[Ferro List] reinforcement, delamination , weak pockets

[chuck east]

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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