$($a$)$ As a graduate structural engineer, you have assumed a $28-$day characteristic$($a$)$ As a graduate structural engineer, you have assumed a $28-$day

characteristic strength of $35\frac{N}{m}m2$ in your design calculations for a

project. You are now required to provide the quantities of materials

needed for the concrete mix for the construction of the following

structural elements which are part of your design:

Reinforced concrete beams $-10$ number of $250mm450mm$ beam

of length $7m.$

Reinforced Concrete Columns $-20$ number of $300mm300mm$

columns of $3m$ height.

Assume a standard deviation of $12\frac{N}{m}m2$ with a $1\%$ defective rate.

Also assume that ordinary Portland $($Class $42\mathrm{.}5)$ or Sulphate

Resistance Portland cement is used, and aggregate are to be

obtained from a nearby river. Coarse aggregate cannot be more than

$20mm$ in size and $70\%$ of the fine aggregate must be finer than

$600m$ in size.

For this project, a workability of $10-30mm$ slump is required, and the

maximum water cement ratio is $0\mathrm{.}6.$ Based on experience on other

projects, you have been advised by your team lead to ensure the

cement content for $1m3$ of concrete is at least $300kg.$

strength of $35$ N$/$mm$2$

in your design calculations for a project. You are now

required to provide the quantities of materials needed for the concrete mix for the

construction of the following structural elements which are part of your design:

Reinforced concrete beams $-10$ number of $250$ mm x $450$ mm beam of length $7$

m$.$

Reinforced Concrete Columns $-20$ number of $300$ mm x $300$ mm columns of $3$ m

height.

Assume a standard deviation of $12$ N$/$mm$2$

with a $1\%$ defective rate. Also assume

that ordinary Portland $($Class $42\mathrm{.}5)$ or Sulphate Resistance Portland cement is

used, and aggregate are to be obtained from a nearby river. Coarse aggregate

cannot be more than $20$ mm in size and $70\%$ of the fine aggregate must be finer

than $600$m in size.

For this project, a workability of $1030$ mm slump is required, and the maximum

water cement ratio is $0\mathrm{.}6.$ Based on experience on other projects, you have been

advised by your team lead to ensure the cement content for $1$m$3$

of concrete is at

least $300$ kg