[JohnMcNamara]

Hi All

I have been thinking; and slowly getting through all the posts on this thread, there has been a great deal of discussion about the ideal ratio of aggregates for the ideal mix and void fill. There has been discussion about the ideal source, the ideal size, should you use microspheres or other high tech stuff……Etc

This certainly is a multivariable equation, and we have not yet talked about the variation in batches even from the same source.

I would like to propose an empirical method that may solve the unsolvable.

Make a rectangular base container that holds 200mm sq by 250 high inside size.
Mark a line exactly 200mm from the inside all around the inside.
Weigh the container carefully.

Take a random sample of the large aggregate you intend to use. (From several parts of the heap)

Fill the container until the top surface is exactly level with the line, shaking as you fill. (Ideally with some form of mechanical shaker)

You now have a 200mm cube of big aggregate full of voids because they do not fit perfectly. Weigh carefully and deduct the weight of the container, This leaves the weight of the large aggregate.

Now tip that out in a clean bucket to keep it separate and then put it back shaking as before (yes the same aggregate). You should get the same fill. If not adjust the quantity used until the test is repeatable. Save the exact weight.

Now for the next aggregate size down; we need to know how much we can get in the container using the now known quantity of large aggregate, without increasing its volume; we only want to fill the spaces between the large aggregate.

With the previously determined large aggregate sitting in the container and shaking
Slowly add the next lower screen size of material you plan to use as filler, it will percolate down and disappear. Watch very carefully. At the first sign of an increase in height above the line STOP.

Now tip it all out into a clean bucket and thoroughly mix by hand.
Now put that back and shake. Hopefully it will level out again, and most likely you can add a little more. Add a tiny bit more, tip out, mix; put back…….Until you can’t get any more in.

Now weigh the mix subtract the container and the weight of the large gravel and you have the weight of the next size down you will be using.

I guess these steps could be repeated right down to micro powders.

I believe it will be more accurate than computer simulation.

It is still not perfect because some of the smaller particles will lodge between larger particles increasing the volume. It relies on the larger particles tending to clump together. Maybe a weight on top would be a good idea while shaking.

Cheers

John McNamara

[johnohara]

Hi John~

Let me try to save you some time and aggravation with your test sample.

Your epoxy granite mix requires essentially three things:
1. A "dust mix" ranging from #36 to sub micron,
2. A "large mix" ranging from 1mm to 6mm.
3. Epoxy binder.

For the dust mix, use various sizes of Aluminum Oxide industrial abrasive. The kind used in sandblasting. It's easy to find in #36, #180, #220 and #320 sizes. Local blasting companies might even have some laying around from previous jobs. Mix even amounts of each size. 50/50, 33/33/33, 25/25/25/25, you get the idea.

For the large mix, buy a bag of washed pea gravel. The sizes will be in the range you need.

Make the dust mix about 14-15% by weight of the total aggregate amount.

Make the epoxy (with hardener) about 10-12% by weight of the total weight of the piece.

For example, if the total piece with epoxy will weigh 5000g., the dust mix should weigh about 640g, the large mix should weigh 3760g, and the epoxy (with hardener) should weigh 600g (2:1 would be 400g/200g).

Try it out in a baking pan, it's easier to use for testing.

~John

[castinite]

This mixture will result in the need for extra epoxy, which will increase the cost of the mix and reduce the mechanical properties. The more fines, the more liquid required. The ideal mix will only require 7% liquid.
~Castinite~, polymer cast, polymer castings, precisions machine grouts, polymer base pumps, base pumps

[JohnMcNamara]

Hi Castinite

What mix do you propose as Ideal?
I am sure all members of the forum would appreciate your knowledge.

Cheers

John McNamara

[anifinindia]

Hi All

I have been thinking; and slowly getting through all the posts on this thread, there has been a great deal of discussion about the ideal ratio of aggregates for the ideal mix and void fill. There has been discussion about the ideal source, the ideal size, should you use microspheres or other high tech stuff……Etc

This certainly is a multivariable equation, and we have not yet talked about the variation in batches even from the same source.

I would like to propose an empirical method that may solve the unsolvable.

Make a rectangular base container that holds 200mm sq by 250 high inside size.
Mark a line exactly 200mm from the inside all around the inside.
Weigh the container carefully.

Take a random sample of the large aggregate you intend to use. (From several parts of the heap)

Fill the container until the top surface is exactly level with the line, shaking as you fill. (Ideally with some form of mechanical shaker)

You now have a 200mm cube of big aggregate full of voids because they do not fit perfectly. Weigh carefully and deduct the weight of the container, This leaves the weight of the large aggregate.

Now tip that out in a clean bucket to keep it separate and then put it back shaking as before (yes the same aggregate). You should get the same fill. If not adjust the quantity used until the test is repeatable. Save the exact weight.

Now for the next aggregate size down; we need to know how much we can get in the container using the now known quantity of large aggregate, without increasing its volume; we only want to fill the spaces between the large aggregate.

With the previously determined large aggregate sitting in the container and shaking
Slowly add the next lower screen size of material you plan to use as filler, it will percolate down and disappear. Watch very carefully. At the first sign of an increase in height above the line STOP.

Now tip it all out into a clean bucket and thoroughly mix by hand.
Now put that back and shake. Hopefully it will level out again, and most likely you can add a little more. Add a tiny bit more, tip out, mix; put back…….Until you can’t get any more in.

Now weigh the mix subtract the container and the weight of the large gravel and you have the weight of the next size down you will be using.

I guess these steps could be repeated right down to micro powders.

I believe it will be more accurate than computer simulation.

It is still not perfect because some of the smaller particles will lodge between larger particles increasing the volume. It relies on the larger particles tending to clump together. Maybe a weight on top would be a good idea while shaking.

Cheers

John McNamara

You done the excellent method, i really impress.
Thanks. regards.

[castinite]

I have been working on the "perfect" aggerate mix for 26 years. We have tested granite versus basalt versus quartz. The mix depends on what properties are needed, what is available that is precisely sized, washed and dried and the part configuration.

We have also developed replication grouts that use low friction materials or high wear fillers.

We do sell a polymer concrete mix for those who want to cast their own bases.

[JohnMcNamara]

Hi Castenite

Great to hear you have been beavering away for the past 26.

However I am not sure why you posted in this thread. “Epoxy Concrete Aggregate Ratio Mixing Method”

This thread is about mixing your own.

I was rather hoping you would contribute a mix or method. Many of the folks in here are inventors or researchers in their own right.

Cheers

John McNamara