My goal is to make rocks people can stand or sit on but I want these rocks to be light enough for me to move around by myself. I welcome any comments or challenges that would help me move farther toward that goal. Making them this strong but even lighter would be great.

Rick, in another thread you asked exactly how I made the rocks. Hopefully the photos will show that. Basically, I used a hula hoop for the bottom. I took 8 ft lengths of chickenwire about 12 inches wide. I squeezed the end of a length over the edge of the hoop to keep it in place and then made an arch over the hoop and secured the other end of the chickenwire to the hoop by mashing the wire. I repeated this with 4 lengths of wire and wound up with a very wobbly mound which I pushed on til it looked vaguely rock-like to me. Next I put black plastic over it so the concrete wouldn't fall thru the wire. I put a layer of mesh/quickwall on starting at the top. About 1/3 of the way down I noticed my quickwall/mesh was getting heavy enough to effect the shape of the rock so I quit and let it dry. The next day it was obvious I could just lift that off so I did. I called it my little rock and put a second coat on it. Meanwhile, I put the original hoop/wire armature over a garbage can for support of the wire mound. I did 2 coats on that and made the big rock. It cupped back under so there was so chance to lift it off the armature and the wire and hoop will always be inside the big rock. It all lifted off the garbage can so that is not inside.

The photos show how sloppy I am at finishing places that don't show. I have not done anything yet to color these rocks to make them look more real. You can see the pictures here.
Laura

Is the hula hoop still inside the large rock?

Love the picture of the guys standing on the rocks. What good sports they are. BTW, have you got them hooked on this yet and did you add in the weight of the wrench?

As for shaping; how about stuffing a plastic bag with scrap styrofoam? Once set-up; you could remove the styrofoam for reuse.

grins

Vicki

Those guys on the rock were concrete workers who tore out and put in my new driveway (1700 square feet- gasp). They do it all day for a big company in town and hire out cheap (around here, five dollars$ a sq ft to dig out and put down new is a good price) to do it some more on their off days. They were wonderful to have around. I had no idea in the world how hard working concrete is. The big truck lets it trickle down that chute at some slow rate the men can deal with. They work like crazy wading in there with tall boots for an hour to get this all just right to suit them. Then the truck leaves and they use long tools to smooth it all out so it is perfectly level. Just when I assume they are finished (it looked good to me) they go eat lunch and let the concrete sit there 30 min and they come back and work 3 MORE HOURS with hand tools on the surface. With just 2 men working, they had to do the drive in 4 parts so it has taken forever but now it is done and I like it.
They were amazed at the stuff I was doing with concrete. They had no belief that the big rock would support them when they saw how I had made it. After they tried it (I didn't have the camera out for that one) they still were amazed - even brought another man by the next day to see it. It was fun to see the looks on their faces when they realized how strong the rocks were.
Laura

Laura - I have lots and LOTS of flexible pvc - purchased when I was making "hoop houses" w/ rebar, pvc, and bird netting to keep the deer out of my crops. It was long before I turned my eyes toward cement and such - and all those pieces of pvc are still here, waiting to be reemployed - oh boy oh boy oh boy!!!!

The other way to get fibers is to buy one of the many concrete dry mixes that have the word Fiber in their names. (be careful - some of these also have gravel instead of sand as the aggregate). Quickwall is the name of a product made by Quickcrete company. Quickwall has the fibers already in the dry mix.
Hope this helps.
Laura

I like those fake rocks, by the way. The hula hoop has had a comeback in another life!! That must be a very large rock. I have a roll of the plastic black tubing they put underground for water. That will work like hula hoop. More flexible than PVC, too. BB

Thanks for the fiber info.
Laura

Dena

Those aren't rocks they're boulders! Great job!!! I'm the last person to be giving advice on anything structural, but I think it's a waste to have the wire armature and not have it IN the concrete. I can see it would be tough to get it to stick to something that big and not fall through, but maybe you could put the trashbag on the inside of the wire, fill it with sand (or anything you want), add the concrete, and then remove the "stuffing" after it cures. Just in case some jumbo concrete workers come by to hang out ob your rocks :)

regards, Justin

I'm sure someone has posted this link already on some thread or other here, but just in case anyone has missed it, here it is again. Lots of information that can be applied to hypertufa rock making.

In my experience (1 rock), filling a bag with stuff to support the chickenwire armature for a rock resulted in a much thicker concrete covering because there was always some air space to fill in order to "reach" the bag and enclose the wire in concrete. I do see that some of the things suggested to use to stuff the bag sound better than what I used but I can't quite imagine that I could manage to construct something where the chickenwire laid absolutely flat against the supporting bag.

When you put the concrete/mesh right on the bag which is stretched over the wire, you can make the cement thickness (with the mesh) 1/4 inch for each layer. This is what results in the lightweight aspect of the rock. My goal is to be able to move the rocks without much help but to still have a rock that supports a lot of weight for safety reasons.

I agree that encasing the wire inside the concrete would make it stronger but I have given up that added strength since I think the other way is strong enough (holding 400 pounds) for the purpose of making a safe rock.

I would be happy to hear any thoughts as to where my thinking is wrong or how I could improve the idea.
Laura

Justin

Ginny

Thanks all, Radd

I think this technique is exactly what I've been searching for. I want to make a couple of fake stone chairs that will be similar in shape to beanbag chairs, but with rock markings. I think the wire armature will work for me. I'll build it, then put something under it and sit on it to make the seat indentation! Then I'll add the quickcrete.

Based on reading lots of websites about hypertufa, I was thinking I'd have to make the concrete or tufa much thicker than you've made yours. Am I right in thinking it's the fibers in the initial layer of quickcrete that make your structure strong enough to hold 400 lbs w/o after the armature is removed?