Pycnometer, wire mesh bucket and water are used to calculate which characteristic property of the coarse aggregate?
- ACrushing strength
- BSpecific gravityCorrect
- CAttrition
- DImpact value
Solution
Concept
Specific gravity of aggregate is found by weighing it in water and in air. A wire basket is used for coarse aggregate and a pycnometer for finer sizes.
Formula
G = C / (C - (A - B)), where A = weight of basket + aggregate in water, B = weight of empty basket in water, C = oven-dry weight of aggregate in air
Step-by-step solution
1. The tools given are a pycnometer, a wire mesh basket and water. 2. These are used to weigh aggregate in water and in air. 3. Weight in air and weight in water give specific gravity and water absorption. 4. So the property is specific gravity.
Explanation
The wire basket test (and the pycnometer for smaller sizes) finds specific gravity and water absorption of aggregate. The aggregate is weighed in water, then surface dried and oven dried, and weighed in air. Specific gravity is the ratio of dry weight to the weight of an equal volume of water.
Why the other options are wrong
A: Crushing value uses a steel cylinder, a plunger and a compression testing machine. C: Attrition uses the Los Angeles or Deval abrasion machine. D: Impact value uses the impact testing machine with a falling hammer.
Shortcut
Water + basket or pycnometer = weighing in water = specific gravity.
Common mistake
Mixing up the pycnometer test with tests for strength or toughness of aggregate.
Correct answer: B) Specific gravity