The formula for specific gravity of fine aggregates as per IS 2386 (part 3) 1963 using the pycnometer is given by the following: Specific gravity = (W2 - W1) / ((W2 - W1) - (W3 - W4)) Where, W1 = Empty weight of pycnometer W2 = Weight of pycnometer + sample W3 = Weight of pycnometer + sample + water W4 = Weight of pycnometer + water
- ACorrectCorrect
- BPartially incorrect
- CPartially correct
- DIncorrect
Solution
Concept
Specific gravity = weight of dry sample / weight of equal volume of water
Formula
G = (W2 - W1) / ((W2 - W1) - (W3 - W4))
Step-by-step solution
1. Weight of dry sample = W2 - W1 2. Standard form: G = (W2 - W1) / ((W4 - W1) - (W3 - W2)) 3. Expand the denominator: W4 - W1 - W3 + W2 = (W2 - W1) - (W3 - W4) 4. So the given formula is the same as the standard formula. It is correct.
Explanation
The numerator is the dry weight of the sample. The denominator is the weight of water displaced by the sample. The given form is the standard pycnometer formula rearranged, so it is correct.
Why the other options are wrong
B, C and D are wrong because the given formula is algebraically equal to the standard pycnometer formula, with nothing missing or wrong.
Shortcut
Denominator = sample weight minus (W3 - W4), which is the weight of water displaced.
Common mistake
Mixing up W3 and W4, which gives a wrong sign in the denominator.
Correct answer: A) Correct