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GATE 2017 CE (CE1) – Question 42

Highway Pavements · Highway materials and tests · 2 marks · Multiple choice

For a pavement aggregate test: oven-dry mass in air = 1000 g; saturated surface-dry mass in air = 1025 g; saturated surface-dry mass under water = 625 g. Choose the correct result.

  1. Bulk specific gravity 2.5; absorption 2.5%.
  2. Bulk specific gravity 2.5; absorption 2.4%.
  3. Apparent specific gravity 2.5; absorption 2.5%.
  4. Apparent specific gravity 2.5; absorption 2.4%.

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Show answer and explanation

Correct answer: (A) Bulk specific gravity 2.5; absorption 2.5%.

Explanation

The bulk volume equals the displaced-water mass $1025-625=400$ g divided by water density. Hence dry bulk specific gravity is $1000/400=2.5$. Absorption is measured against oven-dry mass: $(1025-1000)100/1000=2.5\%$. Apparent specific gravity instead excludes permeable pores and is $1000/(1000-625)=2.667$. Thus A.

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