Question

It is given that an aggregate mix has 260 grams of coarse aggregates and 240 grams of fine aggregates. The specific gravities of the coarse and fine aggregates are 2.6 and 2.4, respectively. The bulk specific gravity of the mix is 2.3. The percentage air voids in the mix is _________. (round off to the nearest integer)

Hint:

Air voids represent the amount of void space in a mix that is not filled by aggregates.

Answer 1

Correct Answer: 8

The bulk specific gravity of the mix (G\(_b\)) is given by the equation: \[ G_b = \frac{W_c}{V_c \cdot G_s} + \frac{W_f}{V_f \cdot G_s}, \] where:
- \( W_c = 260 \) g (weight of coarse aggregate)
- \( W_f = 240 \) g (weight of fine aggregate)
- \( G_s = \) specific gravity of the aggregates.
To calculate the percentage air voids, we use the formula for air voids: \[ V_a = 100 \cdot \left( 1 - \frac{G_b}{G_s} \right). \] From the calculation, we get: \[ \boxed{8} \, \text{percent}. \]