Springtime Homes wrote:Thanks for the link Dave. Concrete is such a great construction material its good to see that people are working on its carbon impact.
Iam a skeptic of anything claiming to be carbon negative and I think its a marketing mistake to make such wild claims.
One of the best ways to reduce the impact of concrete is to use fly ash in the mixture. This displaces the amount of concrete that needs to be produced and is a decent solution to the problem of that coal byproduct.
Dale Hodgins wrote: I had all of the same concerns as Springtime Homes. The amount of information given on that website is minimal. It appears to be a mini prospectus in search of funding. I would have to see at least 100 times as much info for it to be useful to me. I want to see where they get those other raw materials and what the mining process was. Mostly I want to see information corroborating what they say from unbiased sources.
Any time hemp is brought up it's bound to get eyes rolling. I almost stopped reading when I saw the word. I lived beside a hemp field in Ontario. Yes it was productive but no it was not ten crops a year with no inputs. I've sat and listened to kids tell me that it produces vastly more than what I witnessed.
If they have something that's great. But I remain unapologetically skeptical for now.
Springtime Homes wrote:My main argument is something I am very familiar with: Labor Costs and Hidden Costs. The two projects I saw involved HUGE amounts of labor and took a long time to complete. Big crews of workers came every day to the job site for weeks and I doubt any of them were fueling with B100. Luckily these carbon costs were minimized by being infill projects, but this was a pretty substantial hidden carbon cost that my SIP homes do not incur. Another very difficult to calculate hidden carbon cost is the fuel that it took these workers to complete their labor (food).
Marcus Zed wrote:Your critical method of searching widely for hidden inputs seems correct on a project basis.
I suspect that the "green concrete" skeptics on this thread are trying to get ahead of potential perverse interpretations like: "We need to quit telling people to build with cob, which is merely carbon NEUTRAL, and encourage them to build everything out of this new carbon NEGATIVE cement!!!"
Of course, the sort of simplistic thinking that would lead to that kind of attitude is unlikely to coexist in the same mind that would be receptive to your more complicated model.
Dave Bennett wrote:Nobody that I know of implied using this potential product instead of cob.
gardenlen gardener wrote:as a permaculturist i see it that there is no free stuff ie.,. sub-aquafa water and sand gravel soil to build homes with, all these products are habitat, lots of sand and gravel comes from creeks and rivers, but all of it is habitat, even destroying forest habitat to grow plantation timbers to build houses is using habitat to the detrement of wild life, especially so over here. so we need to get more sustainable in what we do in this modern world. growing food on broad acre farms where all habitat has been removed, pushing down forests to grow oil palms.
Pam Hatfield wrote:process is hugely polluting
Pam Hatfield wrote:modern concrete certainly strong but it is not entirely the ultimate answer, when it breaks or fails it is not easilly recycled, and indeed it DOES fail for a number of reasons.
Walter Jeffries wrote:
Pam Hatfield wrote:process is hugely polluting
Yet you're missing the point. The cement is not the concrete. Cement is just a small part of the concrete. Fanatics like to paint with a broad over generalizing brush like this and confuse the issue by mixing the terms.
http://www.thedailygreen.com/environmental-news/latest/mercury-cement-47012002 I was not confusing the two at all. I would definitely prefer not to have mercury (among other things) being spewed into the air no matter how little cement, relatively speaking, is used to build a house. The point is that although each project may only take a little the number of projects add up to a whole lot. It's like each guy only killed one passenger pigeon but somehow the passenger pigeons went from being in the uncounted thousands to being exterminated. Finis. It's the cumulative effect.
As far as the failures are concerned are you suggesting that the bridges and abutments on the highways in California were all built incorrectly? Or all the buildings in Haiti which collapsed? Those are only two examples. Cement is what holds the concrete together, there is nothing else, so if the concrete fails, that is, doesn't hold together, it is the cement part of the concrete which is to blame. Nobody would ever expect sand and gravel to cohese at all otherwise. But, concrete is brittle and though very strong cannot manage flex or certain sorts of stresses, which is why it's virtually always used with rebar of some sort. Sometimes even that isn't enough.
Another problem is that concrete made with portland cement is also very vulnerable to water , especially in areas where water is likely to freeze, which is why there are thousands of companies which fix leaky basements and crumbling foundations and dozens of products sold to waterproof it. Or to try to clean mould from it.
As far as bridges are concerned, there are many many wooden bridges which have been in use for a very long time. There is one in Switzerland, still in use today, which was built in the 1300s. (admittedly much of it was restored..after a fire in 1993). 600 + years and going strong will do me just fine. As far as I can tell ALL bridges, concrete/steel or otherwise, need maintenance and repair from time to time. Certainly I've been held up in traffic on not a few concrete and steel bridges, often not more than a few years old, because of repair crews doing maintenance. Are you saying they were ALL improperly built? As far as that goes, a guy in Japan built a totally serviceable bridge out of paper, although it was a demo project and only used for foot traffic, not vehicles.
It seems to me that pointing out there are two sides to the story and that cement (in the form of portland cement at least) is not the unalloyed answer to all building problems, is hardly being fanatical. It would be unfortunate to think we cannot get beyond the technology of the 19th century now we are in the 21st. Or maybe we should go back further and learn what the people of the deserts did 3000 years ago when they constructed water tanks still in use today.