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GATE 2024 CE (CE2) – Question 46

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

In the context of pavement material characterization, the CORRECT statement(s) is/are

  1. The load penetration curve of CBR test may need origin correction due to the non-vertical penetrating plunger of the loading machine.
  2. The toughness and hardness of road aggregates are determined by Los Angeles abrasion test and aggregate impact test, respectively.
  3. Grading of normal (unmodified) bitumen binders is done based on viscosity test results.
  4. In compacted bituminous mix, Voids in the Mineral Aggregate (VMA) is equal to the sum of total volume of air voids ($V_v$) and total volume of bitumen ($V_b$).

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Show answer and explanation

Correct answer: (C) Grading of normal (unmodified) bitumen binders is done based on viscosity test results.; (D) In compacted bituminous mix, Voids in the Mineral Aggregate (VMA) is equal to the sum of total volume of air voids ($V_v$) and total volume of bitumen ($V_b$).

Explanation

A is false: the origin correction in the CBR test is needed because of an initial concave-upward portion of the curve (surface irregularities or a seating error), and not because the plunger is not vertical. B has the tests reversed: the Los Angeles abrasion test gives the hardness (resistance to abrasion) and the impact test gives the toughness. C is true: the VG grades of unmodified bitumen are fixed by the viscosity at 60 °C. D is true: VMA = $V_v + V_b$ (with the effective bitumen volume).