Air content definition in phase relationships: The ratio of the volume of air voids to the volume of total voids of a soil mass is called:

Introduction / Context:
Describing the state of a soil requires several volumetric ratios. Besides void ratio and porosity, technicians often report how much of the void space is air versus water. This question targets the correct name for the ratio involving air voids and total voids.

Given Data / Assumptions:

• Three-phase soil system: solids, water, and air.
• V_v = V_a + V_w (total voids = air + water volume).
• We seek the ratio V_a / V_v.

Concept / Approach:

By definition: air content a = V_a / V_v. Related but different terms include porosity n = V_v / V_t, percentage air voids = (V_a / V_t) * 100%, and degree of saturation S = V_w / V_v. Distinguishing these prevents misinterpretation of lab results and compaction targets.

Step-by-Step Solution:

Verification / Alternative check:

Check companion definitions to ensure no confusion with porosity or saturation.

Why Other Options Are Wrong:

(b) Percentage air voids uses V_a / V_t, not V_a / V_v. (c) Percentage voids is V_v / V_t. (d) Porosity is also V_v / V_t. (e) Degree of saturation is V_w / V_v.

Common Pitfalls:

Interchanging “air content” with “percentage air voids”; confusing void-based ratios with total-volume ratios.

Final Answer:

Air content