Liquid Limit
Liquid Limit
(OP)
Can anyone explain why, when specifying , a granular sub-base material, a LL OF 20.5 is set for limestone crushed rock fines and LL of 21.5 is set for other rock types, even when the fines are non-plastic?
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RE: Liquid Limit
RE: Liquid Limit
Here's the link below to the spec. Go to page 11 clause 804 type B. This is the specification for sub-base materials used in the Republic of Ireland.
I have a client with non-plastic granular material (LL 23-24 cone method) derived from a greywacke gritstone.
What would be the problem with using this material in relation to the spec?
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RE: Liquid Limit
RE: Liquid Limit
It's not a British thing! The Brits just request non-plastic GSB.
The reason given for the use of LL as a control of sub-base materials in Ireland as given to me is as follows ;'The simple answer to your question is that when we used other methods of
>controlling fines such as you are proposing in crushed rock materials we >had
plenty of failures in unbound bases in Irish road pavements. I had up >to 20
years struggling with this problem and I found that technicians
>invariably had declared materials that caused the failures to be
>non-plastic when they were not. The plastic limit test is very subjective >and
the limits of 20 and 21 were found to be the most likely limits that >would give
some degree of safety to the Client and taxpayer. Incidentally >when I carried
out investigations on road pavement failures, about 95% of >the failed pavements
contained plastic fines and were the most likely
>contributors to the failure that had taken place'.
I'm lost as I have GSB materials with passing 0.063mm removed by washing which have marginal LL values to those specified.
RE: Liquid Limit
Sad, but all too often.