[rad45]

Quikrete Course and Medium Silica Sand available at Home Depots & Lowes (round here):
Grade Predominant Size Range
US sieve number (mm)
Coarse No. 1963 #12 - #30 (1.7-0.6 mm)
Medium No. 1962 #20 - #50 (0.8-0.3 mm)
Fine No. 1961 #30 - #70 (0.6-0.2 mm)
(Quoted from a previous post by others)

I see that other list members have done a lot of work on sizing the ingredients for E/G mixes. I've had to do some of this in industry myself. Without for one minute wishing to denigrate the effort which is being put into sizing, may I make one small point please.

Any form of concrete, whether it is cement or epoxy bonded, really only shines in the strength evaluation when it is in compression.
We have all seen the tonnes of steel or whatever used to increase its strength in other modes. Where E/G shines is that all the material in the mix is bonded so much better with epoxy than is attainable with cement, thus increasing the compressive strength to heretofore unattainable levels. And has a much greater life expectancy before it fails due to fatigue!

Therefore we come back to maximising the compressive strength in much the same way as when used with cement bonding.

The basic premise with concrete, is that the small stones fill the gaps between the large stones, the coarse gravel fills the gaps between the small stones, the fine gravel fills again, the sand fills again until we arrive at the point where the Epoxy fills (and binds together) the remaining minute voids in the mix.

The only way we can properly assess the success of the mix used is to section it by cutting with a laboratory saw and assess the volume of epoxy between all the other load carrying materials in our brew. This really is a case where less (Epoxy) is better. I do this in practice by weighing the components but then the epoxy can float on top of the mix, so even that method can give ambiguous feedback

Typically, in industrial concrete, the mix ratio is somewhere about 3 parts of screenings (stone of about 20mm screen sizing) 2 parts of sand and 1 part of cement. In my experiments with E/G in volumes up to about 0.5m^3 I have typically found this ratio to be followed with the replacement of cement by Epoxy and introducing two grades of sand. Temperature also has an effect as in extreme cold the ability of the Epoxy to creep into every last crevice has been diminished considerably. An ambient temperature of about 15-19˚C I have found to be ideal. The mix is warm enough to flow and compact (using a vibrating compactor as for cement based concrete) whilst it is not too warm which would unnecessarily accelerate the the hardening cycle.

With kind regards,
Russell Dunn
Ferlach, Austria

[rocketflier]

The only way we can properly assess the success of the mix used is to section it by cutting with a laboratory saw and assess the volume of epoxy between all the other load carrying materials in our brew. This really is a case where less (Epoxy) is better. I do this in practice by weighing the components but then the epoxy can float on top of the mix, so even that method can give ambiguous feedback

My thoughts were to play with various epoxy amounts while maintaining a consistent gravel volume. In composite layups you often overwet to ensure through coverage then draw the excess off under vacuum. I'm curious how various mixing/pouring methods would ease/hinder achieving the ideal epoxy content EG.

I've removed the gunk from an axle/bearing set found at the junkyard. Picked it up when I found some various perforated steel sheets. Looking to use it as part of a shaker.

I have 1 large popcorn sized can worth of concrete sand sifted. It's been raining so I've been letting things dry, but my goal was to show the rough size yields. I will say at the finer material is really not worth sifting without some sort of mechanical assistance.

Also had this idea for both shaker and/or mixer:


Paint Shaker - Pneumatic

[rocketflier]

Ok, been sunny for a while so not so much a mess back there. What I have is many tons of course concrete sand which is likely what you see in the bags outside the big box hardware stores now a days. What I should have ordered is masonary sand which would have been finer. But that's neather here nor there.

The first photo shows the sand sample in the lower center of the second photo. The sand I've been playing with has been open to the weather so it's possible rain has cleaned it up over the years, but more likely it contained more dust as we've had may dust storms this season. This sand was also spreading out over a graveled area of the yard, so anything greater than ~1/4" was screened first.

The second photo shows the popcorn tin (in the back) which held the sand after washing and drying (~9"x12"tall). It wasn't quite full and there was loss as I sifted manually. But I think it gives a pretty good idea of the quantities that can be obtained for each size.

The ultra fine and 'everything smaller' (bottom 2) were difficult to sift given the small size of the screens. The ultra fine seems larger than sugar grains. I'll have to blow up some samples when I figure out the microscope thingy in the kids room.

The last photo shows the sand drying in a ultra low humidity oven I developed. I probably shouldn't disclose too many details.

I've watched a bunch of videos on particle separation and sizing and have a better idea how to batch process material. Google 'vibro screen' for some interesting ideas. Without a mechanical separator, I probably would stick to sized initial material or skip may of the sieves.

You can see from the 2nd photo, that the 'large' 2 sizes probably didn't generate a cup worth of material. I'd probably screen those off first into my crushed pea gravel as it's likely those overlap anyway. I'll find out when I play with the gravel more. My favorite screen is the aluminum window screen. It holds up well and filters really quick as you can have long lengths.

Not sure where this boat is headed. I'd like to take several sizes and throw them in with some epoxy.

Closeups of the sifted sand samples and sieves are attached to this post:
http://www.cnczone.com/forums/1016589-post4575.html

[johnohara]

rocketflier~

Most pool suppliers carry bagged quantities of pre-screened silica sand used for filtering. The particle sizes can be very precise (.5mm etc.)

Worth a look.

Another source of fine pre-screened material is sandblasting abrasives. A 2lb. container of #220 grit can be purchased at HF for $10.00

44 lbs. Black Aluminum Oxide Abrasive, 70 Grit
2 Lbs. 220 Grit White Aluminum Oxide Abrasive

A little pricey, I know. But it sounds like you are after precision sizes and these fit the bill. I've seen them at Home Depot too.

Just a suggestion.

Keep up the good work. Wear gloves.

~john

[rocketflier]

rocketflier~

Most pool suppliers carry bagged quantities of pre-screened silica sand used for filtering. The particle sizes can be very precise (.5mm etc.)

Worth a look.

Another source of fine pre-screened material is sandblasting abrasives. A 2lb. container of #220 grit can be purchased at HF for $10.00

44 lbs. Black Aluminum Oxide Abrasive, 70 Grit
2 Lbs. 220 Grit White Aluminum Oxide Abrasive

A little pricey, I know. But it sounds like you are after precision sizes and these fit the bill. I've seen them at Home Depot too.

Just a suggestion.

Keep up the good work. Wear gloves.

~john

Yes, I'm a HF junkie. There are 3 fairly close and 1 is 5 minutes from the house. I can't tell you the number of times I went in a stared at the oxides trying to convince myself to purchase. The 1lb quantity at $10 for the sparkplug cleaner was my first thought, but looking at 1lbs I can't see that little being useful. The white seemed too fine and that jar still seems really small.

I went to a different home depot last night an found they have a pool filter sand. So I grabbed a sample {tablespoon from spillage} to compare to the #20 & #30 silica sand as well as my screened material. It seemed larger than the course silica sand found in building materials.

In going through the thread again (I can't believe how much you don't absorb on a pass), I found a mention of waste from waterjet cutting. There's a waterjet guy on the local metal forum so I'm going to look into that too.

I did a quick sort on some of the 1/4" crushed pea gravel and might have an issue (I was trying to see if/where the crusher fines overlap with the concrete sand). I found a quantity of chip flakes in one of the small bands. From what I've read, flakes would hinder compaction.

To that end, I've loaded the concrete mixer with ~5gal of the pea gravel, sand and water and am letting it run. Should get some nicely rounded particles. We'll see, what the heck, it's free. There are several examples of car tire or 55gal drum tumblers out there for the DIYer.

I've printed the 'ideal' formulas and size tables to see if I can't easily figure out what screens to use and which material to capture. In the long run and for most people, purchasing the sized material is likely best, but since this sand is laying here doing nothing, I'm not out anything.

I did pick up some crushed granite samples from the gravel pit. Each 5gal bucket was $2, but if you get a bunch, they can do it by weight.

Madison Gold (on the left in the second photo) is 1/4 minus. This had the most sparkle and is most abundant in this area. Not to mention I have 3/4 screened all over the yard. The other buckets contain 3/8 screened which was the largest size I think would go into this stuff. I did fill each bucket about 1/4-1/3 with 1/4 minus at the bottom to have more fines for each color.

[rocketflier]

Thoughts?



[ame=http://www.youtube.com/watch?v=M8t-xtn-T0s&feature=related]MESAS VIBRATORIAS - YouTube[/ame]

[rad45]

Hi People,
It feels like I'm missing something here. That vibrating table which is displayed in the previous post has me beat.
It cannot be for mixing or blending E/G as a vibrating machine will cause the material on it to segregate. The heavies will go down whilst the lights are pushed up. Not really what we are after when blending and mixing E/G.
On a not unrelated topic, I have finally bitten the bullet and made the decision to replace the fabricated base for my EMCO Maximat lathe with a E/G Base. Through the winter I'll make the mould for it with the drain tray and some shelves cast in situ. Also integrated into the mould will be the holding down bolts for the lathe itself.
With the other things I have on my plate it should fit just fine in that I hope to have the mould finished and ready to pour by the time the ambient temp is warm enough to work the E/G with a concrete vibrator.
Russell Dunn
Ferlach, Austria.

[rocketflier]

Hi People,
It feels like I'm missing something here. That vibrating table which is displayed in the previous post has me beat.
It cannot be for mixing or blending E/G as a vibrating machine will cause the material on it to segregate. The heavies will go down whilst the lights are pushed up. Not really what we are after when blending and mixing E/G.
On a not unrelated topic, I have finally bitten the bullet and made the decision to replace the fabricated base for my EMCO Maximat lathe with a E/G Base. Through the winter I'll make the mould for it with the drain tray and some shelves cast in situ. Also integrated into the mould will be the holding down bolts for the lathe itself.
With the other things I have on my plate it should fit just fine in that I hope to have the mould finished and ready to pour by the time the ambient temp is warm enough to work the E/G with a concrete vibrator.
Russell Dunn
Ferlach, Austria.

You notice you mention concrete vibrator in your last sentence? That's what the table is for. Drop your mix in the form, it will slowly oogle from a pile to the edge unless you have a runny mix. Runny mix means more epoxy,..

Back around pg70 is a pretty good discussion on consolidation with vibration. Often used for consolidation of dry concrete mixes:

[ame=http://www.youtube.com/watch?v=Kilw0pcj3W0]VIBCO Vibrating Table Consolidates Concrete Quickly! - YouTube[/ame]

[ame=http://www.youtube.com/watch?v=GWImU7CCU8g]How to build a Vibrating table on a budget - YouTube[/ame]

[ame=http://www.youtube.com/watch?v=gqX5ceWgHxg&feature=related]MESA VIBRATÓRIA - YouTube[/ame]


And people keep saying the large particles will fall to the bottom while the small will rise to the top,...

Search the net on "Brazil Nut Effect"

[ame=http://www.youtube.com/watch?v=bkZJ4S8kY-o&feature=related]Brazil nut effect - YouTube[/ame]

[ame=http://www.youtube.com/watch?v=lFzbvbGOAAg&feature=related]Phun Paranusseffekt - YouTube[/ame]

[ame=http://www.youtube.com/watch?v=PGDP5DomhWc&feature=related]Brazil nut effect in a rectangular plate under horizontal vibration - YouTube[/ame]

[ame=http://www.youtube.com/watch?v=hVDQ5TjO-N8&feature=related]Week1_wholenotequaltosum_brazilnuteffect.AVI - YouTube[/ame]

So I am somewhat curious as to the impact of the vibration including extended to/through the gel point. Course too much curiosity costs $$. But if I were to take 6 cups of the same mix and lock them down on the table and remove one at different intervals, the results should show if it helps for compaction/air reduction/epoxy reduction or is more trouble than it's worth.

Plus vibration helps on the front end with sifting of material.

[ame=http://www.youtube.com/watch?v=SVM_DKOmCS0&feature=related]Kason High Efficiency Vibroscreen Separator - YouTube[/ame]

[rad45]

Hi People,
Thanks for your explanation "Rocketflier". I guess I was tricked by the scale of your implication. As I now understand it, you are going to be pouring smaller volumes than I have been envisaging. So you would be able to vibrate the complete mould and its contents on a table. In my experiments and the job I will prepare for over winter, I'm pouring much greater volumes and therefore larger masses are involved.
As a "shot from the hip" my base/stand for the EMCO lathe will be about 0,6m^3 and therefore perhaps 900kg. Just a little too much to put on a vibrator. More a case of bring the vibrator to the job.
Thanks again for the explanation.
Russell Dunn
Ferlach, Austria.

[yancho]

Hello. I made only one test, but use a different approach. Pressed into the mold mixture, then with pellets broke the pattern. I wanted to check how strong svazkata between the particles and how they are distributed. The result is the following: Impact strength greater than 100 N/ mm2, the ideal location of the particles. And the most curious stones were broken, as is the border of mosaic marble they use. Plate which is molded with dimensions 200h150h25mm. I used sand and mosaic.

[ckelloug]

Hi Rocketflier,

For commercial castings, my research suggests vertical only vibration is better for compacting E/G than circular vibration from an ordinary table like the one pictured. Vertical-only vibration comes from two vibrators which are counter-rotating such that the
horizontal vibrations cancel: Less of the "Brazil Nut Effect".

In concrete design, "segregation" is the word used to describe where the small and large particles separate during vibration and placement of the concrete. Segregation can occur in all particle mixtures under vibration. Particle mixtures or E/G designs with the highest possible packing density have the least segregation. Roughly put, if there are small particles filling up most of the voids through which a large particle may move, the large particle won't often find a void large enough for it to move into and will rarely be transported through the mixture.

There is a specific particle size distribution that minimizes the possibility for segregation in the Compressible Packing Model: the deLarrard Min S distribution. The Min S distribution has a slightly lower packing density than the optimal packing density distribution so I normally design mixtures with the optimal packing distribution. Segregation is a major reason to care about mix design beyond physical properties.

Regards all,
Cameron

[johnohara]

Good 12 minute video of a vertical casting machine making pipe. You can hear the vibration motors during the pour and see them mounted at the bottom of the mold when the cast is complete.

vertical vibration casting machine -

~john

[rocketflier]

Hi Rocketflier,

For commercial castings, my research suggests vertical only vibration is better for compacting E/G than circular vibration from an ordinary table like the one pictured. Vertical-only vibration comes from two vibrators which are counter-rotating such that the
horizontal vibrations cancel: Less of the "Brazil Nut Effect".

In concrete design, "segregation" is the word used to describe where the small and large particles separate during vibration and placement of the concrete. Segregation can occur in all particle mixtures under vibration. Particle mixtures or E/G designs with the highest possible packing density have the least segregation. Roughly put, if there are small particles filling up most of the voids through which a large particle may move, the large particle won't often find a void large enough for it to move into and will rarely be transported through the mixture.

There is a specific particle size distribution that minimizes the possibility for segregation in the Compressible Packing Model: the deLarrard Min S distribution. The Min S distribution has a slightly lower packing density than the optimal packing density distribution so I normally design mixtures with the optimal packing distribution. Segregation is a major reason to care about mix design beyond physical properties.

Regards all,
Cameron

Thanks for the feedback. The separator would be a bit of a project. Short term would be a simple screen stack on the vibrator table that I could feed material into the top. I'd have to stop and unload sifted material.

If you look at post #4587 you see 2 tables and an attachment with a photo of some parts. Rather than a vibrating motor (weights attached to either end), the links show tables that have vertical motion vibrators attached to the table run via a belt & pulley to a motor mounted to the table frame. The solid 1" axle followed me home from the scrap yard and included the tire assemblies, bearings and pulley. I've yet to figure out how to remove the tires, but will use them to mount the unbalanced weights (weightbench weights) to the axle.

I don't quite see how you could cancel the Brazil Nut Effect without impacting the vibration. I also don't believe a short vibration period is going to be detrimental to the mix (much as concrete is quickly vibrated once it's poured).

I also have vacuum capabilities to add to the fun.

[rocketflier]

I feel like Dekoda Fred. Cment mixer took a dump. Shaft freezed and fried the motor,..

[Nami]

Hey Guys,

Been a while since I checked this thread out. Noticed the talk has come around to vibrating tables again. Just so happens I'm cleaning my shop and decided to sell one of my Vibco vibrators on ebay. Before I do, I'd like to give anyone here on the forum first dibs.

It's a Vibco US1600 115V 5 amp heavy duty model. I bought 2, but have only ever needed one, so this one has never been used. It comes with an on/off switch, but you really need a speed control to maximize performance with different loads.

I had a post some time back where there is a link to my vibrating table with the same model unit driving it. It's post #3794.

I think I paid around $1000.00 for each of them. Make me an offer if you're interested. I'll give it a week or so; if no one's interested I'll just put it on ebay.

Take Care,

Burt

[castinite]

Rocketflier,

We cast epoxy/quartz machine bases in the Cleveland area. Let me know if we can assist you.

Terry CASTINITE

[greybeard]

Morning all.
Just show the old brain is still working and as odd as ever, I'd be grateful for any pointers on the following.

I'm currently vacuum pressing a 1ft x 3ft multi curved surface (imagine a pair of gull wings), and it occurred to me that it might be a nice project to do in EG.
Thinking about the stresses involved in the product, I remembered from my distant youth seeing a demonstration of photo elastic stress analysis, using polarized light and a perspex model.
While I could set this up quite cheaply, I wondered if there was a piece of software that would allow me to draw a relatively simple section on screen, then show what the results were of applying loads in specific points.
I think it might be a useful bit of e-kit.

I've done a google search but not found anything yet. Any ideas anyone ?

John

[yugami]

I don't know of anything as simple as you are thinking but the concept you're thinking of if FEA or Finite Element Analysis where a model is broken down into geometric meshes and then complex math applied to it to approximate different stresses.

I played around with it on Linux using SALOME which is a software package for frontending a different open source FEA package.

While I could set this up quite cheaply, I wondered if there was a piece of software that would allow me to draw a relatively simple section on screen, then show what the results were of applying loads in specific points.
I think it might be a useful bit of e-kit.

I've done a google search but not found anything yet. Any ideas anyone ?

John

[greybeard]

I don't know of anything as simple as you are thinking............

I always think there must be an easier way
Regards
John

[wschmiedlin]

I know that Milltronics used to use this process and cast some of their machine bases. It was not being used any longer when I worked there many years ago.

William