Experimental water absorption tests are done on fine aggregates to find the: (i) Water holding capacity (ii) Strength of material (iii) Quality of material (iv) Shape of aggregates
- A(i), (ii), (iii), and (iv)
- BOnly (i)
- CBoth (i) and (ii)
- DOnly (i), (ii) and (iii)Correct
Solution
Concept
Water absorption shows the porosity of aggregate. Porosity tells us its water holding capacity, strength and quality.
Formula
Water absorption (%) = [(WSSD − Wdry) / Wdry] × 100
Step-by-step solution
1. The water absorption test measures how much water the aggregate takes into its pores. 2. High absorption means more pores, so it gives the water holding capacity (i). 3. More pores means weaker aggregate, so it gives an idea of strength (ii). 4. A porous aggregate has lower durability and quality, so it also tells us about quality (iii). 5. Shape (iv) is checked by flakiness and elongation index tests, not by water absorption. 6. So (i), (ii) and (iii) are correct. Answer is D.
Explanation
The water absorption test shows how porous the aggregate is. Porous aggregate holds more water, is weaker and is of lower quality. Shape cannot be found by this test.
Why the other options are wrong
A: shape is not found by water absorption. B: the test also indicates strength and quality. C: it also indicates quality.
Shortcut
Absorption means pores. Pores tell you water holding, strength and quality, but not shape.
Common mistake
Students pick only (i) because they think absorption gives only water holding capacity.
Correct answer: D) Only (i), (ii) and (iii)