Question

Consider the following particulars in respect of a concrete mix design:

	Weight	Specific Gravity
Cement	$400kg/m^3$	3.2
Fine aggregates	_	2.5
Coarse aggregates	$1040kg/m^3$	2.6
Water	$200kg/m^3$	1.0

What shall be the weight of the Fine aggregates?

• A. $520kg/m^3$
• B. $570kg/m^3$
• C. $690kg/m^3$
• D. $1000kg/m^3$

Answer 1

The correct option is C $690kg/m^3$

For $1m^3$ of concrete,

$1=\frac{W_c}{{\rho }_c}+\frac{W_{ca}}{{\rho }_{ca}}+\frac{W_w}{{\rho }_w}+\frac{W_{fa}}{{\rho }_{fa}}$

$\Rightarrow 1=\frac{400}{3.2\times 1000}+\frac{1040}{2.6\times 1000}+\frac{200}{1\times 1000}+\frac{W_{fa}}{2.5\times 1000}$

$W_{fa}=(1-0.125-0.4-0.2)\times 2.5\times 1000$
$=687.5kg/m^3\simeq 690kg/m^3$