Soil analysis for earthbags...

My property is low in the middle where a creek runs and is high on all the property lines. Took two samples. The gray one taken from the lowest elevation w/o actually being in the creek or creek bank but where ground is always wet. The other taken from middle to high ground (any higher and the ground becomes a lot of rock. Thinking if I use the soil from high ground and add a little from the low ground, then that would make a good mix for earth bags and other earthen type building. Does that look about right? First pics are prior to adding water, seconds are a few minutes after adding water and shaking, and thirds are 48 hrs later. Also what explains the difference in color between the two?

Pics

Looks like a glaucontitic green sand, some gleying in the clay component, but mostly sandy/silt.

I wouldn't worry about the colour difference - it is the same material, just that the iron oxides as a different colour with relation to the water table.

The samples lean towards silt with sand, I don't see much if any clay forming a cap. As Vetch mentioned iron oxide is the red color, the blue color could be caused by several different oxides including copper, manganese or nickel.

As far as being suitable for building, you will want some clay added to those as a binder agent.

I think you're right about the clay. Practically none there. What clay there was, it stayed suspended in the water. After 4 days I finally dumped it out bc the water wasn't getting clear. Surprising that there's no clay considering I live in ga where he red clay is everywhere. I found some where the driveway and house use to be, but I think that must've been trucked in.

nick bramlett wrote:I think you're right about the clay. Practically none there. What clay there was, it stayed suspended in the water.

You may find clay deeper down. You will want to go deep anyway--get subsoil, not topsoil. You also do not have any coarse sand or gravel. Earth bags are more forgiving in their mix than cob, but I think you will be better off with mainly larger aggregate, as well as some clay. Some people add 10% cement, which is not as cheap but firms things up quickly. Some people buy a load of road base, which is nice because you don't need to do any mixing other than wetting it down. My experience is that the mixing is a laborious process and the rate-limiting step, but I was just doing 1 wheelbarrow at a time. Filling is slow but can be sped up if you make a device to help out.

nick bramlett wrote:My property is low in the middle where a creek runs and is high on all the property lines. Took two samples. The gray one taken from the lowest elevation w/o actually being in the creek or creek bank but where ground is always wet. The other taken from middle to high ground (any higher and the ground becomes a lot of rock. Thinking if I use the soil from high ground and add a little from the low ground, then that would make a good mix for earth bags and other earthen type building. Does that look about right? First pics are prior to adding water, seconds are a few minutes after adding water and shaking, and thirds are 48 hrs later. Also what explains the difference in color between the two?

Hi Nick ,

If you can get fly ash it can be good add on to strengthen the compound making it more stronger. Your worry about soil quality will be minimal.

Your soil is mostly sand+silt and that is fine for earthbag construction, not so much for the plaster though.
If you are super worried about the earth bag you can add lime/cement to help a bit, of you can chicken wire the outside of the earthbag and then plaster with stucco/cob/ferrocement/etc.