Fire clay LTGS reporting

[esbjornaneer]

To keep different feed stock options separate I will report on using fire clay in this thread. The fire clay I can source here in Spain comes from Refractarios Andalucia and in my local supplier cost 4.60euros/25kg bag. He sells it for people to mix their own refractory mortar (2 parts fire clay: 2 parts builders sand: 1 part cement). If I can find the mineral composition of this clay I will add it later.

Other peoples experiments with fire clay are most welcome but as a reader it would be good to be aware that fire clay comes with different mineral compositions and as such will react differently.

[Deleted]

Refractarios Andalucia provides technical sheets only on request.
raceramica.com/contacto

[Orange]

how are you satisfied with the fireclay compared to regular clay?

mine doesn't stick, its like sand, I'd rather use the normal clay.

[esbjornaneer]

Unless I state it in a later post all my binders will have a 1/1 ratio of fire clay/NaOH.
My test pucks/muffins are made from 123g dry feedstock material.
Sample numbers are continuous from my launa experiments, hence starting on 9.

Sample 9    20% binder, 3% fibre (i.e. Binder: 12g fire clay, 12g NaOH. Fibre: 4g toilet paper. Aggregate: 94g fire clay)
made 26th Jan

For my first attempt I used too much water at the early stage of making the binder. I used the procedure specified in the thread of my launa experiments. I added 9g(=ml) straight away. The binder never thickened up and I did not let it rest. Both last points were mistakes. Total added water was 50g.

To improve on the "too much water in binder" issue I found that using Karl's advice to find what will be too much water for a binder 3.7g of water is too much for 24g dry binder contents (0.7g was in the clay when I tested and 3g added).

For sample 10-15 I mixed one larger batch of binder: 75g fire clay (this time dried), 75g lye. I started with 3g(=2%) water, and it was dissolving fine, getting more and more liquid as I was mashing up the soda grains. Then had breakfast and it got stuck in the glass bowl. Added another 12g water to release it while heating it up again. Then another 6g water. Rested for 2-3 hours. Going too stiff another 2 times during the resting time, adding 15g water each time it went too stiff.

Then I mixed:

                % binder, % fibre, [g] lye, [g] clay, [g] fibre, [g] dry aggregate, [g] wet agg, [g] total water added ~, [g] water from binder
Sample 10      2             3         1         1         4         116                     124                 49                            1
Sample 11      6             3         4         4         4         111                     119                 47                            3
Sample 12      10             3         6         6         4         107                     113                 45                            5  
Sample 13      20             3         12      12         4         94                     100                  41                            9
Sample 14      30             3         18      18         4         82                     87                     36                        14
Sample 15      40             3         25      25         4         70                     74                     31                        19
made 31 Jan

The 4g of toilet paper for each sample was mixed with 21g of the total water added (from column above) to dissolve into fibres. The rest of the total water added was mixed with the binder making the total water for each sample 50g.

Samples 10-15 were mixed one after the other and when I got to sample 13 I noticed that there was still some heat generated when I added the extra water to the rested 'binder'. Karl has said before and told me again just now that the binder is not complete until water can be added with no increase of temperature! So none of these fulfil this category! Or at least were not rested after all water needed to complete the binder had been added.

I added the liquified binder portion to the aggregate (I made adjustments in the agg. weight and total water added quantities to get the proportions right). When the mix was almost homogenous I added the fibres with their absorbed liquid. And put it into the mould.

At this water quantitiy it was sort of like warm peanut butter, it was tacky but would just hold peaked shapes.

Torch test to follow.

As can be seen in pic (3 days for sample 9, ~52hrs after going into uncovered moulds #10-15, sitting in 17-45*C environment) there is lots of fuzzy efflourecens on #10, a white covering on #9,11,12 & still hardly any drying of #13,14,15.

[esbjornaneer]

Thank you Karl, they don't really reply to emails though. The only info I have got from them is when I ring so I'll have to do it again.

[esbjornaneer]

Orange I have not used this fire clay for anything other than these geopolymer experiments and can not really compare it with Launa clay that is the only other clay I have worked with for rocket heaters.

[Deleted]

With a 1/1 binder I would not go over 20%.

[esbjornaneer]

What would be the reason for that, Karl? It is the 2% binder that efflouressed most so far. Or is that because of not getting all the NaOH dissolved in the binder stage. It is the 2% binder that had the most water added to it to make up the 50g total water/sample quota. (The reason I use 50g water/sample is that it is just possible to jiggle down into the mould without having to tamp it down or it being too runny.)

[Deleted]

Lye is the most expensive ingredient and it is very dangerous.
Both are very good reasons not to use very large amounts of it.

[esbjornaneer]

Thank you Karl, that makes sense! I was just confused as I thought you had suggested 20-40% binder for the launa mixes. And I added the lower percentages because of the Davidovitz paper.

I have done one more batch with the same percentages as batch 10-15 but getting the binder more fully reacted. Process:
started with 6g(=4%) water, was dissolving fine, used less effort mashing up the soda grains. Started going stiff after ~1.5hrs. Then added 6g water while retaining it on the boiler (total ~2hrs).
When taking it off the heat it solidified within 20min. Added 9g water. 'Melted' it over heat again.
Went liquid when reaching 65C.
Took off heat and kept checking that it would not get too stiff (every 2-5 minutes) and added a further 27g water at 3g at a time. When adding water the temp is still increasing by 5C but is getting quite liquid.
Rested for 12 hours.
Added another 126g water temp increase tailing off.
2g more and no temp increase. By this stage it was more like milk than cream, definately not as thick as thick/double cream, even less a paste. Next time I will make some videos to show consistensies.
Rested for further 2-3 hrs.

Due to the greater amount of water going into the binder I was not able to dissolve the fibres of the last two samples in water but added the toilet paper dry to the mix. As I progressed with greater binder percentages the mixes seemed runnier even though I had calculated that they would each have 50g of total added water, apart from the 40% binder sample that got 65g water total, all coming from the binder.

                 % binder     % fibre     [g] lye     [g] clay     [g] fibre     [g] dry aggregate     total water added ~
Sample 16     2                 3             1             1             4             116                         50
Sample 17     6                 3             4             4             4             111                         50
Sample 18     10                 3             6           6              4            107                         50
Sample 19     20                 3             12         12             4             94                         50
Sample 20     30                 3             18         18             4             82                         50
Sample 21     40                 3             25         25             4             70                         65


Having come across the Metaclay thread I will do the next batch with metaclay and skip the 30&40% binders next time, instead add two more lower percentages. Then I hope to moving on to experimenting with one percentage (the one I like best) and altering the water content so see how/if temps go down on the back during the torch test.

[Deleted]

Quite complicated procedure.
I need only a few minutes to make a working binder.

You could make tests to see if the result justifies the effort.

[esbjornaneer]

Yes, quite complicated. But now I know how much water the binder needs I can add it quicker. It is tricky for us that have not done chemistry since school to catch up with you Karl I have to do it with lots of attempts and lots of questions.