LEED and Concrete Mixes
LEED and Concrete Mixes
(OP)
We're starting to design a new school that will obtain a LEED Silver (or higher) rating. My question is what proportions/requirements for slag, fly ash, etc. are typically specified for concrete mixes in the 3,000 to 5,000 psi range? I would like to contribute to the LEED credit as much as possible, but I also don't want to go beyond "normal" proportions. Any link to articles or other backup information would be greatly appreciated. Thank you.






RE: LEED and Concrete Mixes
50% is OK too.
Probably 25% max for flatwork, but some contractors may be able to finish 50%.
I don't know that you'll be able to get a specific innovation point unless you have a really large volume of concrete. You can help out with the recycled content though.
Check to make sure that the slag/fly ash is locally available and doesn't need to be shipped across the country.
RE: LEED and Concrete Mixes
Dick
RE: LEED and Concrete Mixes
A good person to talk to is Steve Ratchye of Thornton Tomasetti San Francisco. He's considered an expert when it comes to green concrete.
Bruce Kings book Making Better Concrete - Guidelines to Using Fly Ash for Higher Quality, Eco-Friendly Structures by Bruce King, P.E. is a good reference.
PCA's book on concrete design is good as well.
Just remember fly ash is not really green anyway...even though LEED says so...after all, if we elminated the high energy, high pollution, steel mills and concrete planst, we wouldn't have fly ash.
RE: LEED and Concrete Mixes
LEED and Structure pretty much overlap on really only two principles: Recycled content and Regional materials. Steel will be 80-100% recycled (rebar ~60%), so require the contractor to obtain recycled content reports from the mill. It's hard to use steel for regional materials because it requires a chain of finding where the original raw material was harvested that's nearly impossible to obtain. Concrete will get you a lower % of recycled material, but you should realistically be able to get a good % of concrete within the 500-mi region.
RE: LEED and Concrete Mixes
RE: LEED and Concrete Mixes
RE: LEED and Concrete Mixes
You are smart to survey the contractors for opinions.
The other resource you did not mention was the suppliers. In many areas, the concrete and cement suppliers have far more background in the testing and research of mixes that contractors have never seen or been forced/exposed to use. This is particularly true in the case of the vertical integrated companies (cement/aggregate/concrete) that individually spend far more more money on the product you are specifying than the entire contracting organizations spend including the "tag-along" support of some association programs without any real participation.
Contractors are often more interested in flipping forms and doing volumes instead of new combinations of raw materials, the performance and the methods to achieve the results.
If you are designing in a smaller market without good supplier connections. A local contractor is a good choice for a "seat of the pants" opinion for that situation.
Dick