[TanganyikaFreak73]

I built a DIY background with quickcrete and styrofoam. It never completely cured :? I used some suggestions from the board adding ammonia etc. never cured......... dried it out .......same result [/list].

So here I am with a dilema? .........so does anyone have a suggestion for a non -fish -toxic coating over the background too seal it?

I have spent lots of effort on this one and ripping it out is something I do not want to do.

 

[a_c_arnold]

Just go to lows or home depot and buy some Dryloc Concrete sealer. Buy the white and you can use concrete die to color it. All you have to do is paint it on with a brush and let it dry for a couple of days. Look at my tank links for an example, my 40 gallon background was done using this stuff.

 

[R-DUB]

what do you mean it never cured? It never dried hard or it never stuck to the styro?? If it never stuck to the styro then a coating/sealer will only break away along with the crete. Did you use acrylic fortifier with the crete mix?? That is what I really found works well to harden and stick the crete to the styro.

 

[TanganyikaFreak73]

what do you mean it never cured? It never dried hard or it never stuck to the styro?? If it never stuck to the styro then a coating/sealer will only break away along with the crete. Did you use acrylic fortifier with the crete mix?? That is what I really found works well to harden and stick the crete to the styro.

The quickrete stuck to the styrofoam good with the exception of a few very small spots that chipped away. It didnt dry hard enough. After doing tons of water changes, the ph will still not get to the value of my tap water. It seems that the create is leaching back into the tank.

I did not use an acrylic fortifier just mixed it up from DIY archive as it was written, one possible reason is it cured in my basement and it is pretty cold down there? Im not sure....

 

[iceblue]

How long did you wait before submerging the background?

Can't say for sure but it sounds like you either didn't give enough time to cure in the cold air temperature before being submerged or thier was not enough portland cement in your mix to make a strong bond between the aggregates.

For my background project I made my own skin mix of 1 part cement to 3 parts sand and used both acrylic fortifier and water to attain the consistancy I wanted. It worked very well but I did use it to cover lightweight concrete structures instead of styrofoam. My overall thickness was about a 1/2".

 

[R-DUB]

Concrete never drying is strange indeed. The crete mix must have been bad for some reason. So adding a sealer will not help. So that idea is out. I dont understand how it can stick to the styro and still be "wet". Very strange. The leaching will eventually stop. There is only so much alkali in the cement. Keep up with the water changes.

 

[Mcdaphnia]

There are some odd additives out there. If you want to read 66 e-pages and growing, check out The Ultimate DIY Rocks! on ReefCentral. Some failures are reported there, notably with different types of salt, dry pasta, and recipes very low or high from the norms established by extensive research and use of concrete. Premature submersion before the 'crete has cured enough (30 days in moist air or being sprayed regularly, longer with certain additives that retard curing, or temps below the 70's Fahrenheit) has also caused problems, most often the release of alkalies before they could chemically bond with water and oxygen.

Totally cured concrete will buffer slightly because it contains limestone, reconstituted from the anhydrous lime in the mixture. Limestone will buffer very soft and acidic water. That is a good thing for many cichlids that originate from areas geologically rich in limestone, such as Central America and the East African rift lakes. However in a biologically active aquarium, that buffering ability will be lost as "thigmotrophic" bacteria colonise all the surfaces in the tank, sealing off the buffering ability. This takes about as long as the nitrogen cycle does, since they are the "same" bacteria we foster to convert nitrogen fish wastes from ammonia into nitrite, into nitrate.

 

[TanganyikaFreak73]

How long did you wait before submerging the background?

Can't say for sure but it sounds like you either didn't give enough time to cure in the cold air temperature before being submerged or thier was not enough portland cement in your mix to make a strong bond between the aggregates.

For my background project I made my own skin mix of 1 part cement to 3 parts sand and used both acrylic fortifier and water to attain the consistancy I wanted. It worked very well but I did use it to cover lightweight concrete structures instead of styrofoam. My overall thickness was about a 1/2".

I 'm leaning towards not letting it cure enough, I'm letting it dry out and the color has changed in about 4 days. It s definetly much lighter in color

 

[iceblue]

After it has dryed, scrape the surface with your fingernail. You shouuld not be able scratch any mortar off. If you can then the early submersion has removed binder from the stucture. Hopefully this isn't the case but if it is I would remove all the loose mortar and recoat it.

 

[Squinchy]

Epoxy ?

 

[barbarian206]

you say that you left it curing in a cold basement how cold is your basement if it is real cold down there try putting a wet peice of burlap material over it them a old comfritor over it if the temp is to cold concrete will not dry to it fullist and crack i work with cocrete all day long in all kind of weather this is what we do in the winter months by putiing a wet burlap with a thermo blanket in the hot months we just put burlap and keep it wet for 7 - 14 days curing but it would be diffrent curing time here i would let cure for 7 days keeping it moist try burlap :fish: :fish: :fish:

 

[R-DUB]

Does concrete actually create heat as part of the chemical reaction during curing? So barbarians idea seems like a good one for future "cold curing"

 

[iceblue]

Hoover dam would not have been possible without the chilled water lines that run through the structure and are still circulating water as I write. In fact, it is still not cured to this day and the concrete at its center is hot and still of plastic consistancy.

In hot dry conditions slabs set up very quickly so concrete workers try to get a smoothed hard seal over it in a hurry to keep the water in. In cooler moist conditions they'll work the top of the slab with a magnesium or wood float to open up its porosity so the water will dissipate more quickly.

We poured a thick large slab for a paper products plant during the winter very near the coast of Southern California. We started early in the morning and by the time the sun was setting we had to cover it with plastic and come back the next morning to put a finish on it. Calcium chloride would have helped that job but hey, time and a half for Saturday was cool with me. The same slabs that I've poured in the mid desert of California during the summer were poured in the morning and had a final finish by noon the same day.

There are a lot of factors involved in concrete and it has a science all its own. For most of what we do with our backgrounds letting it air cure for longer periods is benificial. In a high moisture area periodic sprays of water will help and in drier areas keeping it moist with a wetted towel and keeping it wet for 2 or 3 days helps. The biggest thing is having patiance. Personally, I would give it a month before submersion no matter the conditions. The longer you let it cure the less likely it will leach at high rates.

 

[Mcdaphnia]

Does concrete actually create heat as part of the chemical reaction during curing? So barbarians idea seems like a good one for future "cold curing"

Most of the heat generated is right away as the water is mixed in, but heat would continue to be generated, just really small ever lessening amounts.

 

[barbarian206]

the reason why we keep it wet is so that the curing process takes a little longer and the concrete gets stronger out here in the east coast we have all types of weather so we need tougher concrete that can handle it we also use calcium chloride in our crete from what i know the longer the cure the harder the concrete :fish: :fish:

 

[TanganyikaFreak73]

After it has dryed, scrape the surface with your fingernail. You shouuld not be able scratch any mortar off. If you can then the early submersion has removed binder from the stucture. Hopefully this isn't the case but if it is I would remove all the loose mortar and recoat it.

Thank you all for the tips.

The background has finally dried. I scaped the surface with my fingernail and I was able to scratch the mortar off. :x So the problem is identified........... now for the solution?

Removing the mortar will commence. As far as temperatures go, when I cured it im estimating it in the 45'- 55's (no thermometer down there)pacific northwest winter and one electric baseboard heater . I submersed it after around 2- 3 weeks.

I used about 8lbs of a 10lb container of Commercial Grade Quickrete Hydraulic Water-Stop Cement.

Thinking about moving it upstairs in warmer temps around the 60's to 70's to cure, after removing loose mortar and recovering the surface.

O.K. I hope that sums it up :thumb:

 

[TanganyikaFreak73]

After it has dryed, scrape the surface with your fingernail. You shouuld not be able scratch any mortar off. If you can then the early submersion has removed binder from the stucture. Hopefully this isn't the case but if it is I would remove all the loose mortar and recoat it.

Thank you all for the tips.

The background has finally dried. I scaped the surface with my fingernail and I was able to scratch the mortar off. :x So the problem is identified........... now for the solution?

Removing the mortar will commence. As far as temperatures go, when I cured it im estimating it in the 45'- 55's (no thermometer down there)pacific northwest winter and one electric baseboard heater . I submersed it after around 2- 3 weeks.

I used about 8lbs of a 10lb container of Commercial Grade Quickrete Hydraulic Water-Stop Cement.

Thinking about moving it upstairs in warmer temps around the 60's to 70's to cure, after removing loose mortar and recovering the surface.

O.K. I hope that sums it up :thumb: