lime vs high moisture content

[boffintech]

Am working on a site where the fill soil is coming out of the borrow pit about 10 points over optimum. The soil is your basic silty clayey sand. They are using Lime Kiln Dust to condition the fill.

It's a professional operation of placement, using a large soil-cement type milling machine, etc. and compaction is being accomplished with a 10+ton vibratory padded roller. So it's mixed to a surprisingly homogeneous mix at 50 lbs per cubic yard of soil.

what is the difference between quick-lime and LKD?

Is there a "reaction" time with LKD? How long does the mix need to set prior to compaction effort being applied?

Do I need additional proctors with the LKD? I read that LKD contains very fine materials, which can modify the particle size distribution of the soil but will this be enough to alter the proctor values?

 

[fattdad]

you need additional proctors.

LKD is about 1/3rd as reactive as quick lime. so 6 pounds LKD maybe like 2 pounds CaO. I'm no expert, just getting the subject rolling.

Not sure about reaction time - I'd think not with CaO. For the proctor however, you'd need an overnight after conditioning.

f-d

¡papá gordo ain’t no madre flaca!

 

[Ron]

BT..agree with F-D. Be careful of a couple of things...first, make sure the LKD does not contain expansive materials (MgO, Excess free CaO). Second, with either material, the measured moisture content will change with time (due to hydration), particularly when measured with a Nuke gage. Make sure you do some comparisons with a Speedy and oven-dried to get accurate moisture contents. Also, make sure your density tests are taken quickly after compaction. If you wait too long, the hydration process will screw up your density measurement relative to the Proctor.

 

[fattdad]

one more thing. . .

check the sulfur content of the native soil. There's recent research on the use of lime in sulfur-laden soils where with natural moisture forms the crystal "ettringite." This mineral, when it forms, grows very slender prismatic crystals that essentially "jack" against the soil grains and lead to swell. It's a different swelling process than clay, but damaging nonetheless.

There was an artical in "Geo-Strata" (ASCE Geo-Institute) about 8 months ago that goes into this process.

f-d

¡papá gordo ain’t no madre flaca!

 

[boffintech]

1) first, make sure the LKD does not contain expansive materials (MgO, Excess free CaO).

How?

2) Second, with either material, the measured moisture content will change with time (due to hydration), particularly when measured with a Nuke gage.

I understand that the MC will change over time, but why when measured with a nuke gage?

3) make sure your density tests are taken quickly after compaction. If you wait too long, the hydration process will screw up your density measurement relative to the Proctor.

Please elaborate on this point. I understand that the MC will drop causing the wet density to drop

proctor without LKD
MDD = 104.4lb/ft3 @ 18.9% (max WD = 124.1 lb/ft3 with 19.7 lbs water)

 

[Ron]

1. Chemical analysis. Xray diffraction is the typical method used.

2. As hydration occurs, the backscatter method becomes less reliable due to dispersion of return counts.

3. As hydration occurs, so does some minor "bulking" as well as the noted moisture measurement issues. The result will be that your density will "appear" less when tested at later times.