High density ferrocement
RECIPE FROM http://www.youtube.com/watch?v=EgOXCjRdHBU
- 1 bucket sand
- 1 bag portland
- 2.5 gallons water
- 16 oz eucon sPJ
- WAIT for watery consistency (cement is all hydrated)
- 12.5 lbs Boral Micron 3
- 1.5 compacted quarts fibers of PVA rec 15- 8mm
- 1 compacted quart of Forta Ferro 3/4" fibers
- 2 more buckets sand
- 5 gallon bucket of properly aerated Mearlcel 3532 foam
YIELDS 3 Cubic Feet of plaster mix
Why is a low water mix important?
- Not only does the low-water content enhance compressive strength significantly, more importantly, it substantially reduces the shrinkage of the cement during curing. This allows several unique advantages: A second coat can be applied without waiting for the first coat to cure and shrink; Cold joints with older plaster bond well, No expansion joints are needed, Cracking is reduced or elliminated, The low-water mix gives up water more slowly and so is easier to cure. All of these makes this mix more forgiving for less experienced plasterers.
Doesn't the 40 ounces of water added with the Mearlcell 3532 boost the water content for the cement hydration?
- No. Aerating compounds such as these provide a stable solution for a stable bubble that will survive past the initial set or initial hydration of the cement. The compression strength drops from 17K psi to 11Kpsi when the 12 to 17 percent aeration is added not because of the extra water, but because hard mineral based aggregate is replaced with air bubbles. This can be proved by simply measuring the shrinkage percent, which is an accurate measure of water content during initial hydration. Also, if the 40 ounces of water were released for the initial hydration phase, the compressive strength would not likely exceed 10,000 psi as test cylinders reveal.
See large tank video at 2:45 of http://www.youtube.com/watch?v=JtmKLVVAgbc
they build a 260000 gallon insulted tank out of ferrocement lamination, but don't discuss the insulation. Inquiry made.
So what would we build out of it?
How about a catchement tank and a tornado shelter?
This guy has piles of pictures of this technique (stressed skin ferrocement)
A movie of how to put cement on lathe