Concrete raise pH?

Well, I know that concrete (or portland and sand) takes 28 days to reach a 90% cure. Wait as long as you can.

If you make a form, say out of styrofoam, you can really add some relief and texture to the portland sand mix. Just remember, whatever is a knob on the mold becomes a hole in the portland sand mix and vice versa. Try using a boxcutter knife heated by a propane torch and tooled into the styrofoam to give some cool effects like striated layering. Also, if you use a coloured aggregate like a crushed marble or crushed granite, and wash away the surface of the portland sand mix gently when it is thumbprint hard, you can get a realistic colour/texture. Using vegetable oil as a form release before pouring on the portland sand mix will save a lot of headaches when form removal time comes. Pam in the can works best (but buy the no name stuff and save $$$)

Experiment!
 
So you are saying to release the concrete from the styrofoam when done? I hadn't thoght of that....

I was just going to cut out a decent looking rock pattern in the styrofoam using a long knife, and then melting it smooth with either a hair dryer, or if that's not hot enough, maybe a mini-torch. Then paint on a thin layer of cement - mainly to give it strength, texture and color - then put the entire thing, styrofoam and all in the tank.
 
I'm not 100% sure but I think if concrete (or any portland based product) is "flash cured" it loses a lot of strength and can get shaly.

Yeah, about the stryrofoam idea, I was suggesting using the stryrofoam as a mold, like for plaster of paris.
 
Originally posted by Matak
I'm not 100% sure but I think if concrete (or any portland based product) is "flash cured" it loses a lot of strength and can get shaly.
Click to expand...
What is a flash cure? If you are thinking of the mini-torch, that will be used BEFORE the cement. It is to melt out the roughness that the knife will leave behind in the syrofoam. (You know how crumbly a bare edge of styrofoam can be.)

I was planning on actually putting the background in either a large basin or bucket, and changing the water every once and a while, or simply putting the cement in a nearby creek. This would wash away any lime that is in the water, and the large volume of water would nullify any pH increases during the curing.

I think I will just paint the thin layer of cement as opposed to the mold technique. It will be much lighter, and less cement will be used, so in the event that something bad does happen, it won't be as severe because there is less of it in the water.
 
Ahhh, I see now. I thought you were going to speed dry the cement with the torch. My dumb.

I thing the creek idea is best. Constant water change. Maybe a 24 hour brine bath after the creek baptism to disinfect before introducing to the tank?
 
wut he sed. LoL! no1s answering my post so i'm just chatting here while i wait.
 
I'm still not 100% clear on the curing business, but I'm finding much shorter periods posted on various concrete sites than I'm seeing here. I think we ought to take the relatively small volumes of concrete we're talking about into account, especially with regards to a skim coat technique. There are also differences in curing time between concretes, and there are quick-curing concretes (and chemical additives of uncertain consequence).

The concrete examples for aquaria I've seen on the web all seem to be used in salty or in Rift Lake Cichlid tanks. For soft and acidic folks like myself there may or may not be a workaround. I'm going to see what I can do about running a few experiments over the next few weeks and will post back my results. Anyone actually know some of this stuff up front? There seems to be a knowledge base behind more than one of the posts up here…

I have managed to work out this much so far (thank you mighty google)… A good cure effects the ultimate strength of the concrete (and we're not using it for strength). A bad cure may result in aesthetically bad results, like cracking and flaking. The cure is a chemical reaction within the concrete called hydration. Hydration likes water, and curing fully submerged isn't a bad thing for the concrete (probably a bad thing for most of our finny friends). One of my most basic questions is this: how reactive is the lime before and after the cure? Is the lime "locked in" after the cure and less able to drive pH up (and if not, why doesn't concrete dissolve)?

Originally posted by ejmeier
I think I will just paint the thin layer of cement as opposed to the mold technique. It will be much lighter, and less cement will be used, so in the event that something bad does happen, it won't be as severe because there is less of it in the water.
Click to expand...

I've been looking at a thin layer approach applying a series of light coats to a wire mesh and styrofoam armature, mostly for the weight. Another approach that would work for a mold would be to build up the concrete in layers in a mold until you had a substantial shell and then filling that with expandofoam (good support and nice and light).

Anything bad thats going to happen is going to be much more a function of surface area than of total mass, and thin layer approaches won't reduce that.
 
mmmm.

interesting topic..

i have some questions.
what is the best material to use to make ponds..
if cement is used. will this cause a high ph?
what if the pond is painted with a waterproofing paint. will this prevent the high ph?
how about installing tiles to the pond?

what is the purpose of curing? and what procedures are involved with this process??
 
I have been corrected. If I recall correctly (I'm in the trowel biz) concrete is 90% cured in 7 days and 98% in 28 days. It never really fully cures, even after 100 years, but the rate of cure gets progressionally less as time marches on.

The only paint that I have seen that actually remains stuck to concrete over time is an epoxy based paint.

If the portland sand mix leaches out, then covering it with anything inert will cure this problem.

I am quite curious to see Carpguy's test results. What would you be testing for?
 
You must log in or register to reply here.
AquariaCentral.com
Top Bottom