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when do you know to use a modified proctor D1557, verses a standard proctor D698.

when do you know to use a modified proctor D1557, verses a standard proctor D698.

when do you know to use a modified proctor D1557, verses a standard proctor D698.

(OP)
I would like to know when I would perform a lab test on material taken from the job site that does not specify what proctor to use, when would I know which lab proctor test to use, modified proctor verses a standard proctor.

RE: when do you know to use a modified proctor D1557, verses a standard proctor D698.

The modified proctor should be used. It's been that way ever since the 1970's / 1980's to account for greater advances in compaction equipment in the field.

RE: when do you know to use a modified proctor D1557, verses a standard proctor D698.

standard proctor is commonly used and perfectly suitable for some uses and modified is recommended for others. you should not just assume one or the other without knowing what kind of construction and equipment is going to be used.

ask the following:

what type of material is it, fine or coarse grained?
what is the loading on the compacted embankment? Is there pavement or structures constructed on top of it?
is the compaction being done to reduce settlement or to reduce permeability or to increase slope stability?
Will this be compacted with a whacker or an 18 ton padded foot vibrating compactor? Is the material gravel base for a road or landfill cover material?
Is this landscaping fill or embankment for a dam?

RE: when do you know to use a modified proctor D1557, verses a standard proctor D698.

The modified proctor energy input is more comparable to non-cohesive/non-plastic soils being compacted with heavy, vibratory equipment.

The standard proctor and its lower input energy is more comparable to light, static compaction, particularly in finer grained soils with some plasticity.

RE: when do you know to use a modified proctor D1557, verses a standard proctor D698.

I guess my experience has only been for the compaction and grading of fill in new subdivisions with heavy vibratory equipment. I stand corrected that standard proctor is commonly used! Sorry I almost misled and thanks to those who corrected :)

Where would the standards/specifications be on which method should be used? Or is it just judgment based upon the principles stated above?

RE: when do you know to use a modified proctor D1557, verses a standard proctor D698.

The choice depends on the project type and some parameters, such as permeability, subgrade support for traffic or perhaps a structure. The spec should be clear on this so there is no such question as this. If you are a test lab, that generally is not your duty to decide.

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