The Ultimate DIY Rocks!

Status
Not open for further replies.
<a href=showthread.php?s=&postid=10108922#post10108922 target=_blank>Originally posted</a> by SilverOne
sunkool,

Your rock looks great! Do you mind sharing what type of portland cement you are using? Also, what kind of sand? :)

I am using whit portland made by Rinker cement. The msds says portland cement and ti dioxide (to make white) same stuff that makes pvc white. I will upload a pic when my video is done uploading.
 
<a href=showthread.php?s=&postid=10109615#post10109615 target=_blank>Originally posted</a> by dngspot
I am putting on a demonstration next week for our local club.

Awesome :)
This make a great group project/money raiser, I think.

Have fun with it :)
 
1) Salt doesn't mix with cement in theory or practice.

If you use water softener salt or fine or medium salt, it will dissolve the cement and make it very difficult to form or set. The hydraulic process is a chemical reaction that cannot take place in the presence of sodium chloride (salt).

The use of large crystals of raw salt (not reconstituted water softener salt) will only release small amounts of sodium and chloride ions, providing the mix is relatively dry and the salt is added late in the mixing process.

I tried using fine salt in my cement mix and it was like watching a milkshake quickly melt. The more you work the cement, the more it goes to mush. Even though we are not looking for great structural strength, the chemical reaction cannot be impeded, or the salt may dissolve in time.

2) Cement mixes and calcareous rock will not absorb/adsorb calcium or carbonates, other than what is used to build tube worm structures and coraline algae.

Cement-based rock will only absorb phosphate & silicates. This process will remove some calcium as it forms calcium phosphate.

3) Dry curing the rock for the required 30 days, greatly shortens the wet cure time (30 days dry = 60 days in water). Dry curing drives the moisture out of the rock, stabilizing PH in the process.

4) Calcium carbonate has a high PH, not a low PH as stated in a recent post. I won't mention names. :)

5) Rock will not absorb, or hold nitrates, just phosphate and silicates.

6) Here are some before and after (7 months) pics of a tank with faux coral end walls made of quick setting (polymer-modified) hydraulic cement and oyster shell. You can see the colour change as coraline algae populates it.

The rock used was dead Fiji rock with very little in the way of unique shapes. Most of the DIY rock in this thread looks much nicer. I used a wetter cement mix with less aggregate to bond the rocks together.

While the tank has progressed well, my photography skills haven't gotten any better.

End wall with closed loop intake concelaed before

IMG_6129.jpg


End wall with closed loop intake concealed after

IMG_7050.jpg


End wall with closed loop returns concealed before

IMG_6130.jpg


End wall with closed loop returns concealed after

IMG_7042.jpg


End wall before

IMG_6131.jpg


End wall after

IMG_7032.jpg
 
Last edited:
Here are some full tank before & after (7 months) shots. To put it into perspective, the tank is 96" long x 30" wide x 36" high.

Full tank shot before

IMG_6154.jpg


Full tank shot after

IMG_70831.jpg


Full tank shot (flip side) before

IMG_6135.jpg


Full tank shot (flip side) after

IMG_7061.jpg
 
Here is a video of diy rock made a year ago with salt mixed in before the water was added. The only thing diffrent is it was made with white tile grout. (white portland and sand pre mixed)
If this is not strong enough for what we are doing then nothing is.

Mr.Wilson
Nice backroud.
I did the same in my tank 2 years ago. again adding salt to the mix. I also added crushed oyster shell.
118997mini-P1000461.JPG

I guess according to Insane Reefer its time is almost up.

Nope just checked it and its still hard as day one.
 
<a href=showthread.php?s=&postid=10108922#post10108922 target=_blank>Originally posted</a> by SilverOne
sunkool,

Your rock looks great! Do you mind sharing what type of portland cement you are using? Also, what kind of sand? :)
cement.jpg

and that is the mixer I use.
 
<a href=showthread.php?s=&postid=10109926#post10109926 target=_blank>Originally posted</a> by mr.wilson
4) Calcium carbonate has a high PH, not a low PH as stated in a recent post. I won't mention names. :)

Let me just post this quote, taken from this article
http://www.lmcc.com/news/winter2006/winter2006-08.asp



quote:
--------------------------------------------------------------------------------
When internal carbonation takes place, the naturally high pH calcium hydroxide is replaced with a lower pH calcium carbonate. This results in an overall lowering of the pH of the concrete. The lower the pH, the greater is the degree of carbonation. Non-carbonated cement paste has a naturally high percentage of calcium hydroxide, which means the pH of fresh cement paste will also be high, about 12.5 to 13. It is well documented that it is this high pH of the cement paste that carries with it the beneficial property of protecting the reinforcing steel from rusting. Without this protection, the structural integrity of concrete members may soon be in question. Fully carbonated cement paste can have a pH as low as 7.

--------------------------------------------------------------------------------
 
<a href=showthread.php?s=&postid=10110434#post10110434 target=_blank>Originally posted</a> by Insane Reefer
Let me just post this quote, taken from this article
http://www.lmcc.com/news/winter2006/winter2006-08.asp



quote:
--------------------------------------------------------------------------------
When internal carbonation takes place, the naturally high pH calcium hydroxide is replaced with a lower pH calcium carbonate. This results in an overall lowering of the pH of the concrete. The lower the pH, the greater is the degree of carbonation. Non-carbonated cement paste has a naturally high percentage of calcium hydroxide, which means the pH of fresh cement paste will also be high, about 12.5 to 13. It is well documented that it is this high pH of the cement paste that carries with it the beneficial property of protecting the reinforcing steel from rusting. Without this protection, the structural integrity of concrete members may soon be in question. Fully carbonated cement paste can have a pH as low as 7.

--------------------------------------------------------------------------------

What he is saying is calcium hydroxide has a very high PH of about 12, while calcium carbonate has a high PH of about 9. It's splitting hairs, but I didn't want people to think calcium carbonate (crushed coral) had a low PH. It's subtle difference between "lower" and "low".

Neutral is 7, so anything above that is "high", and anything below 7 is "low".
 
The article says fully carbonated paste has a pH as low as "7" (neutral).
Fully carbonated means the Calcium Hydroxide has converted to Calcium Carbonate.

If Calcium Carbonate has a pH of 9 as you say, then why does the article say it has a pH of 7?

Can you point me to a better article? - this was one of the few I could find that even mentioned the pH of calcium carbonate...
 
I have some powdered Ca+ Carbonate at home, ya think I could mix it with RO/DI water and check the pH afterwards??
 
One thing I did notice when I put the concrete rock in the first time, for the first year I did not have to buffer. It seemed like a switch turning from off to on DKH dropped. Now I buffer. Has any one had this experience? Does anyone know why?
 
<a href=showthread.php?s=&postid=10110015#post10110015 target=_blank>Originally posted</a> by sunkool

I guess according to Insane Reefer its time is almost up.

Nope just checked it and its still hard as day one.

Don't be a jerk, Sunkool.

I said it COULD craze, crack and EVENTUALLY disintegrate. And it happens from the inside out, usually - and deep within the matrix. You might never know until it fell apart, YEARS later.

You have a technique that seems to work for you, at least at this point. Many, many folks who tried just mixing the salt in complained about friable rock - after we talked about adding it in as the last step, most people haven't mentioned brittle rock much anymore.
So are all those folks wrong?

I have personally seen a batch of rock that went "bad". The rock seemed ok according to the guy who brought it in to the LFS to show them, just some bits coming off here and there he said, until he had to move the tank. More than half the rock had broken up - you just couldn't tell until you went to move it; corals and the like were sort of holding it together. We have no idea why it broke up, he did not use salt when he made it. So I can say with certainty that cement rock can break up in a reef tank.
Granted, it doesn't seem to happen often.

The information is out there if you are willing to look it up and read it - it isn't like I'm pulling this stuff from my butt. Salt retards hydration. Salt degrades cement. Cement in saltwater has a tendency to decompose much quicker. It is mainly caused by something called "Sulfate Attack": http://www.understanding-cement.com/sulfate.html
This site has a lot of great info on it - I recommend it to anyone who actually wants to know about cement and how it really works.

But please, Sunkool post some links backing up your idea's - I would like to read them myself.
 
Last edited:
<a href=showthread.php?s=&postid=10110735#post10110735 target=_blank>Originally posted</a> by dngspot
One thing I did notice when I put the concrete rock in the first time, for the first year I did not have to buffer. It seemed like a switch turning from off to on DKH dropped. Now I buffer. Has any one had this experience? Does anyone know why?

Fresh cement is very alkaline - this would be the reason for high DKH - I saw it recently when I added my backwall. I don't do DKH, but ALK tests, and if I had to guess (since the level was higher than I could test), I would say it was 375-425ppm.

As cement ages, it carbonates (see above), and the alkalinity slowly is reduced.

That is my understanding anyway :)
 
Don't be a jerk, Sunkool.
Now you have to resort to name calling?



<a href=showthread.php?s=&postid=10106118#post10106118 target=_blank>Originally posted</a> by Insane Reefer
"They" are cement chemists and professionals...
Salt acts as a desiccant within the cement, removing "pore water", and ends up messing up the matrix of the cement in a very fundamental way, to put it simply. Salt tainted cement has a tendency to crack, craze and disintegrate over a few years time - a lot worse than normal, traditional rock made with no salt can eventually do.

I'm sure I'm not the only one that has notices that the number of people complaining about brittle rock has decreased since mixing the salt in was recommended to be done last. I certainly noticed a difference in friability and over all strength.
And you aren't the only one to say it - but why take a chance with adding the salt too early, knowing all that?

I said it COULD craze, crack and EVENTUALLY disintegrate. And it happens from the inside out, usually - and deep within the matrix. You might never know until it fell apart, YEARS later.

looks like 2 totally diffrent quotes to me!
first you said a FEW years time. It has been a 2 years and next year it will be a FEW years. Thats why I checked and it is still hard as a rock.
If you want to change your statement to the latter: if my rock lasts me 10 years then starts to crumble down into substrate then I will make new rock for it. Not still be sitting here for the next 10 years trying to figure out a way for it to last to the 11 year mark. You can sit here like Betty Rocker baking your rocks all you want to. I posted some pics for people to see. Neptune777 asked me how I did it and I responded.

NOW I don't know how the person you are speaking of made their rocks but I do know that if you make the mix to dry it will fall apart whether or not you put salt in or not. Same goes for using portland without sand.
 
<a href=showthread.php?s=&postid=10110590#post10110590 target=_blank>Originally posted</a> by Insane Reefer
The article says fully carbonated paste has a pH as low as "7" (neutral).
Fully carbonated means the Calcium Hydroxide has converted to Calcium Carbonate.

If Calcium Carbonate has a pH of 9 as you say, then why does the article say it has a pH of 7?

Can you point me to a better article? - this was one of the few I could find that even mentioned the pH of calcium carbonate...

The article you sited refers to (carbonated) cement paste as having a PH as low as 7, not calcium carbonate having a PH of 7. Calcium carbonate is just one constituent of cement paste.

What we call "crushed coral" in the hobby, is 100% calcium carbonate. Dolomite is comprised of calcium carbonate with magnesium added to form calcium magnesium carbonate. Aragonite is chiefly made up of calcium and carbonate ions.

It is carbonates (carbon) that increase PH. As calcium goes into solution, free carbonate ions buffer the Ph up and raise the DKH.

Calcium carbonate minerals are used to amend soil to a higher PH in agriculture. Aragonite will start to dissolve and buffer the PH up once the PH drops to 8.4 or lower. Pure calcium carbonate (crushed coral) will start to dissolve and raise the PH once the aquarium water drops to 7.8 PH.
 
Actually, I read the quotes as saying basically the same thing. Are they exact, NO, but they are close.

FWIW, I thought the comment in reference to checking the rock was uncalled for and being pretty much a smart you know what. If that was not your intent and you were just joking and giving IR a hard time, then I am mistaken and am all for giving someone grief, but if it was the prior, then...well, that is inappropriate and would have been best left unsaid.

Again, my 0.02....no on to discussing how we are doing making rock...
 
I give up - if you think I said two different things, I am sorry for you, Sunkool - I think it is pretty clear that I said the same thing twice - just with slightly different wording.

Good luck with your endeavors.
 
Mr Wilson, I will admit that my chemistry is next to non-existent; I have read a LOT about cement recently, and feel I have about as good a working knowledge of cement as anyone who isn't in the industry and doesn't have a cement chemistry background.
I understand the basics in most cases; it's the details that get me, lol.

I know that MMLR can get down to the 7 range for pH. I have only had it happen myself a twice, and I have seen it reported in threads - it isn't common, but it does happen. Usually with that batch of rock that got made and sat around forever outside before it was tested or dealt with (another reason I am interested in air kuring as an alternate). The 8 range however is not uncommon.

I am taking the article at face value until I get it from a cement chemist or good article that this article is wrong. Nothing against you, Mr Wilson - I do respect your knowledge and am willing to listen, but I'm from Missouri - Ya gotta 'Show-Me' once I've listened, I then have to explore it myself. Sometimes finding the answers to the more complex questions are hard to find, especially in the cement industry - they often don't have an answer.

The first sentence states "..naturally high pH calcium hydroxide is replaced with a lower pH calcium carbonate..." and the last sentence says "...Fully carbonated cement paste..."
from what I've read, if it is fully carbonated, it is calcium carbonate - there is nothing left to convert, and while there are other things in the paste, they aren't things that effect pH, ALK or anything else that I can find...
I could be mistaken, but that is how I read that and the other articles I've read.

I'm not here to start fights; I simply want to make and help others make the best rock possible.

I am playing "Betty Crocker" because I think there are alternate ways to do pretty much anything, and me and the lab monkeys are proving that rock can be kured in a week or two - something that almost everyone said couldn't be done. Granted I am beating the cement up pretty fierce to do it, so it will be interesting to see how this rock fares in the long term - but I am willing to accept that this rock might fail from Delayed Ettringite Formation, but I am hoping that the vinegar treatment will open the matrix enough that if Ettringite forms, it will have the room it needs to expand and not crack the rock. But I have never said that Jiffy Rock was the end-all, be-all of rock making, nor even unduly encouraged anyone to try it. I still think the strongest, bestest rock is the "Ol' Skool" rock without any salt. That is my opinion. I do add salt to my mix (the LFS likes the lighter weight) now that a good type has been found, but I knowit weakens the rock and since I am selling my rock, I have a responsibility to the end-user to sell the best rock I can make - after all, I'm the one who is going to hear all about it from the LFS's if my rock is bad or fails in a few years...

So I add my salt at the end of the mixing process, and will continue my experiments with Jiffy Rock to see if I can get rock that is ready and stable in a week.

And I will try not to frustrated when heads butt. ;)
 
Status
Not open for further replies.
Back
Top