In a 1:2:4 mix by volume, which component corresponds to the 2-part proportion?

• A. Cement
• B. Coarse aggregate
• C. Water
• D. Fine aggregate (sand)

Answer: (D)

In a 1:2:4 mix by volume, the numbers show how much cement, fine aggregate, and coarse aggregate to combine. The 2-part proportion corresponds to the fine aggregate, which is sand. Fine aggregate fills the voids between cement grains and larger stones, helps with workability, and contributes to the overall strength and density of the concrete. Water isn’t part of this solid-material ratio; it’s added separately to achieve the desired workability and to control the hydration process, via the water–cement ratio. So the 2 parts refer to the sand (fine aggregate).