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RE: Slab on Grade

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Brian,

This is a common problem.  But it is a problem that can be mitigated by a
prudent, detailed slab design.  Fixing the problem once it exists is more
expensive.  You can figure about $5/foot for epoxy injection.

I don't know of any published "acceptable" crack widths.  But aggregate
interlock is lost when the crack width exceeds 0.035" to 0.040" (ACI
360R-92, Sect. 7.1.1).  When aggregate interlock is lost, one side of the
slab deflects relative to the other as wheeled traffic crosses the crack.
This results in the wheels impacting the side of the slab at the crack.
Eventually the side of the concrete will crush and the crack will get wider
at the surface exacerbating the problem, accelerating the crack degradation,
and causing a lot of damage on the hard wheeled vehicles.

Regards,
Harold Sprague 


> -----Original Message-----
> From:	Argue and Associates [SMTP:bemargue(--nospam--at)sentex.net]
> Sent:	Tuesday, February 29, 2000 11:17 AM
> To:	seaint(--nospam--at)seaint.org
> Subject:	Slab on Grade
> 
> We are currently reviewing a 7" thick industrial floor already in service
> for about 4 months with saw cuts at 20' c/c in one direction and 15' c/c
> in the other. There are a few cracks in the floor ranging from about
> 0.016"
> to 0.060" with the majority being around 0.030".  Does anyone know of a
> published acceptable crack width for a slab on grade?
> 
> Tow motors driving across the unsealed joints create an irritating
> thumping noise.  Has anyone had this situation before?
> 
> Brian McDonald P.Eng
>