Proctor Testing Methods

[martin888888]

What is the basic determination of what testing method to use. Example AASHTO T-99 vs ASTM D1557. Is it size of material from the borrow site?

 

[Ron]

AASHTO is primarily used for roadway/pavement work. ASTM is generally specified for all else.

It has nothing to do with material size or source...either would apply for those variables.

As for your example, AASHTO T99 has a similar ASTM designation. It is ASTM D698 (commonly called the "standard Proctor"). AASHTO T180 more closely corresponds to ASTM D1557 (commonly called the "modified Proctor").

 

[fattdad]

Just to add that the T99 standard doesn't have the same criteria for time of hydration. Also, within each method, there are sub-methods that do depend on the grain-size distribution.

f-d

¡papá gordo ain’t no madre flaca!

 

[martin888888]

Just at an elimentary level, what is the difference between standard and modified proctor?

 

[JTRdirt]

Modified proctor applies more energy to the soil specimen than standard proctor does. The amount of energy applied in the modified proctor test is generally more representative of the amount of energy you would get from todays normal compaction equipment.

 

[fattdad]

It's more likely to get over 100 percent compaction with Standard Proctor than with Modified Proctor. That's the only real difference (no joke).

f-d

¡papá gordo ain’t no madre flaca!

 

[dgillette]

Actually, there is one other significant difference, which is the optimum moisture coming out several points lower with modified. Why? Because no matter how much more energy you put into it, you just can't get more density once the air voids are compacted out. Remember that compaction moisture can affect both the permeability that is achieved at a given density, and the stress-strain characteristics (wetter compaction --> less brittle).

 

[fattdad]

agreed. Increased dry density requires a decrease in optimum moisture content (often about 90 percent saturation).

f-d

¡papá gordo ain’t no madre flaca!