Query for Brick compressive strength results

Dhaval Thanki

Senior Member
There are 5 samples taken to check brick compressive strength. Results are following :

1. 6.52
2. 6.09
3. 13.5
4. 6.96
5. 5.22

Indivisual results are below 7.5 but the avg result is 7.65 N/mm2. ( As per spec . strenght should be more than 7.5 )

So results are passed or failed ??
 

amd007

Elite Member
There are 5 samples taken to check brick compressive strength. Results are following :

1. 6.52
2. 6.09
3. 13.5
4. 6.96
5. 5.22

Indivisual results are below 7.5 but the avg result is 7.65 N/mm2. ( As per spec . strenght should be more than 7.5 )

So results are passed or failed ??

Based on your report, I would say that there is only one sample that passes your criteria, so 20% of your specimen is OK and 80% is failing.

This means for every 1000 bricks, 200 nos will pass the compression criteria and 800 will fail, which means the majority is failing the compressive strength.

I would again go for a retest with another 5 fresh samples from the same lot which is received at site test it again and if 80% is passing the strength test then I would say that the bricks are OK else I reject it.
 
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Mech42

Senior Member
Based on your report, I would say that there is only one sample that passes your criteria, so 20% of your specimen is OK and 80% is failing.

This means for every 1000 bricks, 200 nos will pass the compression criteria and 800 will fail, which means the majority is failing the compressive strength.

I would again go for a retest with another 5 fresh samples from the same lot which is received at site test it again and if 80% is passing the strength test then I would say that the bricks are OK else I reject it.
How its rejected?

As per IS, 3.5 N/mm2 is minimum required strength. Then how bricks are rejected?
 

amd007

Elite Member
How its rejected?

As per IS, 3.5 N/mm2 is minimum required strength. Then how bricks are rejected?

Dear Knowledgeable Friend,

First, read the query carefully raised by Dhaval Thanki where he is referring to his required strength of 7.5 N/mm2 so based on his requirement maximum bricks should give his strength requirement. This is not the case as 80% bricks are failing the criteria of 7.5 N/mm2.

Now your question is as per IS, which IS you are referring to?

What compressive strength you want is to be decided by the structural engineer based on his design. Since Dhaval is mentioning 7.5 N/mm2 as his desired criteria hence I have given my opinion based on the samples he has tested.

If he wanted 3.5N/mm2 as his requirement then first of all he wouldn't have asked this query as common sense will prevail in his case.

Now see the table below from IS 1077 below for your clarity.

Table 1 IS 1077.png
 

Mech42

Senior Member
Dear Knowledgeable Friend,

First, read the query carefully raised by Dhaval Thanki where he is referring to his required strength of 7.5 N/mm2 so based on his requirement maximum bricks should give his strength requirement. This is not the case as 80% bricks are failing the criteria of 7.5 N/mm2.

Now your question is as per IS, which IS you are referring to?

What compressive strength you want is to be decided by the structural engineer based on his design. Since Dhaval is mentioning 7.5 N/mm2 as his desired criteria hence I have given my opinion based on the samples he has tested.

If he wanted 3.5N/mm2 as his requirement then first of all he wouldn't have asked this query as common sense will prevail in his case.

Now see the table below from IS 1077 below for your clarity.
Sorry sir i just misunderstood the question. Thank your for the clarity. Yes, me too referred Table 1 only from IS 1077 where Minimum strength mentioned was 3.5, Though I realize it should be as per Tech spec or BOQ.
 
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