Excel calculation problem of the PI value

[K.Lung]

Hi guys,

This is more of a basic mathematics calculation problem I have in my excel spreadsheet calculator.

Let's say I'm blending two types of materials to make up a new material, so it's Material A + Material B = Material C

Assume the Plasticity Index (PI) value is given for Material A and Material B.

So, I'm blending 99% of Material A (with PI=0) and 1% of Material B (with PI=46%) to make up 100% of Material C (with PI=?).

I want to find the overall/final PI when Material A and Material B is combined with a ratio of 99:1.

I have attempted to calculate on my spreadsheet which I have linked you and I got PI=0.5 for Material C. However, another colleague of mine got PI=3.76.

I'll send you both excel spreadsheets to have a look.

FYI for the 'Beenleigh Mix Design 2016' spreadsheet, go to the tab 'Type 2.1 Lot 76 (2)'.

By the way, on the 'NNSW Roadbase Blends 2014-15-16 excel spreadsheet, go to the tab 'CHCC DGB' and the two materials I'm looking at are MB20 1602-1 and Laceys Clay Liner. Somehow my colleague got PI=3.8 and I got PI=0.5 on the other excel spreadsheet.

I just want to know which method of calculation is correct.

If you could resolve our problem, it would be much appreciated!

[xladept]

Well it looks to be .0046 that has rounded to .005 or .5% - I think your calculation is the correct, if imprecise, one

[K.Lung]

Thanks xladept!

So you think mine is correct? Could you provide a brief explanation if possible?

Thank you.

[xladept]

Well the only stuff in the mix is the .46 from the 1% and that's diluted to .0046 by making the solute be 100% - so the mix has .46% stuff

[K.Lung]

Thank you so much, that makes more sense now.

[xladept]

You're welcome and thanks for the rep!