[Cob] Questions about Lime

[Dognyard]

This summer, I want to play around with some agcrete mixtures, in which
I would use lime and a bit of cement in the mix. I'm having trouble
finding a place to buy lime (although I haven't looked much beyond the
big-box hardware stores). In my search though, I've found a mortar mix
which is something like 1 part type S lime, 1 part portland cement, and
six parts fine sand. Do you think I could use that instead?

Our clay here is about 50% sticky clay and 50% sand. I was planning on
using on site clay, some sand, some lime, and some cement and would also
be adding some sawdust and straw. Do you think I could use the mortar
mix, or should I continue my search and buy the lime, cement and sand seperately?

I know that buying these things separately will allow me more room to
play with various mixes, so maybe that's the way to go. Thought I would
ask though.

Oh...I am planning to build a shelf of this mixture (fully supported
from beneath...it's in a window well), as well as trying some outdoor
applications that haven't been determined yet. Just experimenting to see
what strength it might have - both compressive and shear, and to see how
it weathers.

Karen Clouston