Issues with man made LR

[Nykademus]

So... I have read forums on the subject until my head hurt... tossed out every question I could think of to a well educated friend of mine and finally decided to take a shot.

I made rock for my soon to be set up tank. I started the rock process so that the PH was right when it was time to put it into the tank.

Purchase list:

1 - 40lb bag of crushed coral
1- 50lb bag of all purpose sand ( to be used as filler )
1- 94lb bag of Portland cement ( type 1 )
2- 2lb bags of elbow macaroni
3- small boxes of rock salt
1- Mixing tub
1- 45gal trash can ( for leeching the rock )
( the macaroni and rock salt to help make a fairly light weight and porous rock )

Mix list:

3 parts crushed coral
1 part sand
3 parts cement
2 parts macaroni
1 part rock salt
( equal parts, I used the empty box from the rock salt to measure the rest of the ingredients )

( I still have over half of the cement and sand )

I wanted to make sure that the finished product was a good solid rock, so I used what i thought was plenty of cement.. granted I may have used a little too much water at first, since the mix was a little soupy.. so I added more coral and a little more sand.. over all I thought that the consistancy of the mix should work ( based on the concrete work I have done in the past ).. couldnt be that much different could it? =)

I happen to have a horseshoe pit in my back yard, and used that for the rock "molds".. I sprayed it down with water, created the shapes of the rocks.. piled the mix in by rubber gloved hand.. and with some of them used sand in the middle to create cavelike structures.

This was all done in the afternoon and clean up was completed by 6:30pm.

I checked on it before I left for work this morning, and was disappointed to see that the cement was not as set up as what I would think it should be from sitting over night.

Anyone see right off if anything was done wrong?

Could the rock be pulling moisture from the sand?

If so, the cement should still set up over time right?

I would really hate to have this go bad, since the whole point was to save a little money on rock.. doh!

Any suggestions are greatly appreciated!

[rustybucket145]

You should be good to go. My rocks took a couple of days to dry enough to move and even then they were very fragile for almost a week. Just take your time.

In my opinion you might have used to much Crushed Coral. The cement needs the sand. I would have gone with a little more sand. When I did it I pretty much used the opposite of your ratios ie: 3 parts sand 1part CC.
It might still work, only time will tell.

[Nykademus]

Checked when I got home from work.. still wet.. the thicker stuff is quite wet yet.. the sand underneath didnt seem to dry out alot.. no rain ( until later tonight ) and it was a warm breezy day.

I covered the pit as best i could with material that is not waterproof but should shed most of the water if we get rain tonight.

I hope this works.......

Worst case scenario I guess is that I pull out my should have been rocks and try again, since the only thing that will be added is more sand from the horseshoe pit. ( and mushy macaroni )

I was just trying to avoid the silica in the sand causing issues with unwanted algae later on... you live you learn I guess =)

Any more advice on how I can save this project, so I dont have to spend another 75$ to start over?

Thanks everyone!

[Nykademus]

Hypothetically, I should be able to use just water and cement to create a cement rock right?

My train of thought is that with time the cement should still set, given enough time to cure.