Backyard Aquaponics
A place to discuss aquaponics

As far as I know, the difference between ferro-cement and a reinforced slab is
1) dryer mix
2) sand vs larger aggregate
3) more and finer metal reinforcing
4) perhaps 3cm to 5cm thick rather than 10cm or more. (that's 1 to 2 inches of thickness vs 4, for us in the states)

Some cool stuff:
http://flyingconcrete.com/
http://flyingconcrete.com/stairs.htm

Kuda, the ferro part of ferro cement refers to the wire mesh that is used inside to form the framework on which a mixture of cement and sand is applied. You can go from 10mm to 30 mm thick. Yes it is used for water tanks too. See video below.

http://www.youtube.com/watch?v=U7IGsG0TzUo

It highly cost effective - a little labour intensive though! Lasts a liftime. Only issue is that it weighs a helluva lot compared to plastic/fibre glass tanks and therefore needs to be manufactured on site.

Too cool!!! You think his mix is 3:1 (sand:cement) too?

And here is the American Avatar!

http://www.youtube.com/watch?v=_jBrgVqyVLA&feature=fvw

300g for $150.

Sorry Kuda

That was meant to be a rhetorical question- the ferro in ferro cement is the
steel re-inforcing so the name presupposes the wire to re-inforce the cement. Like HP says it is just a cement morter without course aggregate
so ferro-cement rather than concrete.
Steel reinforcing is a must - for a pond it would usually be a few layers of chicken wire pegged to the earth wall with some spacers to give some (very little)room behind it and then the morter trowelled on and worked into the reinforcing.
The morter is used pretty dry so it cant be poured and usually not shot.
John

That is a really neat video KM09. Circular shape is strongest. Perhaps corners on a rectangle need extra reinforcing? I don't want a circular GB or sump.

He says he uses fiber reinforced masonry. This is probably a similar mix, but with plastic or glass fibers mixed in for more strength.

Hi Kuda,
Concrete/mortar is strong under compression but weak under tension, to prevent it from bending you need a thick slab. With ferrocement the steel (or nylon) mesh takes care of the tension and the mortar handles the compression and you don`t need anywhere near the normal thickness.

Thanks guys. I remember all this stuff from uni. I was just under the impression ferro cement was more than bruckies mortar with reo. Thanks for clearing up this particular jargon. I do want to cement my leaky pond.
So... Anybody got an answer on sealing the stuff? Or if you don't use lime is it not necessary?
Lime is nice cos it stops the mud going off so quick.

Cyara,
Rectangle works as good. I have one on my roof top which has been around (I am told!) for over 60 years now and it is still in use! They never had plastic ones those times!

When you make the inside framework you need to make sure the chicken wire mesh continues along the bends - like in a wicker basket. For added strength you could make a grid in 6 mm rods and then wrap the chicken wire mesh over it.

KM

I see you are right HP... about the fiber reinforced masonry. Not something I know how to make in my backyard. Pity. Absolutely love what he has done with it.

That is good to know. 60 years is amazing. When I first started venturing into building stuff I kept being told how hard it was to hold water. This is all so encouraging. Thanks.

Chelle,

Just a normal mix of 1 part cement to 3 parts sand. Then add some fibers: chopped fiberglass, etc are typical. Apparently they used to use horse hair (I've seen that in plaster walls I've taken out). You can also add acrylic fortifiers that are supposed to increase the mix strength. The fibers help prevent cracking, but you can get a pretty darned good result with just sand, cement, lots of wire mesh, and care. Try it with something small....how can you lose?

And wear gloves!



KP,

I would think that your pond could be coated fiber-cement or some chicken wire and a cm or two of cement/sand mortar, but I'm not sure how to get the wire to lay flat.

I wonder if organic fiber would work? Like bush grass.... Is often used to help adobe bricks bind together. What do you think....? or would it just disintegrate inside and be useless for this kind of thing? Probably just weaken the mix?

Chelle,
Organic fibres such as grass, coir, jute denigrate over time and will not give you the requisite tensile strength. It is better to stick with nylon /plastic. But this cannot be a replacement for the chicken wire mesh / steel with gives you both shape and the strength.
Attaching a picture of my "60 year old" tank on the roof.
KM

I figured that would probably be so. Wish I could grow fibreglass... That flying concrete is amazing. I have gone back to that site many times. Seems for fancy extras in terms of curves etc that that extra added by the fibre may be needed. Still plain ferrocement still has super possibilites. That tank looks really solid after 60 years. May my GBs and Sumps look the same! I was just planning to do really thick walls but was still worried.... now not. Going to be a cinch... well ... will think so once I forget the aching muscles....