Karls Geopolymer Experiments

[firewatcher]

I'm kind of set on using a 2 inch thickness...i'm planning on making a mold for a batch box stove and need the thickness for support of the riser in the way that it was designed (as far as i can see). I'll have to pull out the files on my pc and send a couple of screen shots of the design that i've been wanting to use (again the knowledge and work of others has been integral with respect to the design and provided drawings). The design is not mine in any way.

By the way, I understand very well your analogy of gluing wood together as i used to do a fair amount of woodworking for enjoyment.

[firewatcher]

I didn't see anything on the product page specifically and definately calling out particle size for thw slag, but here is the web address that i was looking at for the product...

www.us-minerals.com/us-minerals-products/iron-silicate-abrasives/

[Deleted]

With 2 inch thickness it will insulate very well,
even with 20-40 slag and significantly higher slag/binder ratio.

[firewatcher]

Aug 27, 2016 11:27:36 GMT -8 @karl said:

 With 2 inch thickness it will insulate very well,
even with 20-40 slag and significantly higher slag/binder ratio.

I'm having some difficulty finding the file that I was going to share pictures of with you to show my concern for mold thickness and why I wanted to stick with a 2 inch thickness.  I did quickly find the following picture though.  It's not exactly what I was planning on, but it is close (instead of a two part riser in the vertical direction, I was planning a 3 part riser composed of 3 cylinders.  Still planning on molding the fire box, split vertically in 2 pieces though).

batchrocket.eu/images/rockets/core177d.jpg

I'm having difficulty getting images to attach for some reason...sorry for having to redirect to the link...

[firewatcher]

I did a little math last night based on the latest "working" test puck to determine cost of materials and was a bit surprised...
The refractory made with the latest mix will cost approximately $120/cubic foot (the major cost contributor is the waterglass)...
I'll need to redo my calculations on how much material I'll need based on my thickness reduction from 3 inch to 2 inch, but I'm estimating that I'll still need about 2 cubic feet of material for the batch stove design that I chose. Maybe it's time to rethink which design to use...

[Deleted]

firewatcher with your much coarser slag sand the optimal ratio of slag/pozzolan
is significantly higher, than with my much finer slag.
This will also reduce the required amount of waterglass.

One cubic foot is 28.3 liter, which at your reported density equals about 50kg.
120$/50kg = 2.4$/kg.

45kg slag is just about $18.
11kg Sweet PDZ about $10.

Eighter there are high shipping costs or your lye and waterglass must be extremely expensive.

[firewatcher]

The waterglass is my most costly part of the mix by FAR...at least in the amounts that i used in the mix.
450 g of lye costs around $4
1.82 kg of silica gel (cat litter) was about $8

Quick rough math says that i can get about 3 "batches" of sodium silicate out of 1 bag of silica gel + 3 containers of lye ($20 total)

[Deleted]

firewatcher please cast pucks with just 30mm thicknes with significantly higher slag/pozzolan ratios
and do reverse side tests.
Would save you quite a lot money if you could get away with just 30mm instead of about 51mm.
Even 40mm would save you some money.

BTW could you not get the Red Devil cleaner ?

[firewatcher]

Is this the product that you mentioned?

www.amazon.com/Red-Devil-0261-Heavy-Cleaner/dp/B000LNTXIQ

If so, then it lools like it's more expensive than the 100% lye that I'm currently getting at $4/pound (450g)

I can look more on line for better prices, this was just the first result that i saw for it.

[firewatcher]

@karl

My concern with reducing the thickness is being able to support the heat riser and the riser's functionality once "topped" with the metal drum. From what i understand, the riser must have a significant temp difference inside to outside (ID to OD) even once enclosed in the metal drum to function well. I'm not saying that a thinner wall won't work, just that it's a concern going with a thinner wall thickness. Maybe it is another misconception on my part, but my thought was the thicker the better (within reason-not being excessive).
I just don't want to invest the small amount of funds that i have available for the project without being reasonably sure that it will work...understanding of course that there are no guarantees.

I'll pull out my excel spreadsheet with my calculations on it and pass along some more specific numbers as to the waterglass usage and amounts used/ cost per cubic foot a little later on this evening when i have some time.

I appreciate all the suggestions and help! Keep it coming!

[Deleted]

From Red Devil directly 4.5 lb for $12.99.
Thats enough for at least 6 liters which should suffice for more 20kg dry mixture.
www.reddevil.com/index.php?l=product_detail&p=868

At Ebay 4lb for about $10 + about $5 shipping.

Outside of the riser are not ambient temperatures but many hundred degree Celsius.
My thin test samples can maintain a much higher temperature difference at ambient temperatures,
than the temperature difference of the gas from the inside to the outside of the riser.

I cannot break one of the 17mm plates with my hands once fully hardened.
Requires an hammer or throwing on a concrete floor to break one.

[firewatcher]

Karl,

How does the red devil product fit into the mix? Is it a substitute for the sodium hydroxide in the waterglass mix?

[Deleted]

According to the SDS it is Sodium metasilicate pentahydrate,
also just waterfree solid waterglass, the same as I got as Formsil 113.
www.reddevil.com/sku-docs/sds-0261-0265.pdf

Dilute it in hot water as the dissolution requires energy and will cool down the mix solid waterglass and water.

[firewatcher]

Dillution will be the same as your current recipe?
For example:
550g silica gel + 450g NaOH + 1.5L water would be the equivilant (close enough) of 1000g Red Devil TSP + 1.5L water?

[Deleted]

550 g silica gel, 450 NaOH and two liters of water. is the concentration
to transform quite literally dirt in highly refractory material,
within short time under ambient temperatures with very high strength already in the cold state.

For mixtures with a high slag/pozzolan ratio and elevated curing temperatures
the waterglass can be much more diluted.
In the 4/1 mixture used for the reverse side test one liter waterglass has only 330g solid content.

Give 330g Red Devil TSP/90 in a one liter bottle and fill it with hot water.
In this way 4.5lb (2.04kg) will give you about 6 liter waterglass.

Even lower concentrated waterglass may work for some mixtures.
I have successfully used just 250g solid/liter but would not generally recommend it,
as the risk of failure grows with such low concentrations.

What may work or not depends a lot on the used pozzolan,
the exact composition of a mixture and the curing regime.