Concrete. I mean, I get why cars would be there, and oil, and airplanes, deforestation, unbridled consumption….but concrete? When I bring concrete up people give me a funny look, but most of you at some point or another will have to work with concrete, even if it is just getting your driveway or your foundation redone. So think about this when the time comes. Concrete contributes any wheres from 3%-5% of GLOBAL CO2 production yearly. Were talking millions of tons of carbon. Concrete is far and away the most common man made building material in the world. You have to take it seriously if you are going to build sustainably.
The NY Times has a good piece today that reminded me of the need to talk about concrete. When I remodeled 2139 3th Ave I used close to 30 yards of concrete getting the foundation earthquake strong and pouring a new retaining wall.
30 Yards for a little crappy house in the Sunset – ok not crappy, but you get my drift. Concrete is a major player in building, so how do you do it Sustainable? One option is to use concrete with Fly Ash and/or Slag in it. Bode concrete sells it in the city, and that is what I used here. The problem with concrete is in the Portland Cement used to bind all the stuff toegther. See cement comes from limestone, and you gots to heat it up to over 2,000 degrees to make the limestone into cement – that’s is where the CO2 comes from. Flyash can replace 10% – 20% or more of the cement in your mix. Less cement, less CO2. It is a simple as that.
There are a lot of players trying to make greener concrete, and I give them props. There are pros and cons to all the approaches, but God bless them for working the problem in creative ways – we need more of that and less crying about how bad thigns are getting. One local company that is doing some really interesting stuff is the Calera Corporation. They are mentioned at the end of the times peice and the Chron did a great stort on them in 2008 that is worth reading again…basically they are making cement using sea water similar to how corals form. Don’t ask me for details, I am not smart enough, but I am impressed, it is people like this who are really going to make a difference for our future.