Table 4: Calculation of Standard DeviationĪs per the IS-456, for concrete of grade above M-20, Table 3: Test Result of Concrete Cubes SL No The standard deviation for the 33 number of cubes tests is calculated below. Greater than or equal to - f ck -4 N/mm 2Įxample Calculation of Standard Deviation for M60 grade Concrete with 33 cubes.Ī concrete slab of 400Cum was poured for which 33 cubes were cast for 28 days compressive test. Greater than or equal to - f ck -3 N/mm 2 Mean of Group of 4 Non-Overlapping Consecutive test results in N/mm 2į ck + 0.825 x derived standard deviation Table 2: Characteristic Compressive Strength Compliance Requirement Specified Grade The permissible deviation in the mean of compressive strength of the concrete is as per the below table prescribed by IS-456 Table No-11. When the number of test results available are more than 30, the standard deviation of the test results is derived by the following method -įig 1: Variation Curve for Standard Deviation Note - The above values are dependent on site-control- having proper storage of cement, weigh batching of all materials, controlled addition of water, regular checking of all elements such as aggregate grading and moisture content, and regular checking of workability and strength. However, as soon as the minimum number of test results are available, the derived standard deviation shall be calculated and used. Table 1: Assumed Standard Deviation Sl.NoĬharacteristic compressive strength (N/mm 2) In the case, where sufficient test results for a particular grade of concrete are not available, the value of standard deviation is assumed as per the IS-456 Table 8 (Clauses 3.2.1.2) as shown below: The minimum number of cube test samples required to derive the standard deviation is 30.
The calculation of standard deviation for compressive strength of concrete can done in 2 ways: 1. Example Calculation of Standard Deviation for M60 grade Concrete with 33 cubes.Ĭalculation of Standard Deviation for Concrete.Calculation of Standard Deviation for Concrete.
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