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Post by firewatcher on Sept 12, 2016 12:43:02 GMT -8
Update on latest two brick mixes after 24 hours... Disaster has stricken the first brick...  The second brick is holding strong at the moment...  I'll need to determine if it's from ambient curing or the plywood mold pulling liquid out of the brick...  |
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Post by firewatcher on Sept 12, 2016 18:56:01 GMT -8
Lawry, thanks for sharing that...I don't have anywhere that I've been able to find fly ash, so unfortunately I can't try any recipe containing it at this point. Have you made test bricks or anything like that with the mix. I'm trying to get a feel for how strong a brick/puck/whatever should be without "going overboard". Every mix that I've tried thus far has produced results that I'm less than satisfied with. Maybe I'm expecting too much though. I had the idea this evening of comparing the strength of a standard clay brick to a geopolymer brick, but don't know how I'll do that as I don't know where I could get a 1inch thick clay brick. The thought was just to try and break each 1inch brick by hand to compare clay to geopolymer or to support each end of a brick and apply weights to the middle to give me breaking strength. Right now I just don't have a feel for if I'm in the ballpark. For all I know, comparing material to material, I could be 2-3 times stronger or half as strong as clay. |
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Post by firewatcher on Sept 13, 2016 7:00:50 GMT -8
Commercially sold fireclays have 20%-40% alumina, usually close to 30%. Untreated clay is chemically quite inactive. In the mixture the clay serves mainly as a thickener. Clays are thixotropic, which means slurries become more liquid if stirred or vibrated and unmovable at rest, which prevents segregation. You could activate the clay with acid. Whet activation of clays with organic acids works like a charm. This possibility is actually extremely obvious catching your eyes, I've always wondered why nobody has done that. Guess I could have got a patent on it. For health reasons I could not accompany my wife and son on the visit of our home on the Philippines. For five weeks I was alone, very bored with lots of free time and no wife complaining about the dirt involved with my experiments. Thus I decided to give acid activation a try. Acid can extract metal ions from perlite or zeolite and increase the reactivity in other ways as well. As clays have very small particles acid activated clay is superior to perlite or zeolite. If you want to build a big one or more than one stove you could get 100lb clay for acid activation from Rovin Ceramics Inc. Per lb for 100-499lb: Ball Clay, OM4 $0.24 Kaolin, 6 Tile $0.47 Ball clays have a higher water demand than kaolin. You can mix the clay with the pozzolan you already have. Hi Karl, I activated 35g of fire clay last night. I'm wondering if this should be used in a "clay only " mix as you have done in some experiments or if this could be used in the type of mix that I have been testing recently with pozzolan/ waterglass/lime. The purpose of activating the clay is only to make it more reactive correct? So it shouldn't matter what mix it is used in I would think. I had planned on using it in one of my currently used testing mixes, which is why I only activated such a small amount. 35g is all that i need to make a recipe for a 25mm thick puck, 127mm in diameter. If it doesn't make sense to use it in that way, I'll follow your example directions (as closely as I can with the materials I have) and see what results I can get. |
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lawry
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Post by lawry on Sept 13, 2016 7:34:57 GMT -8
Just over a month ago I tried casting a 200 mesh grog brick.... Unlike the Fly Ash bricks, it didn't harden at all instead it oozed out the liquids. Even after a week it was still soft I broke it into two pieces and I forgot about it. Today I tried to crumble it and smash it but I couldn't.  Here is a video of me cutting it to show its structure. vimeo.com/176041605Recipe : Grog 180 Aggregates 245/245/210 NaOh 71 NaSiO 29 Notes: since this mix oozed liquids out so much, I am guessing I need to reduce the solution quantity. Maybe let the mix of grog and 45g NaOh solution rest overnight. " firewatcher" I have done a number of tests with the materials I could find. The grog brick was impressive because it was ambient cured but long curing time. The fly ash bricks have been impressive due to ambient curing and the time to cure and strength properties. I'm quite confident that these bricks are as strong as clay bricks if not stronger |
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Post by firewatcher on Sept 13, 2016 16:21:33 GMT -8
Just over a month ago I tried casting a 200 mesh grog brick.... Unlike the Fly Ash bricks, it didn't harden at all instead it oozed out the liquids. Even after a week it was still soft I broke it into two pieces and I forgot about it. Today I tried to crumble it and smash it but I couldn't. Here is a video of me cutting it to show its structure. vimeo.com/176041605Recipe : Grog 180 Aggregates 245/245/210 NaOh 71 NaSiO 29 Notes: since this mix oozed liquids out so much, I am guessing I need to reduce the solution quantity. Maybe let the mix of grog and 45g NaOh solution rest overnight. " firewatcher" I have done a number of tests with the materials I could find. The grog brick was impressive because it was ambient cured but long curing time. The fly ash bricks have been impressive due to ambient curing and the time to cure and strength properties. I'm quite confident that these bricks are as strong as clay bricks if not stronger Lawry, It looks strong for sure! Had you ever done "reverse side tests" to determine a rough idea of the material's thermal conductivity? Making a mix that is hard is a great thing...on the other hand, if is not insulative it won't work as well as something that is insulating for a rocket stove...especially in the heat riser. The "reverse side test" as Karl did it, is really nothing more complicated than pointing a torch at the middle of the test piece and seeing how long it takes for the opposite side to get to some criteria temperature. My opposite side tests have been as unscientific as pointing a MAPP gas torch at rhe center of the test piece and keeping my hand or a finger against the opposite side of the piece...timing how long it takes before I can no longer keep my hand/finger on the material. Knowing how hot the flame temperature is and how long it took the opposite side of the test piece to get "hot to rhe touch" gives an idea (although only a concept) of how insulating the material is. Obviously the thickness/thinness of the test piece plays a part in how quickly the opposite side heats up as well, but the idea of this type of very basic and non-quantitative test is just to get an idea of thermal conductivity. |
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lawry
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Post by lawry on Sept 13, 2016 23:27:01 GMT -8
I have done some tests. On the left is a Fly Ash and aggregate brick. The middle one has FA, small size aggregate and perlite. The dark brick has FA, Clay and aggregate. I cured them after 24 hrs at 90⋅C left them overnight in the oven. these bricks are rock hard! The fly ash one is the only brick that does well at ambient curing. After seven days I couldn't break it by hand. I m trying an ambient cured perlite brick currently. I will update once it's dry.  The structural ones will be for the body of my stove. I plan to get them mix tested at a lab for strength. The perlite will be for the riser.  " firewatcher" these are the other samples I made. I don't have a torch to do the test as you did. I have put the samples on top of my tlud directed flame. The sample with silicon carbide was 650*C flame side and 298*C on the other. The insulative mix didn't go above a 100*C I will need to do the test in a systematic way in order for my results to be correct. |
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lawry
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Post by lawry on Sept 14, 2016 1:02:42 GMT -8
 This is what I mean by my TLUD directed flame.😁 |
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Post by firewatcher on Sept 14, 2016 2:25:10 GMT -8
I have done some tests. On the left is a Fly Ash and aggregate brick. The middle one has FA, small size aggregate and perlite. The dark brick has FA, Clay and aggregate. I cured them after 24 hrs at 90⋅C left them overnight in the oven. these bricks are rock hard! The fly ash one is the only brick that does well at ambient curing. After seven days I couldn't break it by hand. I m trying an ambient cured perlite brick currently. I will update once it's dry. The structural ones will be for the body of my stove. I plan to get them mix tested at a lab for strength. The perlite will be for the riser. " firewatcher" these are the other samples I made. I don't have a torch to do the test as you did. I have put the samples on top of my tlud directed flame. The sample with silicon carbide was 650*C flame side and 298*C on the other. The insulative mix didn't go above a 100*C I will need to do the test in a systematic way in order for my results to be correct. Thanks for sharing this (again), I guess i missed it the first time somehow. It looks like you have a better testing method in place than I'm currently capable of. I've been trying to think of a better way to cure and test my bricks (more controlled curing and actual temperature measurements). So far my only method of curing has been in a "camp fire" in the yard my wife would not be happy if i used our oven! I'm also trying to find an IR thermometer to borrow to get some quantitative results, but so far I've had no luck. Thanks for the pic of the tlud too...I was wondering what that was. |
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lawry
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Post by lawry on Sept 14, 2016 3:43:11 GMT -8
My wife was also not impressed with me using her own.😓 So I decided to make a solar curing box, which should be far better than just ambient.  I Took these readings in winter. Mid summer they should get to about 60*C... I hope.  I will leave the bricks in the box for a week. They should be up to strength by that time. |
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Deleted
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Post by Deleted on Sept 14, 2016 4:33:03 GMT -8
By activation with either acid or high heat clay is converted into a highly reactive pozzolan, a Meta-Clay.
Due to their very small particles Meta-Clays are more reactive than grinded minerals like perlite or zeolite
and can form very strong bonds.
However the very small particles cause also a high water demand.
The high water demand can be reduced by using superplasticizers.
Some fire clays seem to be actualy grinded mud stone, clays which became stone again, not true clay.
With Meta-Clays you need to keep about the same Aggregate/pozzolan ratio as with other pozzolans.
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Post by firewatcher on Sept 14, 2016 4:59:01 GMT -8
I'm anxious for the weekend, as this will mark 5-7 days of ambient drying time on three test pieces that I've made in the past few days.
Karl, today I am planning on trying out a variation on your LTGS test recipe "for the fun of it". Again, using the materials that i have, and because it was free...I am trying out the bentonite clay from dessicate packets to see what happens.
In your recipe description, I didn't see a time frame for drying time before heating at 250C. Do you recall how long you waited before curing at temperature?
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Post by Deleted on Sept 14, 2016 5:36:50 GMT -8
The LTGS recipe is for pressed bricks and with 10% binder it works also for a kneadable ram mass.
A mixture castable under vibration requires about three times the amount of water as a kneadable ram mass,
thus I assume it will also require three times the binder content also about 30%.
Superplasticizers could reduce the requirements for water and binder, but are not free either.
Mixtures with the LTGS binder likely cannot be loaded with as much aggregate as mixtures with waterglass.
As I have mentioned before about 3 hours at 50°C then 2 hours at 75°C.
At 100°C about one hour.
For every following temperature step the time can be shortened.
The time depends on the amount of water still there.
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Post by firewatcher on Sept 14, 2016 6:23:50 GMT -8
The LTGS recipe is for pressed bricks and with 10% binder it works also for a kneadable ram mass. A mixture castable under vibration requires about three times the amount of water as a kneadable ram mass, thus I assume it will also require three times the binder content also about 30%. Superplasticizers could reduce the requirements for water and binder, but are not free either. Mixtures with the LTGS binder likely cannot be loaded with as much aggregate as mixtures with waterglass. As I have mentioned before about 3 hours at 50°C then 2 hours at 75°C. At 100°C about one hour. For every following temperature step the time can be shortened. The time depends on the amount of water still there. I'm OK with "tamping" this test mix into a test mold instead of pouring...just to try out the concept using bentonite. I'll use the same size pucks as i have been, making it fairly easy to do so unless it's necessary to use some sort of lever to gain mechanical advantage for "ramming". It sounds like aggregate is recommended? Should aggregate be used even if I use the more dry 10% binder "ram" method? I had not planned on using any aggregate at all... |
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Post by Deleted on Sept 14, 2016 7:20:20 GMT -8
The result of my Proof of Concept ram mixture without aggregate
is actualy much harder and stronger than the castable mixtures with aggragate.
I cannot see any reason to use aggregate with a ram mixture,
except maybe about 20%-30% by weight to reduce the risk of cracks
while drying.
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Post by firewatcher on Sept 14, 2016 7:31:09 GMT -8
The result of my Proof of Concept ram mixture without aggregate is actualy much harder and stronger than the castable mixtures with aggragate. I cannot see any reason to use aggregate with a ram mixture, except maybe about 20%-30% by weight to reduce the risk of cracks while drying. Since bentonite soaks up so much water, I'll give 20% aggregate a try in the mix to prevent cracking. If that doesn't work, I'll test some more. The bentonite was free to me and it only took 30mL of vinegar for the activation of 35g of the bentonite, so it's an inexpensive experiment. |
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