In building materials terminology, “Jhumb” (also spelled Jhama/Jhama) bricks refer to bricks that have been excessively fired during the kiln process. These over-burnt units become dark, vitrified, and distorted; they are often crushed and used as aggregate rather than for face masonry. Such Jhumb bricks are:

Introduction / Context:
The classification of burnt clay bricks depends on the degree of burning in the kiln. Correctly identifying “Jhumb/Jhama” bricks is important for selecting suitable uses on site, such as structural masonry versus road sub-base or aggregate applications.

Given Data / Assumptions:

• The term “Jhumb” refers to bricks that have undergone abnormal heating.
• We compare against standard categories: under-burnt, well-burnt, over-burnt, and unburnt (kutcha).
• No numerical calculation is required; this is a definition/identification item.

Concept / Approach:
Over-burnt bricks are exposed to excessive temperature and/or longer firing periods. The result is vitrification, warping, bloating, and very dark color. Such bricks are extremely hard but dimensionally distorted; therefore, they are rarely used in masonry courses and are commonly crushed for sub-base or as a coarse aggregate substitute.

Step-by-Step Solution:

Verification / Alternative check:
Traditional civil engineering texts consistently use “Jhama/Jhumb” for over-burnt bricks and describe their typical repurposing as aggregate in road works and foundations.

Why Other Options Are Wrong:

• Under burnt: these are pale, weak, and absorbent; not vitrified.
• Kutcha: sun-dried, not fired at all.
• None of these: incorrect since “over burnt” exactly matches.

Common Pitfalls:

• Confusing the high hardness of over-burnt bricks as desirable for masonry without considering their distortion.
• Assuming “Jhumb” means under-burnt due to defect association; it actually indicates over-burning.

Final Answer:
over burnt