The Ultimate DIY Rocks!

[G-money]

Looks great, Travis!

I wouldn't sweat the aragonite addition. Your rock (or sand for that matter) isn't going to contribute to your buffering capacity to any functional extent. The pH isn't (shouldn't be) low enough to dissolve it much. Definitely not enough to do much buffering. I've had the same live rock for 6 years and it hasn't shrunk at all.

I may have to try this out myself...

 

[Travis L. Stevens]

I guess you're right, G-money. If you are being responsible in your reefkeeping and testing regularly, you should be able to pinpoint any problems before it gets to the point where the Calcium Carbonate will dissolve. Plus, isn't Portland Cement crushed limestone? Wouldn't this have a buffering agent if the pH dropped low enough anyways? I guess Randy Holmes-Farley would hav to say for sure

 

[G-money]

I suppose sand wouldn't hurt, though. It may allow you to use a little less cement....do I have that right - you only used salt and cement?

 

[Travis L. Stevens]

Yes sir. Just 4:1 Salt to Cement. I have made about 60lbs of rock in all out of the three batches, and I still have a good 30-40lbs of cement left. Plus with a ratio of 4:1, one bag of cement will make ~90lbs+ of rock. But you would need 320lbs of Rock Salt :eek1: If you think about it, you can imagine how light this stuff is by basically thinking how big a mound of rocks the size of a mound of 320lbs of rock salt would be. That's pretty big! Now, it's only going to weight no less than 90lbs! Maybe about 100-120lbs because of residual salt. But you can fix that by just leaving it to cure a few more weeks after it is done with it's pH.

 

[Qwiv]

I am sorry, I love the thread but baking the rocks is a bad idea. Concrete does not cure by drying, it gets hard by a proccess called hydration. It is actually using the water as fuel in the chemical reaction to get hard. The strongest concrete is cured in water. Backing the mix is only making it weaker. If you are looking to speed up the cure time, you want to use an accelerator in the concrete, not bake it.

Other than that, good work man.

 

[Travis L. Stevens]

I'm not curing it by cooking it. I'm drying it by cooking it. The curing process is a good 4-6 weeks in water. So far, it's structural strength has been quite sound. It took a lot of work just to break that hunk of rock in half

 

[Qwiv]

Why are you drying it, just leave it outside. You mentioned that it takes a long time to dry, this is because you are evaporating the water inside the concrete. The concrete uses this water to hydrate.

I know a lot about concrete, I work with it every day. Baking it can lead to crazing, dusting and all types of problems. I typically use concrete in a structutal way, but it also applies here.

If you are getting great strength now/density, you could do better if you cured it right. The best way to do it would be to set it outside and mist it for a few hours. Then throw it in a tub of water.

Why did you stop using the oyster shells, I liked the texture it produced.

 

[Travis L. Stevens]

Leaving it outside and misting isn't an option for me since I live in an apartment, and with two little kids, leaving it still wet inside is also not an option. Messy kids... So, just baking it solved the problem. Instead of taking 24 hours, two works for me. If you have the chance of not cooking it, go for it. But I don't. I doubt in the future that I will leave 100 lbs of wet rock lying around the apartment for 24 hours either since it seems to work fine for me

I stopped using the oyster shells because it looks too "unnatural" for my taste. And it is really sharp. When taking out a 10lb piece of rock afer having your hands in the tank for an extended amount of time makes it really easy to cut your skin. The Salt/Cement is very smoot, on the outside of course.

 

[hmott]

<a href=showthread.php?s=&postid=7031685#post7031685 target=_blank>Originally posted</a> by Qwiv
I am sorry, I love the thread but baking the rocks is a bad idea. Concrete does not cure by drying, it gets hard by a proccess called hydration. It is actually using the water as fuel in the chemical reaction to get hard. The strongest concrete is cured in water. Backing the mix is only making it weaker. If you are looking to speed up the cure time, you want to use an accelerator in the concrete, not bake it.

Other than that, good work man.

will an accelerator still leave the rock "reef safe"? What accelerator should be used or won't it matter?

 

[tekknoschtev]

<a href=showthread.php?s=&postid=7029891#post7029891 target=_blank>Originally posted</a> by Travis L. Stevens
tekknoschtev - Did the Sand and Cement stick together well? Thanks for sharing your experiences.

The sand + concrete + rock salt (I used the driveway ice melting stuff, works great, but I've only used solid rock salt, not the calcium chloride or Mag Flake stuff) works great and provides very light rocks. I'll get a picture in a week or so when I'm home with my batch that has been curing for a while. The sand gives the outside a nice natural texture. The sand I used is a mixed grain size from dust to 3-5mm. Nothing huge, but the variances in the grain size allow for some cool textures.

<a href=showthread.php?s=&postid=7031882#post7031882 target=_blank>Originally posted</a> by Travis L. Stevens
Leaving it outside and misting isn't an option for me since I live in an apartment, and with two little kids, leaving it still wet inside is also not an option. Messy kids... So, just baking it solved the problem. Instead of taking 24 hours, two works for me. If you have the chance of not cooking it, go for it. But I don't. I doubt in the future that I will leave 100 lbs of wet rock lying around the apartment for 24 hours either since it seems to work fine for me

As long as it works. I found that with my first mixture with more concrete to sand ratio that it hardened in my sand molds over night, but with the less concrete per volume it took longer in the mold to cure. We kept the sand damp to make the molds, but after that the slow evaporation did the trick. Two weeks later we have some pretty strong rocks. The best part of doing it this way is that we did it in rubbermaid tubs so the lids could be put on and they could be stored out of sight for a while. But if baking them did the trick for you (and by the appearances of it, it did) thats great. I molded it in the sand to get some intricate shapes and caves, and overhangs, etc.

 

[Qwiv]

<a href=showthread.php?s=&postid=7032146#post7032146 target=_blank>Originally posted</a> by hmott
will an accelerator still leave the rock "reef safe"? What accelerator should be used or won't it matter?

There are so many accelerators on the market, that you would need to read the MSDS on them. The only problem with using an accelerator is aquiring it and getting it mixed correctly. This would be a tough task my hand. Quickctete at HD had a pretty fast cure time as is, so for a DIY job, should work fine.

As to putting the concrete in the oven, if it works for you, that is fine. For others following the thread, don't do it unless you have a strong reason too. The concrete would have be hard enough to handle in 4 hours and putting it in the oven only makes it weaker.

http://www.popularmechanics.com/home_improvement/how_it_works/1275111.html

Another experiment people following this thread can try is to make you rock and a few hours later dig into it with something hard to get a more unique shape. Then after a little wait, spray the rock with a preasure washer. This should clean the smooth concrete off the surface and expose the arrgagate below. This is how you pour the concrete you see that shows the pebbles inside of it, common on walk ways. It is called exposed aggregate concrete.

 

[M.Doshier]

I was wondering, after you make your mold and its sitting to dry, what if you threw some salt on it to make little indentions. Also, if this rock is so light and stuff, would any of it ever crush under the weight of other rock on top of it?

 

[M.Doshier]

I was wondering, after you make your mold and its sitting to dry, what if you threw some salt on it to make little indentions. Also, if this rock is so light and stuff, would any of it ever crush under the weight of other rock on top of it?

 

[Travis L. Stevens]

So far, weight of other rock doesn't seem to effect it. This isn't testing it with very much. Maybe I should go home and stand on one. I'll let you know if it fails. Afterall, I weigh 250lbs and if only one rock can hold up that weight, then a large pile of rocks should be fine. But that is a great question.

As far as the indentions on the outside goes, I've thought about either molding my rocks in a bucket of rock salt similarly like you would with a bucket of sand. This way, you can wash of the rock salt incasement unlike sand molded DIY rock where it sticks to the outside. Also, the outside of the rock is already rather "bumpy" as it is. But I guess it's more of a personal preference.

 

[afelder]

How many shapes have you tried. I have the GARF style rock and have made all sorts of shapes. Plastic shopping bags make a great interior to artificial tonga style rock. You just mold around it and it holds branching shapes well.

 

[Travis L. Stevens]

Truthfully, I haven't tried to make very many shapes, I just wanted to make sure that it worked first. It has the same consistancy as any other DIY Rock, so I would venture to guess that you can make it into any shape that you want.

 

[itstheantitang]

I ended up making some, and the problem is a few pieces float. Even some of the big pieces float. This confuses me, because it would seem the cement would be less dense with the water.

FWIW, the rocks have been curing for 1 month now.

 

[Stonepost]

Anyone thought of using PVC tubing for holes / crevices? wouldn't be to hard to mold around it and could make diffrent sizes fairly inexpencive.

 

[exoticaquatix]

<a href=showthread.php?s=&postid=7343239#post7343239 target=_blank>Originally posted</a> by itstheantitang
I ended up making some, and the problem is a few pieces float. Even some of the big pieces float. This confuses me, because it would seem the cement would be less dense with the water.

FWIW, the rocks have been curing for 1 month now.

the reason your rocks floats is beause the total density of your rock is less than water. basicly you have enough air trapped in the rock to make it float. have you ever seen pumice? sometimes you get little pieces in the pockets of new jeans. its volcanic and as it cools enough air is trapped to allow it to float. same thing.
-nick

 

[Travis L. Stevens]

<a href=showthread.php?s=&postid=7343239#post7343239 target=_blank>Originally posted</a> by itstheantitang
I ended up making some, and the problem is a few pieces float. Even some of the big pieces float. This confuses me, because it would seem the cement would be less dense with the water.

FWIW, the rocks have been curing for 1 month now.

VERY interesting. None of my rocks have ever done it. Was your mixture straight salt/cement? Or did you put some PVC in the middle or some sort of plastic as well?