Definition check: An aggregate is termed “cyclopean” when the nominal size of individual stones exceeds

Introduction / Context:
Cyclopean concrete is mass concrete in which very large stones (often field boulders) are embedded to reduce cement consumption and heat of hydration. Recognizing the size threshold helps classify the work and choose appropriate placement methods.

Given Data / Assumptions:

• Terminology used in traditional building/construction texts.
• Nominal stone size defines the category.

Concept / Approach:
While maximum aggregate sizes in ordinary concrete are commonly 20–40 mm, cyclopean work uses much larger stones. A practical threshold often cited is stones larger than about 75 mm being treated as “cyclopean” rather than standard coarse aggregate, with many applications using stones 150 mm or more in mass foundations.

Step-by-Step Solution:
Compare options with ordinary aggregate limits.Select the earliest threshold that clearly exceeds standard coarse aggregate sizes → 75 mm.Note that in practice, stones may be much larger, but the classification begins once size exceeds typical maximum aggregate limits.

Verification / Alternative check:
Older specifications for cyclopean masonry/concrete reference hand-placed stones well above 75 mm; anything at or above this threshold departs from normal aggregate grading.

Why Other Options Are Wrong:
4.75 mm, 30 mm, and 60 mm fall within fine or normal coarse aggregate ranges; 90 mm could also qualify but 75 mm is the commonly accepted threshold in many texts.

Common Pitfalls:
Confusing maximum aggregate size in standard mixes (20–40 mm) with boulder sizes in cyclopean work; neglecting the need for careful placement and mortar bedding around large stones.

Final Answer:
75 mm.