[Ferro List] reinforcement, delamination , weak pockets

[Richard McCabe]

Chuck,

I don't sell PVA fibers anymore, but the work done by Drs, Naaman and  
Shah suggest that a steel and PVA hybrid may well be the best  
approach.  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.  Many  
studies about R/ECC (rebar and ECC) show tremendous results and are  
being used for bridges and columns.

In case of fire, you should have a sacrificial fiber to allow water  
vapor to escape.  This helps to avoid explosive spalling.  Check out  
the tunnel fires in Austria and Switzerland a few years back.

Nycon.com is still the distributor.

Richard

On Apr 1, 2008, at 1:13 AM, chuck east wrote:

> As I hone in on engineering and design considerations for my  
> subterranean
> thin-shell LFC home (famous long ago as a 'flipped boat'), I'm  
> paying very
> close attention to the issues of 1) mesh vs lath and the size  
> thereof and 2)
> fibre reinforcement.  Regarding the latter, have there been any  
> conclusive
> tests as to the best fibres - steel vs glass & other? - for 1)  
> penetration,
> 2) strength and 3) lasting-power?  Along these lines, has anyone  
> run tests
> with or actually used Microcells/E-Spheres in thin-shell LFC  
> structures?  Is
> it redundant to add 'thin-shell' to 'LFC'?
>
> ABILITY claims the following:
> Because 'E-Spheres' are lightweight they are easy to carry and  
> transport.
> They are exceptionally resistant to high temperatures, fire, strong
> chemicals, impact and wear. They insulate effectively against  
> temperature
> variations and noise, as they deaden sound. They have the capacity  
> to reduce
> binder shrinkage, a factor of concrete that causes cracks. Because  
> of their
> shape, the 'E-Spheres' have less drag than aggregate, so they  
> improve the
> flow and thus the workability of the unset concrete, making it  
> easier to
> pump and extrude, if necessary and in shotcrete (projected concrete)
> applications. In most cases, these features result in reduced cost  
> because
> the composite can be made with less binder for the same  
> characteristics and
> performance.
> http://www.abilityproducts.com.au/admixtures/afc_espheres.html#top
>
> I haven't looked into the energy requirements for the production of
> E-spheres.
>
> Best
> Chuck
>
> -----Original Message-----
> From: list-bounces at ferrocement.net [mailto:list- 
> bounces at ferrocement.net] On
> Behalf Of tp sing
> Sent: Sunday, March 30, 2008 8:33 PM
> To: list at ferrocement.net
> Subject: [Ferro List] reinforcement, delamination , weak pockets
>
> Just to add my bit to the present discussion, I have extended the
> "conclusion 3" on my crudtest2 page
> http://www.geocities.com/tps_har/crudtest2.html
> It starts with giving a possible explanation to the weak pockets  
> around
> wires and extends on to some comments and pictures on DELAMINATION.
> Regarding Bo's suggestion of thinner wires  I feel that smaller the  
> wire
> thickness (and mesh aperture), the more the 'springiness' or the  
> movement of
> the mesh which may lead to voids during application. At the same  
> time too
> large an aperture affects the stress distribution adversely.  
> Therefore one
> may like to optimize the two parameters. Having seen delamination  
> in my own
> trials I would always choose a mesh with aperture larger than 10  
> mm. I guess
> 10 - 12 mm is ideal.
> Fibres increase the "mortar to mortar" bond and are definitely  
> beneficial
> provided they do not become a hindrance for good penetration. That  
> is why
> they also have "small" fibre lengths. Therefore with a fibre  
> reinforced
> mortar( which has better stress distribution characteristics), one  
> may like
> to take a higher mesh aperture  to aid penetrability.
>
> -- 
> T.P. Singh
>
> Director (R&D),
> Construction Research Centre,
>
> Ph.: 91-11-26802388
> http://www.geocities.com/tps_har
> E-mail: sing.tp at gmail.com
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