IS 456 concrete grades: approximately how many standard grades of concrete mixes are designated in the code (e.g., M10, M15, M20, …)?

Introduction / Context:
Indian Standard IS 456 designates concrete grades by characteristic compressive strength (e.g., M10, M15, M20…). Awareness of the range of grades is foundational for specifying concrete in structural and non-structural applications.

Given Data / Assumptions:

• The question references the commonly taught count of standard grades used in general practice.
• Lower grades (M10–M25) were historically linked with nominal mixes; higher grades require designed mixes.

Concept / Approach:
Educational summaries often present a set spanning about seven commonly referenced grades for routine building work (e.g., M10, M15, M20, M25, M30, M35, M40). Modern editions list additional higher grades, but the classic count frequently cited in exam contexts is seven.

Step-by-Step Solution:
Identify the standard lineup used in basic design education.Recognize the exam convention of seven principal grades.Select 7.

Verification / Alternative check:
While current practice covers many grades beyond seven, the question’s options point to the classical exam reference set.

Why Other Options Are Wrong:
3–6 underestimate the widely used range; they do not match the conventional teaching scope.

Common Pitfalls:
Confusing historical exam conventions with the full modern list of grades; always consult the latest IS 456 for project specifications.

Final Answer:
7