I've made a bunch of patio blocks but maybe that's not what you're asking. However, the mix I used was soil cement, with about three parts of my native sandy soil sieved to remove larger bits, two parts Portland Cement. They worked out great, and I used styrofoam blueboard to make the molds out of:
Here's what it looks like finished:
You can see more about how I made them here;
http://www.bluefoxfarm.com/pat...
