[Ferro List] FERROCEMENT-AERATED CONCRETE SANDWICH BLOCKS

[Doug Lacy]

That technical paper about the ferrocement encased aerated concrete is simular to what I am doing in a few ways but very different for the most part.  The final mode of failure in their samples during compression were delamination.  That couldn't happen using the Parabolic Stress Skin Process because of the evenly spaced cross ties of steel bonded to both surface shells.  Maybe it could happen in some manner due to some state of hypothetical outerspace decay but it would be on the list of stuff not likely to happen on earth because of the tight bond between the mortar and the lath due to the low-shrink mix and the tight bond between the lath and the internal welded wire cubical structure that also reinforces the 30 pcf 600 psi closed cell neat cellular concrete fill that occupies a 12 inch thick cavity.
 Some interesting thing about that paper is that:  They showed that even after failure, these hybrid ferro and cast aerated maintened 20 percent of their strength in thier semi squashed form.
 They had an interesting mix for the aerated fill, complete with blastfurnace slag, sifted sand, super P, very specific dry material to water ratio, and only 20 percent aeration, all for a wimpy 1100 psi mix. But when it came to describing the ferrocement mortar paste, it was just reffered to as a 1 to 2 binder and an adjusted water binder ratio and and .2 percent super P. to achieve a certain flowability. No water to binder ratio stated and not too many other specifics revealed there. And then after going on about where the ferrocement mortar cube's  psi was tested and how much they weighed, they forgot to include that psi data so we have to do surface area calculations based on their shell area and aerated area to figure that out to make a guess at how their mortar augments compression before the inclusion of any steel.
They seem really excited about the 1100 psi 20 percent aerated mix for the inside of their sandwich because one of the reasons sited for using a ferrocement surface is to protect this precious and complex aerated mix from moisture because  the aerated cement can absorb a lot of moisture.  This is true of their mix because they used powdered alluminum as an aerating agent which produces open cell aeration -open pores.  Closed cell aeration, from aerating compounds like Cellucon and Mearlcell 3532, blocks moisture intrusion.  My own test cylinders held under water for days were dry in the center region.  
It is a great paper in that they are making some basic testing about hybrid materials and showing some significant strength increases with the inclussion of FC and some important information about how ferro encased low-density mixes fail. This is some needed data.
 If their studies are pursued I will bet that their focus will shift from the aerated fill to the composite surface shells as it did for me. They may not make it all the way to using wine bottles as an internal fill any time soon, but who knows.
Doug
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