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What is the meaning of the designation ‘M30’ concrete suggested for a reinforced cement concrete work?

What is the meaning of the designation ‘M30’ concrete suggested for a reinforced cement concrete work? Correct Answer The mix characteristic compressive strength of 150 mm size cube at 28 days is 30 N/mm<sup>2</sup>.

The strength of a concrete mix is specified as its characteristic strength.

The characteristic strength of a concrete mix is defined as the compressive strength of 150 mm cube at 28 days expressed in N/mm2 below which not more than 5 per cent of the test results are expected to fall.

The different concrete mixes are graded, and each mix is identified by its grade designation. In the designation of the concrete, mix, a letter M is used to denote the mix and a number is specified, which is numerically equal to characteristic strength at 28 days.

∴ In the designation of a concrete mix, the letter 'M' and the number stands for Mix and characteristic compressive strength of 150 mm cube at 28 days.

∴ The M 30 grade of concrete means the concrete mix which attains 28 day strength (characteristics) as 30 MPa or 30 N/mm2.

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