Terminology in concrete materials: In a cement concrete mix, which component is referred to as the “inert” material that provides the bulk of the volume?

Introduction / Context:
Concrete is a composite of active binders (cement paste formed by cement and water) and relatively inert fillers (aggregates). Understanding which component is considered “inert” clarifies the roles each plays in performance and economy.

Given Data / Assumptions:

• Ordinary Portland cement concrete without chemical reactions from aggregates (i.e., non-reactive aggregates).
• Aggregates are clean and stable.

Concept / Approach:
Aggregates primarily provide volume, dimensional stability, and restraint to shrinkage. They do not participate in the hydration reactions (except in problematic alkali–silica or carbonate reactions). Cement and water are the active components forming the binding paste (C-S-H and other hydrates); water is also a reactant and a medium for workability.

Step-by-Step Solution:
Identify binder system → cement + water = reactive paste.Recognize aggregates as bulk filler → inert under normal conditions.Hence select “Aggregates.”

Verification / Alternative check:
Specifications and textbooks define aggregates as inert granular materials embedded in the cement paste matrix.

Why Other Options Are Wrong:
Water and cement are chemically active; “air” is not a constituent deliberately added as inert material (except in air-entrained mixes where micro-air improves durability, not volume bulk).

Common Pitfalls:
Assuming aggregate quality is unimportant because it is “inert”; in fact, its properties profoundly affect concrete behavior.

Final Answer:
Aggregates.