[ckelloug]

Martin,

Problems with wetting of smaller aggregates may not be borne out by Gupta's data but I think you were spot on about the wetting problem explaining some of the results walter and others have posted. Small aggregate appear to pose both wetting problems and binder skin effect problems. Some rather iffy back of the envelope graphs I drew suggest that the binder skin effect problem addressed by Gupta explodes at 200 micron and less aggregate size. . .

--Cameron

P.S. I'm working on reducing walter's data to flexural modulus numbers but a few beers and a bit of extra stupidity today are making it harder than it should be.

[walter]

Quoting the famous actor:



"Say hello to my little friend!"
_

[greybeard]

Could anyone give me a considered opinion on the idea of building larger E/G structures from smaller pre-cast blocks on the Lego priciple ?
Is there a unanswerable disadvantage in this approach ?
I'm assuming that the interfaces would be suitably prepared, though I'm not sure what that would entail.

I have in mind a block design that would use protrusions greater in size than the largest aggregate, so that there would be no simple cleavage plane through the assembly.

The idea is that with a smaller block, the problems of air entrapment/packing fractions/curing might more easily be overcome for the diy builder.
John

[greybeard]

I've recently been trying to get some understanding of the information in this report, and wonder if it might be of interest to the theoreticians in the thread.
http://www.niss.org/technicalreports/tr104.pdf
One thing I now understand concerning the packing of the aggregate particles in the E/G is that there is a considerable space between the largest aggregate into which the smaller sand particle wont fit, using the suggested three sizes. There just isn't the headroom !
Perhaps this is where the nanosand comes into play.

John

[walter]

Could anyone give me a considered opinion on the idea of building larger E/G structures from smaller pre-cast blocks on the Lego priciple ?

I could be totally wrong, but I would cast that 2000 lbs machine in one piece.
Vibrocompaction seems to be the key and I would rather vibrate the whole thing at once.

Multiple pours should not exceed 24hrs for secondary bonding.

[greybeard]

It's the possibility of getting something wrong at an even smaller scale that concerns me.
Besides, I'd have a job vibrating a ton of E/G in the kitchen !

John

[walter]

I know what you mean...

That's why I made all these samples- to get the feeling for this stuff.


My 36" gantry project starts within the next 45 days and I'll try to come up with a good system. All results will be posted here.

I'll try to post some videos next week.

[martinw]

Quoting the famous actor:



"Say hello to my little friend!"
_

Dear Walter,

His samples were white....yours is "sporty" and black.

Err...."rock on", dude!


Best wishes


Martin

[walter]

Thanks Martin!

btw, what a scene that was!

[martinw]

Thanks Martin!

btw, what a scene that was!

Dear Walter,

Let me guess..... that's you in the chair, the epoxy in the decanter, and the fine aggregates on the table....

Best wishes

Martin

[walter]

Heh..

[martinw]

Heh..

.....and the people about to come up the staircase are the commercial manufacturers of Polymer Concrete.....

[walter]

commercial manufacturers of Polymer Concrete lol!

* * *

One thing I forgot to add, that the precise formula for that last sample is still unknown. (chair)

Once I get the details worked out, I'll let everyone know (my 0.1gram scale just showed up in the mail).






Here again is the list of contributors that I would like to thank for making this possible :


Mcgyver, Igalla, Episs, RotarySMP, pminmo, Geof, greybeard, schrupphobel72, dansutula, turmite, JWOOD, the4thseal, Aramon, nMotion, atenman1, BobWarfield, Xerxes, RICHARD ZASTROW, Chris-Jennings, digits, Oldmanandhistoy, JerryFlyGuy, fyffe555, stlc1, ger21, myinisjap, vger, wizard, brunog, CNCAddict, oldpoopie, skippy, Eson, WilliamD, vacpress, sposl, martinw, lerman, Big S, jsage, Zumba, WYLD, svenkala, mhasting2004, Armstrong, davo727, RogerH, djshop, merl, ahlbebuck, yugami, ericdwilso, Mike Mattera, pupa, Stepper Monkey, wjfiles, LeeWay, speed33317, gt3073b, Switcher, max_imum2000, hansa, victorf, ckelloug, eloid, HBFixedGear, jkeyser14, VoxLimbo, garfieldsimons, DAK3333, mholden, harryn, hotponyshoes, thkoutsidthebox, SORCHEROR


Special thanks to Larry (for igniting this fireball) and Cameron (for pushing it over the top)!
:cheers: :cheers:



This will be my next attempt:




(But let's not get ahead of ourselves! lol)



Our POLL will remain open throughout the project, so go ahead and express your views:

http://www.cnczone.com/forums/showthread.php?t=37019

Thanks!
_

[ckelloug]

Looking for something else. I spotted this but I bet you all know where you can get one cheaper. . . If I just knew how to clean it afterwards. . .

[walter]

Crap, I've been washing that drill paint mixer in lacquer thinner. Could this weaken the samples?

[lgalla]

Walter con grats.No time to review posts in detail{18 hr days at work.18/24}:violin:
Being new guy,here is a few quick observations.
MIX:A&B first as epoxy is a diffucult mix.Carbon black next,Large aggregates next,then the fines.
Lacquer thinner for cleaning,bu, his, smelly.Methyl hydrate is an excellent epoxy break downer.
Cameron your mixer,Humbolt,looks like a donut batch mixer.Perhaps our local bakery is willing to mix our batches.
Cameron,I agree any posted sucess storys or failures should be described in detail.
Time to:cheers: :cheers: for the nu-be
Lgalo

[brunog]

Nice works Walter,
I was wondering, before you go to the next step, you should do another sample of E/G with larger aggregates of about 5-6mm (3/16"- 1/4") in size.

My reasoning is simple in masonry you cna find cement/sand mix and concrete mix. Obviously cement sand is composed of portland cement as a binder in opposition to concrete which is composed of portland cement sand and larger aggregates. To the best of my knowledge the strongest cement mix is concrete as it is used in structural applications vs cement sand that's use is more as a finishing layer.

have tweaked up my appgrete ratio calc. spreadsheet, if it can help it is based on Fuller's parabola.

I am attaching it, it presently works for 3 sizes of sand aggregate, I will make a version tonight that can use up to six sizes in aggregate.

Best regards

Bruno

[ckelloug]

greybeard,

I don't think the lego approach to a machine base would be a problem if done in a well considered fashion. I would however try to make sure that all of the joints in the system are placed in planes that may experience shear but no moment. I'd figure on trying to make the pieces solid in the strength axis.

I suspect but cannot prove (and may be wrong) that lego style pieces will show more deflection and perhaps vibration. This is a hunch, until somebody tries it with small pieces and gets strength numbers.

Secondly, The attachment you posted, http://www.niss.org/technicalreports/tr104.pdf is a remarkable paper. It seems to suggest that we have the aggregate theory all wrong. According to this paper, we need 32% (of the aggregate volume only) the largest aggregate by mass or volume and only about one percent of all the smaller aggregates down to the size of carbon black or nanosand. This will yield 70% dense packing which is almost as good as perfectly aligned perfect spheres. Their 70% probably indicates that our mixes are nowhere near 75 or 80% packing efficiency now. Thank you very much for posting this attachment. I've done a graph of log of percent volume of aggregate vs. aggregate radius from the last data table in their paper which demonstrates the effect.


brunog,

I'm still trying to double check the calculation but I don't think that the design you asked me about in http://www.cnczone.com/forums/showpo...postcount=1162
will hold .0001 deflection. It will however hold less that .0002 if my calculation is right. I'm going to PM Geof and ask him if I send over a pdf of the derivation if he will check it. Make sure that the metal beams are laid so that the shallow dimension is the one embedded in the granite and not the deep dimension. I know this is counterintuitive but since you're already way below the neutral axis due to the E/G, you want to keep the strong material as far as possible from the center of the beam so it has the most chance to "absorb deflection". If my calculation is right, you would be better off putting two tubes in near the bottom and running piano wires through and post tensioning. It would also work to casting a rectangular tube so as not to have to support the useless material near the neutral axis.

walter,

I'm still working on your modulus and strain calculations. The last result I got for flexural modulus of your good piece was 2.9ksi or 1 ksi better than the standard 2ksi minimum strength from the nist report. I'm going to ask Geof if he can check my calculations.

I need to go work on leveling the concrete pad around my shop.

[uhrgerat]

Hi,
I've looked at concrete as a building material a couple of times. A couple of things that might be of interest are the lecture notes from Alexander Slocum at MIT and one of his students Eberhard Bamberg, now at Utah (?).

One of the things that Slocum found was that standard concrete, i.e., portland cement and sand, works quite as well as epoxy-aggregrate concretes. And, is definitely much cheaper. There's also an article on the web--I'm trying to relocate the reference--regarding "alternate materials for machine tool beds". Basically the authors found the same thing, portland cement and sand works better in many ways than epoxy.

Another of Slocum's contributions was the ShearTube. In order to build a gantry type grinder frame for one company, he designed the tube which consists of a inner and outer tubes of steel. Cast between the tubes is standard cement with the inclusion of a vibration dampening material--appears to be very much like closed-cell foam that's used for mats. The foam is inserted so that it radiates outward from the center. He used 4 pieces of the foam. The design is now patented--you can find particulars by going to the USPTO site and, under advanced search, searching for Slocum as the name of the inventor.

Regards
Jim

[ckelloug]

Hi,

I talked to an apps engineer at Reichhold about our project and he said he would forward the request to the epoxy guy as he was the polyester guy. He did give us this little powerpoint of a formula for polymer concrete that seems to bear out the stuff in greybeard's niss paper!