Hey Rick --- Very Cool! How "rock-like" are you gonna take the finish and when do we get to see pix? Oh...and how thick (or thin) is it? Knowing you, I'm guessing less than an inch for sure. And since concrete typically runs about 125 lbs. per cubic foot, that puppy only contains about one-fifth of a cf! Way to go!

You're right about thickness.About 1/2 to max 3/4 inch.Since this kind of science is somewhat beyond me,and I know that it's a strong suit for you,I'll say that what I did was with blind ignorance and a little research.And,a large dose of good luck,with HUGE input from Laura(Thank you,Laura!)on her creating with Quikwall and mesh.I just extrapolated from her initial work.Don't know what I'd be doing without her threads on the forum...
Cheers from here

Did you have to use a bonding admix on Saturday before adding the second layers? I wondered why you didn't just do it all in one "sitting". Why the day's delay? Could you have done it all on the same day? I agree about the help and inspiration Laura is to all of us. Ditto Dena. I love people who think outside the box.

Fleur-thanks for your comments.I did two layers,allowing 24 hours between for the mix to "set".I used 100% admix.Generally speaking,that's all I use.Doing such thin work(my choice)and,with very little done in this area,I thought I'd work on the side of caution.Perhaps it IS possible to do it in one go,I really have no idea.I'm content with my work to date.And,my faithful readers,that's what keeps me going.
Cheers from here

Rick - wow! I'm so glad you did this. Isn't it a thrill when you jump up on these thin things and they don't crush! I wonder about the limits of this idea of making objects that stay light enough to be handled by one person yet strong enough to hold a lot of weight.......Keep writing about your successes - I love reading your stories. I am getting close to being inspired again; I went to Lowe's today for some Quickwall. Sadly they didn't have any which worries me but.... it has to be somewhere here in town this summer.
Laura

Hi Rick, sounds like an interesting project. You said you put in 5 to 7 hours and with all of the material costs, are you finding a project like this actually "paying for itself" or is it one of those labor of love/learn projects?

Did you paint the admix over your first set of layers and then put on the second set? I realize you use it 100 in mymud. Just wondered if after the first day's work you covered it with bonding agent before the second day's application. Now how are you going to cure it and for how long? Lucky you to have creting weather already. I languish with wet cold...still. Sigh.

Hi-first,Lazydaisy,I'm getting $200 for this piece.Fair return for labour,materials and reasonable profit.
Fleur-sorry,I DID skip that step.I applied a coat of admix before applying the 2nd coat.As to curing,the forum has been divided in the past when I inquired.My own experience(with our own cover)was,no cure,put it to work right away.Rain,freeze,thaw,no problems.On the other products using the same mix,same story.Put it together,put it to use.
I've done balls to 26 inches or so,put water in them the day after finishing,went away on holidays,came back to no leaks.I know,weird and I'm unable to give you an explanation as to why it works-it just does.Long term?Again,I'm no forecaster on it.I'm gearing towards our local craft sale in August;any problems should show up by then.I've been using my very first creation(basketball size ball with mister inside)since October(I think),and no problems,nothing at all.The stuff gives a very solid structure for garden art.I'm hopeful that this lightweight 'crete will be my forte in the local art community.
Again,thanks for the kind words and questions.Keeps one sharp to have your peers comment.
Cheers from here

Good for you Rick!!
Debbie

Sorry to jump in so late in the day. What's Mymud? I don't live in the US, so don't have access to QuickWall. Is your mixture something that can be made up using supplies from any DIY store?

What did you use for making the form? Any reinforcement in it, like chicken wire?

Rick,
Glad to hear of your success. I would not venture to guess your weight, can only imagine the controversy that would start. Although it may be more than 185 :)
I too ? why or if you painted bonding agent between layers. It is easy reassurance. It will make the first layer stronger, and provide a damp surface for the next. In my experience brushing that bonding agent/admix also provides a sort os slick surface and allows you to 'push' the next coat even more, possibly thinner in some cases. Sort of like in clay work using a kidney to smooth the surface and release/find air pockets that can create problems down the road.
Of course would love to see pics sometime.......
Dena

Rick, I find your experiment so fascinating. It really does open the doors to so many projects that just would be to big and heavy for me to move any where with out some real challenges.I would love to see a pic, and also of your basketball sized piece with the mister. I got an exersize ball and a mister, and was hoping to do the same thing you have. I was concerned with keeping it thin and light but now I think this process of yours is so intriguing. I also just installed a little pond and was trying to figure out the best way to make some water falls for it. I think your method would be perfect.Are you just using dirt mounded to get your initial shape? If so are you putting a layer of plastic over it, or just going right over the dirt?When you talk about putting sand over the final layer, would you just mix sand with some admix and then brush it on?
Thanks
Cindy

Running dog-Mymud is a blend of my own making.I've listed the ingredients before,and I'll do so again for ya.1:1 cement and silica flour(pottery sand,at about 130 mesh),either silica fume or metakaolin to 8% by weight of your cement,fibres(I personally prefer the short strand made by Harbourite,aboue 1/4 inch),colour of your choice(or not)and admix(I use the mortar admix from Home Depot,you'll have to search out what works for ya over there!),no water.The reinforcement is detail mesh(or EIFS in the US)an alkali-resistant fibreglass mesh used in stuccoing houses.
This mix has no slump;I can work on vertical surfaces without the mix sliding.And,it sets FAST!
This isn't for everyone.Costs are high here,due to pozzollans and the admix.The quick set won't appeal to all either.There is little chance of corrections after a couple of hours.And,although I've not tried it,I believe Tango mentioned that it might not take stains very well.
As to photos-same as before.We'll have them on our website in 2 weeks,with pricing.Where's our website?E-mail me.Some of you have visited it,and thanks for that.This isn't our primary business,just one of a few.
Off to put on the finishing coat this AM.I reinforced the edge yesterday,so it won't be TOO thin.And,yep,I'll use the admix as an interface(?)to assist in bonding new to not so old.One note here is that I found on our first cover,done over a longer period(got busy elsewhere)that applying the final coat to a cover that had set for more than a few days was a disappointment.It did not adhere very well,hence our naked cover(although guests have said that it looks very rocklike-maybe they were being kind).
Good luck to all that try it.
Cheers from here

Thanks for a repeat of the mymud recipe. To what consistancy do you aim for? I'm trying to figure out how much admix you ad per your 1:1 mix. Thanks.

Fleur-The dosage varies slghtly but it appears to be about 3/4 of the volume of the cement.Like many of you,I hand mix these smaller batches,and I add the liquid in small doses,thoroughly mixing at each addition.I find it useable when very stiff for edging(such as around the ball openings or the edge of the masks)and a little softer to apply to the mold and smoosh(huh?) the detail mesh into it.When its stiff,it feels and acts like clay,so its easy to mold(at least to the degree that I do)the edging.I edge all the pieces as the finished product in some cases is only about 1/8 to 1/4 of an inch thick at the outside edge.Too thin for what I want to sell.
klinger-I made a very Orville-and-Wilbur Wright-type mold from chicken wire and stiff plastic pipe that the plumber had left over from our construction.I made a circle/oval shape that at its minimum diameter would fit over the septic cover.I wrapped this in plastic bags and stuffed the void with scrap styrofoam and then sprayed expanding foam to complete the support.Thanks,Laura,for the idea.
for your waterfall idea,A mound would work,as long as you have the plastic sheeting in place.I've done 2 exercise balls with slightly different sizes of openings.On one,I put a hole opposite the opening for wires,or plumbing.I used those widgets you buy for stuffing computer cables thru your desk.I cemented the female portion in,creating the opening.the plugs,I'll use one on each side of the opening.Put the wiring thru,put on on cover,fill the opening(about 1/2 inch in depth)with silicone,and put the other cover in place on the inside of the ball.No leaks!
for a pond mister,usually there's a lead from the misting unit to the transformer that has an"audio style"plug on it.If this is the case(as it was with mine)Forget the bigger hole,just drill to the size of the jack,pass it thru and silicone the tiny opening.And,if you're really anal(aren't we all?),use a coloured silicone to seal that little hole.Clear lets in stray light(ours is also wired with a flashing U/W light-plug in the mister,get a light show as well!)-OK,enough with the typing,already!Work to do.
If more info,you can call as well.Number's on the website!!
Cheers from here

I completed the final coating this afternoon.My wife will take a few pics later.I used garnet,black slag,some silica sand,cement and MK.I added a few fibres and admix.the mix clung well to the prior coat,and i used admix to moisten the surface.
we'll see what tomorrow brings!
cheers from here

rick, where do you find silica flour (pottery store?), silica flume, pozzollans and can you give me your website. Thanks, Marie

Hi,Marie.I found the silica fume and the metakaolin through research in the Vancouver area.If you search www.metakaolin.com you should get a provider near you.The SF I got at a concrete supply company.That stuff won't be found at your local Home Depot!!
as to our website,I'll e-mail you.
thanks for asking
cheers from here

Hey Rick --- I don't wanna' sound like a worry-wart and I hope you won't hate me for this but... I now have some concern regarding the reinforcement on a span like what you've described. Are you using only the fiberglass and no metal at all? If so, I would advise reconsidering based on fiberglass meshes inability to prevent fractures from causing a catastrophic failure. Without something that can span a fracture and still basically "hold the pieces together", it could potentially let go all at once. Concrete has a bad habit of doing that and glass mesh alone won't be able to transfer the load to another segment without failing. Something like standard 4x4 steel mesh could be easily incorporated to spread out the load and span any fractures, plus it would have almost no impact on the overall weight. Steel can do that, fiberglass mesh cannot and will not.

While it is possible to carry enormous loads with unreinforced concrete...it only works when the load is just about perfectly distributed. A good example is the design of monolithic dome structures. There are some storage units here at the Post of Houston well over 200 feet tall that have no reinforcing steel at all, except in their foundations...but, and this is a very big "but"...they are almost perfectly shaped domes that have almost perfectly uniform wall thicknesses. As long as the shape distributes the load uniformly, and, the wall thickness is uniformly engineered...they can support an incredible amount of weight...just like the eggshells that the engineers copied. However, if there is any deviation in thickness or in the way the load gets distributed...they will also collapse in the same manner as an eggshell under unequally applied stress.

As you probably know by now, I am very big on experimenting & pushing the limits, but I do honestly have some concerns after having re-read the initial post. And I also want you to know that it was David that pointed out this consideration and asked me what I thought. Not to dampen your spirits my friend, but I have to absolutely agree that his concerns are very real and warrant some rethinking on the design. Something like a cover for an opening that will be exposed to the long term effects of the elements and have to absolutely never fail under weight really needs the extra insurance that only a sturdy continuous steel mesh can provide. Even better if it were secured to a rebar ring in the rim. I apologize that I missed this the first time around. In my enthusiasm for your work and progress in this area I simply didn't pick up on it.

I think you are on the right track and definitely want to keep following your work, but in this particular case I do think there is a fundamental flaw that could potentially have very bad consequences. I guess the good news is that retrofitting steel mesh could be easily accomplished by applying another layer or so to the underside, but ultimately, it's your call. I just ask that you think about it.

Look at it this way...there is a good reason that manhole covers are all made of steel...and not concrete.

As Always, All my very best --- Tango

Thanks,Tango.Your comments are more cogent,and based on some science.Unlike our "friend".As I've only made a couple(one for us,one for a neighbour who doesn't have and won't have jumpers !)I'll look at retro for theirs;I'm going to continue ours without for the experiment of it.As mentioned,the total drop on these is only 6 inches,to the hardshell cover of the septic tank itself,so if it goes,it goes on a very short trip.I'm also waiting for the supplier to send me the test results.And,as one of the senior 'cretists,I take what you say with a large grain of salt.
So,recommended wire?I've got quite a bit of chicken wire laying about(dumpster dove for it!).I envision that I could either lay the wire down first,then do the layering as before,or do a layer as I'm doing now,then wrap that in wire,then a another layer of fibreglass,then a finishing coat.You're quite right in that the weight gain would be minimal.this is my only(so far)project where there is interaction,or the potential thereof,with people.I've "interacted"with ours several times,no problems.But,it's only a few months old.I'll keep on doing so to see what the life of the product would be.My other works with mesh and Mymud are not weight bearing at all,other than a few gallons of water in the fountains.
again,thanks for the insight.I appreciate the cautionary note of your missive,not"the sky is falling!run for your lives!"approach.
Cheers from here

Tango-more I thought about it,the idea of "wafering"the steel between layers makes more sense.With a rigid backing,it would be easier to put the wire/diamond mesh(discovered some of that,too!)on it,tape it down,do the second layer,then finish.I was just playing with the new cover.Without weighing it,it's heavy!!Not in the vein of lightweight concrete art as I'm doing with my other pieces.It will work as a cover,it will be moveable,and,should be durable.BUT,it's too heavy,in the range of 50 lbs or so;it's a pig to carry because of its shape so the weight is a guess.Right now,I have 3 layers of concrete on it.The first one took the most material,the second one the least.The final coating weighs in more because I used a coarser sand to more emulate the neighbours rocky surroundings.As it stands,this exceeds my weight requirements(no hernia-weighted pieces!),so I may rethink the idea of producing them,except for friends and neighbours.But,I'll reinforce each of them.
So,at this juncture,it ain't just the additional reinforcement that puts me off.It's the bloody weight!!
I'll stick to my other uses for Mymud and mesh for the moment.Your thoughts do carry some "weight" with me,but I would have been put off making more by the reason stated.
Thanks to all for listening in-if anyone has an upgrade on my concept,I'm all ears.That's what this forum is all about!!
cheers from here

So I'm driving into the village,looking at the dogwoods in bloom,the salmonberry bushes in a riot of pink blossom,and,like a swift blow to the head,it came to me."What about styrofoam?"I says."Indeed!"I replies.Well,this goes on for minute or two,discussions,meetings,a little backstabbing,then a fully thought out format to do septic covers,lighter and well supported."How",you ask.
Here's the deal:Using the thickest of blue styro sheets(2+ inches in thickness),cut to fit over the round septic tank cover.I'll glue approx. 4-5 sections together,with the necessary hollow to accomodate the dome shape.Shape the outside of the styro to approximate that of the local rocks.Then,do the mesh and concrete finish DIRECTLY on the styro.The concrete is fully supported,I can use one layer less,and I've disguised the tank cover.Should some little beggar actually break the cover,it should simply flake off the styro.Suddenly,my hernia potential drops!
cheers from here

rick, I'm sure you're familiar with this site, which has useful info about using expanding foam as a base.

Here is a link that might be useful: rocks

Hey Rick --- just remember to make sure that the reinforcing is more or less centered in the mass of concrete material. If it is positioned under the crete it cannot transfer any load. It's the same thing when you pour a driveway or a slab...that's why they set the rebar up on those little "chairs"...to get in up inside the mass.

Rick - I enjoy your clever writing as well as your clever concrete ideas. I could just hear the conversation you had with yourself:

"So I'm driving into the village,looking at the dogwoods in bloom,the salmonberry bushes in a riot of pink blossom,and,like a swift blow to the head,it came to me."What about styrofoam?"I says."Indeed!"I replies.Well,this goes on for minute or two,discussions,meetings,a little backstabbing,then a fully thought out format to do septic covers,lighter and well supported."

Keep experimenting and sharing!
Laura

Just a thought...have you thought about it being a two-piece? The sculptured rock on top of a "frame" base that lock into each other? Yes, the combined weight might be high but the individual pieces would be light and manageable. Maybe the frame base could be the rebar arch structure, a wood arched frame base, maybe aluminum, or even a split concrete/hypertufa solid arch. The bottom piece wouldn't be exposed to weather all that much (unless it's flooded?). For the frame base, you could also consider using something that already exists that, combined with the partial strength of your sculpture, would support someone standing on it when retrofitted with the sculpture portion...hmm, metal trashcan lid, something like that possibly?

Well,to finish off the story...
This morning,we moved the cover out of the studio and we'll take it to our neighbours.It is now hernia-worthy.It weighs WAYYYYY too much to fit our lightweight concrete concept.The neighbours aren't just getting a cover for their cover,they're getting a fake rock that probably weighs like a real rock.
No more of this kind. Stay tuned for a new,improved and well supported model.
Cheers from here.

Rick, you mentioned your mud sets up fast and you can even apply it to a vertical surface without it slipping. I don't have access to all the goodies you put in your formulation but wonder if you have an opinion on adding the fortifier full strength to quikwall, which I do have. What do you think? Would this make it set up faster and allow me to work around a ball, for instance? I'd like to get as much as possible covered in the first go round, if you'll pardon the pun.

Worth a shot.As I said,this stuff,at least what I was doing,sets up pretty fast.Has a soft clay /plasticene type consistancyWhen I use it.Too little moisture,it becomes problematic.You want something"smooshy-like"...
Cheers and let me know.I have some Greatwall(like Quikwall) in the studio,and would give it a try!

Hi Rick,
I'm having a senior moment here and don't recall if the admix you use is the bonding adhesive or the acrylic fortifier? Thanks.