Rammed Earth Wall Mix Design - posted by Taj
The soil that came out of the ground during pre-construction excavation and grading activities at Terra’s house is a rich-red, kaolin clay, a material that has been used effectively in earthen construction for thousands of years. The red clay has powerful binding properties that help to achieve high compressive strengths without the need for much cement. Furthermore
While it is not a major concern with adobe
The last important stage in building confidence in our mix was to determine the water content that we would aim for in production. In the simplest iteration of an optimum moisture content test, we made up a small batch of our mix material and separated it into three piles. We then added differential amounts of water to these three batches of material, using our intuition to try and get a range of moisture contents surrounding what would seem to be ideal. We cast cylinders of the three mixes and compared aesthetics and compressive strength results. A mix that is too dry can create a final product with some loose areas, or <>that may be a bit dusty. A mix that is too wet may not compact as well as one that is in the optimum range, and the final product
The photos in this post show Taj conducting soil testing in his field laboratory, Terra setting the test block form, Abe and Junior ramming soil into the form, and the finished test block, used to evaluate moisture and compaction.