Problem $4-$ Fire Ratings for a RC Column

A reinforced concrete column $($made of normal strength concrete$)$ is to be provided in a

multistory building. The required fire resistance rating for columns is $3$ hours. Determine the

minimum design specifications needed to achieve the required fire ratings if the concrete is of:$-$

$($a$)$ Quartz aggregate

$($b$)$ Limestone aggregate

$($c$)$ Light$-$weight aggregate