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Engineering materials notes for the topic properties of aggregriate
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04/10/23
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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GRADING REQUIREMENTS OF COARSE AGGREGATES
Grade Range IS sieve Designation
(mm)
Percent by Weight passing
II 63mm to 45mm 90 100
63 90-100
53 25-75
45 0-15
22.4 0-5
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GRADING REQUIREMENTS OF COARSE AGGREGATES
Grade Range IS sieve Designation
(mm)
Percent by Weight passing
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
Aggregate Impact value IS: 2386 (Part 4) -1963
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
Aggregate Impact value IS: 2386 (Part 4) -1963
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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