Cement. We all understand it to be the essence of Babylon, true? So in the end, after all the rationalizations
less cement = better,
Some builders say "use 10%." Sure. You are doing a great job. Cutting down Babylon by 90% is a stellar accomplishment.
But why not really hit a home run?
In Experimental Houses Nicolas Pople includes the Convent Avenue studios designed by architect and contractor Rick Joy.
Here's from the book
"Rammed earth is a building technology that uses no material or support other than itself. It is identical externally and internally, being one material with no layers--it thereby achieves an effect that modernists have often (and not always successfully) tried to achieve. Historically, its application is extremely diverse--about one fifth of the great wall of China is rammed earth; the Romans used it; and as well as being common in South and Central America, it was introduced by Moors in Europe around 1000AD. Building with rammed earth belongs to the vernacular tradition of the Tucson region and Joy has seen the potential for its present day application; allowing a large part of a building to be constructed simply with unskilled labour, and contrasting this with targeted areas for highly crafted elements."
(And for the technically inclined)
"In the Convent Avenue studios, the earth was cast monolithically into 450-mm (17 1/2 inch) slip forms in 250-mm (9 3/4 inch) lifts. On each lift, the carefully combined soils from three different local sources were mixed with 3 percent portland cement and then compacted to 50 percent of their original volume before being exposed prior to the next lift taking place."
By going to such extrordinary lengths as carefully combining soils from 3 different sources, Joy was able to get a compressive strength sufficient to build a two story structure using only three percent cement.
If your job required 50 bags of cement at 10% would it require 15 bags at 3 percent? (help me with the math someone.) Is that a difference of 35 bags? Even if you were getting your bags of cement for $10 a bag (that's a close figure, right?) you'd be saving $350. I'd pick that up if I saw it on the street. (Then I would change it all into one dollar bills and drop them like chum from the 2nd story of a shopping mall upon the shoppers below.)
So let's hear it for conscious, diligent soil science!
Oh, and last but not least
"The 969 sq ft units were priced at $90,000 per unit."