Question

An asphalt concrete mixture includes 94% aggregates by weight. The specific gravity of aggregate and asphalt are 2.7 and 1.0, respectively. If the bulk density of the mix is 2.317 g/cm3, what is the percent voids in the total mix?

Answer 1

Answer:

The correct solution is "5.74%".

Explanation:

The given values are:

Gravity of aggregate,

$G_{agg}=2.7$

Gravity of asphalt,

$G_{asp}=1.0$

Asphalt concrete mixture,

$W_{agg}=0.94 \ W_m$

We know that,

$W_{asp}=W_m-W_{agg}$

        $=0.06 \ W_m$

Now,

The theoretical specific gravity of mix,

⇒ $G_t=\frac{W_{agg}+W_{asp}}{\frac{W_{agg}}{G_{agg}} +\frac{W_{asp}}{G_{asp}} }$

By putting the values, we get

         $=\frac{0.94 \ Wm+0.06 \ Wm}{\frac{0.94 \ Wm}{2.7} +\frac{0.06 \ Wm}{1} }$

         $=2.45$

hence,

The percentage of voids will be:

⇒  %V = $\frac{G_t-G_m}{G_t}\times 100$

           = $\frac{2.45-2.317}{2.45}\times 100$

           = $\frac{0.133}{2.317}\times 100$

           = $5.74$ (%)