For Coars Aggregate

EXPERIMENT- DETERMINATION OF PARTICAL SIZE DISTRIBUTION OF COARSE AGGREGATE OBJECTIVE: To determine the particle size distribution, fineness modulus, grading curve for Coarse Aggregate. APPARTUS: Balance, set of standard sieves in following size: For Fine aggregates: 80mm, 63mm, 50mm, 40mm, 25mm, 16mm, 12.5mm, 10mm, 6.3mm, and 4.75mm PROCEDURE: 1.

2. 3. 4.

5.

Take 20kg of fine aggregate. Arrange the sieve in descending order with largest size on top. Sieve the material passing through the sieve and note the weight of sample on the sieve. Sieve the material passing through previous sieves by using the next lower size of the sieve and not the weight as in step 3. Repeat steps 3 through 4 until you have used all sieves.

OBSERVATION AND CALCULATION: Table-1 Weight of coarse aggregate taken =20 kg i.s. sieve size

Weight retained

(mm) 40 31.5 25 20 16

Nil Nil 0.250 14.8 4.8

Cumulative weight retained (kg) 0 0 0.250 15.05 19.85

Cumulative % Passing % retained

0 0 1.25 75.25 99.25

100 100 98.75 24.75 0.75

EXPERIMENT- DETERMINATION OF PARTICAL SIZE DISTRIBUTION OF COARSE AGGREGATE 12.5 10 Table-2

0.1 0.05

19.95 20.00

99.75 100

0.25 0

Weight of coarse aggregate taken = 10kg i.s. sieve size

Weight retained

(mm)

Cumulative Cumulative % Passing weight % retained retained (kg)

12.5 10 6.3 4.75 2.6

CLASSIFICATION OF AGGREGATES ➢ According to Source: 1.

Natural aggregate: Native deposits with no change in their natural state other than washing, crushing & grading. (sand, gravel, crush stone)

2.

Artificial aggregates: They are obtained either as a by-product or by a special manufacturing process such as heating. (blast furnace slag, expanded perlite)

➢ According to Unit Weight: 1.

Heavy weight agg.: Hematite, Magnetite Gravity, Gs > 2.8

Specific

EXPERIMENT- DETERMINATION OF PARTICAL SIZE DISTRIBUTION OF COARSE AGGREGATE 2.

Normal weight agg.:Gravel, sand, crushed stone 2.8 < Gs < 2.4

3.

Light weight agg.:Expanded perlite, burned clay Gs < 2.4

➢ According to Size: 1.

Fine aggregate: d ≤ 5 mm

2.

Coarse aggregate: d > 5 mm

Aggregates have 3 main functions in concrete: 1) To provide a mass of particles which are suitable to resist the action of applied loads & show better durability then cement paste alone. 2) To provide a relatively cheap filler for the cementing material. To reduce volume changes resulting from setting & hardening process & from moisture changes during drying.

Need and Scope: The grain size analysis is widely used in classification of soils. The data obtained from grain size distribution curves is used in the design of filters for earth dams and to determine suitability of soil for road construction, air field etc. Information obtained from grain size analysis can be used to predict soil water movement although permeability tests are more generally used.

EXPERIMENT- DETERMINATION OF PARTICAL SIZE DISTRIBUTION OF COARSE AGGREGATE

Sieve

Grading of Aggregates Grading is the particle-size distribution of an aggregate as determined by a sieve analysis using wire mesh sieves with square openings. Fine aggregate―7 standard sieves with openings from 150 μm to 9.5 mm Coarse aggregate―13 sieves with openings from 1.18 mm to 100 mm

Factors Affecting a Desired Grading 1) Surface area of the Aggregate The lower the surface area, the lesser is the paste requirement. 2) Relative Volume of Agg. in Concrete

EXPERIMENT- DETERMINATION OF PARTICAL SIZE DISTRIBUTION OF COARSE AGGREGATE

Limitations of sieve analysis: Sieve analysis has, in general, been used for decades to monitor material quality based on particle size. For coarse material, sizes that range down to #100 mesh (150μm), a sieve analysis and particle size distribution is accurate and consistent. However, for material that is finer than 100 mesh, dry sieving can be significantly less accurate. This is because the mechanical energy required to make particles pass through an opening and the surface attraction effects between the particles themselves and between particles and the screen increase as the particle size decreases. Wet sieve analysis can be utilized where the material analyzed is not affected by the liquid - except to disperse it. Suspending the particles in a suitable liquid transports fine material through the sieve much more efficiently than shaking the dry material.

EXPERIMENT- DETERMINATION OF PARTICAL SIZE DISTRIBUTION OF COARSE AGGREGATE Sieve analysis assumes that all particle will be round (spherical) or nearly so and will pass through the square openings when the particle diameter is less than the size of the square opening in the screen. For elongated and flat particles a sieve analysis will not yield reliable mass-based results, as the particle size reported will assume that the particles are spherical, where in fact an elongated particle might pass through the screen endon, but would be prevented from doing so if it presented itself side-on.

Engineering applications Gradation is usually specified for each engineering application it is used for. For example, foundations might only call for coarse aggregates, and therefore an open gradation is needed. Gradation is primarily a concern in pavement mix design. Concrete could call for both coarse and fine particles and a dense graded aggregate would be needed. Asphalt design also calls for a dense graded aggregate. Gradation also applies to subgrades in paving, which is the material that a road is paved on. Gradation, in this case, depends on the type of road (i.e. highway, rural, suburban) that is being paved.