Backyard Aquaponics
A place to discuss aquaponics

funny I was watching myth busters tonight for five with dinner...some where on the road.
they were maling concete planes(gliders)
splat

Why? they run out of lead to make ballons....

It is amazing how "coincidences" like that occur. Been around for 30+ years treated concrete as a mysterious and arcane art not to be indeavoured. Then I start consider concrete tanks, find out about conrete boats and few days later concrete gliders.

How would the concrete respond to flexing. I'm guessing not very well.
It would be very bad to try and come out of a dive and have a wing break off.

I first heard about concrete boats from my grandfather. I guess he was on a team of engineers that built a concrete rowboat for a competition. Theirs won, of course. He said reinforced concrete was pound for pound stronger than steel or fiberglass. I have no doubt that a concrete airplane could be flown, but I doubt if it could be sold or financed.

Ok I get he idea of concrete tanks now but here come the questions.

How paranoid do you have to be about the base that the conrete tank sits on?

My soil is about .5 to 2m of volcanic red soil (not very stable, quite soft and friable really good for growing stuff) and below that solid clay subsoil.

I've read that the tanks will take about a month to cure before water can be added. How temperature, moisture dependent is that? Heading into winter its getting colder pretty quickly and hopefull its going to rain at some point. Will this be a problem?

What problems will the fresh tank cause fish?

I believe fresh concrete can affect the pH. I think it raises it since I seem to recall that the remedy was to wash it with vinegar. I could be off. Second opinions?

the tank will take 28 days to set. Going by standard concrete rules. For a base the best is to see how house construction is done where you live or talk to a builder. The tank can flex a bit while its curing and if any cracks occur just slap another coat on.

Concrete love moisture when it cures. usually they recommend adding a little water to the tank (about 3cm) at the bottom for the concrete to absorb moisture. as for cold as long as you stay above freezing it should be all right you could always plastic sheet it over to keep the warmth in.

Stuart-
a concrete tank is supposed to be a monolithic structure and as such will maintain it shape.
The pad for construction is important for construction process beyond that the structure should be stand alone and to some degree 'float'.
water- best to cure with water and plastic to slow the cure.
add water after 72 hrs 10% volume.
You may need to empty the water and in the process, sluce(sp) the sides.
Free lime will continue to exude from the base and walls for the next 30 yrs.
28 days is the cure to 40% the rest will take 6 months
freeze/thaw should do no harm as the mass of a decent sized tank will take ages to completely cool down before approaching freezing.
The key is to pour continuous( wet on wet) no more than 8 minutes break between placing conc.
C1

6 months

Do I hav to wait that long before I add fish?

No, PM Jaymie and see how long she waited, and what the result was.

Went to the hardware and have spoken to a bunch of people re the concrete tanks and growbeds.

JT said


The people I was talking to (included the supplier) recomended that a mix of 1 part cement: 3 sand: 2 gravel. Thats quite a bit different than what JT was recommending. Any idea as to why? Is cement in Indonesia of lesser quality/reliability? The people I was talking assured me that the 1:3:2 mix was very strong/waterproof concrete.

Stuart- there is a ratio of (X) sized agregate to wall thickness
From memory was thinking agg(25mm) x 3 = 80mm .
(14mm) x 3 = 45mm .
for concrete to be water tight and without coatings, a wall for eg.
needs to be 100mm to stop seepage from 2 mtr head of water (please argue if you have the numbers)
C1

1;3;2;

Sorry c1 I'm not sure I understood that last post.

Bigger aggregate necessitates thicker wall - makes sense.



Tank wall containing aggregate of 25mm needs to be 80mm thick. Yes?
Whats the x 3 bit mean?

Since this would be for a fish tank of max depth 1m deep how much less than 100mm could the wall be?

Another question. If you need Xm3 of concrete how do you calculate the amount of cement that you need by volume in the 1:3:2 (cement:sand:gravel) mix? I'm guessing that it probably depends on the particle sizes in the sand and gravel used (hoping for a simple answer).

Sorry I just caught this now



First off Ferrocement does not use gravel (aggregate) as a filler. Mainly for two reasons: 1 We need to apply it like a mortar (hence sand and cement) and number 2 aggregate can be the weak link in good concrete work

As for why so much cement that is because cement is the strongest part of the mix and also the waterproofing/binding agent.

I still need to get a photo of one of our tanks here but picture this. The tank is 1.5m Radius and 1m high. The edges of the tank are 1.5cm. The steel is just 3 layers of chicken wire.

JT