Constructing a ferro-cement (steel-fibre) pond without plastic
Yes, Cement is usually porous. It has to be mixed correctly to ensure it does not leak water. Many commercial stores will tell you it cannot hold water without plastic additives in the mixture, but we created a pond that does hold water. The first construction did leak, so we simply used one more bag of cement, mixing it very carefully to ensure there were no air bubbles and presto, It holds water.
This is how we made the pond with only a small amount of cement (about 4 bags) and a shoebox of steel fibres the thickness of darning needles but the length of a small match. The whole cost of the pond was only $80 Australian.
First we needed form-work to hold the pond in shape while the cement dried. We used straw-bales and you should probably use a spirit level to check that the all tops are level.
James mixed the cement very thoroughly, pouring only a little water at a time and being absolutely careful that no bubbles appeared in the mixture. A second mixture was made for the walls, we added the steel fibres to the mixture. Steel fibres make strong walls if they lie randomly across one another. They will cross each other in a hatch-like pattern if the wall is thin. However, when the wall is thicker than the length of the fibres, then the fibres are free to form 3 dimensional patterns and it will not be as strong.
James Hill is a contact we discovered through our LETS [Local Exchange Trading System]. He came to show us his technique of making fibre cement structures. He wants to be able build a house out of fibre cement because it is so cheap and strong.
The mixture has to be the consistency of a soft ice-cream. It should stick to your glove but then slowly slip off.
We then lay each bale over and started pasting the cement onto the bales. We could have had a smoother surface if we had covered the bales in plastic, but we preferred to minimise the use of plastic.
After putting the ferro-cement on each bale we covered the mixture in old plastic bags to slow down the drying process. Once the cement was dry we turned them upright onto their sides, rolling them back into position to form the sides of the pond. Then we made a new batch of cement to join the walls together and fill the base. 
James Hill and Robert Kebakovski (a permaculture student of ours) trampled the base of the pond with a bit of a dance, because we were nearing the end!
We waited a few days and then filled it with water and plants and constructed a garden around the pond. Now the gutter runs down from the house under a new deck beside the pond and out into the pond with a little waterfall. Here is the pond just a few weeks after its construction.
