Thanks, John.
This really looks interesting. It's hard to believe that so little cement will be so strong. It seems counter-intuitive. We're told that we have to build everything bigger and stronger and thicker with more and more rebar. Amazing that this works.
I'm not really clear about the cement material that you are using. In one place you describe it as mortar/stucco and others cement and sand. Not being that familiar with cement work I'm not sure what if any difference there is. Could you clarify?
When using pilings is it the same mixture? And how big are those holes (diameter)?
I was thinking of building a small pond in my yard. I wanted to built it out of concrete (I hate how this EPDM liners look). I wonder if this system would work for that. I'd probably have to cover the surface with surface bonding cement to seal it though. I could also go much thicker than 1/2 or 1".
Ken Kern discovered this floor in India where the people are too poor to waste resources and often they experiment with cheaper but still durable technology.
Concrete easily reaches a compressive strength of 2500 PSI but many times especially with cement rich mixtures it reaches much more that in it's normal complete cure time of 28 days (It can cure for a lifetime actually but the major curing is complete in 28 days - code work allowed in 7 days). Reinforcement of steel or other fiber gives it tensile strength keeping it from pulling apart. Concrete without reinforcement may crack and separate.
The cement in concrete readily attaches to the jute, hessian, burlap or fibermesh making it a strong composite material somewhat on the order of fiberglass. One piece of reinforcing fiber may take 50 or a hundred pounds to break it... multiply that times hundreds or thousands and that gives you an idea of where the strength of this material is achieved.
The US military successfully experimented with bamboo reinforcement in concrete for bridges though they did use special procedures. They have also built house shells spanning wide areas in India using similar techniques and materials.
A tractor can easily sit on a 4 inch concrete floor. As an example, a human or a bunch of them no where near reach the weight of a tractor.
Cheap but good low tech methods do not sell lots of materials or increase the tax base, hence you will not hear any of this from domestic sources in the US.
My use of different terms is just an effort to get people to understand what the material is. Since it is not in common use in the US few understand the concept or materials. Stucco is about the nearest thing we commonly use in the US that is similar to this floor, but it is sand and cement with some lime used over a steel wire or mesh reinforcement.
In my experimenting with this material I find that the steel mesh or chicken wire as used in stucco does not perform as well as the jute reinforcement. Don't limit steel out - it may have it's place in one of your projects or is great in ferrocrete and stucco, but for the floors the jute performs best, The steel likes to poke up and spring back when you trowel the sand/cement mix onto it. Wetting the jute makes it lay flat and readily bond with the cement in the sand/cement mix.
Stucco is a sand, cement, lime mix used for concrete walls on buildings in a lot of California and other places, and was invented in Rome around 2000 years ago as I recall.
Note Kern first mentions that the floor is 1" thick, but in another couple sentences he mentions that it is a lightly reinforced concrete floor consisting of two layers of concrete 1/4 inch thick --- total actually, not including the sand below it is 1/2 inch concrete. I find that the 1/2 inch is sufficient with the jute reinforcement and especially if Fibermesh is added. Even if you go 1 inch - you are saving 75% over a 4 inch floor.
Clarification on the concrete. I hesitated to call it concrete because most think of concrete as having rock. It is not really mortar or stucco as they usually contain lime making it too soft and weak for this application. It really is a concrete but no aggregate bigger than sand is used. That is why we use the cement rich mix of 1 cement to 3 sand (Not specified by Kern that I noticed - found by my experimentation). Sand is rock, - just very small rock. Kern touched on a lot of things but did not always go into great detail on some of it. There is more to glue together than if there are rocks in it, so I richened the mix. Possibly less cement would do upon further experimentation but I am happy with that mix.
I use the same mixture for grouting the pilings, usually making the holes through the jute reinforcement then filling the holes before putting the first layer on top of the jute. You could experiment with filling the piers before applying the jute but it works for me. I just knock the top level with a wood float if I mess up the sand.
I have successfully used holes of varying depth to even no holes on hard ground or soft ground where I wanted the patio floor to just follow the ground if it settled around the above ground pool. I was interested in drainage there anyway.
I use a post hole digging bar with about a 3/4" to 1" end and repeatedly forcefully hit the same spot with it until I reach undisturbed soil then fill the hole with grout. I usually do about an 80 square foot area at a time sometimes putting permanent wood partitions in to level with. That is not essential though.
I would try this method for the pond though you might want to change to chicken wire (usually 3 or 4 layers wired together against the sides of the pond in the shape you want) and a bit thicker for it due to possibly having a bit more moisture and possibly rotting the jute. The jute is cheap and you could put a layer of it against the ground as a separation from the soil and additional reinforcement. I use a rubber tile grout trowel for irregular surfaces - the slick flexible black ones - not the spongy ones.
Fibermesh could be used and will not rot as it is a type of poly fiber. Fibermesh makes it easier to plaster with. Using the multiple layers of chicken wire makes it into ferrocrete. I have been told neat cement will seal it (cement powder and water to make a paste). Even thicker cement will leak without a sealer.
Sani-tred, Thoroseal or Moxie all make sealers, though it will likely not leak enough to worry about and it will eventually pretty well seal with algae and other materials. Rinse it out with vinegar water - remove it then put fresh water before putting plants or fish in it. Concrete is highly alkaline when first poured or plastered.
I have successfully instructed others on making a 400 gallon septic tank effluent reservoir from ferrocrete and the county approved it. It has worked several years with no problem. Actually it was a lady who built the tank as she wanted to learn to make the ferrocrete herself.
