Check out Stanford Graduate School of Business’ profile, “Paving the Way to Healthy Homes“, featuring EarthEnable, an Extreme project from 2013 that has now blossomed into a startup operating in Rwanda.
From the article:
“[EarthEnable] sells floors to poor people. Specifically, the social enterprise, which [Gayatri Datar, CEO] cofounded and runs, makes paved flooring from compressed earthen materials that are sealed with a proprietary oil. Both the product and the business were incubated four years earlier  when Datar was a student at Stanford Graduate School of Business and took a course there called Design for Extreme Affordability.
EarthEnable’s floors, marketed in Rwanda under the Tube Heza brand, cost about 75% less per square foot than concrete, dirt’s most common flooring alternative. The price averages about $80 per home ($60 for materials, $20 for installation) — exceedingly cheap by Western standards but a significant expense in a country where most people live on less than $2 per day.”