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View Full Version : best concrete for DIY rock?


iwanaclown
10/25/2010, 12:57 PM
What is the best concrete for DIY rock. im looking for the lighter shades of concrete and didnt want to get one that had harmful chemicals or negative affects later down the road. if anyone can please advise :reading:


thanks

widmer
10/25/2010, 01:53 PM
I just used the standard, super-cheap portland #2, no special advertisements on the package.

I think what makes the most difference in the color of the DIY rock is what you actually use to make the rocks. I used nothing but different sizes of aragonite (reef sand, crushed coral etc) and mine turned out very light gray color, close to white. I would imagine that if you use other ingredients like crushed oyster shells, or regular terrestrial sand, it would cause the color to be darker.

I would also guess that darker color could be caused by using an excessive portland:aragonite ratio. I used somewhere between 1:4 and 1:6 of portland:aragonite, and couldn't ask for my rocks to be any harder than they are..

lordofthereef
10/25/2010, 01:55 PM
I used oyster shell and it turned out pretty white. Crushed oyster shell, at leas tthe stuff I got, is almost as white as aragonite.

The most important thing to remember is that you will need to cure the rock to leach out all of the lye. This takes about three months.

iwanaclown
10/26/2010, 07:18 AM
thanks alot for the advice.

i was planning on using crushed oyster and aragonite with my mix. i found that crushed oster is a little cheaper.since im taking my time finding a stand for my tank i was gonna cure the rock in the tank in the mean time.

JasonBJones
10/26/2010, 09:06 AM
I built mine using portland, but if I were to do it again I would use hydraulic cement, much faster curing times.

You can learn more about it by reading this thread http://reefcentral.com/forums/showthread.php?t=993625&highlight=crushed+oyster+shells+epoxy

Rhodophyta
10/26/2010, 11:30 AM
Use the resin for fiberglass as a substitute for Portland cement. Make a form and cover it with layers of wax paper, the only thing I know the resin won't stick to.

It does not take much resin. The aragonite will still be more on the dry side than damp. You definitely don't want drippy wet. No need to go thicker than a half to quarter inch and it can be feathered.

Once dry, tacking a few pieces together with resin creates a rock with lots of internal open space, resembling the pieces of storm or bleaching event broken coral you'd see as live rock on a trip to some parts of the Great Barrier Reef.

The resin sets fast and does not raise pH or hardness.