alleryStart learning →Compressive strength of M40 concrete at 28 days:
A400 MPa
B20 MPa
C40 N/mm² (= 40 MPa, by definition of M40)
D4 MPa
Answer & Solution
Correct answer: C. 40 N/mm² (= 40 MPa, by definition of M40)
**M-grade concrete:** M_x where x = characteristic compressive strength in N/mm² at 28 days (cube test).
M40 = 40 N/mm² = 40 MPa.
**Common grades:** M20 (typical residential), M25 (commercial), M30, M40 (high-rise, bridges).
Higher grades (M60+) for special structures.
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