[peteeng]

Hi Thomas - When you get the Silimix get a container and scale and place some in the container (tamp to neat fill) and weight it. Then add water until neatly filled and weight it. Publish ratio here please.

This will tell you the Silimix void content. You can convert your water weight to epoxy weight via a volume calc or density ratio. This will tell you the max weight ratio of epoxy to use... As explained before weight ratios are not absolute. If you have a light/heavy aggregate then weight ratios for epoxy are different. Even the epoxy can be 1000-1300kg/m3 so that's a variable as well... Peter

[badhabit]

Hi Thomas - When you get the Silimix get a container and scale and place some in the container (tamp to neat fill) and weight it. Then add water until neatly filled and weight it. Publish ratio here please.

I already have some Silimix inhouse and tried your suggestion. Here is a container with approx. 1liter of dry Silimix282 and then wetted out afterwards:
Attachment 458760Attachment 458762
(1liter of Silimix282, container weight 35g, so dry weight: 1994g and wet weight: 2143g)

...maybe a tad too much water if it should ressemble final EG-mix...if my batch was looking like this, i would properly go down another 0,5-1% in ratio...

Edit: or did i misunderstand your procedure? Was it important that the volume was consistant? Because i started with 1L dry and had about 950ml wet...so adding the water compacted it a bit somehow...

/Thomas

[peteeng]

Hi Thomas - No procedure is good for weight ratio...Dry is 1994g wet is 2143g so water is 149g addition ratio is 149/1994=7% so not much void there... just turn out the mix and check its all wet out... no dry spots, or leave for a while to check it has seeped thru or give it a stir. What is the density of the epoxy you are using? Ta Peter

Hi Thomas some quick calcs. Silimix is described as quartz. Quartz density is ~2600kg/m3. So unless there is some very light aggregate in there the Silimix has the highest solid volume ratio I have seen. Its 84% solid using your numbers. If you use equal spheres the highest ratio you can get is about 65% so unless there are dry spots in the mix (please check its wet out entirely) then this is a very close pack graded mixture... good to know. Quartz average modulus (stiffness) is about 70GPa so this mix will achieve (about) (0.84*70*0.5)+(3.5*0.16)=30GPa modulus. Which is about what others publish... Thanks Peter

[badhabit]

Hi Thomas - No procedure is good for weight ratio...Dry is 1994g wet is 2143g so water is 149g addition ratio is 149/1994=7% so not much void there... just turn out the mix and check its all wet out... no dry spots. What is the density of the epoxy you are using? Ta Peter

Yeah, i had to turn it into another container just to wet it out properly, so i'm sure there is no dry spots... but Silimix282 is also marketed for a "Grading curve for liquid-tight concrete" so i guess it makes good sense...

The resin i'm using is having a density of 1,14g/cm3 and the hardner is around 0,95g/cm3(my estimate, can't find data in specific hardner). In a 100:30 mix that would give somewhere around 1,1g/cm3....cirka... (ResinL + GL2, http://www.ezentrumbilder.de/rg/pdf/...+Hardeners.pdf)

/Thomas

[peteeng]

Hi Thomas - Epoxy looks good. Its viscosity is 880mPas. The epoxy I use is 220mPas for infusion.... It says virtually free of shrinkage which is good but it also says it has a diluent. Interesting to have a di-functional diluent... I think that's the Bis-F component.. They formulate epoxy different in Europe as it has to cope with the cold and will crystallize in cold weather. In Oz we are always hot so this does not happen as much... Also the mechanicals are good... Happy mixing Peter

I worked in New Zealand for a while and in winter laminating or infusion was a pain as the resin got too thick. Had to wait till afternoon for the temp to get up then it plunged when the sun set. Only a small window to get stuff done... unless you where in heated premises...

[Obivan]

I use stone of gabro diabaz 3-20mm and sand 0.1-1.2. 6 types of dimensions at all. Vibrate very strong 2-3 hour. Epoxy CR80 350mPas if it have diluent and will be shrinkage .. it very bad for as. Later will see after precision tests

[pippin88]

Got to be careful with percentages.

9% weight of aggregate - what does that mean?

1000grams of aggregate, plus 90 grams of epoxy added? (=8.26% epoxy content be weight in final part)

910grams of aggregate plus 90grams of epoxy?

Volume is different again....


Re: the water void check. If your aggregate volume appeared to change then it was not properly compacted and the results are suspect.

I think you are better off with a container of fixed size (e.g. a big jar). Measure volume of container fill with water then pour that into a measuring cup). Fill dry container with aggregate mix. Vibrate or tamp (compress) aggregate. Make sure completely full. Then add water from a known volume. Wait as it may take time to wet out. Vibrate or tamp. Add more water as needed. Amount of water able to be added = void volume (well a less viscous fluid might be even better at true void content).

Void content / volume just tells you the maximum amount of epoxy you can add before you start wasting epoxy or separating the aggregate. It does not tell you the minimum epoxy content.

[peteeng]

Hi Pippin - Interesting concept "minimum matrix content" Depends on how much of a sponge you are happy with. Since we are building a structural part my guess would be we don't want any porosity. Porosity is lost stiffness (but see ahead). If I use the Silimix figures prior and use 8% resin (resin volume ratio not addition rate) by volume vs 16%Vepoxy the stiffness drops from 29.96GPa to (70*0.84*.5) + (3.5*0.08) + air = 29.68GPa so on paper seems to be a good cost cutting approach. The calc assumes adequate strain transfer across the aggregate/matrix interface and hopefully this is the case with the sponge... Perhaps a two part cast? The mould would have a countermould so the outside skin is cast at full epoxy content then once cured fill the middle with minimum epoxy material. Minimum to be established by test.... ??? Peter

[pippin88]

Peter, I think if you can fill porosity with stiff aggregate that is worthwhile.

If you can only fill the pores with epoxy then you are not gaining much stiffness. Better to spend the $$$ making bigger sections rather than filling voids with epoxy

As you know the epoxy is just to stick the aggregate together

[pippin88]

For size limited parts (where you cannot use a bigger section size) a small loss of stiffness might matter more. Epoxy granite probably not the best material for these parts anyway....

[peteeng]

Hi Thomas - If I may ask what is your estimated cost for 1m3 of Silimax and your resin? The CSA grout I have works out at $5040AUD /m3 for a 33GPa stiffness... Peter

[badhabit]

If I may ask what is your estimated cost for 1m3 of Silimax and your resin?

I depends on the quantity you buy, quite a lot actually. Using "back of the envelope calculations" i have, for my project, numbers like ~15AUD/kg for ready mixed epoxy and ~0,95AUD/kg for the Silimix282. With a 10% mix this gives 2,39AUD/kg for mixed epoxy and aggregate. Looking at my weight measurements from last night seems to have a density around 2100kg/m3, this adds up to ~5.020AUD/m3....give or take... this does include shipping(my material prices had shipping included), but not additional things like wax, PVA, gloves, acetone etc...and i've converted my numbers from DKK and Euro to AUD(via google) for easy comparison...

[badhabit]

The CSA grout I have works out at ... a 33GPa stiffness...

It could be interesting to test the stiffness of the Silimix282 10% mixture... are there any recommendations for getting reliable results in a "DIY setup"? Any recommendations for material shape/cross section, experiment setup etc? I have plenty of material to test with...and some pretty good measurement equipment...

/Thomas

[peteeng]

Hi Thomas - So CSA $5040AUD and Silimax Epoxy $5020 AUD so close!! Re testing for stiffness. 1) There maybe a concrete testing lab nearby you 2) Most DIY people that do this in house make a long thin bar and bend it. What is the thinnest cast you can do that represents the cast material? and I'll do some numbers for two types of test.

This morning pulled out my first CSA block so going down the same path... Just measured its density and its 2173kg/m3 now next block will have steel fibres added... Test block is 200x200x37mm thick Decided to get some rubber feet for it and use it as a trivet in the kitchen...Peter

[peteeng]

Hi Thomas - Here's some ideas on modulus testing. Up to block 3 with the CSA getting a feel for its pouring and filler content.. Peter

[badhabit]

Hi Thomas - Here's some ideas on modulus testing. Up to block 3 with the CSA getting a feel for its pouring and filler content.. Peter

Thanks! I've just reached out to the local university as they have a concrete lab. I've also contact a couple of local business who might have the knowledge and tools to do the testing. I've also awaiting response from the Danish Technology Institute regarding their pricing for the tests. But i expect the latter to rather expensive....but i'll get back to this thread when i have any news... if noone can/will help or if it is insanely expensive, i'll try to do the testing myself...

/Thomas

[pippin88]

Doesn't seem to be anything like Silimix (pregraded aggregate for epoxy granite) available in Australia

[badhabit]

Doesn't seem to be anything like Silimix (pregraded aggregate for epoxy granite) available in Australia

Well, there was a business idea ;-) Import a 40ft container of the stuff and sell locally :-)

[peteeng]

Hi Thomas - I tried to buy Silimix and duragid from the suppliers there but they would not sell it out of the EU. That's why I'm working on my own solution.... Peter

[badhabit]

Thanks! I've just reached out to the local university as they have a concrete lab. I've also contact a couple of local business who might have the knowledge and tools to do the testing. I've also awaiting response from the Danish Technology Institute regarding their pricing for the tests. But i expect the latter to rather expensive....but i'll get back to this thread when i have any news...

So....the technology institute responded to my inquery and it wasn't cheap, but not as crazy expensive as i thought... the only caveat is that there is a minimum of 3 tests. I had already planned to test the Silimix282-batch with and without postcuring.... but what am i going to test in the third test? I was thinking about testing with some coarse gravel? Maybe replace 20% of the silimix with 15-20mm crushed granite or "lake pepples"(round quartz) and see what it does to the stiffness...other ideas?

/Thomas