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Diy lightwieght concrete background (56k beware)

Fri Nov 09, 2007 12:02 am

Beginings.
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Completed sections out of tank.
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Protective foam.
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Starting a stack.
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Getting taller.
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Stack almost complete.
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Before skin coat.
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Section with skin coat.
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Comments and questions welcome. :)

Fri Nov 09, 2007 12:06 pm

What concrete did you use? did you add fortifier or something to make the mix stronger/more rigid?

Fri Nov 09, 2007 10:34 pm

The rough structure is a mixture of type II cement, some sand and a lot of perlite. I experimented with a lot of different mixtures and came up with a with a formula that is just heavier than water but more lightwieght than regular concrete. I didn't use any fortifiers but did use more cement than would normally be found in regular concrete. Sometimes refered to as a "Hot mix". For the pipework I also added a couple of cups of shreaded fiberglass to help prevent cracking around the pvc.

Sat Nov 10, 2007 8:34 am

Did you use any color dyes in the mix, or is that natural?

Sat Nov 10, 2007 9:13 am

The last picture has concrete dye painted over the skin coat. Heres what a completed section looks like without the color added.

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Some of the pictures were taken without flash using a low wattage bulb for illumination. They show a little more detail but it does skew what the actual color is.

I'm going to have to do somemore experimenting with the liquid concrete dye. I painted it directly to the dried skin coat but it does not stick very well. You can rub it off with your fingers. :( I'm going to try mixing the dye with powdered cement and water to see if this will help with drying the color onto the structures.

Sat Nov 10, 2007 10:02 am

iceblue wrote:The rough structure is a mixture of type II cement, some sand and a lot of perlite.
This is very interesting! Any chance you could write up that recipe?

Sat Nov 10, 2007 10:49 am

I've adjusted the mixture a bit while building the structures but am happy with this formula.
9 cups portland typeII cement
3 cups plaster sand
12 cups of water
24 cups of perlite

Dry mix the sand and cement together and add 10 cups of water holding 2 cups in reserve. Stir well.
To this slurry add 24 generous cups of Perlite and mix gently. I use a 1" pvc pipe for this part. It works well and is pretty easy on the perlite. Stir while at the same time pulling up the slurry from the bottom of the bucket. Mix untill the perlite is well covered adding a little water from the reserve to help in the mixing. Careful as you add the reserved water at this point. You want a high slump that will hold its shape to build your structures. To much water and you won't be able to work with it.

For the skin coat I use a mixture of 1 part Type II cement to 3 parts plaster sand. Be carefull here also with the water. Add it a little at a time and mix well. You wan't a mix thats not to dry as it won't stick or to wet as it will sluff off. When I skin the rest of my structure I'm going to add concrete glue to the mix to help with stickiness.

I might also add that as I build these structure in tank a layer at a time. I use a cold moisture humidifier to keep the humidity up. Once I start a structure thier kept in high humidity untill thier done. Usually 3-4 days. I use a bedding sheet to cover the front of the aquarium to keep the moisture in.

Sat Nov 10, 2007 6:05 pm

The mix I described will do this much. The three dark structures plus one of equal size in the other back corner of the tank.

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The beer bottle will give you a good idea of the size of this project. This is one of only a few diy projects I would recommend the drinking of libations because there are no power tools involved. :D

Sat Nov 10, 2007 6:25 pm

awesome, thanks... nice photo! I'll use it as proof that the recipe called for beer! ;)
I just wont say where the beer is poured :lol:

Sun Nov 11, 2007 11:47 am

Thought I would show what my design is based on. It actually is a Lake Malawi biotope. I had thought about making the usual jumbled rock background but was having problems designing the number of caves into it that I wanted and still have a natural look. Mara point solved many of these issues.

The stuctures are based on the center right photo.
http://home.cogeco.ca/~ductapediver/Lar ... %20pg4.htm

Larry Johnson (aka Larryochromis) was kind enough to give me a few tips on the formations and give me a link to another diy background thats going to help later on in the project. :thumb: Thanks again Larry.

Wed Dec 12, 2007 9:05 pm

hello iceblue, just wanting to check in and see how your project is going. Looking good so far! :)

Wed Dec 12, 2007 10:12 pm

Looks like Sulfer Vents in those pictures.. I'd be curious to see if they were.

Wed Dec 12, 2007 11:09 pm

Hey bibbs68.
I haven't been able to get as far as I wanted when i started these new sections. We're short handed at work and I've been putting in 12 - 14 hrs a day and weekends. Not a whole lot of energy left at the end of the day to mix concrete by hand. :lol:

I have the 4 new sections almost built to the top and I'm hoping to finish the stacks and get them skinned this weekend.
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I already have 30 caves with with 40 entrances of different sizes built into what I've completed so far. The areas in between the stacks won't have any so they should go a lot quicker.
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Interesting thought on the Mara Point "Pagoda stones" formations Rivermud. I was thinking along the lines of vertically striated rock that had been weather worn and then submerged somewhere along the line.

Here's another picture of these formations that are a little different in look. Bottom left hand side. http://users.pandora.be/cichlidae/Themas/biotopen_1.htm

Thu Dec 13, 2007 11:09 am

Careful as you add the reserved water at this point. You want a high slump that will hold its shape to build your structures.


Just for clarification, did you mean you want LOW slump? Because high slump would mean its turning into a puddle. But thanks for the recipe, it will come in handy when i get around to formations in my 180.

-matt

Thu Dec 13, 2007 8:57 pm

Turtlemaxxx wrote:Just for clarification, did you mean you want LOW slump? Because high slump would mean its turning into a puddle. But thanks for the recipe, it will come in handy when i get around to formations in my 180.

-matt


It's been a long time since I've poured any slabs. We use to have the truck pour a little out on the ground to see how it stacked. If it stacked too high we would have them add a little water so it was easier to work. Pouring concrete in the desert in the middle of summer is sooo much fun. :D

Thanks for the clarification Matt. I would hate for somebody to mix a batch and then write back that my recipe sucked because of a terminology mistake. :lol:

The mix should be just wet enough to be sticky and hold its shape but not so dry that it will crumble apart when you try to form it. If its too wet and won't hold its shape you can add a little more cement and perlite to the mix untill you get something your comfortable with.
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