The construction industry is (slowly) beginning to see increased focus on the environmental impacts of buildings and construction. One area that seems to be getting a lot of attention recently is the carbon emissions due to cement and concrete. This seems at least partly due to Bill Gates’ book “How to Avoid a Climate Disaster”, which talks about emissions from cement (and I’ve been told everyone in Silicon Valley read.) Cement production is a huge industry, and is responsible for somewhere around 5-10% of global CO2 emissions [0]. Because concrete is such a fundamental part of the built environment, it’s worth taking a look at this problem in the context of how, as a civilization, we use concrete.