STRENGTH REQUIREMENTS OF CONCRETE. Controlled concrete shall be in the following grades, M 15, M 20, M 25, M 30, M 35 & M 40. The concrete mix shall be designed to produce the grade of concrete having the required workability and characteristic strength not less than the appropriate values (as per I.S. 456) as given in table below: 1. M 15 20 15 2. M 20 26 20 3. M 25 32 25 4. M 30 38 30 5. M 35 44 35 6. M 40 50 40
STRENGTH REQUIREMENTS OF CONCRETE. Group Grade of Concrete Compressive Strength of 150mm cubes at 28 days after mixing, conducted in accordance with IS:516 N/xx.xx Ordinary concrete M - 10 10 M - 15 15 M - 20 20 Standard Concrete M - 25 25 M - 30 30 M - 35 35 M - 40 40 M - 45 45 M - 50 50 M - 55 55 High Strength Concrete M - 60 60 M - 65 65 M - 70 70 M - 75 75 M - 80 80 Note:
STRENGTH REQUIREMENTS OF CONCRETE. Where Ordinary and Low Heat Portland Cement conforming to IS: 269, Portland Pozzolana Cement conforming to IS: 1489 or Portland Blast Furnace Slag Cement conforming to IS: 455 is used, the compressive strength requirements for various grades of concrete shall be as given in Table 2.7. Where Rapid Hardening Portland Cement (IS: 8041) is used, the 28 days compressive strength requirements specified in Table 2.7 shall be met at 7 days. The strength requirements specified in Table 2.7 shall apply to both Controlled Concrete i.e. Design Mix Concrete and Ordinary Concrete i.e. Nominal Mix Concrete. In order to get a relatively quicker idea of the quality of concrete, optional works tests on beams for modulus of rupture at 72 + 2 hours or 7 days or compressive strength at 7 days may be carried out in addition to 28 days compressive strength test. The Engineer-in-Charge may suitably relax the frequency of 28 days compressive strength test specified in Table 2.7 of IS: 456 - 2000 provided the expected strength values at the specified early age are consistently met. For this purpose, the values given in Table 2.8 may be taken for general guidance in the case of concrete made with Ordinary Portland Cement. Where the strength of a concrete mix, as indicated by tests lies in between the strength for any two grades specified in Table 2.7, such concrete shall be classified for all purposes as a concrete belonging to the lower of the two grades between which its strength lies.
