Concrete strength classification: what is the permissible compressive strength of M300 grade concrete expressed in kg/cm^2?

Introduction / Context:
Concrete grades are designated by their characteristic compressive strength after 28 days of curing. The letter “M” refers to mix, and the number denotes compressive strength in N/mm^2. This can be converted to kg/cm^2 for interpretation.

Given Data / Assumptions:

• M300 grade concrete.
• Standard conversion: 1 N/mm^2 = 10.2 kg/cm^2 (approx.).

Concept / Approach:
M300 grade = 30 N/mm^2 = 30 × 10.2 = 306 kg/cm^2 ≈ 300 kg/cm^2. This is the permissible compressive strength value in the given unit system.

Step-by-Step Solution:
M300 → 30 N/mm^2.Convert: 30 × 10.2 = 306 kg/cm^2.Rounded → 300 kg/cm^2.

Verification / Alternative check:
Design tables and IS code conversions confirm this mapping between N/mm^2 and kg/cm^2.

Why Other Options Are Wrong:

• 100–250 kg/cm^2 correspond to lower concrete grades such as M10–M25.

Common Pitfalls:

• Confusing kg/cm^2 and N/mm^2 units, leading to major errors in design.

Final Answer:
300 kg/cm2