Anyone have any suggestions on where to buy fly ash? I can't seem to find any sources online. Any help is appreciated.
Don't know about fly ash but you can get metakaolin and other good things at concretecountertopsupply.com .
you might be able to buy some at a redi mix plant call around.i use metakalin also.fly ash comes in high and low densities and is grey.hard to measure low density because of the volume.also hard to get light colors.i would buy the metakalin $40 a bag and it is white.
I wouldnt use fly ash even if it was free
IMO a good type C fly ash does more for a mix than MET. Because of the spherical shape of the particles it actually lowers water demands instead of increasing them. I have run the type C as high as 30% in precast. It does not retard the set or have a dark color like type F. If you are looking for a white pozz you can use VCAS from blueconcrete.com and it will not increase you water demand like met.
Check with these companies and they can tell you distributors in your area. A lot of block producers use fly as a partical filler. It can increase strength, reduce weight, and cost. It is one of the least expensive most widely used pozzolans that I am aware of.
Please explain your statement.
With the popularity of fly ash, if you know something we don't, please share.
Quickrete has a bagged fly ash, but you have to call and ask for it.
From what I understand, Class F flyash (the more common type in the West U.S.) can delay set, does reduce water demand, and helps make concrete less poreus. It is available at Redi-Mix businesses.
Class C, which has cementing reactions (not just pozzalanic) may set faster. It is more common in the midwest and east coast.
The main use of flyash is as a cheaper cement sub. admixture.
There are three admixtures that are more expensive, but also more effective:
All three dramatically lower permeability, reduce effloesence, and strengthen. Aside from price differences, each have advantages and disadvantages according to the literature:
Silica Fume is "sticky" and makes troweling more difficult. It also requires the most water. Very low permiability however.
Metakaolin requires less water than Silica Fume, but more than cement. It makes a creamy mix more easily worked, and makes for very low permeability. At the same ratio of water/cement I think it is better than Silica Fume.
VCAS requires the least amount water, less than cement. It is also satisfactory for working and has equal compressive strength to S.F. and MetaK. . However, it does seem to require a higher content in the mix to equal Silica Fume or MetaK in lowering permeabilty (what S.F. does at 9%, VCAS does at 15% of mix).
I'd be curious if anyone has tried at least TWO of the above admixtures and can make a comparison?
A pretty good synopsis of useful pozzolan, minus natural sources which I only am familiar with one. Lassenite from Mt. Lassen has good color but does have its own nuances when it comes to batching. About the only pozz I haven't tried steel furnace slag.
It is funny about the class F fly. I heard it was only an east coast thing. In reality is a coal source thing. I recently have had quality of my fly change. I had a batch with more carbon which tends to occur during the start up and shut down phase of the coal fired electrical power plants. The one down side of fly is sourcing quality. I am now sourcing larger quantities to have better quality control.
I was told by a fly ash distributor that coal fired plants with air quality scrubbers(ie California) produce ash that is unfit for concrete production. Unfortunately it is the dirty source of electricity that produces the good quality ash. Fortunately, I have no problem saving it from the landfill @ about $ .10/lb.
I do use a combination of pozz although I dropped Met mostly because its increased water demand and cost. It is as much about particle packing as it is pozzolanic reaction. Without the former you have poor execution of the latter. I have tried met,fly,VCAS, and Lassenite individually. I have tested most of our mixes at 7 and 15 days for compression. Using a combination of pozz I get better results. I get better rheology with less water using my fly ash. With 50% of our electricity coming from coal fired power plants there is probably a bagging facility within 500 miles of anyone in the U.S.. The type of your ash depending on your coal.
This fun of concrete is obtaining the best quality ingredients available in your region. The engineer that does my testing also tests aggregate. Hardness and strength of aggregates also plays a large part in overall strength. There is a lot of things that can complicate mix design. So developing your own system is of the utmost importance.
I have never used fly ash, but I am curious about Class C. However, it seems everyone around here uses Class F.
I noticed you did not mention silica fume, and experience with it?
If it is not a trade secret, what combonation of pozzilians do you find that is most cost effective and why? Do you have your testing include permeability?
I run about 18% cement blend of type III grey and Lehigh I white. My pozz is about 7-9% upping my cmt to about 25-27% of my mix.
I blend my pozz about 50% C fly,30% VCAS, 20% white sf. I have tried a few different ratios. I just find a better mix with the fly. I have not run permeability tests but it is a very tight high early strength mix. My lab is limited to visual inspection and compression testing at this time.
Permeability is more of an issue with things like dams and roads. Countertops and sinks need to be sealed to prevent things like staining and etching.
You can take AAC block, slurry, and seal and achieve impermeability. In fact I have seen a few countertop mixes that resemble AAC. It may not be as strong but it is much lighter.
I'm just starting out, so while I have "book learning", my only experience has been with metK and Type I/II.
That is a very specific formulation - I could see that whatever the small amount of water the addtional SF requires, it is more than offset by the lower water req and easier workablity of VCAS and FA.
Thanks - something to think about.
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