SI. No.

Expos-ure

Plain concrete

Reinforced concrete

Min. cement content kg/m³

Max. free water cement ratio

Min. Grade of concrete

Min. cement content kg/m³

Max. free water cement ratio

Min. Grade of concr-ete

1

2

3

4

5

6

7

8

(i)

Mild

220

0.60

-

300

0.55

M20

(ii)

Moderate

240

0.60

M15

300

0.50

M25

(iii)

Severe

250

0.50

M20

320

0.45

M30

(iv)

Very severe

260

0.45

M20

340

0.45

M35

(v)

Extreme

280

0.40

M25

360

0.40

M40