[walter]

I tested the 14.5% sample from post #1283.

Very poor performance, only 10 ft*lb, but at least we know that epoxy sticks to the aggregates.

This was pretty much expected, these aggregates came from Home Depot and aquarium store- you get what you pay for...
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[ckelloug]

Awesome Walter,

The picture shows that it broke down the middle of the aggregates like you said. That means the matrix effectively carried the load to the aggregates. I suspect that aggregate much less than twice the void size are probably completely ineffective so I assume that the only aggregate which was particularly effective was the really large stuff.

DAK3333, the materials chemist, thinks that carbon black is probably the wrong dispersion hardener for this material. I'm thinking it's adsorbing some of the hardener. He's thinking silica fume is more appropriate here. I'm thinking along the lines of Cabot TS-530 or TS-610 silica fume or equivalent. Given that you don't have silica fume in stock, I'd suggest dropping the carbon black if you happen to make any more samples any time soon until we can figure out what to replace it with and how much.

The message I take form this test is that either much better deairing is needed either via a vacuum pump and/or additives or much bigger and stronger aggregate must be used. I might also try the technique suggested by harryn and wash the aggregate in 91% grade rubbing alcohol.

One last thing: You take great pictures but if you have a ruler, it would be a great thing to put in the picture so the rest of us can get the scale of features.

Finally, I spent the day trenching for sprinklers but I'm about 75% done and should have sprinklers down and be starting on sod by Tuesday along with the concrete approach for my workshop.