Greetings:
A concrete guy I used in the past told me he had flyash added to the mix to give it more of a grey color for stamped concrete. It seemed to work well and saved money as opposed to adding dye to the concrete. Now I’m working with a different concrete guy and made the flyash suggestion. He was unfamiliar with it. So what would be a typical amount of flyash to specify to get the grey tone but so as not to weaken the slab significantly? It will be a 3000 PSI mix – and BTW – around here, we don’t use the “4 bag” (example) mix terminology here – we just specify PSI, slump and any admixtures.
TIA
Replies
flyash is a pozzolanic material , meaning although it has no cement material, it itself with moisture will have a psi rating. Flyash will break 1500psi by itself. By reducing the cement content of the mix, it will cool off the mix. flyash particles are more rounded so the mix becomes more creamy and easiler to handle. Flyash will start its cycle when the calcium hydration of the cement product starts. In other word a flyash mix will be a weak mix the first couple days till the byproduct of cement. calicum start its cycle. Usually seven days. Flyash is a free byproduct of coal buring.
So a flyash mix will be, cheaper, easily to handle, less prone to cracking due to less heat. Cons are slow gaining strength.
Flyash mix run 15% to 30% flyash. and will not gain equal strength till late 20's days. But because of slow strenth, flyash is not a cold weather concrete, it will retard the mix in regular weather. cold weather it will never get hard.
I like flyash mix. everything I pour is a flyash mix. also its the perfect mix for pumping.
You know some very cool stuff. I'm going to print this one out and file it.
Johnny, is flyash available anywhere? Or just areas where coal is used?
Joe H
flyash is a product of power plants. If they cannot give it away, it has to be landfilled. we have a concrete company in west louisana that come to Mississippi for it. My answer would be yes.
Thanks BB - I was hoping you would answer...
What you said about cold weather concreting concerns me a bit...
If you don't mind look at our local weather page:
http://www.weather.com/activities/other/other/weather/tenday.html?locid=27615&from=36hr_topnav_undeclared
My guy said he wanted to pour on Tuesday, but It's kinda looking like Wednesday.. What do you think of those temps? Not bad but not great. Thanks much...
PS - My guy usually orders accelerator in his mud. Any thoughts about how accelerators work with a flyash mix?
Thanks much...
it be fine, just slow to take off2+3=7
Thanks.. sorry... what's "2+3=7"?