Halloysite and Moisture Content

[BigH]

I was wondering if anyone has any information on halloysite and its moisture content determination. I've read a paper by some Polish researchers and the "exchanges" are a bit over the top for me.

TP&Mesri state that "interlayer" water can start to disappear, and not being reversible, at 65 to 70degC. If this is the case, would drying at the conventional oven temperature of 105 to 110 be too great to determine the "free" water content?

We are doing our own experiments now - we might not even have halloysite but we have residual volcanic soil we are using in fill. If we dry at the 110degC oven and we drive off bonded interlayer in addition to "free" water, is this then leading us to too high of a reported moisture content?

Appreciate any thoughts you might have.

 

[fattdad]

I guess you could turn down the oven and do some bench testing to see how reversable the moisture content determinations end up. You know, get moisture content using just air-dry methods and rewet. Then do moisture content using a 70 degree oven (or some other level) and rewet. Then try at the 105 or such?

I don't have any experience in this topic, but find it interesting. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[emmgjld]

My library wasn't much help. Seems like a similar problem to my dealing with high sulfate content & Gypsum deposits in Western Colorado. My thoughts are as Fattdad's, Try to get a handle on the 'in-situ' moisture condition and then work the soils fast, assuming added moisture not being incorporated into the mineral chemistry nor any significant additional drying.

I have used warm air drying, about 50-55 degC. Literature seems to indicate 50 degC is about the lowest temp used for the older dehydration thermal curve research on halloysite.Grim, R.E., Clay Mineralogy, McGraw-Hill, 1953.

I could only find a very short discussion in Compacted Fill, Winterkorn & Fang, 1975 & a longer discussion in Fang, 1991. BigH is back on the frontiers of science.

 

[Ron]

BigH...agree with emmgjld...similar to gypsum in the way it needs to be dried. Hard to determine where free water starts and binding moisture stops. As f-d noted, bench testing would be in order, but considering this is YOU....you started that before any of us read your post! Try using chemical dessication (calcium chloride or other), rather than thermal drying. Maybe compare the two.

 

[BigH]

Thanks for the inputs so far.

We have initiated the following - and had just about started when I posted:
1. Air dry under cover
2. Air dry under sun
3. Oven dry at 50degC
4. Oven dry at 110degC
5. Oven dry at 180degC (mainly because the contractor's lab screwed up after a oven temp calibration and didn't set it back - about 2 weeks or so of screwed up data.)

the problem we have is that the field density test results lie, about 50% of the time lie above the ZAV line. Changing the specific gravity from 2.63 to 2.65 doesn't help much which is why we are looking at the possibility of drying causing the problem.

I'll keep you all informed.

 

[Ron]

BigH...are you using the same method of moisture determination for the field density test and the Proctor? Do you have a Speedy Moisture Tester and if so, have you tried using it for both the field and lab testing?

 

[BigH]

Yes, we get field moisture by the nuclear gauge but also take a sample to compare it to the lab moisture at normal temperature. Proctor always done by oven - at normal temperature. We do not have a speedy moisture tester on site.

 

[Ron]

Nuclear gauge....
If you are getting fast hydration of the halloysite then the nuke gauge will give flaky readings. Similar to the problems you see with nuke moisture and soil cement. Check the moisture at the same location for a couple of hours after final compaction. If you see it drop significantly, you are getting fast hydration. Obviousl, aluminosilicates will hydrate, but the rate of hydration might be affecting things.

 

[oldestguy]

Ron: Doesn't the nuc measure the density of hydrogen atoms? If so, they don't disappear.

 

[Ron]

OG... It does but different materials will scatter the radiation differently. It doesn't know the difference between bound water and free water

 

[oldestguy]

Ron: Maybe right. My experience has been with ordinary earth only and slowing of "fast" neutrons. As to the Speedy, it tells me you ain't no spring chicken. I used one in my Master's thesis work and had one up until recently.

 

[Ron]

OG...you're right...no spring chicken! Been doing this stuff for 38 years. More fun than anyone should be allowed to have!

 

[BigH]

BTW, I am also familiar with the speedy moisture tester and we used it in India as well back about a decade ago.

 

[Ron]

BigH....the reason I mentioned the Speedy is because of the issues than I've run into with accurate moisture determination using a nuclear gauge in hydrating materials. Timing of the test is critical and the results are transient. The Speedy generally only reacts with free water. Yep...it's an old method, but properly used it is reasonably reliable. Since most of us in your private forum have been around a few days more than the general membership, I was pretty sure most would know of it or had used it. OLD GUYS RULE and OldestGuy can rule us all!!

 

[oldestguy]

OK Ron, nice endorsement, but I would guess Speedy is still used by foundries. Anyhow as to creating acetylene from "carbide", how many of the group ever had a toy cannon that used the stuff? I understand they still make them. At age 13 I used to fire off the thing on my front porch and in between take a few snots with a .22 at a target down the street. All of this in town. Try that these days and get arrested.

 

[BigH]

One of the problems we had with the Speedy Moisture is the delivery of the chemical . . . wasn't as straightforward as calling your local lab supply shop. I'll see if the contractor has one down in KL - then we can see if we can try it.