Metakaolin is considered superior to silica fume in the concrete industry, but difficulty with handling and mixing have limited its use. That shouldn't be an issue in small quantities. It reduces slump (basically because it sets fast), decreases setting time (more even than silica fume), and increases strength. It is almost white.

rickharmer, have you found a source for metakaolin? I tried finding it a few months back, no luck. People didn't even know what I was talking about. I did find kaolin at a pottery supply store, my understanding is that metakaolin is a finer grade of kaolin. I finally gave up.

I'll be following this thread to see what others have to say.

I think both metakaolin and silica fume are next to useless in hypertufa or light weight concrete.
They certainly increase the density/strength of regular concrete.

I have stopped using them both as well as fly ash because I'm trying to make a light weight product and they appear to be of no benefit at all.

For those who asked,I've found a bulk source for metakaolin,in Richmond,BC.I'll post the name and details after the 12th,as I'll be out of town.As I've been reading on a number of sites,there are differences between brands of metakaolin.
BTW,55 lbs will cost me 41.25(CDN).I'm going with this source because of convenience.Other sources were in the U.S.,and I know that there are other providers here in Canada.
I'll let you know the results of my mud experiments!
Cheers from here

Hi Rick,

I'm right here in Surrey, B.C.
I'd love to get the name info on that supplier for metakaolin in Richmond! That is close to me!!!! I'd like to see what it does for my sculptures.

try UNIVAR.I picked up and no problems.i'll get to play next week!
Cheers from Seattle and thanks,Dena!

Continuing this thread about metakaolin,I've been playing in the mud,using my "mymud" formula,subbing in the MK instead of SF.Here's what I've got so far:
This stuff sets up fast,which I like.
It's damn near white.
It defies gravity(I can work upside down and it adheres no problem).
I'm working on a three coating arrangement for strength,and that'll be done tomorrow.I'll deflate the ball and let you know what the results are.
Cheers from here

looking forward to it rick!

I realize that this string is very old, but I was directed to it while searching for Metakaolin. I thought I'd chime in on some of the comments.
Research suggests that Metakaolin is superior to silica because it has less problems cracking in lightweight concretes.
I am currently a civil engineering student. You might be surprised to know that in universities across the US and Canada, there are engineering students who participate yearly in a Concrete Canoe competition. Our challenge is to make a strong, lightweight concrete. All the mixes I have seen obtain unit weights of 58-75 lbs/cu ft. This is about 16 kg/cu m for those Canadians. You might note that 58 lbs/cu ft is lighter than water (62.4 lbs/cu ft). Many of these mixes use silica fume, metakaolin, fly ash and slag in addition to portland cement to obtain strengths of generally around 1900 psi (about 703 kg/sq m)
Traditional concrete generally has a unit weight of around 145 lbs/cu ft (2322.67 kg/cu m) and strenght of 3000-5000 psi (2.109*10^6-3.515*10^6 kg/sq m). You can see that the weight to strenght ratio of these lightweight concretes is actually better than that of traditional concrete!
I thought this might be an interesting addition to the discussion on lightweight concrete.

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