Water–Cement Ratio Expression – common site convention In many site references, the water–cement requirement is expressed as the volume/mass of water needed per one standard cement bag. This “bag-basis” convention is generally stated per how many kilograms of cement?

Introduction / Context:
While the true water–cement ratio (w/c) is a mass ratio (water mass divided by cement mass), many field guides and rules of thumb historically refer to water per cement bag to communicate target water in liters or kilograms. Recognizing this conventional basis avoids confusion in site communications and mix tickets.

Given Data / Assumptions:

• Standard cement bag mass in Indian practice is 50 kg.
• Rule-of-thumb values (for example, ~28 kg of water per bag for “normal” workability) are often cited.
• Design mixing still requires w/c by mass; the “per bag” expression is a convenience.

Concept / Approach:

The bag-basis convention ties practical water dosing to the ubiquitous 50 kg bag. For correct proportioning, convert any bag-based figure to w/c by mass. For example, 28 kg water per 50 kg bag implies w/c ≈ 0.56.

Step-by-Step Solution:

Verification / Alternative check:

Mix design sheets often present both forms: w/c ratio and equivalent liters per 50 kg bag for field convenience.

Why Other Options Are Wrong:

10–40 kg do not correspond to the standard cement bag commonly used in practice and would mislead on dosing.

Common Pitfalls:

Treating “liters per bag” as universal without converting to w/c; ignoring aggregate moisture which changes effective water content.

Final Answer:

50 kg