What is the flakiness and elongation index of an aggregate?
What is the flakiness and elongation index of an aggregate?
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 aggregate elongation index?
Elongation index of an aggregate is the percentage by weight of particles whose greatest dimension (length) is greater than one and four-fifth times (1.8 times or 9/5 times) their mean dimension. It is measured on particles passing through mesh size of 63mm and retained on mesh size of 6.3mm.
How do you determine the flakiness index of road aggregates?
Then the flakiness index is calculated as the total weight of material passed through various thickness gauges, expressed as a percentage of total weight of the sample gauged. Flakiness Index of aggregates used in road construction should be less than 15% and normally does not exceed 25%.
What is flaky aggregate?
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.
Why do we do flakiness and elongation?
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; Due to high surface area to volume ratio, the flaky and elongated particles lower the workability of concrete mixes.
What is the purpose of flakiness and elongation test?
This test gives the percentage of flaky and elongate aggregate present in the total aggregate sample. Aggregate shape, size, and surface texture majorly affect the properties of freshly mixed concrete more than the properties of hardened concrete.
How do you calculate elongation index?
The Elongation index of aggregate is the % by weight of the particles (aggregates) whose length is greater than 1 and 4/5th (1.8 times) of their mean dimension.”
Why do we determine the elongation index?
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 is the purpose of flakiness index?
The test Flakiness index of aggregate is used to determine the particle shape of the aggregate specimen and each particle shape being preferred under specific condition.
Why are flaky aggregates not preferred?
Flaky particles tend to orient in one plane and cause laminations which adversely affect the durability of the concrete. Flaky aggregate was shown to have lower compatibility and higher breakage . Highly flaky aggregates have more voids and reduce the workability.
How are flakiness index and elongation index values determined in the laboratory?
The flakiness index of an aggregate sample is found by separating the flaky aggregates by sieving. Flakiness index is expressed as their weight as a percentage of the weight of the sample tested. The Elongation index of an aggregate sample is found by separating the elongated aggregates by sieving.
