AGGREGATES

Sieve Analysis Test

Sieve Analysis Test • To determine gradation (size distribution) of aggregates. Standard Sieves Are : 80mm,40mm,20mm,10mm,4.75mm,2.36mm,1.18m m,600 microns, 300 microns, 150 microns, 75 microns

Aggregate Gradation IS:2386-1963 Part I The gradation and size test (Figure 1) is used to determine aggregate particle size distribution

In a gradation and size analysis, a sample of dry aggregate of known weight is separated through a series of sieves with progressively smaller openings. Once separated, the weight of particles retained on each sieve is measured and compared to the total sample weight. Particle size distribution is then expressed as a percent retained by weight on each sieve size.

Sieves and Sieve Shaker for Coarse Aggregate

Sieve Shaker for Fine Aggregate

FM= 277/100=2.77

STONE AGGREGATE Desirable Properties 1.Strength 2.Hardness 3.Toughness 4.Durability 5.Shape 6.Adhesion with Bitumen

AGGREGATE CRUSHING VALUE TEST Cylinder Machine steel, 154 mm dia. Plunger Machine steel Base Plate Metal Measure 115 mm dia., 180 mm deep. Tamping Rod Galvanized steel, 16 mm dia., 500 mm length, hemispherical at both ends.

TEST PROCEDURE Sample Preparation Load Application 40 KN/min Total Load 400 KN. Crushed Material is Passed through 2.30mm sieve CALCULATIONS AND RESULTS Mass of test specimen = M1 g Mass of material passing 2.36 mm sieve = M2 g Aggregate Crushing Value (ACV) = 100 xM2 M1 Report the average ACV

IRC Specifications For Surface Courses : Not more than 30% For Base Courses : Not More than 45%

AGGREGATE IMPACT TEST Used to determine the Toughness Apparatus: Impact Machine Cylindrical Measure Machine steel, 75 mm dia., 50 mm deep. Tamping Rod Galvanized steel, 3/8" dia., 8" length Sieves of Size 12.5mm, 10mm , 2.36

Test Procedure Sample Preparation Place the Cup into the machine Apply 15 blows by lifting the hammer of 13.5 kg to 14 kg to a height of 38 cm. Remove the material from cup and sieve it through 2.36 mm sieve. Impact Value = M2 x100 M1 Where M2= weight of Crushed material in gm M1 = weight of Sample taken

IRC Specifications For Surface Courses : Not more than 30% For Bituminous Macadam Courses : Not More than 35% For WBM courses : not more than 40%

ABRASION TESTS Used to Evaluate the Hardness Property of Aggregate. Los Angels Abrasion Test Deval’s Abrasion Test Deval’s Attrition Test

Los Angels Abrasion Test Hollow Drum 12.5mm thick steel plate; 70cm inner diameter 50cm inner width Drum Speed 30-33 RPM IS sieves of specified sizes Abrasive charge shall consist of a solid, steel sphere having a mass between 390 and 445 g. with a diameter of 46.5 ± 0.5 mm.

GRADINGS FOR TEST SPECIMENS A, B, C, D, E, F and G Total Mass = 5000 ± 10 gm for A, B, C and D Total Mass = 10,000 ± 20 gm for E, F and G.

TEST PROCEDURE Take the sample as per specifications Place it in the drum Also place the abrasive charge as per Sp. Apply the Rotations 30-33 r.p.m. 1000 revolutions are to be given Remove the shutter and sample is passed through the 1.70mm sieve. Abrasion Value = W2 x100 W1 Where W2= weight of abraded material retained W1 = weight of Sample taken

IRC Specifications For CC Roads&High Bituminous Roads : Not more than 30% For WBM courses : not more than 50%

DEVAL’S ABRASION TEST

FLAKINESS INDEX TEST ELONGATION INDEX TEST ANGULARITY NUMBER TEST SHAPE TESTS FLAKINESS INDEX TEST ELONGATION INDEX TEST ANGULARITY NUMBER TEST

The particle shape of aggregates is determined by the percentages of flaky and elongated particles. Flaky and elongated particles are considered undesirable as they cause weakness of the pavement. Rounded aggregates are preferred in cement concrete pavements as the workability of concrete improves. A regular shape of particles are desirable for granular base course due to increased stability desired from better interlocking.

FLAKINESS INDEX TEST Definition: Aggregate particles are classified as flaky when they have a thickness (smallest dimension) of less than 0.6 of their mean sieve size. The flakiness index of an aggregate sample is found by separating the flaky particles and expressing their mass as a percentage of the mass of the sample tested. This test is not applicable to aggregate passing 6.30 mm sieve and retained as 63.0 mm sieve.

7.3.1 Apparatus Metal thickness gauge Test sieves, balance, trays

1 This dimension is equal to 0.6 times the mean test sieve size.

Procedure The sieve sample with sieves mentioned in Table 7.1. Weigh each of the individual size fractions (w1, w2, w3, ...) retained on these sieves, other than the 63.0 mm sieve and store them in separate trays marked with their size. 2. Gauge each fraction from the respective slots in the thickness gauge weigh pieces which pass through the slots (x1, x2, x3, …. etc.).

Calculations and Results Flakiness index = Where x1, x2, ... etc. are the weight of the fractions passing from the thickness gauge. w1, w2,…, etc. are the weight of the original sample retained as the corresponding sieves.

IRC SPECIFICATIONS Normally should not exceed 15% In any case it should not exceed 25%

ELONGATION INDEX TEST Definition: Aggregate particles are classified as elongated when they have a length (greatest dimension) of more than 1.8 of their mean sieve size. The elongation index is found by separating the elongated particles and expressing their mass as a percentage of the mass of sample tested. The test is not applicable to material passing 6.30 mm sieve or retained on 50 mm sieve.

Apparatus Metal Length gauge Test sieves, balance, trays

2 This dimension is equal to 1.8 times the mean test sieve size.

PROCEDURE 1. Sieve the sample with sieves mentioned in Table (7.2) weight each of the individual size fractions (w1, w2, w3, … etc.) retained on these sieves other than the 50.0 mm sieve. 2. Gauge each fraction as follows, select the length gauge appropriate to the single fraction under test and gauge each particle separately by hand. Elongated particles are those whose greatest dimension prevents them from passing through the gauge. 3.Weigh each fraction which doesn’t pass through the gauge (y1, y2, …etc.).

Calculations and Results Elongation index = Where y1, y2, ... etc. are the weight of the fractions passing from the thickness gauge. w1, w2,…, etc. are the weight of the original sample retained as the corresponding sieves.

IRC SPECIFICATIONS In any case it should not exceed 15%

Angularity number Angular particles possess well defined edges and are commonly found in aggregates prepared by crushing of rocks. Angularity or absence of rounding of particles in aggregate is a property which is of importance because it affects ease of handling a mixture of aggregate and binder. The degree of packing of particles of single sized aggregates depends upon the shape and angularity of the aggregate.

Angularity of aggregate can be estimated from properties of voids in a sample of aggregate compacted in a particular manner. Rounded gravel particles possess lesser voids (mostly 33%, i.e. 67% solids, by volume) as compared to the angular particles. Angularity number measures the percentage of voids in angular particles in excess of that in the rounded gravel particles.

Angularity number = % of solid volume in a vessel filled with aggregate in a standard manner - 67 (i.e. % volume of solids of the rounded gravel) The higher the angularity number, the more angular the aggregate. The range of angularity number for practical aggregates is between 0 and 11

Unit Weight (unit mass or bulk density) The weight of the aggregate required to fill a container of a specified unit volume. • Volume is occupied by both the aggregates and the voids between the aggregate particles. • Depends on size distribution and shape of particles and how densely the aggregate is packed • Loose bulk density • Rodded or compact bulk density