[gt40]

Mark,

Was this the "flour" you used ... Laguna Silica, 200 Mesh in Bulk ...

I am in search of "flour" locally and need to have something as an example as "quartz flour" is getting the deer-in-the-headlights look when I ask about it.

Thanks,
Arvid

This is what I got:

Laguna Custer Feldspar in Bulk

FYI, After looking grading curves and reading the giant thread, I ended up using displacement measurement to come up with the following for a mix. I really wanted to use local aggregates wherever possible to save shipping and reduce overall cost. Empirical observation and practical considerations are the basis for the mix:

Attachment 272692

[gt40]

Update:

I have washed all of the aggregate and have it drying spread out on tarps. For anyone wanting to work with epoxy granite, wash, clean and dry the aggregate. I had issues on a test without doing this.

I washed it by filling 5 gallon buckets with material and then stuck a hose into it and washed it until the water cleared. The larger stones weren't bad but the decomposed granite is really dirty. Anyway, I think you need to remove the moisture out and have things clean when you go to cast.

It is taking longer than I thought to dry - I have raked it out to rotate stuff each day when I come home from work. Looking forward to casting the base this Sunday...

[RotarySMP]

I used some fine powdered alumina which was left over from my foundary furnace build. I bought it at a local pottery shop. Unfortunately the mesh size is not stated, but it has that fine powder feel like icing sugar.

I added a little laser printer toner to the 10% epoxy test, as it make the E/G look cooler.

You have a nice grading there. I only used 5 different aggregate sizes. 12-14% resin is lot. My test peices were with 10%% and 8% epoxy, and the ten percent was easy to vibrate, but the 8% settled as well with good vibrations. The Youngs modulus of the 8% measure nearly 20% higher (on my limited, poorly controlled experiment).

The scientific papers I have browsed on the web agreed that the aggregates need to be really dry, otherwise the strength dropped something like 20-30%.

[gt40]

I am shooting for a lower amount but I haven't seen the impact of the mineral flour on viscosity. Made test batches with everything else and was happy at 8%. The base is really over built so If I have a higher epoxy level, I think it will be okay and I would prefer not to have any inclusions in it.

[RotarySMP]

The jump from 8% to 10 % was significant in how quickly it sagged under vibration (I just tapped that test mould on the floor for a couple of minutes. The 8% needed the rivetting hammer on the mould. I can imagine that 14% would be very wet, and leave a thick layr of epoxy on top once it settles.

[G59]

That thick layer of epoxy that has floated to the top is called waste of money. It is the result of too much epoxy used, which, once the aggregate is fully saturrated, just floats to the top, creates a shinny flat surface that adds little to no increase in the rigidity. Sometimes it's just better to use less and work a little harder or longer and end up with little waste.

[gt40]

That thick layer of epoxy that has floated to the top is called waste of money. It is the result of too much epoxy used, which, once the aggregate is fully saturrated, just floats to the top, creates a shinny flat surface that adds little to no increase in the rigidity. Sometimes it's just better to use less and work a little harder or longer and end up with little waste.

Thanks for the feedback. I have 2 people coming over this morning and should be mixing and casting in a few hours...

[mcphill]

Please post some in-process pix! I am considering using EG as an addon to a steel I-beam build I am considering. Would love to have some of you learnings to save me some headaches!

[gt40]

On to it:

First off, weight for all materials for the mill base was 737 lbs/327kg

This doesn't include the sub base which I am still working on for a design- leaning towards 1/2" thick 4" square tube welded frame...

Finished mounting 70 feet of rebar in the casting:
Attachment 273566

Attachment 273568

Next we mixed the epoxy in a five gallon bucket with a drill rotary mixer. Added the epoxy to 130lb batches of aggregate. The epoxy and hardener weighted 13lbs for 10% epoxy by weight. I went a little higher because of the mineral flour and chopped carbon I added to the mix and it seemed about perfect. It wetted out and yet left no epoxy pooled on top. Mixing:

Attachment 273570
Here is a close up of the mix:
Attachment 273572

We tamped the mix with a dirt tamping tool- basically a 8" square of steel on the end of a pole. I didn't get a pic of the tool but here is the result:

Attachment 273574

We vibrated the mold by bolting a bench grinder with an eccentric weight- this made a big difference and parts of the mix dropped as much as 3/4":
Attachment 273576

I would say definitely vibrate your molds...

After vibrating and adding more mixed aggegate, we screeded the top to provide a flat top surface:

Attachment 273578

End result was flat and I was very happy with my mix and the epoxy ratio as well as the US composite 635/slow hardener epoxy system. We had time to mix 4 batches, pack the mold and vibrate and weren't rushed. Temp was 70F/21C btw.

This what it will look like for the next 4 days during cure. I checked 3 hours later and things were warm to the touch and setting up nicely:

Attachment 273582

I read somewhere here that post cure at elevated temps by putting a box with a small heater can add to strength I will look for a box and maybe do that tomorrow. Now I just have to wait..

Thanks for looking

[Voyager77]

Great work Mark! Can't wait to see the de-molded result

[gt40]

Great work Mark! Can't wait to see the de-molded result

FYI I rolled it out so it could bake in the sun (socal and all) and everything was already setup. I tapped on it and it was really solid the epoxy is already hard- still going to force myself to be patient.

I am very happy with the aggregate blend and US composite 635/slow hardener combo because I had enough time to do the pour and it seems to have cured properly

[hanermo]

This looks good.

I am interested in what your final results re: mass and rigidity become.

[mcphill]

Awesome job, thanks for updating the post!

[RotarySMP]

Nice work. I like your bench grinder vibration solution.

[gt40]

Update:

I came home and the slab was baked by a full day in the sun and solid, so I took a peek by removing a corner. Good news it is really tough- inadvertently smacked it a few times with sledge hammer removing the mold material and it didn't even dent, let alone crack. The 4lb sledge fairly bounced off of it. The part I removed looks good - feels and acts like a solid rock. I took a grinder to it and it grinds like a rock too- you can see that part on the upper right part of the pic.

The bad news is I didn't use enough wax or a proper mold release. Fortunately I taped the entire saddle section and all corners which are radiused and those areas are coming off easy- the flat side- not so much. I spent an hour with a chisel and crow bar with the sledge to remove the end and a little part of the long side. Any secrets to making this easier?

[ger21]

Maybe a belt sander with the roughest belt you can find?

[rocketflier]

Update:

I came home and the slab was baked by a full day in the sun and solid, so I took a peek by removing a corner. Good news it is really tough- inadvertently smacked it a few times with sledge hammer removing the mold material and it didn't even dent, let alone crack. The 4lb sledge fairly bounced off of it. The part I removed looks good - feels and acts like a solid rock. I took a grinder to it and it grinds like a rock too- you can see that part on the upper right part of the pic.

The bad news is I didn't use enough wax or a proper mold release. Fortunately I taped the entire saddle section and all corners which are radiused and those areas are coming off easy- the flat side- not so much. I spent an hour with a chisel and crow bar with the sledge to remove the end and a little part of the long side. Any secrets to making this easier?

It's just wood, no? Particle board in fact? Straight edge and cheeeeeeeeap circular saw blade. Take care of the sides in no time. Hit the epoxy/granite with wet diamond blade on a grinder after that. Watch some videos on grinding concrete countertops.

Or, soak it those areas with water, the particle board will expand and break apart leaving only that which is truly attached. At least that's what anything particle boardy around here does.

Router was my first thought. Parallel pipes/boards in the same plane as the stuck wood and shave it down to the epoxy. That's when I thought circular saw and 4" at a time is better than 1/2" per pass.

If you go with water, cut slitting groves for better penetration.

One of these

Attachment 273892

or

Attachment 273894

Maybe even

Attachment 273896

Down around the 40-60 range.

[edit]router as a planer
Joint and Thickness-Plane with a Router - YouTube

Looking at this I thought of a table with 4 legs
simple Router Planer Jig - Woodworking - YouTube

[gt40]

It isn't too bad- making progress- this was done in a half an hour...

[Voyager77]

Not sure but on the photo it looks like the bottom left did not compact very well. Are there voids in the surface?

[gt40]

Not sure but on the photo it looks like the bottom left did not compact very well. Are there voids in the surface?

Yeah, there are a few spots with small voids. No major inclusions though. I have gotten most of the mold off and it is pretty consistent. I made some test pieces also and it looked prettier with more epoxy but was not nearly as durable as the mix I ended up with that you can beat, drop and abuse without issue. It is a balance getting a large piece to optimum 8-10 percent epoxy levels - at 14% everything is really nice looking but not nearly as durable...

I figure I can fill in the voids with quartz flour and epoxy mix and do a final coat to make it all shiny and smooth if it still bugs me. Lessons learned are vibrate more if you can and use enough/proper mold release. We will see more after I flip it and finish the demolding. I need a crane at this point just to do that...