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Properties of aggregrate
The document discusses the properties of aggregates used in road construction. It describes the types of aggregates derived from igneous, sedimentary and metamorphic rocks. Several tests are used to evaluate aggregates including crushing value, impact value, Los Angeles abrasion and shape tests. The results of these tests are used to determine whether aggregates meet requirements for sub-base, base or surfacing layers. Requirements include maximum values for impact value, flakiness index and water absorption.
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Properties of aggregrate
- 1. 09/13/14 PROPERTIES OF AGGREGATES DR.M.Heeralal NIT WARANGAL
- 2. TYPES OF AGGREGATES 09/13/14 • Natural aggregates are from – Igneous Rocks – Sedimentary Rocks – Metamorphic Rocks
- 3. Road Making Aggregatesin India 09/13/14 • 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
- 4. 09/13/14 DESIRABLE PROPERTIESOF ROAD AGGREGATES Desirable Property Test Resistance 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 Combined flakiness and elongated particles elongation index Resistance to weathering Soundness test Good adhesion with bituminous materials Stripping test Resistance to polishing action under traffic Polished stone value
- 5. Laboratory Tests Gradation Test In order to have perfect degree of interlocking 09/13/14 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 Test II. Elongation Test
- 6. 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 metal 09/13/14 Nominal Size Metal Graded size Metal
- 7. Grading requirements forNominal size CA 09/13/14 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
- 8. 09/13/14 Grade I Size varying from 90mm to 45mm and to be laid for minimum 100mm compacted thick (for Bottom layer only) Grade II Size varying from 63mm to 45mm and to be laid for both 100 and 75mm thick (For both Bottom and Middle layer) Grade III Size Varying from 53mm to 22.4mm and to be laid for 75mm thick (For Top layer)
- 9. GRADING REQUIREMENTS OFCOARSE 09/13/14 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
- 10. GRADING REQUIREMENTS OFCOARSE 09/13/14 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
- 11. GRADING REQUIREMENTS OFCOARSE 09/13/14 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
- 12. AGGREGATE CRUSHING VALUETEST Assess the strength of aggregate. Resistance to crushing under roller during construction Low ACV - Stronger aggregates High ACV - Soft aggregates 09/13/14
- 13. 09/13/14 LOADING NATURE Gradually applied compressive load
- 14. 09/13/14 APPARATUS SteelCylinder 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.
- 15. CRUSHING TEST 09/13/14 Metal Measures and Tamping Rods
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- 28. 09/13/14 PROCEDURE Aggregatepassing 12.5 sieve and retained on 10mm sieve Heated 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.
- 29. 09/13/14 Place thecylinder 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.
- 30. 09/13/14 CALCULATION Totalweight of dry sample = W1 Grams Weight of the crushed material passing 2.36mm = W2 Aggregate crushing value = 100 x W2/W1
- 31. Aggregate Impact Test APPARATUS 1. Impact Testing Machine 2. Measure : Metal Cylinder internal dia 09/13/14 7.5cm and depth 5cm 3. Tamping Road 4. Sieves : IS sieves 12.5mm, 10mm and 2.36mm 5. Balance : Capacity >500gms, up to 0.1gm accuracy 6. Oven
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- 43. PROCEDURE Test sampleaggregates passing through 12.5mm sieve and retained on 10mm Sample over dried at 100 C for 4 hours Fill 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. 09/13/14
- 44. Allow free fallof 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 % 09/13/14 W1
- 45. CHECK Weight ofmetal retained on 2.36mm sieve (W3)+Weight of metal passing through 2.36mm W2=W1(up to 1gms accuracy) 09/13/14
- 46. 09/13/14 RESULT AIV< 10% Exceptionally strong AIV 10% to 20% Strong AIV 20% to 30% Satisfactory
- 47. WATER ABSORPTION TESTAND SPECIFIC GRAVITY Concept: In order to know the porosity of the 09/13/14 metal. If the metal is porous the water absorption will be more, less strength of the metal.
- 48. APPARATUS Balance ofCapacity : 3 Kgs (Accuracy up 09/13/14 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.
- 49. SPECIFIC GRAVITY TEST 09/13/14 Buoyancy Balance With Accessory
- 50. 09/13/14 PROCEDURE 2Kg 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)
- 51. Place the aggregatein 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 09/13/14 Dry Weight
- 52. 09/13/14 RESULT SpGravity 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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- 54. 09/13/14 SHAPE TEST 1. Flakiness Index 2. Elongation Index 3. Angularity Number FLAKINESS INDEX APPARATUS 1. 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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- 58. 09/13/14 PROCEDURE Particleswhose 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
- 59. FI = (w1+w2+w3+…….)x 100 09/13/14 ( 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.
- 60. 09/13/14 ELONGATION INDEX APPRATUS 1. Length guage 2. Set of sieves as stated above 3. 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.
- 61. Elongation Index=(X1+X2+X3+….) x100=100X % 09/13/14 (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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- 66. Angularity Number 09/13/14 • 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
- 67. SHAPE TEST 09/13/14 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%
- 68. Stripping Value ofRoad Aggregates 09/13/14 • IRC has specified the max. stripping value as 25% for aggregates to be used in bituminous constructions like surface dressing, PM, BM and carpet
- 69. Los Angels AbrasionTest 09/13/14 • Abrasion – rubbing action between different particles • Attrition – rubbing action between similar particles
- 70. LOS ANGELES ABRASIONTEST 09/13/14 Los Angeles Abrasion Machine
- 71. Los Angels AbrasionTest 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- 09/13/14 2.36mm 5kg 6 500 E 80mm-40mm 10kg 12 1000 F 50mm-25mm 10kg 12 1000 G 40mm-20mm 10kg 12 1000
- 72. PHYSICAL REQUIREMENTS OFAGGREGATES FOR SUB-BASE, BASE COURSE AND BITUMINOUS SURFACING LAYERS (As per Rural Roads Manual) Layer Test Test Method Requirement 09/13/14 (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
- 73. PHYSICAL REQUIREMENTS OFAGGREGATES FOR SUB-BASE, BASE COURSE AND BITUMINOUS SURFACING LAYERS (As per Rural Roads Manual) Bituminou s Surfacing 09/13/14 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
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