Question

The specific gravities and weight proportion for various ingredients of bituminous mix are as under:

Ingredients	Specific gravity weight	Weight (gms)
Coarse aggregate (20 mm)	2.63	825
Coarse aggregate (12 mm)	2.51	1200
Fine aggregate	2.46	325
Filler	2.43	150
Bitumen	1.05	100

If the bulk specific gravity of the mix is 2.316, then the percentage voids filled with bitumen is :

• A. 72.21%
• B. 62.32%
• C. 69.67%
• D. 66.67%

Answer 1

The correct option is C 69.67%

$G_t=\frac{825+1200+325+150+100}{\frac{825}{2.63}+\frac{1200}{2.51}+\frac{325}{2.46}+\frac{150}{2.43}+\frac{100}{1.05}}=2.406$

$G_m=2.316\left(given\right)$

$V_b=G_m\times \frac{W_b}{G_b}=\frac{2.316}{1.05}\times \frac{100\times 100}{825+1200+325+150+100}=8.48\%,$

$V_v=\frac{G_t-G_m}{G_t}\times 100=\frac{2.406-2.316}{2.406}\times 100=3.74\%$

$V_{FB}=\frac{V_b\times 100}{V_v+V_b}=\frac{8.48\times 100}{8.48+3.74}=69.39\%$