I have a clay soil: how to add sand?

I need to mix my clay soil with sand, as I will be building an earthbag structure, and also some CEB bricks for paths and floors.

The question is, how do I get the sand (and cement in the case of the CEBs) evenly mixed with the clay? Wet clay is extremely hard to work. Also, an initially dry mix is better, since it is easier to add some water then take it back out. Dry clay turns into rock hard lumps. I have been crushing and screening it dry, and then mixing in the additives, but it is labor intensive.

I add it as a layer when I am building up a hugelkultur mound. Kind of like one of the sheets in a sheet mulch. If you make it one of the lower sheets, say a half-inch or so, and then use your regular clay soil on top, the action of rain falling on the clay will wash the clay particles down until they begin to coat the sand and organic matter underneath.

I think you always want to have a good bit of organic matter either mixed in with the sand, or have the sheet of sand between two layers of organic matter. That way there is less chance of the clay washing down into pure sand and then cementing the sand particles together.

Another thing to do is to add biochar to the sand and get it good and black by mixing it up before you add the sand. This serves the same purpose; with a coating of biochar on the surface, the sand particles are less likely to get covered by little tiny sheets of clay particles, which can then cement together.

Here are some resources I've gathered for you if you're interested in changing the tith of your soil in the long-term.

At the Royal Horticultural Society's website, they have a list of useful plants that can survive in clayey soils. Many of them have long thick roots that break up clay and inject organic matter into the soil. This is important because the plants are working to balance the ratio of clay, silt, and sand (the 3 main components of soil).
http://www.rhs.org.uk/advice/profile?PID=305
At the bottom of their page, they have useful links to pages about soil types and suitable płants.


Here is a paper by the Missouri Botanical Garden on altering clayey soils with a list of plants that can be used. The paper also includes information on the plants' height, season, and common names.
http://www.missouribotanicalgarden.org/Portals/0/Gardening/Gardening%20Help/Factsheets/Clay%20Soils%20-%20Annuals5.pdf

Gilbert Fritz wrote:I need to mix my clay soil with sand, as I will be building an earthbag structure, and also some CEB bricks for paths and floors.

The question is, how do I get the sand (and cement in the case of the CEBs) evenly mixed with the clay? Wet clay is extremely hard to work. Also, an initially dry mix is better, since it is easier to add some water then take it back out. Dry clay turns into rock hard lumps. I have been crushing and screening it dry, and then mixing in the additives, but it is labor intensive.

A tractor with a front loader would be a big help in mixing a very large batch of soil and sand... even a bucket on an earthmover too... on a small scale, you could use a mortar mixer to mix them thoroughly using dry ingredients.
All the best,
Clayton

If you have a suitable area to do it in I'd use a rotary cultivator.

What about using a tarp. Dump a workable amount of each ingredient on a tarp then two people can each grab a corner and roll the mixture on itself. Then repeat on opposite corner. Keep it up til satisfied.