In lime classification for construction, the lime containing a high percentage of calcium oxide (nearly pure, low clay) is generally called what? Pick the standard term used in civil engineering.

Introduction / Context:
Limes are grouped by composition and setting behavior. Recognizing the name for high-calcium, low-impurity lime is basic in materials courses and site practice for mortar selection and plastering work.

Given Data / Assumptions:

• High CaO content, minimal clay/insolubles.
• Air-setting (carbonation) behavior predominates; poor underwater setting.
• Common synonyms appear in literature.

Concept / Approach:

High-calcium lime is traditionally termed “fat lime” because it is plastic and workable, “rich” in lime content. Some texts use “rich lime” as a synonym, but “fat lime” is the standard term in exam keys and specifications. It contrasts with hydraulic lime, which contains reactive silicates/aluminates enabling setting under water.

Step-by-Step Solution:

Verification / Alternative check:

Traditional plastering specs refer to fat lime putty for high-finish work requiring slow set and fine workability.

Why Other Options Are Wrong:

Rich lime: sometimes used synonymously but not the standard single best choice. White lime: color descriptor, not classification. Hydraulic lime: compositionally different due to clay.

Common Pitfalls:

Thinking “rich” is a separate category; in most exam contexts, “fat” is the accepted name for high-calcium lime.

Final Answer:

Fat lime