$5-$ Design a concrete mix using ACl$211\mathrm{.}1-91$ for the following information:

Cement type $=$ OPC

$-f^{\text{'}}C,=,30$MPa

Slump $,=,50mm$

Exposure $=$ thin section exposed to sea water

NMS $,=20mm$

$FM$ of sand $,=,2\mathrm{.}5$

Bulk density of sand & coarse aggregate $=,1650k\frac{g}{m^3}$

Specific gravity of sand & coarse aggregate $=,2\mathrm{.}6$&$2\mathrm{.}65$ respectively

Admixture dosage $,=,1\%$ of cement weight

Density of admixture $,=,1\mathrm{.}2k\frac{g}{l}it$

$6-$ Repeat problem $(5)$ if the concrete structure is thin section exposed to moderate freezing & thawing cycles.