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RE: Concrete flat slab strengthening

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My observation of laboratory tests and field experience has indicated no
effect of polypropylene fibers except in reducing rebound of shotcrete.  I
have seen PPF used on slabs on grade, and slabs on deck in Louisiana,
Colorado, Missouri, Kansas, Wyoming, and in many other states.  The cracks
tend to be fewer than in unreinforced concrete, but the overall shrinkage
remains the same as plain concrete.  The combined shrinkage manifests in the
fewer cracks resulting in wider cracks.  The crack width is such that
aggregate interlock is lost and the slabs experience differential curling
resulting in tripping hazards.  The cost of repair runs about $5 per lineal

If you feel comfortable with PPF in slabs and you think it has merit, that
is fine.  My experiences with PPF have been too expensive to consider it.  I
will either go with no reinforcement for slabs on grade or I will use steel.

Harold Sprague

> -----Original Message-----
> From:	Murat ERBAS [SMTP:merbas(--nospam--at)]
> Sent:	Tuesday, January 11, 2000 1:02 PM
> To:	seaint(--nospam--at)
> Subject:	Re: Concrete flat slab strengthening
> I am user of POLYPROPYLENE Fiber successfully in Turkey. Infact I donot
> have
> any test reports about non shrink effect of FIBERMESH.
> But my personnel experience showed me that it reduces bleeding water.
> Therefore it kept concrete non shrink.
> As far as I know, concrete shrinks because of water bleeding and fast
> evaporation. therefore people uses curing agent or wet blankets to keep
> water inside. Fibermesh makes homogenous gravel distribution and not let
> to
> gravels sink bottom of the concrete while it is plastic phase.
> This mechanism provide us less bleeding and low water lost. Therefore you
> can reduce the shrink effects where coming from settlement and bleeding.
> Of
> course to reach better results, you should use cure products to cover
> concrete against evaporation of water. This is one of the main reason to
> use
> On the other hand, PP fibers also reduces shrinkage cracks. When concrete
> turn into hardened state from plastic phase, (in three hours period) the
> resistance for carrying inland loads power not enough to inland strength.
> Therefore it cracks. Fibers helps to concrete to carry inland strengths
> better during hardened state.