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Wed, Jan 11, 06 at 11:27
| A question this morning for those with experience in these two additives.I'm very familiar with silica fume-great stuff for the thin crowd,but have not used the metakaolin.I understand it might be similar but not dark in colour.Has anyone used it with success in cement/sand combinations?
thanks Cheers from here |
Follow-Up Postings:
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- Posted by shrubs_n_bulbs z8/9 UK (My Page) on Wed, Jan 11, 06 at 11:47
| 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. |
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- Posted by garden_chicken (My Page) on Wed, Jan 11, 06 at 20:35
| 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. |
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| 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. |
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- Posted by rickharmer z4British Colum (My Page) on Thu, Jan 12, 06 at 0:11
| David-with the right mix,you get great lightweight results,like I have.I just completed a 26 inch hollow ball that weighs less than 14 pounds,and masks from molds weigh in at 3 pounds.This is with detail mesh and my own formulation.I've had a test ball(16 inches,about 6-7 pounds)with water in it for about 3 months.No cracks and water tight.And that is using silica fume.Metakaoloin I want to try as well,but only for the colour aspect.I'm quite happy with my experiences with fume. But,that's just me. cheers from here |
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- Posted by rickharmer z4British Colum (My Page) on Sat, Mar 4, 06 at 18:35
| 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 |
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| Hi Rick, I'm right here in Surrey, B.C. |
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- Posted by rickharmer z4British Colum (My Page) on Thu, Mar 9, 06 at 13:10
| try UNIVAR.I picked up and no problems.i'll get to play next week! Cheers from Seattle and thanks,Dena! |
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- Posted by rickharmer z4British Colum (My Page) on Thu, Mar 23, 06 at 17:31
| 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 |
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- Posted by garden_chicken 3b (My Page) on Thu, Mar 23, 06 at 19:52
| looking forward to it rick! |
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| 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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