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Why flakiness and elongation test is done?

Why flakiness and elongation test is done?

This test is used to determine the particle shape of the aggregate and each particle shape being preferred under specific conditions. The significance of flakiness & elongation index is as follows; The degree of packing of the particles of one size depends upon their shape.

What is the importance of testing aggregate?

Hence it is essential that they should be thoroughly tested before using for construction. Not only that aggregates should be strong and durable, they should also possess proper shape and size to make the pavement act monolithically. Aggregates are tested for strength, toughness, hardness, shape, and water absorption.

Where is the flakiness test used?

This method uses to measure the Flakiness Index and Elongation index of aggregate use in the construction of Highway pavement and concrete structures.

How the shape flakiness and elongation of the aggregate can affect the strength towards pavement?

Flaky and elongated particles have larger specific surface area, which results in higher demand of cement paste in cement concrete mix. These particles impede compaction or break during rolling and decrease the strength of pavement layer.

What is the significance of flakiness index?

The flakiness index is defined as the percentage (by mass) of stones in an aggregate having an ALD of less than 0.6 times their average dimension. Flaky aggregates tend to produce seals with less voids due to their tendency to pack more tightly than cubical aggregates, consequently flaky particles require less binder.

How are flakiness index and elongation index values determined in the laboratory discuss the importance of the test?

The Flakiness Index of aggregates is the percentage by weight of particles whose least dimension (thickness) is less than 0.6 times their mean dimension. The Elongation Index of aggregates is the percentage by weight of particles whose greatest dimension (length) is greater than 1.8 times their mean dimension.

What is flaky aggregate?

What is elongation index test?

Elongation index test of an aggregate is the percentage by weight of particles whose greatest dimensions is greater than 1.8 times their mean dimensions. This test is also applicable to aggregates having size larger than 6.3 mm.

Which test is performed first flakiness or elongation?

First you need to separate out the flaky particles. Now you are left with non-flaky particles. Now, you need to find the amount of elongated particles to the aggregates which passed flakiness test. Finally, you can have numerical sum of flakiness index and elongation index to get Combined F&E Index.

What is the significance of shape of aggregate?

Aggregate particle shape and surface texture are important for proper compaction, deformation resistance, and workability.

What is effect of flaky and elongated aggregates?

The results reveal that the effect of elongated aggregates is more than flaky aggregates, on the characteristic compressive strength of concrete. Concrete with 1:1 ratio of flaky to elongated aggregates possesses minimum weight.

What are the tests for flakiness and elongation index?

FLAKINESS AND ELONGATION INDEX INDEX TEST 1 SHAPE TEST. The particle shape of aggregate is determined by the percentage of flaky and elongated particles contained in it. 2 FLAKINESS INDEX TEST. To determine flakiness index of a given aggregates sample. 3 ELONGATION INDEX. AIM: To determine elongation index of given aggregate sample.

Why is the flakiness and elongation index of aggregate samples important?

Determination of the flakiness and elongation index of an aggregate sample is important for the following reasons: The degree of packing or inter-locking of an aggregate sample depends on the shape of the particles in the mix, therefore, too many flaky or elongated particles can prove an obstacle in achieving the desired packing of aggregates.

How to calculate flakiness index of elongation gauge slot?

Note: Test can be conducted for each range of elongation gauge slot. Flakiness Index = weight of aggregate retained on length gauge of 10 mm to 6.3 mm (W2) / Total weight of aggregate sample taken (W1)

What is the maximum flakiness index allowed in BS 1241?

According to BS-1241, a flakiness index should not exceed 30% irrespective of the aggregate size. Maximum permitted elongated index is 35%, 40% or 45% for aggregate size 21/2” – 2”, 11/2” – ¾” and 1/2” – ⅜”. Both Flakiness index Elongation Index tests are not applicable to the materials of sizes smaller than 6.3 mm i.e. ¼” sieve.