Drying out Building Pad

[ridgeline]

We are testing the compaction for a building pad. Per the Proctor Test, the optimum moisture content is 8% but the pad right now is at 16%. The pad is about 18" thick. Is there a rule of thumb as to how long it might take to dry to the optimum moisture content?

 

[hokie66]

Depends on the material in the pad and the weather. Rule of thumb, no.

 

[ridgeline]

It is undoubtedly dependent upon the soil type and weather. Just wondering what someone with a lot of experience in this industry may recommend based on their experience.

Soil Classification: SM
Temperature: 90High/60Low
Pad Thickness: 18"

 

[MiketheEngineer]

Ask God

 

[Ron]

With an SM material, drying without scarifying and modifying the soil mix will be difficult for an 18" lift.

I'm curious....8% optimum seems awfully low for that type of material. Could you post the Proctor curve?

 

[ridgeline]

Here is the Proctor curve.

 

[oldestguy]

If this is inside, under cover and there is a hurry and you can't wait a long time, I'd go for something like adding cement and making a cement stabilized pad. 5% should be tested first to see if that is sufficient and of course it has to be mixed as best as you can,followed by compaction and don't worry about that 95 percent, since it will be a weak form of concrete. A spec change maybe in order then.

If outside, of course, good weather and more mixing will be needed.

And if you can't get good weather, look at cement stabilization there also.

Finally, if only for floor support, maybe the spec is too rigid.

 

[Ron]

Agree with OG....

I'm not a fan of 3-point Proctors. Not sure why this was done, but it can be problematic.

Assuming an accurate Proctor, you will have to scarify the soil to get any drying. Further, compacting 18 inches of SM material with a unit weight of 130+ pcf is difficult, even at optimum moisture.

Check the organics. Check for calcium absorption. Add cement if both of those parameters check out.

 

[fattdad]

Not a fan of 3-pt proctors either. That said, where is 16 percent on that proctor? Nowhere to be found. I'm struggling with the notion that the field condition is at 16 percent as that would mean the soil is just loosely placed and then allowed to get wet. Even a smooth drum would have helped in advance of the rain.

Don't get into cement stabilization without first learning how to do field control on the modified fill materials. I'm not saying it's hard, but the time to do compaction testing is reference by ASTM and if you don't understand these logistics you may end up with a poorly documented QC program.

f-d

¡papá gordo ain’t no madre flaca!

 

[hokie66]

Isn't 132.2 pcf unusually heavy for an SM material? The density is what it is, but this seems a strange material.

 

[grabens]

i think you could also consider adding and mixing some dry, clean granular fill material (SP) if avialable to change the moisture content/moisture sensitivity of the soils. of course, you will need a new proctor for the composite mateiral.

otherwise, scarify and hope for dry weather to dry out the soil. It is too wet.

 

[darthsoilsguy2]

Is it possible that you have a bathtub right now?

I'm imagining an underlayer of soil that is less permeable than the SM material and nowhere for the SM to drain to. if that were the case, i would be suspicious about the validity of the 16% m.c. Going a step further in speculationland, it would be worth looking at the situation for slab vapor regardless of the vapor barrier.

What method(s) are you using for testing in-place compaction and moisture content?