"Soil-Cement" as back-fill for underground wall?

[Mmathis]

In repairing a couple of places where my ponds walls are collapsing, my plan is to rebuild those wall sections with concrete block. Our soil is mostly clay and we have ground water issues.

--- Actually, I think I've figured out that it's not so much a HIGH water table, as it that there are layers of solid clay, hardpan, that are preventing the soil from draining. Whatever, it's still an issue.... ---

--- Since the dry clay is clumpy and hard to work with, I thought about tilling some sand in with it so it would be a better consistency. It would be easier to back-fill the space behind the block wall, and would be easier to compact. But clay is still clay.... ---

Then I started seeing "soil-cement" popping up in several of my internet searches. It's mostly used in commercial practices, but it's main purpose is to stabilize soil, serves as a moisture barrier, and is excellent to help with clay soils. It's also economical and easy to make. You see where I'm going with this?

What if I mixed some Portland cement in with my clay/sand mixture, tilling them all in well, then used THAT soil-cement mixture as part of my back-fill? From what I understand, I would have to add some of the mixture, compact it, then sprinkle it with water, etc. Not sure if you could mix the soil-cement with water first, then slop it in.... Whichever method, the proportions would be hit-or-miss, but don't know if that would be an issue in this case. Commercial sites talk about precise proportions for their construction applications, but DIY sites don't really address it.

Anyway, comments? See my drawing --- the red, circled area would be the layered soild-cement.

 

[Catfishnut]

Turtle Mommy,

Hi!

If you mix portland, sand and clay and then sprinkle with water, you will create a solid wall, no doubt. You really don't have to be very precise on the proportions in this endeavor, however. If you were building a roadway, a driveway, a patio or a foundation for a house, that would be a different story altogether. You desire major structural integrity in those projects. Here I assume that your goal is just to have some better reinforced soil for the walls of the pond so that it does not erode. It does not need to support an 18 wheeler fully loaded or many of them traversing it constantly.

Go for it! It'll work just fine for what you need to do here.

If you want to save some money on the concrete (cause it is higher priced now) there may be another option. Do you have a coal burning power plant near you? If you do, ask them for a five gallon bucket of flyash to mix in with your sand and clay instead of the portland cement. If they are allowed to give it to you, you won't need the portland concrete and it will work just as well for this purpose.

Eh, You probably don't need that much concrete mix anyway, but it is a neat bit of information if you ever need a LOT of concrete type material. The flyash acts a lot like portland. Definitely not as strong, but much cheaper.

Gordy

 

[Mmathis]

Turtle Mommy,

Hi!

If you mix portland, sand and clay and then sprinkle with water, you will create a solid wall, no doubt. You really don't have to be very precise on the proportions in this endeavor, however. If you were building a roadway, a driveway, a patio or a foundation for a house, that would be a different story altogether. You desire major structural integrity in those projects. Here I assume that your goal is just to have some better reinforced soil for the walls of the pond so that it does not erode. It does not need to support an 18 wheeler fully loaded or many of them traversing it constantly.

Go for it! It'll work just fine for what you need to do here.

If you want to save some money on the concrete (cause it is higher priced now) there may be another option. Do you have a coal burning power plant near you? If you do, ask them for a five gallon bucket of flyash to mix in with your sand and clay instead of the portland cement. If they are allowed to give it to you, you won't need the portland concrete and it will work just as well for this purpose.

Eh, You probably don't need that much concrete mix anyway, but it is a neat bit of information if you ever need a LOT of concrete type material. The flyash acts a lot like portland. Definitely not as strong, but much cheaper.

Gordy

Gordy, I don't think we use too much coal around here, but could be wrong, LOL!

Yes, for the back-fill idea I was mostly going for stability. My experience with our clay soil is that it's very hard to get it to compact well -- if it's moist, it squishes out everywhere, and if it's dry, it's too clumpy just won't compact [leaves voids]. That's why my original idea was to roto-till some sand in with it. That would make it more like plain old dirt [dirt? what's that?] and it would be easier to handle and to compact.

The bare soil wall that I'm excavating right now [to give me room to work with the concrete block construction] has a few areas that weep with ground water. So, for that reason, thought that using the soil-cement as back-fill might help keep that wet soil from being a problem if it was right against the blocks.

 

[Mucky_Waters]

It should help, but you need to mix the cement in with the solild very well. Do you have a cement mixer?
I do stucco work and often at the end of the day I'll often throw extra sand (no cement) in the mixer and let it run to help clean out the mixer.. The resultant mix that comes out is mostly sand and just a little bit of residual cement that got cleaned off the sides of the mixer, but if you pour it out it makes a surprisingly stiff mixture once it sets.
Mind you I am just using sand, not clay so your results may not be the same.
The best thing you could do is just try a batch of your clay with a small amount of cement and let it set overnight and see if it does what you want it to.

 

[sissy]

I would worry a little by your pic as liner will be rubbing against each one of those stepped blocks .

 

[Mmathis]

I would worry a little by your pic as liner will be rubbing against each one of those stepped blocks .

No, I have plans for that -- carpet underlayment AND a nice bead of GREAT STUFF along each little ledge.

 

[Mmathis]

It should help, but you need to mix the cement in with the solild very well. Do you have a cement mixer?
I do stucco work and often at the end of the day I'll often throw extra sand (no cement) in the mixer and let it run to help clean out the mixer.. The resultant mix that comes out is mostly sand and just a little bit of residual cement that got cleaned off the sides of the mixer, but if you pour it out it makes a surprisingly stiff mixture once it sets.
Mind you I am just using sand, not clay so your results may not be the same.
The best thing you could do is just try a batch of your clay with a small amount of cement and let it set overnight and see if it does what you want it to.

We can rent a small mixer from Home Depot. And that's a good idea to try a little mixture. At the moment I don't have any Portland, but do have some mortar mix.

 

[Catfishnut]

Turtle Mum,

I brought in approximately 2,500 cubic yards of pure yellow clay to fill in errosion damage from a flood back in 2010 at my cabin. It was free fill, but I had to pay to haul it. I was worried about growing grass upon it so I thought to add sand and mix it in. I did some research and was told not to do so. Not to mix the sand with the clay. I was told that it would set up as hard as concrete then and nothing would grow in it.

I don't know if this is true, but I wasn't about to test it, so I just left it pure clay and went searching for varieties of grasses that might grow in pure clay,

I found a variety and planted it. I merely raked the top of the clay and threw the seeds down by hand during a rainstorm and it germinated within about 2-3 weeks. I have never watered it since (other than by rain) and have only mowed it three to five times in four years. But it is green and 3-4 inches tall and relatively thick in most areas.

We have been drought stricken here since 2002 so my grass hasn't done the best that it could, but it has outperformed the grasses that other people have in town which are fertilized, watered regularly and mowed regularly. And I drive my truck and four wheeler ATV all over my yard and it doesn't seem to affect this grass. It is some great stuff!

The grass is RTF fescue from Todd Valley Farms here in Nebraska. It is a strain created here in Nebraska through the university in Lincoln. It is drought tolerant and one of the only if not the only strain of fescue that will propogate or spread via rhizomes. The RTF refers to Rhizominous Turf Fescue or something close to that.

It is awesome grass. I threw it out, it germinated, it grew and I really only mow it to keep the other plants out and to mulch the tree leaves. Otherwise, this grass only gets 4 - 5 inches high. For a cabin lot, that is so perfect! Oh, and it remains green all year long, haven't seen it brown ever since it was planted.

OK, don't know where the grass came in exactly, I started out talkin about mixing sand and clay. Well, it doesn't matter, this is all good information.

Gordy

 

[Mmathis]

Gordy, I'd always heard that about not mixing clay soil with sand, but have recently read some articles that debunk that myth.

 

[Tula]

My pond guy came on Friday and is proposing some kind of cement block to stabilize the area that holds our skimmer. I'm hopeful he can work with my existing liner. I keep following your project with interest, as we're having same problem. Kim

 

[Mmathis]

My pond guy came on Friday and is proposing some kind of cement block to stabilize the area that holds our skimmer. I'm hopeful he can work with my existing liner. I keep following your project with interest, as we're having same problem. Kim

Oooh, not good! Let me know what your pond guy ends up doing. We did a lot more digging today, and the water is finally slowing down, which means the soil [clay] is drying out and is more workable. That, of course, means that we'll be getting more rain in the next few days.....

 

[Big Lou]

A simple suggestion that will not cost you a cent.

Call the Louisiana Soil & Water Conservation Department @ 225-922-1269 and ask for help dealing with your soil. You will surely be referred to a specific office. Even living here in Texas the LSWCD has helped me with pond related soil and tree issues.

Just saying..........

 

[Tula]

Oooh, not good! Let me know what your pond guy ends up doing. We did a lot more digging today, and the water is finally slowing down, which means the soil [clay] is drying out and is more workable. That, of course, means that we'll be getting more rain in the next few days.....

I know....I'm seeing $ signs! - ugh! I just don't think we can do this job ourselves....if they do it properly, it will be worth it. I wish I'd never gotten the Savio skimmer, or had paid much better attention to how it should be installed! We're awaiting the proposal....will keep you posted Kim

 

[Mmathis]

A simple suggestion that will not cost you a cent.

Call the Louisiana Soil & Water Conservation Department @ 225-922-1269 and ask for help dealing with your soil. You will surely be referred to a specific office. Even living here in Texas the LSWCD has helped me with pond related soil and tree issues.

Just saying..........

LA is a rather, um, dysfunctional state..... No, actually that IS a good suggestion.

 

[Big Lou]

A proper excavating and or foundation/foundation repair contractor may also be a free source of information. We know from experience the perils of Louisiana soil.