Check out this thesis paper for most of the info I think you are looking for:
GUIDELINES FOR BUILDING BAMBOO-REINFORCED MASONRY IN EARTHQUAKE-PRONE AREAS OF INDIA
I read somewhere that some people building rammed earth houses are doing this without any sort of reinforcing.
I wondered if it would be worth it to do this with tires. Build using them like an earth ship, only instead of ramming the earth into the tire, cut out one sidewall, lay it down like normal, then fill it with the earth cement mixture, compact it with a plate compactor or similar, and let it set. Don't know if it would be necessary or not but it is something we are thinking about. Thought about it for use with earthbags too.
One was that they would mix one part portland cement with 14 parts soil. Then they would fill burlap sacks with this mix and build dams for ponds.
Another was where they would fill a sort of long balloon with air, lube it up and then cover it with the mix. When it had cured, they would deflate the balloon and pull it out: instant pipe-like thing!
In some cases (my part of the world, for example), I've heard lime is more appropriate.
Lime has only every limited effect on soils with a high organic matter content (content higher than 20%) and on soils short of clay. It is more effective and can be more effective than cement on clay-sand soils and especially on very clayey soils. The effects of lime are thus highly dependent on the nature of the soils involved but a comparison with the effects of cement can, in many cases, be attempted.
The ebook that produced this quote (link below) seems very good from what I've read so far.