APSC AE WRD 2019 PYQ: Brick Crushing Strength

First-Class Brick Crushing Strength Multiple Choice Question

Question: A first-class brick should have a minimum crushing strength of:
(A) 7.0 MN/m²
(B) 10.5 MN/m²
(C) 12.5 MN/m²
(D) 14.0 MN/m²

Answer: (B) 10.5 MN/m²

Explanation

According to the Indian Standard (IS 1077:1992), a first-class brick must have a minimum compressive (crushing) strength of 10.5 MN/m² (or 105 kg/cm²). This standard ensures that first-class bricks are suitable for use in high-quality, load-bearing structures due to their strength and durability.

Characteristics of Brick Classes

Brick Class	Crushing Strength (Min)	Key Characteristics	Typical Usage
First-Class Brick	10.5 MN/m² (105 kg/cm²)	Made from high-quality clay, well-burnt, uniform red color, smooth surface, sharp edges, water absorption ≤20%.	Load-bearing walls, exposed masonry, permanent structures.
Second-Class Brick	7.0–10.5 MN/m² (70–105 kg/cm²)	Moderate quality clay, slightly over/under-burnt, minor cracks, water absorption ≤22%.	Internal walls, plastered surfaces, non-load-bearing walls.
Third-Class Brick	< 7.0 MN/m² (< 70 kg/cm²)	Poor quality clay, under-burnt, irregular shape, water absorption >25%.	Temporary structures, low-cost construction in dry climates.
Fourth-Class Brick	Varies (irregular)	Over-burnt, distorted shape, brittle, clinkered surfaces.	Aggregate for road construction, foundations, or filling material.

Key Notes

• The crushing strength of a brick determines its suitability for structural applications, with first-class bricks being the strongest and most reliable.
• First-class bricks are characterized by their uniform texture, compact structure, and low water absorption, making them ideal for high-quality construction.
• Second-class and third-class bricks are used in less critical applications due to their lower strength and quality.
• Fourth-class bricks are typically considered waste and repurposed as aggregates rather than used in structural work.

Note: The minimum crushing strength of 10.5 MN/m² for first-class bricks, as per IS 1077:1992, ensures their reliability in load-bearing and permanent structures in civil engineering projects.

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