GATE 2026 CE (CE1) – Question 61
In a bituminous mix, the percentage by weight of coarse aggregate, fine aggregate, filler, and bituminous binder is 58, 25, 12, and 5, respectively. The corresponding specific gravity of these materials is 2.68, 2.45, 2.42, and 1.15. The bulk specific gravity of the mix is 2.2.
The Voids Filled with Bitumen (VFB, in percentage) is ___________ (*rounded off to the nearest integer*).
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Correct answer: 50
Explanation
The theoretical maximum specific gravity is $G_t = \frac{100}{\frac{58}{2.68} + \frac{25}{2.45} + \frac{12}{2.42} + \frac{5}{1.15}} = \frac{100}{41.153} = 2.430$. The air voids are $V_v = \frac{2.430 - 2.2}{2.430} \times 100 = 9.47\%$. The volume of bitumen is $V_b = \frac{5}{1.15} \times 2.2 = 9.57\%$. Then $\text{VFB} = \frac{V_b}{V_v + V_b} \times 100 = \frac{9.57}{19.03} \times 100 = 50\%$.