Standard Deviation and Its Use in Concrete Mix Designing

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,352
4,042
Pune
Standard deviation is a measure of the variation of concrete strength of a set of data from its mean.

If the strength results are away from the mean, the deviation will be higher and vice a versa.

Its a statistical measure for Re-designing the mix base on results achieved.

In initial mix design process, where actual standard deviation is not known, we use to take it from the relevant codes as per our degree of quality control.

It is denoted as "σ".

Once, we get actual results of at least 30 set, we then check for actual standard deviation and accordingly correct the mix proportions.

Standar Deviation Curve.png

it is similar to six sigma process where we plot a normal distribution curve to get a better idea.

Normal Distribution Curve.png

I will not go in deep on standard deviation and six sigma processes.

I just made this thread to share a ready-made content attached here to work with it for correcting the mix design issues (higher or lower strengths than expected)

If you have any query or want to say thanks, you can do it by liking and replying to this thread.
 

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Avinash Vanarase

Apprentice
May 15, 2019
13
1
Pune
Standard deviation is a measure of the variation of concrete strength of a set of data from its mean.

If the strength results are away from the mean, the deviation will be higher and vice a versa.

Its a statistical measure for Re-designing the mix base on results achieved.

In initial mix design process, where actual standard deviation is not known, we use to take it from the relevant codes as per our degree of quality control.

It is denoted as "σ".

Once, we get actual results of at least 30 set, we then check for actual standard deviation and accordingly correct the mix proportions.


it is similar to six sigma process where we plot a normal distribution curve to get a better idea.


I will not go in deep on standard deviation and six sigma processes.

I just made this thread to share a ready-made content attached here to work with it for correcting the mix design issues (higher or lower strengths than expected)

If you have any query or want to say thanks, you can do it by liking and replying to this thread.
Sir please explain " How nominal Orders are calculated/taken?" its calculation and link are not in your excel sheet. Thanks
 

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,352
4,042
Pune
What are the implications of higher standard deviation values than assumed
Standard deviation indicates the degree of Quality control on concrete. higher the value, bad is the control on concrete quality. lower value of standard deviation indicates superior quality control.

Standard deviation value is assumed during mix designing process where previous data is not available for reference.
 

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,352
4,042
Pune
Sir please explain " How nominal Orders are calculated/taken?" its calculation and link are not in your excel sheet. Thanks
Numerical order is nothing but cube test results which are in n/mm2 are re arranged in next column in numerical increment order.

If my results in series are say 23, 25, 21 and 22 the column of numerical order contains value re-arranged 21, 22, 23 and then 25.
 

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,352
4,042
Pune
For me also sir
Standard deviation value is calculated in same way for each grade of concrete.

In order to calculate the standard deviation of concrete you need 30 concrete results of same grade.

standard deviation value will help in doing optimization of concrete mix designs.
 

Avinash Vanarase

Apprentice
May 15, 2019
13
1
Pune
Standard deviation is a measure of the variation of concrete strength of a set of data from its mean.

If the strength results are away from the mean, the deviation will be higher and vice a versa.

Its a statistical measure for Re-designing the mix base on results achieved.

In initial mix design process, where actual standard deviation is not known, we use to take it from the relevant codes as per our degree of quality control.

It is denoted as "σ".

Once, we get actual results of at least 30 set, we then check for actual standard deviation and accordingly correct the mix proportions.


it is similar to six sigma process where we plot a normal distribution curve to get a better idea.


I will not go in deep on standard deviation and six sigma processes.

I just made this thread to share a ready-made content attached here to work with it for correcting the mix design issues (higher or lower strengths than expected)

If you have any query or want to say thanks, you can do it by liking and replying to this thread.
Is it necessary to revise or review the mix design according to Standard Deviation obtained through 30 results? AND is it necessary to obtain and apply standard deviation for just first 30 results only or we have to obtain SD for every 30 results? Will you please give discriptive guide line to USE standard deviation for the review and revise mix design? please.
 

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,352
4,042
Pune
Is it necessary to revise or review the mix design according to Standard Deviation obtained through 30 results? AND is it necessary to obtain and apply standard deviation for just first 30 results only or we have to obtain SD for every 30 results? Will you please give discriptive guide line to USE standard deviation for the review and revise mix design? please.
To obtain a standard deviation, you need to have minimum 30 results, having more is good.

Deviation can also be controlled by tracking daily test results, if variation or something abnormal is observed in testing, need to take immediate action by reviewing all processes.
 

vanaraseavi

Newbie
Oct 7, 2019
1
0
Pune
Standard deviation is a measure of the variation of concrete strength of a set of data from its mean.

If the strength results are away from the mean, the deviation will be higher and vice a versa.

Its a statistical measure for Re-designing the mix base on results achieved.

In initial mix design process, where actual standard deviation is not known, we use to take it from the relevant codes as per our degree of quality control.

It is denoted as "σ".

Once, we get actual results of at least 30 set, we then check for actual standard deviation and accordingly correct the mix proportions.


it is similar to six sigma process where we plot a normal distribution curve to get a better idea.


I will not go in deep on standard deviation and six sigma processes.

I just made this thread to share a ready-made content attached here to work with it for correcting the mix design issues (higher or lower strengths than expected)

If you have any query or want to say thanks, you can do it by liking and replying to this thread.
Sir Please guide:-- From 1st Graph, you have mentioned the "Produced concrete base on standard deviation shows grade of M39". How to decide that the Mix Design is of M39?