

Aggregate Impact Test

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IMPACT TEST

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PROCEDURE

Test sample aggregates passing through 12.5mm sieve and retained on 10mm

Sample over dried at 100 C for 4 hoursFill the aggregates in three layers in the

cylinder and tamped for 25 times with tamping rod. Repeat it 3 times

Surplus aggregates trimmed off with tamping rod

Weigh the sample say W1 gms Transfer the test sample to the cup and

compact it with 25 strokes.

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Allow free fall of hammer from 38cm above the aggregates to a total of 15 blows at an interval of 1 second between each blow.

Sieve it through 2.36mm sieve, and weigh the fraction passing 2.36m sieve (W2 gms)

Weight the fraction retained on 2.36m sieve (say W3 gms)

AIV = 100W2 %

W1

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CHECK

Weight of metal retained on 2.36mm sieve (W3)+Weight of metal passing through 2.36mm W2=W1(up to 1gms accuracy)

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RESULT

AIV < 10% Exceptionally strongAIV 10% to 20% StrongAIV 20% to 30% Satisfactory

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WATER ABSORPTION TEST AND SPECIFIC GRAVITY

Concept: In order to know the porosity of the

metal. If the metal is porous the water

absorption will be more, less strength of the metal.

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APPARATUSBalance of Capacity : 3 Kgs (Accuracy up

to 0.5gms)

1.Oven : 110c

2.Wire Basket : 6.3mm mesh

3.Container :”Capacity”- C

4.Air tight container of “capacity” - C

5.Shallow Tray, Clothes.

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SPECIFIC GRAVITY TEST

Buoyancy Balance With Accessory

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PROCEDURE2 Kg of washed aggregate free from dust is

weighed In water with basket (say W1 gms)Measure weight of basket suspended in

water (Say W2 gms)Wt of aggregate in Water=W in water=(W1-

W2) gms.Weight of Dry aggregates after removing its

wetness by cloth (Say W with Water, gms)

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Place the aggregate in an oven at 110C for 24 hours cool it (Dry Weight W gms)

Weight of water equal to the volume of aggregates= (W with water-W in Water in gms)

Specific Gravity=Dry weight of aggregate/Weight of equal volume of water

Water Absorption =

W With water-Dry Wt.of Aggregate x 100

Dry Weight

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RESULT

Sp Gravity of Aggregates Ranges from 2.5 to 3.0

High Sp. Gravity aggregate means High Strength. Average Value – 2.68

Water absorption is measure of its porosity of aggregates

Water absorption Ranges from 0.1% to 2%More absorption of water of aggregate,

more porous material – less strength

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SHAPE TEST

1. Flakiness Index

2. Elongation Index

3. Angularity Number

FLAKINESS INDEX

APPARATUS1. Standard Thickness guage

2. I.S.Sieves 63,50,40,31.5,25,20,16,12,5, 10 & 6.3mm

3. Weighing balance, to an accuracy of 1 gms

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PROCEDURE

Particles whose least dimension (thickness is less than three fights (0.6) of their mean dimension.

Not applicable for sizes of metal smaller than 6.3mm

A minimum of 200 pieces of each fraction to be tested are to be taken

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FI = (w1+w2+w3+…….) x 100

( W1+W2+W3)

Where w1, w2, w3 are weights of the materials passing each of the specified gauge

Where W1, W2, W3 weight of the materials passing & retained on the specified sieves.

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ELONGATION INDEX APPRATUS

1. Length guage2. Set of sieves as stated above3. Weighing balance 0.1 gms accuracy

PROCEDURE A minimum of 200 pieces of each fraction

is taken and Weighed Particles whose greatest dimension

(length) is greater than one and four fifth times (1.8 times) their mean dimensions

Not applicable to size smaller than 6.3mm.

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Elongation Index=(X1+X2+X3+….) x100 =100X %

(W1+W2+W3+…) W

Where X1+X2+X3 are weight of materials from each fraction retained on the specified length

W1, W2, W3……… Total weights of each fraction

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Angularity Number

• The amount by which the % voids exceeds 33 after being compacted in a prescribed manner.

• Angularity Number= 67 – 100W/CG

• AN = 0 Highly rounded gravel

• AN = 11 Freshly Crushed Angular Aggregate

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Type of pavement Maximum combined flakiness and

elongation index

MoRTH specifications

Bituminous layers 30%

WBM / WMM / CRM 30%

Rural Roads Manual

Sub-base course (Flakiness index) 40%

Base course (Flakiness index) 30%

Bituminous layers (Combined index) 35%

SHAPE TEST

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Stripping Value of Road Aggregates

• IRC has specified the max. stripping value as 25% for aggregates to be used in bituminous constructions like surface dressing, PM, BM and carpet

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Los Angels Abrasion Test

• Abrasion – rubbing action between different particles

• Attrition – rubbing action between similar particles

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LOS ANGELES ABRASION TEST

Los Angeles Abrasion Machine

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Los Angels Abrasion Test

Grading Sieve Range Sample Wt. Wt. Of Charge Revolutions

A 40mm-10mm 5 kg 12 spears 500

B 20mm–10mm 5 kg 11 500

C 10mm-4.75mm 5 kg 8 500

D 4.75mm-2.36mm

5kg 6 500

E 80mm-40mm 10kg 12 1000

F 50mm-25mm 10kg 12 1000

G 40mm-20mm 10kg 12 1000

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PHYSICAL REQUIREMENTS OF AGGREGATES FOR SUB-BASE, BASE COURSE AND BITUMINOUS SURFACING LAYERS (As per Rural Roads Manual)

Layer Test Test Method Requirement (Percent.

Max.)

Sub-base course

Aggregate Impact value IS: 2386 (Part 4) -1963

50

Flakiness Index IS: 2386 (Part 1) -1963

40

Moisture or water absorption

IS: 2386 (Part 3) -1963

06

Base course


40

Flakiness Index IS: 2386 (Part 1) -1963

30

Moisture or water absorption

IS: 2386 (Part 3) -1963

03

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PHYSICAL REQUIREMENTS OF AGGREGATES FOR SUB-BASE, BASE COURSE AND BITUMINOUS SURFACING LAYERS (As per Rural Roads Manual)

Bituminous Surfacing

Los Angeles abrasion value

IS: 2386 (Part 4) -1963

40


30

Combined Flakiness and Elongation Index

IS: 2386 (Part 1) -1963

35

Stripping value IS: 6241- 1971 15

Soundness Loss with Sodium Sulphate (5 cycles) Loss with Magnesium Sulphate (5 cycles)

IS: 2386 (Part 5) – 1963

12

18

Water absorption IS:2386 (Part 3) – 1963

02

Thank You!

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Engineering

Properties of aggregrate