[Ferro List] PVA Lath Penetration + Hybrid

[Doug Lacy]

Richard - 
I use between 2.5 and 3.5 pounds of PVA  rec 15 per yard in addition to another 3 pounds of 3/4 Forta Ferro 3/4 inch coarse spiral fibers and still get good penetration. If I were to exceed those quantaties (3.5 compacted quarts and 2 compacted quarts respectively)   penetration of lath becomes a real problem very fast.  An ultra low water mix also helps the mix grip the lath in situations, such as overlaps of lath, where the mix cannot push all the way through the eyelets because it doesn't shrink enough to pull away after it cures.  The special fluid lava like properties of ultra-low water mixes may be why the substantial fiber content does not interfere with lath penetration.   Penetration problems due to large amounts of fibers seems to be more of a problem is standard mortars that don't use water reducers.  The fibers certainly help keep the mud from falling through the other side.  Combining the two fibers seems to help but no testing yet.  Even with very partial penetration of lath of a low water mix, it is hard to rip the lath from the shell, not like with regular plaster where it is easier to rip the lath free from the shell.  This has to do with shrinkage.  Perhaps Dr. Fischer focused on standard mortar pastes that have higher than 0.3 water cement ratio.  With a large volume of PVA, you don't have to worry about shrinkage cracks if you are using a lot of water so the low-water PVA mixes may not have been fully evaluated.  Absence of shrinkage is the most remarkable thing about low-water mixes, in my opinion, because it changes so many things we are use to, not the tremendous increase in P.S.I.  
Doug

Richard said: "You will not get penetration with fibers and lath.  I used  
> PVA as a layer over lath and mortar like Martin Iorns lamination  
> system.  You need steel openings of a minimum of one inch according  
> to Dr. Fischer, who is probably one of the top three experts on the  
> subject.  So that means PVA-ECC with 6 x 6 WWM works great."

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