Definition of water–cement ratio — choose the correct expression In concrete technology, how is the water–cement ratio (w/c) defined?

Introduction / Context:
Water–cement ratio (w/c) is a foundational parameter controlling the porosity of the hardened cement paste, and thus strength and durability. Precise definition is essential for calculations and quality control.

Given Data / Assumptions:

• Conventional practice defines w/c on a mass (weight) basis.
• Batching by mass is assumed for accuracy.

Concept / Approach:
The standard definition is w/c = mass of water divided by mass of cement. Volume-based ratios are sometimes discussed conceptually but are not the standard definition used in design or specification, because densities vary with temperature and entrained air, making mass-based control more reliable.

Step-by-Step Solution:

Verification / Alternative check:
Codes, mix-design methods, and batching systems all specify w/c by weight (e.g., 0.45, 0.50).

Why Other Options Are Wrong:

• Volume ratios are not the standard definition and can be misleading.
• Options (c) and (d) do not define w/c at all.
• Option (e) is incorrect because only the mass-based definition is standard.

Common Pitfalls:
Confusing water–cement ratio with total water content per cubic metre; not accounting for aggregate moisture when calculating effective water.

Final Answer:
Weight of water to weight of cement