Atterberg Limits

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We all know that both the liquid and plastic limits are percentages, and the subtraction between LL and PL is the result of what we know as plasticity index (PI).

My question is, the correct way of expressing this plasticity index (PI), do you think it is by adding the percentage?

Many geotech books use different terminologies. There are some which only include them using the LL and PL, but not for the PI. There are other few which do include percentages as units for LL, LP and PI. And there are others which do not use the percentage symbol at all.


I have always presented the values as just an integer…no “percent” reference.

Same here… no decimal value, only whole numbers. PI is expressed as an integer… clays in this area can have a PI of 70.