This set of Railway Engineering Multiple Choice Questions & Answers focuses on “Laboratory Tests for Physical Properties of Ballast”.
1. Los Angeles machine is used for which of the following tests?
a) Aggregate abrasion value
b) Aggregate impact test
c) Water absorption test
d) Flakiness index
Explanation: The aggregate should have resistance to abrasion. The aggregate abrasion value is checked by using Los Angeles machine.
2. What is the diameter of the cylinder used for Aggregate impact value?
c) 75 inches
Explanation: The ballast sample is oven dried and placed in a metal cylinder with 75mm diameter and 50mm depth. The ballast is duly tamped in different stages while placing.
3. What is the weight of the test hammer used for Aggregate impact value?
b) 140 grams
d) 1200 grams
Explanation: Weight of the test hammer is about 14kg and it’s made to fall on the surface of the cylinder from a height of 380mm. The sample is subjected to 15 such blows.
4. Flakiness is the percentage by weight of particles with a least dimension less than ________ of their mean dimension.
Explanation: Flakiness index of an aggregate is defined as the percentage by weight of particles with least dimensions less than three fifths of mean dimension. Size smaller than 6.3mm are not suitable for test.
5. What is the temperature for oven drying of aggregates for Specific gravity and water absorption test?
Explanation: Weight of saturated aggregates in water, saturated dry aggregates in air and oven dried aggregates in air is taken for calculation of specific gravity and water absorption of aggregates.
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