## Atterberg Limits

## Atterberg Limits

(OP)

Experts,

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?.

For example:

LL =30%, PL = 12%, PI = 18%.

OR do you think without the percentage (PI = 18) is ok?.

I asked you this because I noticed 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.

Please advise.

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?.

For example:

LL =30%, PL = 12%, PI = 18%.

OR do you think without the percentage (PI = 18) is ok?.

I asked you this because I noticed 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.

Please advise.

## RE: Atterberg Limits

## RE: Atterberg Limits

## RE: Atterberg Limits

Thanks a lot for your replies.

## RE: Atterberg Limits

That said, it is of some value to read the actual ASTM Standard to learn more about the reporting requirements.

f-d

ípapß gordo ainÆt no madre flaca!

## RE: Atterberg Limits

Mike Lambert

## RE: Atterberg Limits

## RE: Atterberg Limits

## RE: Atterberg Limits

ASTM D4318-05, in the report section, it says "19.1.4 Liquid limit, plastic limit, and plasticity index to the nearest whole number, omitting the percent designation.".

## RE: Atterberg Limits

## RE: Atterberg Limits

For Liquid Limit: "The liquid limit, LL, is the average of the two trial

liquid-limit values, to the nearest whole number (without the

percent designation)." (Clause 14.1.1)

For Plastic Limit: "Compute the average of the two water contents (trial

plastic limits) and round to the nearest whole number. This

value is the plastic limit, PL." (Clause 17.1)

Plasticity Index: does not say that PI is reported as whole number, but must be as "Both LL and PL are whole numbers. If either the

liquid limit or plastic limit could not be determined, or if the

plastic limit is equal to or greater than the liquid limit, report

the soil as nonplastic, NP." (Clause 18.1.1)

And for the record - I only use whole numbers (integers) - never the percent sign - and when in a soils report (say for percentage of sand sized particles), we always used "percent" and never "%".