Creating rockscapes using Hydraulic Cement

So I was helping a friend make some rock structures and decided to make a little thread going over the process. We used Hydraulic cement, purchased at Home Depot, and that was it. Originally he wanted to drill holes and cement rods into place. Once he saw the strength of the bond, he opted to just cement everything into place.

Pros=easy, cheap, super strong, won't crumble rock from drilling, reef safe
cons=don't get to buy tons of 2 part epoxy, cant buy acrylic or fiberglass rods, can't use a drill

Equipment=Hydraulic cement, water, mixing stick, and container
First thing you have to do is mix your cement. It cures quickly, so only mix what you can use in 5 minutes. You want to follow the mixing directions, but the end product is thick, and almost stands on its own.

If you want to use rods, I suggest going to Home Depot and getting these driveway markers. They are made of fiberglass, and you can cut to size using a hacksaw. Drill your holes with a 3/8 mason bit.





Your rocks should already be fitted in the way you want them. I will use other rocks, boards, whatever it takes to hold my rocks into place. Then you take a liberal amount of cement, and apply at the joint, and all around it. Dont worry, you can either leave it like it is, or spread some sand over each joint. Coralline will cover it eventually, and it also makes a good spot to epoxy encrusting montiporas on.




Once you get all your rocks cemented, wait an hour or two, and it should be fully cured, and very strong. This is best done with dead rock, some people soak their rock in RO/DI for a week, I never have. Now your four rocks lift as one, super strong and won't crumble.




Later I'll get a pic of how strong it is.

 

That looks like a fun project to me BTowned

the finished item does look sturdy and despite the temporary color difference
it still looks reasonably natural to me

Steve

 

It really can be masked if you use substrate in the joints, but to me, I never cared, because It gets covered with coralline. It's rock solid, you can make a 100 lb structure, and lift it up in one piece.

 

You recommended dead rock but will it work with wet live rock?

Sent from my DROIDX using Tapatalk

 

Yes, you have to just get wet towels, or paper, and mist the rock while you wait for it to dry. The rock we used was live rock I have in a brute trash can. But since it's being cooked, we didn't bother to keep wet rags over it.

 

Less than an hour later I can pick the rock up without supporting it from underneath.

 

Wow. im gunna use this on my 65g im building. thanks for the info!! K+

 

yea i would not use that in my tank. I had to use it in my basement to patch the wall and if it gets on the skin it burns bad. It has chemicals like lye and what not. Please educate me if i am wrong but that doesn't seem good for a tank.

 

i donno what kind of chemicals added to this cement. but i'm sure there is tons of them. cause the natural cement takes 28 days to fully cure. they added some kind of chemical to speed the reaction and there is another chemical or sets of chemical to make it water tight (since it sais on the box leak stopper) and in my experience these chemicals deteriorate by time and you'll find them one day dissolved in your water.
it burns cause cement dries up due an exothermic reaction, this type burns cause of the additives that makes the reaction (that takes 28 days) ends in 5 min. i hope this helps

 

i dont mean to hijack this thread but did anyone try the white cement (i donno if it is called like that here in the US) it takes a whole day to harden but you can mix it with pure chalk (CaCO3) and the curing time will become around 1 hour. this is more natural solution and the mix will be closer in texture and color to the rock.