Answered What is purpose of Standard deviation calculaton for Cube Strength ?

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,602
4,510
Pune
Standard deviation shows the degree of quality control at production unit.

it helps in understanding performances of mixes and for doing further optimization of it.

I hope below article might help you in that regard.

 

Dhaval Thanki

Junior Member
Jan 7, 2020
31
4
Gujarat
I have read your article. I have one more question regarding this.

What should be frequency to check standrad deviation at site ? Monthly or when design mix is changed ?
 

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,602
4,510
Pune
To check the standard deviation, you need to have minimum 30 results (30 samples, 1 sample made of 3 cubes) of the concrete which is in question.

Once you have 30 results, you can plot it and see the control level.

following possibilities can be seen in deviation report
SD is on higher side - it shows the very poor control on either production, sampling, cube casting, curing or deviation in cube testing machine.

SD is Good and results are on higher side - indicates the need of optimizing the mix so that you can reduce the national resource wastage.

SD is good but results are falling below required or very marginal - indicates the need for optimization of mixes.

There is lot you can see by plotting the results or by using line control graph to see deviation every day and doing corrections in process wherever required.

SD is a mathematical calculation figure, so might be a value of SD can be excellent or good but your concrete might be having bad control which giving you some time very high results and sometime very low results.

We are the processor of the data and we need to detect it so that we can avoid failures.
 
  • Like
Reactions: tausif khan