# Civil Engineering - Concrete Technology - Discussion

Discussion Forum : Concrete Technology - Section 1 (Q.No. 34)
34.
The preliminary test is repeated if the difference of compressive strength of three test specimens, exceeds
5 kg/cm2
8 kg/cm2
10 kg/cm2
12 kg/cm2
15 kg/cm2
Explanation:
No answer description is available. Let's discuss.
Discussion:
13 comments Page 1 of 2.

Sandesh Nepal said:   1 year ago
As per IS code, the average compressive strength of three values shall be taken as the representative of batch provided the individual variation is not more than 15% of the average strength or difference of 1.5 N/mm2 or 5% cubes fails. Then the test is repeated.

Sagar said:   4 years ago
What action shall be taken if the sample result is invalid based on individual variation is more than 15% despite having the individual test result is 35.17 mpa for M30 grade concrete.

Shall one go for in situ tests?

Ashish said:   5 years ago
The individual variation of test reading should not exceed 15% of the average.

BHARANEEDHARAN said:   5 years ago
15kg/mm2 means 1.5N/mm2.

Am I right?

Uday said:   5 years ago
Strength difference of 15kg/cm2 for 3successive cubes or 5% cubes fails, then test repeated.

Raja said:   6 years ago
I'm agreeing with you complete Galileo.

Galelio said:   7 years ago
Question is wrong "Allowable difference can be known if values of compressive strength is know", is 15% of what?

Option should be in %, how you are going to know the value 15kg/cm2. It should be 15%.

SHIVAM said:   7 years ago
AS PER IS-456 "The test results of the sample shall be the average of the strength of three specimens".

The individual variation should not be more than +15 percent of the average. If more, the test results of the sample are invalid.

Jinx said:   7 years ago
I didn't get the specimens details it is a cement mortar or concrete cubes.

Abhi said:   8 years ago
5% difference is not considered during test. It is the difference of 15%.