[brunog]

Hello all...

I finally got around doing some experimenting..

I wanted to try making a mix that was dry (not pourable). I made the mix with the following ratios:
Epoxy: 8.3%
Small Aggregate: 9.8% (0.35 mm)
Medium Aggregate: 22.4% (0.8 mm)
Large Aggregate: 59.5% (2.5 mm)

Sandi,
Nice Work!!

Are the ratios by weight or by volume?

Best regards,

Bruno

[romihs]

Thanks for the complements Walter and Bruno!

Bruno, yeah... I remembered a little earlier that I had forgotten to mention that... I measured all components by weight.

Regards

Sandi

[walter]

Walter the carbon black is extremely black and fluffy.Opening a bag carefully would create a large black cloud.

Whoa, no kidding... I almost dropped the kilo on the floor.
And did you see the black cloud? It floats in the air like a cigarette smoke! Unbelievable..

It's so dark I can't even... see it.
Good stuff.

Now check out the video:
http://www.boardsmag.com/screeningro...mercials/1504/
...

[pupa]

Hi Very interesting Thread. Very good responses. Great (group) work effort. My first post on this subject and 2c's worth on Vibrating the mix. It came to mind that the Audio vibrators in music industry could well suit the application. You could play your favorite rhythm while working :idea: or via a computer control the exact frequency and amplitude of the vibration required. Some vibrators have a wide frequency range and is used for music and gaming feedback. See links as idea and Google for same to get OEM versions instead of the more expensive Aesthetic music versions.

http://www.google.com/search?sourcei...udio+vibrators

I am (nuts) AND LIKE TO :argue: BUT HEY That's how we all learn and stimulate good thinking.

Re concrete I doubt that concrete can withstand the various high frequency vibrations of the bigger CNC''s to the same degree as EQ, over time, without some special treatment, like epoxy additives, Yet they may be a cheaper "filler" to add to the proposed EQ mixes ???? ie epoxy cement mixes ???


http://www.musiciansfriend.com/produ...ker?sku=444721

http://www.musiciansfriend.com/perc/...=100001+202926

Please forgive non English grammar as it is not my strong point as I am a Afrikaans (Dutchey) South African

Regards
Chris

[lgalla]

Hi Sandy,good work.I assume you are not married,as our spouses in North America do not allow us to post cure epoxy in the oven.Waiting to hear your results.
Audio transducers or but kickers are low frequency devices generally 40to80Hz.
Walter glad to see you got the" black hole"A very low % will will work well.A kilo will last a long time.
Larry

[brunog]

Sandi,
I have checked your aggregate ratios by weightand you should get optimum mix with the following:

0.35mm:.177
0.8mm: .263
2.5mm: .473

I will try to upload a small excel spreadsheet where you enter the epoxy ratio by weight and 3 aggregate sizes and it calculates the rest. All input cells are in red. I hope this will help, let me know how it works out for you.

Best regards

Bruno

[romihs]

Hi Sandy,good work.I assume you are not married,as our spouses in North America do not allow us to post cure epoxy in the oven.Waiting to hear your results.

Hi Larry,

Actually, I am 'almost' married, and Tina hasn't given me any grief yet about wanting to bake the E/Q in the oven.. Lets wait and see until I actually do bake the E/Q...

Regards

Sandi

[romihs]

Sandi,
I have checked your aggregate ratios by weightand you should get optimum mix with the following:

0.35mm:.177
0.8mm: .263
2.5mm: .473

I will try to upload a small excel spreadsheet where you enter the epoxy ratio by weight and 3 aggregate sizes and it calculates the rest. All input cells are in red. I hope this will help, let me know how it works out for you.

Best regards

Bruno

Hi Bruno,

Thanks for the advice. I'll go try it out.
I will also check the specs of the three sands I have and maybe adjust the excel spreadsheet to better reflect the material I have.

Regards

Sandi

[pupa]

Audio transducers or but kickers are low frequency devices generally 40to80Hz.
Larry

Actually the butkicker operates at 5-200 Hz with highly variable amplitude. Its made to shake the fat lady's but in home theatre systems. I am sure there is higher frequency OEM units available as the same principle is used in Industry to fluidized powder and gravel beds. Will do some research.

At what frequency would they vibrate concrete for improved structure and flow or removing of trapped air? 180HZ to 300HZ (10800VPM to 18000VPM) seems the norm with the correct value the natural frequency of the mix depending on slump (Dry or wet) and aggregate size

PS Many commercial concrete vibrators run at standard 180-200 HZ? The highest I can find is 18000 HZ (Not VPM?) air driven.
http://www.sullair.com/corp/details/...TI5905,00.html

Some invaluable info and advice I found
http://www.multiquip.com/multiquip/p...3-handbook.pdf
http://www.precast.org/publications/...nVibration.htmhttp://www.precast.org/publications/...nequipment.htm
http://www.speedcrete.co.uk/vibrtech.asp
http://www.denverconcretevibrator.co...-EFV042006.pdf

B. VIBRATING TABLES.
For Compacting material - Dense or fine materials respond best to high frequency vibration (3000 RPM or more) while light, fluffy or flaky materials respond best to low frequency vibration (1500 RPM or less).

For packing or settling materials, use a-vibrator with an impact force of (1.5) to 2 times larger than the weight of the material plus container.



C. VIBRATING SCREENS.
Rule of thumb: For self-cleaning screen use a vibrator with a centrifugal force (impact) four (4) times the weight of the material plus the weight of the screen.

NOTE: Coarse and lumpy materials respond best to 3000 VPM (vibrations per minute), powdery and dry materials, to 1500 VPM, but for sticky and wet materials recommend over 3000 VPM.



D. CONSOLIDATING CONCRETE.
Rule of thumb: For 3" "slump" concrete use a vibrator with the same force (impact) as the weight of concrete and form.

For 1 - 2" slump concrete, an additional 30 -50% impact is needed.

For dry mixes (0 - slump) add 100 - 200%.

NOTE: For additional sizing consult VIBCO, or request the concrete catalogue.

9.64 CONCRETE VIBRATION AND CONSOLIDATION

Specification 2301.07.A.6.a requires vibration frequency to be maintained between 5000 and 8000 vibrations per minute for concrete paving finishing machines. To ensure proper consolidation of the plastic concrete, the vibration system used in the finishing machine should provide continuous and full coverage.
The depth of penetration into the concrete of internal vibrators should be set to mid slab height or as deep as possible while passing above any reinforcing steel. An operating position locking device should be provided so that no part of the vibrating unit can be lowered to the extent that it will come in contact with reinforcing steel or tie bars while paving.
http://www.erl.dot.state.ia.us/Apr_2...ntent/9-60.htm

Some info from a expert I picked up on a discussion vibrating the whole frame or structure. Make sense?

I speak with the experience of having placed and finished thousands of cubic meters of concrete and I say this would never work. The obvious reason would be the lack of control of which sections get vibrated. With a concrete vibrator (also a sonic device) quite often a quick dip is all that is needed for an area of 1 square meter @ 150-200mm (Roughly 1 sq yard @ 6-8inches ).

If your idea was to vibrate the entire steel reinforcement then it still wouldn't work. As .. have pointed out some portions of the steel wouldn't vibrate. I won't get into how some portions would be overvibrated.
Pouring concrete requires alot of finnesse, strength, speed, and a level eye.

[lgalla]

Vibrating the test mixes the guys have been doing at 8to10% epoxy look to dry to vibrate like concrete mixes.Concrete is much more fluid and pourable.I would assume a lot of force or power would be needed or we may have to up the epoxy ratio.With the concrete transducers you just dip it in.You won't be dippin in the E/G.This is a problem.Any thoughts or solutions?
Larry

[pupa]

Vibrating the test mixes the guys have been doing at 8to10% epoxy look to dry to vibrate like concrete mixes.Concrete is much more fluid and pourable.I would assume a lot of force or power would be needed or we may have to up the epoxy ratio.With the concrete transducers you just dip it in.You won't be dippin in the E/G.This is a problem.Any thoughts or solutions?
Larry

I suggest vibrating the complete mould direct via side tabs for mounting the transducers (as suggested in one of the articles) or on vibrating table. I still believe there is value in the audio transducer from 5-300hz as the amplitude can be adjusted via volume from pc or music player. Simple and hopefully effective. Only a trial can really determine the value and effectiveness of the solution. The probe types do not seem to be going to work as you suggests. No low viscosity water but rather syrup. Alternative would be to use lower consistency thus greater slump (longer cure time) epoxy mixtures and wait longer for settling or apply curing heat with lamps?

Maybe longer vibration time is required or/and Vibrators in the Khz range will be required as at this high frequencies the action is too much for standard concrete mixes.

Will do some more research
Regards
Chris

[romihs]

Larry,

I agree, the dry E/G E/C mixes require a different solution compared to concrete.
As was pointed out earlier, vibration frequencies up 4kHz are required.

Anyway, I have removed the samples I made from the 'molds' and taken a look at the 'compactness' of the E/Q. On the surface, I can see that about 70 - 80 % of the surface is E/Q, the remaining 20 - 30 % is air. I will try post some pictures of this later.
The poor fill ratio could be a cause of one or both of the following:
- poor compaction, which I know is the case with my test runs.
- incorrect quartz granulation, which I will be able to rule out with further testing that I will be doing.

I like the idea of keeping the epoxy quantity to a minimum, as it is the week link in the E/Q mix, so I will focus my efforts in solving the problems with compaction some other way. I don't know if I will be successful, but I have try.

Regards

Sandi

[walter]

Guys, what about press compaction..
Wouldn't that solve both problems? (air entrapment and compaction)

[romihs]

Walter,

I have thought of that too, but never mentioned it because I believe that the mold will then have to withstand the pressure, which will increase the cost of the operation again...

But, I may be wrong again, because the tests I've done so far could have been done with the incorrect grain sizes. I'm saying this because I did manually compact the mix into the mold by pounding on it, and I see 20 - 30 % void area on the surface.

Regards

Sandi

[martinw]

Guys, what about press compaction..
Wouldn't that solve both problems? (air entrapment and compaction)

Dear Walter,

IMVVVHO, I would have thought you want negative pressure, not positive pressure.

Best wishes

Martin

[Stepper Monkey]

This is my first jump into this particular forum, but I thought I'd throw in two minor points I have experience with;

First and most importantly, positive pressure is bad. Very bad! The last post was right, you do absolutely need negative pressure to de-bubble and compact. This is precisely why I operate two very large vacuum pumps in my shop. Shaking, striking, or roughly vibrating the forms while under vacuum is also very helpful to dislodge the bubbles and get them to surface.

In another note, liquefaction still happens very nicely with dry mixes. I have used vibratory feeders to dispense and to compact everything from explosives to gold dust that can't be handled with normal frictional feed devices.
It doesn't need to be wet to flow like water!

[pupa]

Effect of Binder Content and Coupling Agents on Mechanical Properties of Epoxy— Aggregate Composites

Have some interesting information and tables re strenth using %ratio and preteatment of aggregates with silane coupling agents.

http://jrp.sagepub.com/cgi/content/abstract/1/4/370

PDF File download
http://jrp.sagepub.com/cgi/reprint/1/4/370

[romihs]

Hi all,

As promised, some more pictures.

I used a marker pen to highlight the surface of the E\Q...

Here we have the two compacted results..




And then, for comparison, the un-compacted result...


The difference is quite noticeable. I may have been wrong earlier, the E\Q appear to cover 60 - 70 % of the surface only.

Stepper Monkey, how would one go about vibrating a large mass? Some kind of audio 'speaker', as Pupa is suggesting, might work if one is able to get the needed power and frequency response out of it...

IMVVHO vacuum and vibration are the way to go...

Regards

Sandi

[wjfiles]

I use epoxy's for impregnation and the manufacturers suggest that almost a complete vacuum is needed to remove entrained air from the liquid mixture.
I found that if much less than 29 in vacuum air was still present.
For what it is worth.
WJF

[martinw]

This is my first jump into this particular forum, but I thought I'd throw in two minor points I have experience with;

First and most importantly, positive pressure is bad. Very bad! The last post was right, you do absolutely need negative pressure to de-bubble and compact. This is precisely why I operate two very large vacuum pumps in my shop. Shaking, striking, or roughly vibrating the forms while under vacuum is also very helpful to dislodge the bubbles and get them to surface.

In another note, liquefaction still happens very nicely with dry mixes. I have used vibratory feeders to dispense and to compact everything from explosives to gold dust that can't be handled with normal frictional feed devices.
It doesn't need to be wet to flow like water!

Dear Stepper Monkey,

Thanks for that. I think that a partial vacuum is one of the ways of removing air. I couldn't see how possitive pressure would help ....but maybe it could, in retrospect.

When air is compressed, it heats up. That is why bicycle tyre pumps get hot when you pump (is this right????).

If that is the case, it could be a useful mechanism to distribute heat evenly through the exoxy mix to make it less viscous, and flow more evenly amongst the aggregates. Air heats up, epoxy heats up, mix heats up.

Maybe one should compress the mix to begin with, and then put in a partial vacuum???

Just chucking this idea out.....shoot me down!

Best wishes

Martin